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3 theories to outfitting brake pads on wknd track car....brake bias.

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Old May 8, 2009, 01:10 PM
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3 theories to outfitting brake pads on wknd track car....brake bias.

I've heard three ways to skin this cat when outfitting your car for the track. Personally I'm taking my DD to the road course, so some of these questions I have don't necessarily pertain to me, but I'd like to understand none the less. I'd like some of you more experienced guys to correct me or help me understand.

Theory 1:
-Have matching pads at the front and rear. This would maintain OEM (read: safe) brake bias provided you have not done any significant weight removal.

-Downsides...you're paying for more expensive rear pads, they wear the rotors more vs. a less aggressive track pad, they may just not be needed because the rear doesn't handle as much braking as the front simply. I see a lot of people on forums like this using this setup.

Theory 2:
More aggressive pad up front and lesser pad in the rear. Because the front of the EVO does the lion's share of the braking, you put the beefier pad up there with the higher MOT (Maximum Operating Temperature) and then you can get away with a less expensive, lower MOT, longer lasting, easier on rear rotors, pad in the rear provided the 'bite' or torque of the rear pad matches the beefier front. I see a lot of people on forums like this using this setup as well.

Downsides...The reason they have to match is because you don't want to upset your brake bias. If you upset this the rear may come around on you during heavy braking.....

I need better clarification about this 'upsetting,' and how it happens/works.

Theory 3:
Less aggressive track pad up front, but one that can still handle the added heat and give you the bite you are looking for out of a track pad, and then a more aggressive pad in the rear. The pros here would be 1) less rotor wear up front 2) more aggressive pad in the rear allows for the rear to shoulder more of the total braking load the front brakes take a beating, and 3) if you remove significant weight from the rear of the car, it would help to restore a more balanced brake bias.

I need more info here:

On a car where u want to modify the factory brake bias due to weight removal at the rear of the car, even if you go for a more aggressive pad in the rear, you have two things working against you with a stronger pad in the rear as opposed to the front.

-Weight transfer. The physics of braking alone transfer a lot of weight off the rear to the front. (Stiffer/properly setup suspension can compensate here?)

-You've removed weight at the rear that was helping to press the tire down and giving the tire traction to bite down into the asphalt when you apply the brakes.

By putting a more aggressive pad on a lightened rear of a track car, wouldn't this just foster the ABS kicking in since you have less traction in the rear (less weight back there on a stripped track car), weight transfer to the front, and a more biting rear pad clamping down on the rotor harder?[/B]
Old May 8, 2009, 01:30 PM
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There are allot of Ideas I have on this subject, None of which I have tested or know of being tested.

First, I am a believer of using the same pads on all four corners. Unless the car is a race car, you shouldnt need a different bias, and if its a race car, you likely have an adjustable brake bias valve. Otherwise, you can usually tune the cars attitude while braking with suspension changes, i.e. spring rate and alignment changes.

There are a few reasons to run more pad up front. The simplest is that people swap their pads out for track pads when going to an event, and its easier to just do it up front than on all four corners, and its cheaper. I would take the extra time and money to do all four, but thats up to the driver.

Another is the Evo has a tail wag under braking; due to alignment changes when the rear suspension droops. The rear goes toe-out when the rear of the car comes up under braking. Running less pad out back can theoretically reduce the amount of rear grip being used to stop the car, thus more grip can be used to keep the car straight. But, this can also help the car rotate when trail-braking. So, its also a driver preference. There are also bushing kits that eliminate this problem.

I have no idea why anyone would run more pad in the back, that doesnt compute with me...
Old May 8, 2009, 01:31 PM
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Overall, I'd recommend using the pads front/rear. It's just easier that way imo and I think the car handles better - just my .02. So I suppose I agree with Theory 1.
I actually asked a lotta die-hard guys this when I was buying my first few sets of pads. I got a few different responses, but the majority said use the same. It makes sense as it's 1 less thing you have to concentrate on when dialing in your other zillion ongoing suspension changes!

Originally Posted by Bster13
Theory 1:
-Have matching pads at the front and rear. This would maintain OEM (read: safe) brake bias provided you have not done any significant weight removal.
I like this best. I wouldn't worry much about the weight removal. I've got everything gutted from my front seats backward. Of course, you should worry more about removing weight from the front - small battery, etc.

Originally Posted by Bster13
Theory 2:
More aggressive pad up front and lesser pad in the rear. Because the front of the EVO does the lion's share of the braking, you put the beefier pad up there with the higher MOT (Maximum Operating Temperature) and then you can get away with a less expensive, lower MOT, longer lasting, easier on rear rotors, pad in the rear provided the 'bite' or torque of the rear pad matches the beefier front.
Yeah, a lot of people do this, but imo it's a sacrifice. I want to my car to stop like I'm throwing out an anchor. Given our cars are usually in the 3200lb range; that's not gonna happen. But using 'street' pads - even just in the rear - is a sacrifice. Sure it's cheaper, but the rears last about 3x as long. If you're looking to save a little change here, you probably can't afford the track entrance fee. Don't skimp on safety...

Originally Posted by Bster13
Theory 3:
Less aggressive track pad up front, but one that can still handle the added heat and give you the bite you are looking for out of a track pad, and then a more aggressive pad in the rear......
I would caution against this. This will upset the braking balance of the car and make it feel unstable. Ask me how I know...
I tried this (by mistake) one track day. I switched to new pads, but left my previous set of pads in the rear - figured why not use them all up right! Turns out the rears had more 'bite' but I wasn't aware of this being they were different brands. Braking down from 125mph was the worst part of it. The car felt unsteady and a bit unsafe. I don't recommend.

Originally Posted by Bster13
-Weight transfer. The physics of braking alone transfer a lot of weight off the rear to the front. (Stiffer/properly setup suspension can compensate here?)

-You've removed weight at the rear that was helping to press the tire down and giving the tire traction to bite down into the asphalt when you apply the brakes.

By putting a more aggressive pad on a lightened rear of a track car, wouldn't this just foster the ABS kicking in since you have less traction in the rear (less weight back there on a stripped track car), weight transfer to the front, and a more biting rear pad clamping down on the rotor harder?[/B]
Ah, weight transfer. You need to first realize, those serious about tracking use higher than stock spring rates, more exaggerated camber and toe settings, and are corner balanced. Plus as I mentioned above, they remove as much weight from the front as possible.

Last edited by boomn29; May 8, 2009 at 01:35 PM.
Old May 8, 2009, 01:48 PM
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Been through this loop myself, like the guys above have. Most of the time if you are doing threashold braking, you'll sometimes get the "wobble" in the rear for several reaons that i've witnessed and been told from the Evo setup guru's. Either

A - It isn't slowing as fast as the front, so the rear tires are technically moving faster, thus they start to go sideways (just like slamming the gas in a RWD it goes sideways because the front tires are moving slower).

B - You actually lift the rear off the ground due to "squat" like stated already, and get the same effect.

So when it comes to the pads you touched a few good points. Most brake manufactures, from a pure paper point of view, recomm option C, with the heavier pad in the rear to comp for the reduction in size, caliper force, and surface area trying to slow the same (say) 17x8 wheel/tire as the front. But when you take into effect the weight distro this is the opposite on the Evo, all your G's are up front so the rear "shouldn't" need more. Mostly because your trippling the weight up front Vs. the rear at that speed.

What it really boiled down to for me was my car setup and my driving skill. When I started out in the car, it was street trim with stock suspension, so the springs/shocks were not attempting to push the weight back to the rear and keep her level. In this case I'd use (and used) racing pads up front, and some aggressive street pad in the rear - like in PFC's, PF01's up front and PF Z's in rear, or DS3000 up front and DS2500 rear, etc etc. (because the 2500 isn't considered a race pad for reasons not important to this post) That and I wasn't braking late or hard so I didn't need the added advantages.

When your skill gets up there, and/or the car goes to the next level, then it's best to run the same compound in both for the same reasons above, the car is now acting differently due to the 50% increase in brake force (threashold) and the suspension distributing the weight faster and more efficiently. So the whole "system" acts in harmony.

Last edited by Balrok; May 8, 2009 at 01:51 PM.
Old May 8, 2009, 02:25 PM
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most of the time i adapt to whatever pads are back there... sometimes we loose rear pads (as in they fall apart, not physically 'lost') at the track & have to use whatever is floating around.. sometimes its a crazy mix-n-match.... i dont mind the rear end dancing around so oem pads in the rear dont scare me....

balrok broke it down pretty good... just depepnds what u prefer as a driver... untill you go 9-10/10's it doesnt really matter anyways.



n
Old May 8, 2009, 03:56 PM
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Unless you are in it for the microseconds (as in competition), you can be just fine with just front race pads and aggressive rear street pads. I do that in the advanced group due to lower cost and not having to swap the rear pads.

I use Hawk HP+ in rear (Extremely High Friction Output according to the specs) and DTC 60 for the front (High torque with less initial bite than DTC 70). The DTC 70 state they are Extremely high torque with aggressive controllable initial bite.

Never had fade issue with HP+ in the rear, but they are no good for the front. My rear does do some dancing around - all stock except for R-comps. Hope it helps you.
Old May 8, 2009, 04:05 PM
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Thanks for everyone's advice and Prostar's advice over PM.

I'm worn down and tired of reading threads and marketing materials, hehe.

I've placed an order for Hawk HT10s for all four corners based off the following:

-No chance of messing with brake bias whether that's a reality for me or not.

-Hawks are cheaper than PFC track pads.

-Seem well suited for "weekend warriers."

-Smikeevo currently runs them () for street tires w/ no fading and good stopping power and I will have similar mods in power, tires, and suspension.

-Some BMW friends running them with no troubles and they mentioned the PFC97/01 were corrosive to wheel finish.

I figure for first time on track I'll have track pads all the way around just to play it safe. Perhaps over time I can save time and $ by going to the HP+ in the rear (or PFZ if I go to PFC 97s or 01 up front).

Again, I appreciate all the help....I just wish y'all lived closer so we could go to the track (road course) together!!!
Old May 8, 2009, 07:15 PM
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This is the BS I spewed to Bster13 over PM and he asked me to post:

"In my understanding, there are two issue to mating a set of pads. There are bite and fade characteristics. You absolutely want to keep the bite characteristics the same between front and rear, otherwise you will upset the bias. Pads like the Axxis Ults and PFZs have high bite but relatively low fade resistance. It makes them good choices for the rear pad as they bite like a race pad but They wont have issues fading out on you because the rear does less than half of the braking job so the pads wont fade.

So, in context to your thread, I would say matched front and rear identical pads is the best. Almost as good (and cheaper) would be the high bite race pad in front and high bite aggressive street pad in the rear. I ran all PFZs last season to the dismay of a number of track guys on here. Honestly, I beat on the car and it was not horrible on track, bite remained good but fade and fluid boil was noticeable after a 20 min session, sometimes less. Many vendors classify the PFZ and Ults as aggressive street/ light track and I think that is very accurate. This season I have moved to front race pads for a reason, I think I put undue stress on the braking system with LESS aggressive pads. I now have much larger and stickier street tires and a good 20-40 more whp. Lastly, I would not recommend using a less aggressive pad on the front and more on the rear, this will upset your bias and likely overwork your rears. The more I look at pad wear ratings the more confusing it gets. Some high torque pads are easy on the rotors, some not. In my opinion and in general, there is no way that you can have a very aggressive pad not do additional damage to the rotor. I am sure there are advancements in pad design that limit the damage done but you simply can't ignore the physics and heat transfer. If you don't wear the rotors out, you will likely crack them (I did with the PFZs).

If you have heard otherwise with regard to anything I have written please let me know"

Bster13,
SmikeEvo was the main man who convinced me to go for the front HT10s. I would still recommend you just get front HT10s and move up from there. If you find you are still not braking to your needs, then get the rears, or if you are blazing the pads on the back then do it. The difference between these race pads in the rear and aggressive street pads will be fade and performance, not failure. There is no safety issue at hand between these two scenarios, so in my opinion, why not save your money and see if the fronts do it for you. I don't think you can go wrong with a four corner set up though.
Old May 8, 2009, 08:14 PM
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I ran HT10's today with DS2500's in the rear and it worked out pretty well.

HOWEVER, I did have a little bit of sketchyness whn threshold braking, especially if the wheels weren't straight.

I like the HT10's though
Old May 9, 2009, 04:20 AM
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I run same pads front and back now. I've run less grippy pads in the rear before but the car didn't turn as well for me and the fronts also wore quicker. The best pad setup really depends on driver and the suspension set-up. Try different combos and see what works for you. It's not something that you can just theorize about and make a decision in the abstract. As with suspension, you need to do what it takes to make the car fast for you.
Old May 9, 2009, 07:37 AM
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There's some misinformation in this thread. First of all, the axle whose pads have a higher coefficient of friction will get more brake bias.

I have messed with brake bias more than most but I want to keep this short:
1) If you have EBD and ABS you won't notice much difference changing your rear pads.

I have an RS and I have noticed dramatic differences btw using pads with different coefficient of friction. For example, ST43s in front with DTC60s in back = front lockup. ST43s all around = better braking but slightly unstable rear. When I had the 332x28 RacingBrake BBK the bias was shifted to the rear and with DTC60s all around the rear would lock up, especially without a wing or when threshold braking downhill.
Old May 10, 2009, 07:55 AM
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NICE! Probably one of the better threads I've read lately with regards to technical insight.

Since this seems to have run it's course - I'd like to take the topic a step further. How many of you that have been tracking for multiple seasons have needed to rebuild/redo the brakes? I know some have smoked through parts of them or melted their ABS sensors. I don't want to have an issue!
Old May 10, 2009, 08:10 AM
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^^Very good point on ABS above. I would highly advise against #3.
Old May 10, 2009, 08:52 AM
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Originally Posted by goofygrin
I ran HT10's today with DS2500's in the rear and it worked out pretty well.

HOWEVER, I did have a little bit of sketchyness whn threshold braking, especially if the wheels weren't straight.

I like the HT10's though
Were they the ones you bought from me? How'd they do? I think I am switching back() or going to 3000's. the 2500's did not give me the confidence of the ht10's but did have better modulation. many claim better feel but I think that is subjective.
Old May 10, 2009, 09:00 AM
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I have another aspect I would like some of the more experienced to touch on. I would like to suggest a fourth otion:

4: Changing pads AND rotors at the track. Or before if trailering

I have been told (by professional racers BTW) that it is not good to change pads without changing rotors at the same time. Reasoning is the pad material begins to travel into the metal. If you change pads to a pad made of a significantly different material it will have trouble binding with the base metal, and you will not get maximum performance. Additionally this can cause delaminating of the rotor.

I have experienced significant rotor damage after switching to race pads, but chalked it up to aggressive pads not the delaminating that was described to me.

Does anyone have experience with this? Is there a way to get around it without having to buy another full set of rotors? any recommendations?


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