So basically, today it snowed, woo! And I needed to go to university, boo! :mad:

So before I set off, I removed my ABS fuse, essentially disabling the ABS system as the road was covered with about an inch or so of snow.

Naturally all my mates ridiculed me, saying ABS was designed to work in situations like that to stop the car if it starts skidding, but my argument was it is designed to reacquire grip when grip is available, i.e. when you lock up the wheels on a dry road, but try as they might ABS brakes can't stop a car on a surface with no grip, hence if you disable the system and lock up the wheels under braking it will gather the snow up in a wedge under the front wheels and stop the car better. That, and my brakes are ridiculously strong and lock up under the slightest of force on snow, and ABS pumping constantly annoys me.

So, knowledgeable people, am I right in my assumptions and leave the ABS fuse in the ashtray until the snow melts to water, or should I replace it poste haste?

To make this thread a bit more interesting, relate to me your snow driving techniques. I find stopping is much easier if brakes aren't used at all and you just work your way down through the gears, using the engine to slow the car down.

I'm pretty sure locking your breaks is the last thing you want to do, and the abs will be better at dealing with it than you.

Well, your logic that the ABS can't function because there isn't any grip isn't quite on the spot. There is grip, just less of it. The whole system will still work the same as usual, ABS will still attempt to hold static friction.

However, there are arguments to be made that if you lock up the tyres you can dig them into the snow, providing far superior deceleration than static or kinetic friction, by using normal forces and other such things.

Whether your car will skid over the top of the ice or actually dig in, and whether it digging in is in fact superior to conventional static friction, I cannot answer.

Best thing for snow: Allow plenty of time for stopping or maneuvers.

ABS should be marginally better than 'non' in the snow. There really is no point to turning it off, unless the throbbing (heh) pedal really upsets you (it DOES bother me a lot actually). Using the engine to stop is more effective but please believe you can still lose traction, it just takes a bit more. Caution is the key word.

I can't wait till it snows here and I can take the T-bird out for some RWD action.

Best thing for snow: Allow plenty of time for stopping or maneuvers.

ABS should be marginally better than 'non' in the snow. There really is no point to turning it off, unless the throbbing (heh) pedal really upsets you (it DOES bother me a lot actually). Using the engine to stop is more effective but please believe you can still lose traction, it just takes a bit more. Caution is the key word.

I can't wait till it snows here and I can take the T-bird out for some RWD action.

You can brake harder with the brakes than you can do with engine braking, since engine braking brakes only one pair of wheels. This is pretty much undeniable fact.

However, since your brakes were likely not designed specifically for the 'holy-fuck-no-traction' regime, the brake balance will likely be a bit too far forward, since it will assume more load transfer than you will be achieving with your small friction coefficent. This means the rears are relatively unused. In a RWD car, adding some engine braking to your ordinary braking can therefore give you higher decelerations.

Go too far though, and it will give you even higher, higher decelerations, as you lose rear traction and hit a tree.

Personally I'd leave it on and just drive slow, but really when you lose control on the snow it's not going to help you.

Using the engine to stop is more effective but please believe you can still lose traction, it just takes a bit more. Caution is the key word.

I thought it was opposite in a car with only 1 or 2 wheels powered. Downshifting puts resistance on only the powered wheels, which would the wheel that's being engine braked skid before the others. Applying your brakes puts ~equal resistance on all of them, meaning there wouldn't be a wheel that's braking harder than any others.

^^^ assuming that your brake bias is set up correctly... which is not likely if you have a used car with non-oem brake pads on the front or rear, or different brands on front or rear... or if your car has weight in the trunk... but the differences would be marginal, really.

The thing I HATED about the WRX was the ABS.

That car ROCKED the snow. Most amazing snow vehicle I've ever driven. I had amazing snow tires, and it had a rear limited slip. It had nice balance and would rip through turns and drifts.

but the ABS sucked donkey balls.

Even a slight press of the brake could cause the ABS to engage, causing you to barely slow at all. I remember going down hills toward an intersection and the ABS not stopping me worth a shit, so I ripped the e-brake causing the rears to lock and the fronts to slow (I bet the center diff LOVED that!).

The ABS wasn't TOO bad with my Nokian Hakkapelitta snow tires, but occasionally it would really piss me off. The Nokians made it bearable though, since they would find grip in almost any situation. Those tires were seriously AMAZING.

On ice, ABS finds you have very little traction, so it does very little braking.

Honestly, I liked it when I didn't have ABS in the snow.

The best I can tell you is to drive with the ABS in the snow for an hour, then drive around without it for an hour in the same snow. You'll know which is better.

ABS is good at keeping you straight, but I'd rather the car stopped and I had to counter steer or correct sliding than the ABS doing it and not stopping.

If you don't have awesome snow tires (blizzaks are pretty decent... nokians are better!)... I'd disable the ABS. But test it out like I said.

It's funny... on ice you can need to counter steer at 15mph.

everyone knows the best way to stop is to throw it in reverse and floor it :P

abs in the snow in my old a4 when i spent a winter in michigan was well well worth it. i know theres a few times i would have slid out if i didnt have abs, and awd. traction control barely went off, but the abs kicked like hell on the ice, and actually stopped me. i rode with a friend of mine who had a 1990 audi coupe quattro, and it had a switch to disable the abs. we would take it out to icy parking lots, and hilarity would ensue. along with four wheel drifts. even in the snow in 20 degree weather, with pirelli p6 all-seasons, my car handled confidently.

i remember a friend of mine who did repo's, repossesed a fairly new corolla, and we were blasting through the back roads in it, he coulda sworn it had abs, until he slammed on the brakes at 60-70 mph, and the car slid right towards a ditch, after locking 'em up. he let off the brakes and counter-steered before going off road, we both we a little pale after that. an unexperienced driver would have wrecked that POS, with abs it would have stayed straight. abs works wonders in low traction situations. but the proper tires are what matter the most.

if i was a fairly unexperienced driver in the snow (i.e. less than 12 months total of snow/ice driving under my belt) i would keep the abs, it could save your ass one day. hell if my car has abs, i'm going to take full advantage of it, it seems retarded the other way. traction control, however, is pretty useless with awd, i like to keep it off, so i can power through corners, rather than be strangled by that blinking light. abs can save your life in a situation you have to react quick to. i learned how to properly use my abs in a wet skidpad for an audi advanced handling school i took when i was 16, the kickback really isnt bad for the benefits of abs in inclement weather.

What Rockon said


Naturally all my mates ridiculed me, saying ABS was designed to work in situations like that to stop the car if it starts skidding, but my argument was it is designed to reacquire grip when grip is available, i.e. when you lock up the wheels on a dry road, but try as they might ABS brakes can't stop a car on a surface with no grip, hence if you disable the system and lock up the wheels under braking it will gather the snow up in a wedge under the front wheels and stop the car better. That, and my brakes are ridiculously strong and lock up under the slightest of force on snow, and ABS pumping constantly annoys me.

Your friends were right, by the way.

everyone knows the best way to stop is to throw it in reverse and floor it :P

They tested that on mythbusters. It doesnt work at all.

I've heard lots of experience drivers and mechanics, as well as the boy on carbibles.com talk about the idea that non-ABS is better in the snow. Also, ridiculously good brakes? Well fuck you.

They tested that on mythbusters. It doesnt work at all.

Doesn't work until I try it this winter and it fails me :)

Also, ridiculously good brakes? Well fuck you.

Yeah, it's the only bit of 'tuning' I usually do to my cars, as standard Rover brakes tend to fade with even normal usage. Calipers and pads off a ZT-260, then cross-drilled, grooved and vented discs designed for the 620 turbo, and about 1/4 of an inch space left inside the wheels.

Yeah, it's the only bit of 'tuning' I usually do to my cars, as standard Rover brakes tend to fade with even normal usage. Calipers and pads off a ZT-260, then cross-drilled, grooved and vented discs designed for the 620 turbo, and about 1/4 of an inch space left inside the wheels.

Cast or drilled? Ricer chav or anti brake fade heat dissipation on a working class budget?
You may find the following article enlightening.

Part I:

wow
Here is an interesting forum post I plucked from another forum:

Since I know folks will be eventually asking about this I figured it would be better to head off this disaster before it gets ugly. Here is the response I made to a different forum a few months ago after collecting some information:

===========
First, lets get some physics. Tell me how a heatsink with less mass will cool better? You do realize that a brake rotor acts as a large heatsink to transfer heat from the brake pads to the rotor. The heat generated from pads has to go somewhere and so it transfers to the rotor and caliper.

Porsche claims: "Discs are cross-drilled to enhance braking in the wet. The brakes respond faster because the water vapour pressure that builds up during braking can be released more easily."

They have said nothing about enhancing normal braking circumstances and the larger diameter rotors probably make up for the lack of material present in a smaller cross drilled rotor.

From Wilwood's website:
QUOTE

Q: Why are some rotors drilled or slotted?
A: Rotors are drilled to reduce rotating weight, an issue near and dear to racers searching for ways to minimize unsprung weight. Drilling diminishes a rotor's durability and cooling capacity.

Slots or grooves in rotor faces are partly a carryover from the days of asbestos pads. Asbestos and other organic pads were prone to "glazing" and the slots tended to help "scrape or de-glaze" them. Drilling and slotting rotors has become popular in street applications for their pure aesthetic value. Wilwood has a large selection of drilled and slotted rotors for a wide range of applications.



As for the porsche rotors, a few notes from a forum I frequent:
QUOTE

1) The holes are cast in giving a dense boundary layer-type crystalline grain structure around the hole at the microscopic level as opposed to drilling which cuts holes in the existing grain pattern leaving open endgrains, etc, just begging for cracks.

2) The holes are only 1/2 the diameter of the holes in most drilled rotors. This reduces the stress concentration factor due to hole interaction which is a function (not linear) of hole diameters and the distance between them.

3) Since the holes are only 1/2 as big they remove only 1/4 as much surface area and mass from the rotor faces as a larger hole. This does a couple of things:

It increases effective pad area compared with larger holes. The larger the pad area the cooler they will run, all else being equal. If the same amount of heat is generated over a larger surface area it will result in a lower temperature for both surfaces.

It increases the mass the rotor has to absorb heat with. If the same amount of heat is put into a rotor with a larger mass, it will result in a lower temperature.

3) The holes are placed along the vanes, actually cutting into them giving the vane a "half moon" cut along its width. You can see that here:



This does a couple of things:

First, it greatly increases the surface area of the vanes which allows the entire rotors to run cooler which helps prevent cracks by itself.

Second, it effectively stops cracking on that side of the hole which makes it very difficult to get "hole to hole" cracks that go all the way through the face rotor (you'll get tiny surface "spider cracks" on any rotor, blank included if you look hard enough).

That's why Porsche rotors are the only "crossdrilled" rotors I would ever consider putting on my car.

BTW, many of the above features are not present in older Porsche brakes. The above is for "Big Reds" and newer.

Part II.



This is quite different from the standard drilled rotors you get from brembo/kvr/powerslot/"insert random ricer parts brand name here" brake rotors.

Further proof of the uselessness of cross drilled rotors are found here:

http://www.teamscr.com/rotors.htm

QUOTE
Crossdrilling your rotors might look neat, but what is it really doing for you? Well, unless your car is using brake pads from the 40’s and 50’s, not a whole lot. Rotors were first ‘drilled’ because early brake pad materials gave off gasses when heated to racing temperatures – a process known as ‘gassing out’. These gasses then formed a thin layer between the brake pad face and the rotor, acting as a lubricant and effectively lowering the coefficient of friction. The holes were implemented to give the gasses ‘somewhere to go’. It was an effective solution, but today’s friction materials do not exhibit the same gassing out phenomenon as the early pads.

For this reason, the holes have carried over more as a design feature than a performance feature. Contrary to popular belief they don’t lower temperatures (in fact, by removing weight from the rotor, the temperatures can actually increase a little), they create stress risers allowing the rotor to crack sooner, and make a mess of brake pads – sort of like a cheese grater rubbing against them at every stop. (Want more evidence? Look at NASCAR or F1. You would think that if drilling holes in the rotor was the hot ticket, these teams would be doing it.)

The one glaring exception here is in the rare situation where the rotors are so oversized (look at any performance motorcycle or lighter formula car) that the rotors are drilled like Swiss cheese. While the issues of stress risers and brake pad wear are still present, drilling is used to reduce the mass of the parts in spite of these concerns. Remember – nothing comes for free. If these teams switched to non-drilled rotors, they would see lower operating temperatures and longer brake pad life – at the expense of higher weight. It’s all about trade-offs.


From Stoptech:

QUOTE
Which is better, slotted or drilled rotors?

StopTech provides rotors slotted, drilled or plain. For most performance applications slotted is the preferred choice. Slotting helps wipe away debris from between the pad and rotor as well as increasing the "bite" characteristics of the pad. A drilled rotor provides the same type of benefit, but is more susceptible to cracking under severe usage. Many customers prefer the look of a drilled rotor and for street and occasional light duty track use they will work fine. For more severe applications, we recommend slotted rotors.



That almost sounds like an excuse to use cross drilled rotors, and for your street car which probably is never driven on the track, the drilled rotors are fine, but as Stoptech states, they will crack and are not good for severe applications.

From Baer:

QUOTE
"What are the benefits to Crossdrilling, Slotting, and Zinc-Washing my rotors?

In years past, crossdrilling and/or Slotting the rotor for racing purposes was beneficial by providing a way to expel the gasses created when the bonding agents employed to manufacture the pads...However, with today’s race pad technology, ‘outgassing’ is no longer much of a concern...Slotted surfaces are what Baer recommends for track only use. Slotted only rotors are offered as an option for any of Baer’s offerings."


Then from Grassroots Motorsports:
QUOTE
"Crossdrilling your rotors might look neat, but what is it really doing for you? Well, unless your car is using brake pads from the '40s and 50s, not a whole lot. Rotors were first drilled because early brake pad materials gave off gasses when heated to racing temperatures, a process known as "gassing out." ...It was an effective solution, but today's friction materials do not exhibit the some gassing out phenomenon as the early pads. Contrary to popular belief, they don't lower temperatures. (In fact, by removing weight from the rotor, they can actually cause temperatures to increase a little.) These holes create stress risers that allow the rotor to crack sooner, and make a mess of brake pads--sort of like a cheese grater rubbing against them at every stop. Want more evidence? Look at NASCAR or F1. You would think that if drilling holes in the rotor was the hot ticket, these teams would be doing it...Slotting rotors, on the other hand, might be a consideration if your sanctioning body allows for it. Cutting thin slots across the face of the rotor can actually help to clean the face of the brake pads over time, helping to reduce the glazing often found during high-speed use which can lower the coefficient of friction. While there may still be a small concern over creating stress risers in the face of the rotor, if the slots are shallow and cut properly, the trade-off appears to be worth the risk. (Have you looked at a NASCAR rotor lately?)




And then, let's check out what was said on the aforementioned Altima thread [[[ Long thread at altimas.net that was deleted by that server. it is hosted here ]]]:

QUOTE
Here is how it works. The friction between the pad and rotor is what causes you to stop. This friction converts your forward energy into heat (remember Einstein: Energy is neither created nor destroyed, it is converted). Now that heat is a bad thing. Yes it is bad for the rotors but it is a lot worse for the pads. A warped rotor will still stop the car - it will just feel like shit. Overheated pads however WILL NOT stop the car. It is here where the rotors secondary responsibility comes in. Its job now is to DISSIPATE the heat away from the pads and DISPERSE it through itself. Notice that DISSIPATE and DISPERSE are interchangeable? Once the heat is removed from the pad/surface area it is then removed. Notice where the removal falls on the list of duties? That's right - number 3. Here is the list again. Memorize it because I will be using it a lot in this post:

#1 Maintains a coefficient of friction with the pad to slow the forward inertia of the vehicle

#2 DISSIPATE the heat

#3 REMOVE the heat from the brake system

Let's look more in-depth at each step now shall we? No? Too bad assclown we are doing it anyway.

#1 Maintains a coefficient of friction with the pad to slow the forward inertia of the vehicle:
This one is pretty simple and self-explanatory. The rotor's surface is where the pads contact and generate friction to slow the vehicle down. Since it is this friction that causes the conversion of forward acceleration into deceleration (negative acceleration if you want) you ideally want as much as possible right? The more friction you have the better your stopping will be. This is reason #1 why BIGGER brakes are the best way to improve a vehicle's stopping ability. More surface area on the pad and the rotor = more friction = better stopping. Does that make sense Ace? Good. Let's move on.

#2 DISSIPATE The Heat:
Let's assume for a second that the vehicle in question is running with Hawk Blue pads on it. The brand doesn't really matter but that is what I am using as my example. They have an operating range of 400 degrees to 1100 degrees. Once they exceed that 1100 degree mark they fade from overheating. The pad material gets too soft to work effectively - glazing occurs. This means that a layer of crude glass forms on the surface of the pad. As we all know glass is very smooth and very hard. It doesn't have a very high coefficient of friction. This is bad - especially when I am coming down the back straight at VIR at 125MPH. Lucky for us the rotor has a job to do here as well. The rotor, by way of thermal tranfer DISSIPATES the heat throughout itself. This DISSIPATION lessens the amount of heat at the contact area because it is diluted throughout the whole rotor. The bigger the rotor the better here as well. The more metal it has the more metal the heat can be diluted into. Make sense? This isn't rocket science here d00d.

#3 REMOVE the heat from the brake system:
Now comes your favorite part of the process. This is what you thought DISSIPATION was. It is ok. I will allow you to be wrong. This is the step where the rotor takes the heat it DISSIPATED from the pads and gets rid of it for good. How does it do this? By radiating it to the surface - either the faces or inside the veins. It is here where cool air interacts with the hot metal to cool it off and remove the heat. Once again there is a reoccuring theme of "the bigger the better" here. The bigger the rotor, the more surface area it will have which means more contact with the cooling air surrounding it. Got it? Good.

Now let's look at why cross-drilling is a bad idea.

First - as we have already established, cross-drilling was never done to aid in cooling. Its purpose was to remove the worn away pad material so that the surfaces remained clean. As we all know this doesn't have much of a purpose nowadays.

Next - In terms of cooling: Yes - x-drilling does create more areas for air to go through but remember - this is step 3 on the list of tasks. Let's look at how this affects steps 1 and 2. The drilling of the rotor removes material from the unit. This removal means less surface area for generating surface friction as well as less material to accept the DISSIPATED heat that was generated by the friction. Now because of this I want to optimize step one and 2 since those are the immediate needs. If it takes longer for the rotor to get rid of the heat it is ok. You will have a straight at some point where you can rest the brakes and let your cooling ducts do their job. My PRIMARY concern is making sure that my car slows down at the end of the straight. This means that the rotor needs to have as much surface as possible to generate as much friction as possible and it needs to DISSIPATE the resulting heat AWAY from the pads as quick as possible so they continue to work. In both cases x-drilling does nothing to help the cause.

Now let's talk about strength - and how x-drilled rotors lack it. This one is simple. Explain again just how drilling away material/structure from a CAST product DOES NOT weaken it? Since you are obviously a man of great knowledge and experience surely you have seen what can happen to a x-drilled rotor on track right? Yes it can happen to a non-drilled rotor as well but the odds are in your favor when pimpin' bling-bling drilled y0! Since you are also an expert on thermodynamics why not explain to the group what happens to a cast iron molecule when it is overheated. I will give you a little hint - the covalence bonds weaken. These bonds are what hold the molecules together boys and girls. You do the math - it adds up to fractures.

Part III:


So why don't race teams use them if they are so much better? Consistency? Hmmmm . . . no. I am gonna go with the real reason her chodeboy. It is because of several factors actually. They are as follows but in no particular order:

- Less usable surface area for generating friction
- Less material to DISSIPATE the heat away from the pads
- Less reliable and they are a safety risk because of fatigue and stress resulting from the reduced material

And what are the benefits? Removal of particulate matter and enhanced heat removal. I gotta tell ya - it is a tough choice but I think I am going to stick with the safe, reliable, effective-for-my-stopping needs solution Tex.



Thank you, please drive through.

======================

So basically, buy them if you think they look cool, but not if you think this will be an acceptable performance upgrade.

--------------------------------------------------------------------------------

iracemine10-31-2006, 09:21 AM
OMG
Brake information and educational materials

I found this article on the Mazda6 Tech forum. Its a very good summary by a moderator on that forum about brakes in general. If you're a gluten for punishment read "the famous altima brake thread" referenced at the end. I believe I referenced that thread several years ago. Its a very painful (but informative) discussion wherein an individual (also a vendor on the altima forum) catagorically stated the positive virtures of drilled and slotted rotors. Several altima forum members challenged his comments. In the end there were participants from just about every major car forum on the web including some major race car builders participating. The results of those discussions (that's putting it politely) is summarized below. Its long but worthwhile reading.

"The Working of Brakes"

Over the past several years I have seen many myths perpetrated by the main stream. The purpose of this article is to dispel some of those myths while explaining basic concepts. Through the course of this article you will learn about how brakes work. You will also learn the advantages and disadvantages of cross-drilled, slotted, and vented rotors. Lastly, you will learn about brake bias.

There is a common fallacy out there that increasing your brake pad size in terms of swept area will increase the stopping power of your car through greater friction. From a standpoint ignoring operating temperatures this is in fact false. The force of friction is determined by physics as the force down on the object times the coefficient of friction. As such there is no surface area in the friction equation. However, the temperature of the pad varies throughout its use changing the coefficient of friction at each point along its temperature slope in a non-linear/non-progressive manner. As such it is possible that a larger pad will change the friction force favorably given pad makeup. It certainly will change the amount of time before the brakes enter the proper range and when they leave the range. It will also influence when and how long it is at the peak performance point. Meanwhile, modifying the pad material can change this operating range. As such the affect of increase in pad size on braking friction would depend on the makeup of the pad. Also note that the only way to modify the force down is to change the brake piston force (by size changes or number for example).

This does not mean that a larger brake pad does not help braking! The benefit of a large brake pad comes into effect when you consider thermal dissipation. The larger the pad the more this thermal temperature (created by the interaction between the pad and rotor) is spread amongst a pad. This means less temperature is concentrated at one point on the pad and the rotor absorbs more heat. This decreases the likelihood that the pad itself will heat beyond operating temperature. If the pad were to go beyond operating temperature it would glaze over resulting in brake fade. Furthermore, a larger pad results in a longer service life of the pad since there is more pad material to consume.

**Note: This is not to say that a huge pad is the way to go. I am simply telling you the benefits of a bigger pad. Do not. I repeat do not buy a huge pad thinking that will be the end all. However, consider a pad with a better material makeup for a large difference.

Part IV:

Cross-Drilled /Slotted Rotors

The second thing you can do to improve your brake performance is often to go to a larger rotor. We all know that this gives the rotor further ability to dissipate heat away from the pads through itself and through the air (conductive and convective heat transfer). So obviously a larger pad, a larger rotor, or both result in better brake performance by avoiding brake fade.

But what about cross drilled or slotted rotors? Well the common belief in the main stream is that somehow slotted or cross-drilled rotors allow for better performance by handling heat. This is 100 percent false. The individuals involved in such fallacies mention that air through the holes or slots work to cool the rotor (convective heat transfer into the air from the rotor). The issue is that from physics we know that metal transfers heat better then air by a significant amount. As such the larger mass of the rotor becomes more important then the larger surface area of the rotor in any situation other then the optimal. Cross drilling and slotting rotors are not optimal manners of creating metal to air transfer through larger surface areas. There is not much airflow through the holes or slots. Furthermore for cross drilling the holes will fill with brake dust in effect lowering the cooling ability of the rotors vanes they pass through.

Rigidity

From the information above we can glean that the rotor begins to work as a heat sink. Now by cross drilling or slotting we are decreasing the overall amount of metal to transfer this heat to. Clearly we are decreasing performance of the rotor to dissipate heat amongst itself. Furthermore, the holes of a cross-drilled or slotted rotor decrease the area of the pad that contacts the rotor. This concentrates the heat more on certain areas of the pad, which has similar effects to that of using a smaller pad. As such the pad heats up more quickly.

We are also damaging the brakes structural rigidity. The iron in a brake rotor is made of a crystalline structure. By drilling holes in said surface we cut the end grains creating a situation that breeds cracks. Furthermore, even if we were to cut the rotors correctly to avoid cutting the end grains structural rigidity is still decreased. The temperature around the holes will be slightly less then that of the entire rotor leading to temperature stress. Moreover, the decreased mass will result in lowered rigidity.

Advantages

So what do cross drilled and slotted rotors accomplish? The main original purpose of slotted and cross-drilled rotors was to vent gases that buildup between the pads and the rotors. However, this reasoning is no longer valid. As the years have gone by pads have been designed that produce very little gas. Furthermore many pads come with groves in themselves that allow for the removal of any minor gas that is created. A slotted or drilled rotor always decreases the rotors capability to dissipate heat amongst itself. A slotted or drilled rotor will also clean off the brake pad as it passes the slots at the expense of faster pad wear. As such there are benefits for rally and dirt tracks. Furthermore, the slots or holes themselves can serve to wipe off the top layer of glaze that tends to appear on your brake pads. Some racers say this last part is beneficial while others question whether the slots will fill before the deglaze affect is ever helpful. I have yet to determine the answer to this question.

The answer of slotted and cross-drilled rotor usefulness seems to lie with whether the benefit of cleaning the pads outstrips the loss in heat dissipation. In terms of cross drilling there are so many costs that nothing is accomplished beyond perhaps giving you a certain bling look. In a motorcycle or other extremely light vehicle the decrease in rotational inertia and unsprung mass might perhaps be useful (once other more efficient avenues are exhausted). However, in a street car or race car the speeds and weight of such vehicles will make the relatively miniscule decrease be outweighed by the need for more heat dissipation. Slotted rotors, meanwhile, share the positives of cross drilling but notably are slightly less subject to the costs. They do not impede airflow through the rotors vanes, nor do they have as large an affect on structural rigidity. Therefore, the need for slotting depends on your application.

Vented or Vaned

So what do ventilated rotors accomplish? Well, the concept is that they will help cool the rotors. We discussed earlier that giving up mass for surface area to gain cooling of the rotors should only be done when optimal. Vanes are the optimal method of achieving these goals. The rotors are designed to increase surface area and to flow air in the middle of the rotors. The increased surface area to the air clearly provides for more cooling from the air at the cost of mass. So why does this method work while the others fail? The first reason is that a ventilated design flows a lot of air through a rotor. A ventilated rotor acts as a centrifugal pump sucking air into the rotors. This is why rotors with curved vanes provide better braking.

A slotted or cross-drilled design will flow very little air under heavy braking. As such the vanes of the ventilated system are far more efficient. Moreover, air moves through the center of the rotor cooling the rotor more evenly and efficiently. Furthermore, the ventilated design does not decrease the contact patch of the pad on the rotor. Finally, the design has different structural rigidity qualities then that of a cross-drilled or slotted design.

Brake Bias

So now you know that increasing your pad size and rotor size will help to stop your brake fade. You also know that swapping the pad, increasing the rotor size, or increasing the force of the pistons on the pad can increase your stopping force at the tires. Finally, you have learned to stay away from cross-drilled and look very closely at whether to use a slotted rotor.

So does that mean it is time to go get that fancy front brake kit for your car? Well, potentially no again. The first thing to consider is that in any braking setup the tires are the ultimate limiting piece. You cannot stop faster then your tires allow you to stop, ever. As such, if your car can lock it’s tires under braking consistently then better brakes will not improve your braking performance. (I stress the consistent part, as brake fade must also be combated.)

Furthermore, most people understand the idea of brake bias, but fail to understand its application. A typical car is setup with the front brakes being far more effective then the rear. Now the first thing we must realize is that from a dynamic stand point your car should have stronger front brakes. When you brake physics transfers more weight to the front axle that must be accounted for. However, in this dynamic state we also have brake bias. Your typical street car is slightly dynamically biased towards the front. This leads to the front tires locking up before the rear tires under heavy conditions. Such a situation is obviously not optimal for a car stopping quickly.

You want the stopping bias to be roughly equal given the acceleration you are traveling at (please note that the bias depends on the acceleration of the vehicle). When you have a front bias you get a more stable stop (as opposed to a rear bias where a lock can cause spins), but you also get further forward weight transfer and longer stopping distances. Most cars stock come with a minor front bias for the layman. So it is clearly discernable that by going with a bigger front brake kit you are possibly increasing your stopping distance if you do not equally modify the rear brakes, change your pads, change your tires to ones that do not lockup, or set the clamping forces lower on the front brake. Without making such changes the larger effective radius can lead to an earlier lockup of the front wheels.


For further information please try:

Ruiz, Stephen and Smith, Carroll. “Brake Systems and Upgrade Selection”
McCready,Tom and Walker, James. “Brake Bias and Performance”

http://www.stoptech.com/whitepapers...performance.htm

Corner-Carvers.com altima brake thread discussion.
http://corner-carvers.com/forums/sh...+drilled+rotors

Corner-Carver discussion on this article.
http://corner-carvers.com/forums/sh...?threadid=14827

The famous Altima brake thread.
http://www.altimas.net/forum/showth...mp;pagenumber=1

Additional thanks to Dennis for writing this informative article!

he more friction you have the better your stopping will be. This is reason #1 why BIGGER brakes are the best way to improve a vehicle's stopping ability. More surface area on the pad and the rotor = more friction = better stopping. Does that make sense Ace? Good. Let's move on.

Lulz, surface area cancels out of the equation, so this is completely false, according to the coulomb friction model.

He needs to tone down the arrogance level if he makes mistakes like that.

Stopped reading after that because I have some better things to get to.

***When I said 'engine braking is better' I didn't mean it would necessarily stop you faster and I should have said 'in combination with regular braking' as well as stating that I was thinking more of RWD and AWD cars. Generally in the RWD I will engine brake while lightly applying the pedal, same thing in FWD although I understand it is somewhat less effective. In the AWD I usually primarily use the engine with the brakes as more of a fine tune or emergency thing.

Thus far I have not really had a car with exceptional brakes and I have found that the engine frequently provides a smoother and more controlled force. This could really apply for people with touchy brakes or lead feet as well. As for the ABS thing, for your average person the ABS will do a better job of controlling the traction than you could. I'm not saying that you couldn't get a better stop time with no ABS and some concentration, and I understand that some ABS systems seem to fucking suck (from experience). However, ESPECIALLY in an emergency situation, it is generally better to have it than to try and fuck with the pedal like your life depends on it (which it might).

same thing in FWD although I understand it is somewhat less effective.

Yeah... pretty sure that's gonna make things worse.

Yeah, it's the only bit of 'tuning' I usually do to my cars, as standard Rover brakes tend to fade with even normal usage. Calipers and pads off a ZT-260, then cross-drilled, grooved and vented discs designed for the 620 turbo, and about 1/4 of an inch space left inside the wheels.

How much does that cost you? The brakes on both my nice cars are crap.

Lulz, surface area cancels out of the equation, so this is completely false, according to the coulomb friction model.

He needs to tone down the arrogance level if he makes mistakes like that.

Stopped reading after that because I have some better things to get to.

How/in what way?
Also, lul at the underlined.

My 3000GT has stock calipers with Hawk HPS pads, and slotted and dimpled rotors.

The celica we have has EBC greenstuffs in stock calipers, with slotted and dimpled rotors.

Dimples and slots are good stuff, cross drilling is shitty. The dimples mostly are for looks, but the slots do help in the wet and with removing glaze after I stop from 150 or something a couple times.

Regardless the 3000 needs a big brake kit, but I'm not sure what to do with the rears since most kits are front only. I know a couple experienced racer guys, but their kits are so much money. But 380mm front rotors... ::drools::

http://supercar-engineering.com/sc2/product_info.php?cPath=1&products_id=167

$5,495 for a balanced front and rear kit. Christmas anyone?

I might just go for VR-4 stuff, with nicer rotors and pads.

http://supercar-engineering.com/sc2/product_info.php?cPath=1&products_id=135

These rotors are awesome, but my car is so light compared to a VR-4 that they might not be necessary. I could probably do with VR-4 calipers, stock (or slightly aftermarket) rotors, and some porterfield pads.

I want big brakes a lot. Damn this topic for coming up!

How/in what way?

There are three ways to explain it:

1) The fact:

force of friction according to the conventional and accepted though not always right coulumb friction model is:

[Kinetic friction]=[normal force]*[kinetic friction coefficent]

Note that area does not come into this equation.

2) The mathy explanation:

This is a slightly more intuitive equation for some:

[Kinetic friction]=[pressure]*[area]*[Kinetic friction coefficient]

However since [pressure]=[force]/[area]

One can substitute:

[Kinetic friction]=([force]/[area])*[area]*[Kinetic friction coefficient]

And notice area canceling out.

3) The wordy explanation:

If you think about it, the harder you press on the two surfaces, the harder they will grip together. This is all well and good. Also, one might imagine that if you now had two sets of two surfaces instead of one, they will grip twice as hard as before. However, if you are still applying the same force as before, then the force being reacted in each mating surface is halved (i.e. the pressure is halved), such that your final 'grip' is the same as it was in the first place. The area cancels out.

Infact, in reality if you had your brake pads at distance x from the center of your rotors, but then added a second pair of pads, or added some material on to the current pads, at distance x-y (both x and y being positive numbers), then you would be reducing the amount of 'grip' you can get out of the setup for a given force, because some of the force you put on the pads will be reacted closer to the center of the rotor, and any friction force acting here has a smaller lever arm than the friction force acting further from the middle of the rotor, making it less 'efficent' at converting normal force into frictional force.

The above isn't to say that there is no advantage to increasing surface area - there is. It can help deal with the heat generated.

[QUOTE=Cowboy of the Apocalypse;10770178]Also, lul at the underlined.

Blimey, not exactly a great thing to try to wrap your head around first thing in the morning, but I think I grasp it.

So mainly, my increased braking power is due to the fact that the discs and pads are a lot larger, thus dissipating heat better. Interesting.

I thought that grooving a brake disc followed the same principle as fullering (I collect old bayonets and general Imperial weaponry as a hobby, so I read up on them). Basically, look at this picture :

http://www.ebayonet.com/8300/8390.jpg

That big groove down the middle allows the bayonet to be a lot lighter, whilst providing the same structural rigidity as if the fuller was filled with steel, and I simply assumed grooving a brake disc followed the same principle.

But I have to admit, a small factor in them discs is the coolness. There is a guy who works on the same complex as me who has a BMW 318is with big brakes and wheels you can see straight through to the brakes, so I just wanted to say to him "Yes, not only is my equally sized engined Rover about 2 seconds quicker to 60mph than your car, my brakes are decidedly better looking too, ha!" as his brakes are his pride and joy.

Zonko, there is a post on one of the MG-Rover forums I frequent with instructions and the like I can find later if you want, as well as the website I bought things off, but I'll have to have a look later cause I'm off to the pub to watch the football now as I have 2 bets on. If I recall correctly it was in the region of £500-£600, but that was only because the ZT-260 is so rare and they had to order the calipers and things from a specialist company.
Bit off topic, but if anyone cares, I have an accumulator on all the games over the weekend, but I deliberately picked all the worst teams with the highest odds, but if all 32 of my teams win, my £5 will net me a £10,000 win! But the other one is that the Man City - Fulham game, Man City will be up by half time, and by full time Fulham will have equalised and the game will end in a draw. £75 off my fiver if that happens.

Blimey, not exactly a great thing to try to wrap your head around first thing in the morning, but I think I grasp it.

So mainly, my increased braking power is due to the fact that the discs and pads are a lot larger, thus dissipating heat better. Interesting.

I thought that grooving a brake disc followed the same principle as fullering (I collect old bayonets and general Imperial weaponry as a hobby, so I read up on them). Basically, look at this picture :

http://www.ebayonet.com/8300/8390.jpg

That big groove down the middle allows the bayonet to be a lot lighter, whilst providing the same structural rigidity as if the fuller was filled with steel, and I simply assumed grooving a brake disc followed the same principle.

But I have to admit, a small factor in them discs is the coolness. There is a guy who works on the same complex as me who has a BMW 318is with big brakes and wheels you can see straight through to the brakes, so I just wanted to say to him "Yes, not only is my equally sized engined Rover about 2 seconds quicker to 60mph than your car, my brakes are decidedly better looking too, ha!" as his brakes are his pride and joy.


Additionally, larger disks will usually afford longer lever arms for the friction force to work on, requiring less force for the same braking torque.

BTW, a fuller in a sword will make the sword weaker. The idea is that the decrease in strength is disproportionately small compared to the decrease in weight. It's like a softcore I-beam.

Zonko, there is a post on one of the MG-Rover forums I frequent with instructions and the like I can find later if you want, as well as the website I bought things off, but I'll have to have a look later cause I'm off to the pub to watch the football now as I have 2 bets on. If I recall correctly it was in the region of £500-£600, but that was only because the ZT-260 is so rare and they had to order the calipers and things from a specialist company.

Naw, I was just curious, thanks though. There's a group that do a few crazy set of brakes for the Capris, and I could probably put some good vw brakes (oxymoron?) on the 'rocco. Plus I don't have a rover. :P

Edit: I also thought a bit part of the fuller was to allow air to flow in and out of the wound, so the knife wouldn't get jammed, although I've explained that badly.

There are three ways to explain it:

1) The fact:
force of friction according to the conventional and accepted though not always right coulumb friction model is:

[Kinetic friction]=[normal force]*[kinetic friction coefficent]

Note that area does not come into this equation.


Not directly, but I - in my uneducated opinion - would rekon that it does come into play. The larger the surface area of contact, the more force there is for the same amount of pressure. And force is in the equation. Touche?

I think the author of the article should have written this part clearer, because the importance is confusing. I was sure heat dissipation was easily the primary and almost sole reason you get larger (diameter) and thicker (so you can have larger 'flow' cooling vanes through the centre) rotors.


2) The mathy explanation:
This is a slightly more intuitive equation for some:

[Kinetic friction]=[pressure]*[area]*[Kinetic friction coefficient]

However since [pressure]=[force]/[area]

One can substitute:

[Kinetic friction]=([force]/[area])*[area]*[Kinetic friction coefficient]

And notice area canceling out.


I don't speak math, so would you kindly repeat that in the Queens English? Just to make sure my translation isn't incorrect. I beleive that you just said exactly what I said about area coming into it indirectly, but then advanced to some more of that Greek stuff. Howcome they cancel each other out?


3) The wordy explanation:

If you think about it, the harder you press on the two surfaces, the harder they will grip together. This is all well and good. Also, one might imagine that if you now had two sets of two surfaces instead of one, they will grip twice as hard as before. However, if you are still applying the same force as before, then the force being reacted in each mating surface is halved (i.e. the pressure is halved), such that your final 'grip' is the same as it was in the first place. The area cancels out.


Alright, stop for a second - if you're applying twice as much pressure to increase friction twofold, then you're also intesifying the heat produced and affecting the area by a shitload more, no? So the larger surface area option isn't out of the question, or the equation, because they (the brakes) need to effectively dissipate the heat produced - which is critical to the function of the brakes, and their wellbeing. I have before witnessed what appeared to be brake calipers spontaneously combusting, and see rotors glowing cherry red* all the time in some forms of motor racing where Ceramic brakes aren't used. I can tell you off the back of my hand that means they get to at least 750 - 825°C.

That's farkin hot.

*(cause, as you should know, the colour of steel is indicative of it's temperature)



But I have to admit, a small factor in them discs is the coolness. There is a guy who works on the same complex as me who has a BMW 318is with big brakes and wheels you can see straight through to the brakes, so I just wanted to say to him "Yes, not only is my equally sized engined Rover about 2 seconds quicker to 60mph than your car, my brakes are decidedly better looking too, ha!" as his brakes are his pride and joy.



Lullers, true, but it can get out of control. I saw a Lancer with it's drums painted silver, and bright green where his calipers would be vaugely located if he had discs.


BTW, a fuller in a sword will make the sword weaker. The idea is that the decrease in strength is disproportionately small compared to the decrease in weight. It's like a softcore I-beam.

On the money with that. Don't overlook the details though: Your I beam is slightly weaker than the solid beam it was, but now you compare it to other options with the same weight for strength. And it'll be right up there, with LVLs.

Edit: I also thought a bit part of the fuller was to allow air to flow in and out of the wound, so the knife wouldn't get jammed, although I've explained that badly.

I know what you mean, I've seen it discussed many a time. The fuller was also known as a blood groove, to let the blood out and air in and not create a vacuum. Tis very debatable though. The old pig-sticker on the SMLE in WW2 didn't get jammed. It was just a spike though.

I know what you mean, I've seen it discussed many a time. The fuller was also known as a blood groove, to let the blood out and air in and not create a vacuum. Tis very debatable though. The old pig-sticker on the SMLE in WW2 didn't get jammed. It was just a spike though.

Does it add rigidity to the blade? (http://www.orsm.net/fem/2008/hannah_hilton_02/)

Not directly, but I - in my uneducated opinion - would rekon that it does come into play. The larger the surface area of contact, the more force there is for the same amount of pressure. And force is in the equation. Touche?

Yes but the larger the surface area the less pressure applied for a given force.

The pads have a certain amount of work they can do to apply themselves, which, ignoring losses, is equal to the work you do with your foot plus the work done by vacuum boost or w/e. The work is given given by forceon brake pad * distance brake pad moves.Force is the given here, force is what you have to play with, and pressure is then derived from it. It's just like the torque/RPM/horsepower argument. Horsepower is to torque and RPM as force is to area and pressure.

I think the author of the article should have written this part clearer, because the importance is confusing. I was sure heat dissipation was easily the primary and almost sole reason you get larger (diameter) and thicker (so you can have larger 'flow' cooling vanes through the centre) rotors.

Let's not mince words. It wasn't clear because it wasn't right.

"More surface area on the pad and the rotor = more friction" = wrong

The cooling effect is a different beast.

I don't speak math, so would you kindly repeat that in the Queens English? Just to make sure my translation isn't incorrect. I beleive that you just said exactly what I said about area coming into it indirectly, but then advanced to some more of that Greek stuff. Howcome they cancel each other out?

Because [area]/[area]=1, and then because 1*[something]=[something]

Alright, stop for a second - if you're applying twice as much pressure to increase friction twofold, then you're also intesifying the heat produced and affecting the area by a shitload more, no? So the larger surface area option isn't out of the question, or the equation, because they (the brakes) need to effectively dissipate the heat produced - which is critical to the function of the brakes, and their wellbeing. I have before witnessed what appeared to be brake calipers spontaneously combusting, and see rotors glowing cherry red* all the time in some forms of motor racing where Ceramic brakes aren't used. I can tell you off the back of my hand that means they get to at least 750 - 825°C.

That's farkin hot.

*(cause, as you should know, the colour of steel is indicative of it's temperature)

No. Higher pressure does not increase heat produced.

The heat generated by your brakes is equal to the kinetic energy they wipe off the car. For a given cars mass, and for a given change in speed, this is a constant.

Higher mass of the rotors and well shaped rotors can help store and dissipate the heat better. This is a different animal, and is not what the author was writing about:

'the more friction you have the better your stopping will be. This is reason #1 why BIGGER brakes are the best way to improve a vehicle's stopping ability. More surface area on the pad and the rotor = more friction = better stopping. Does that make sense Ace? Good. Let's move on.'

Yes but the larger the surface area the less pressure applied for a given force.


What in the damn fuck? Reiterate, because I think you just re-phrased what I said. And if that's what you did indeed do, then doesn't that mean what you initially said is incorrect? Also, use English please. You used brackets and other pencil pusher shit last time, nyurd.

He needs to tone down the arrogance level

You're the last person that can get away with saying that now.

You're the last person that can get away with saying that now.

'...if he makes mistakes like that.'

I wouldn't have made a mistake like the one he did, it's year 10 or 11 physics ;)

If I seriously made a mistake like that that wasn't just a typo/slipped-my-mind-because-it-was-a-minor-detail, and I was being arrogant at the time, I would be perfectly fine with you all verbally raping me.

What in the damn fuck? Reiterate, because I think you just re-phrased what I said. And if that's what you did indeed do, then doesn't that mean what you initially said is incorrect? Also, use English please. You used brackets and other pencil pusher shit last time, nyurd.

[Pressure]=[force]/[area]

Example, pounds per square inch. Pounds is a force, square inches are area. Its a force per a unit of area.

If you increase the area and leave the force the same, then you are dividing by a larger number, so the pressure will go down.

I'm not sure what you are referring to with 'what you initially said', but if you point it out to me I will have a look.

Ah, sorry. I forgot you're infallible.

Ah, sorry. I forgot you're infallible.

I'm not, I've been wrong before, and I'll be wrong again.

However, I avoid acting arrogant when I'm not treading on ground I know very well.

Even when I am fairly sure of myself, unless I am annoyed by the other party in some way (as in this case), I will avoid it.

Even when I am fairly sure of myself, unless I am annoyed by the other party in some way (as in this case), I will avoid it.

Would this be myself that you are referring to? Why?

Would this be myself that you are referring to? Why?

Not you, the guy you quoted.

Though there is a background story to you I'd like to get sorted, but my usual methods of contact are failing here. Can you throw me an email? I'm asking as a regular here, so I've no problems if you say 'no'. My email is in my profile.

Not you, the guy you quoted.

Though there is a background story to you I'd like to get sorted, but my usual methods of contact are failing here. Can you throw me an email? I'm asking as a regular here, so I've no problems if you say 'no'. My email is in my profile.

Do you have MSN? I'm on there right now, but I ought to be going.

Issue solved.