Brake Disc and Pads

[satmarshall]

Hi,
I've tracked my R8 4 or 5 times replacing front OEM pads with another set of OEM pads once. I'm now getting a lot of brake pulsating when high speed braking. The new pads are 2 track days old.

Guys at the track think it's being caused by pad transfer onto the rotors. The theory is the OEM pads are soft and transfer compound to the rotor after getting very hot. The compound then hardens on the rotor.

1st question: Do you think the above theory is sound?
2nd question: I'm ready to buy new discs and pads.
I'm thinking of going with Pagent pads. What kind should I use? I do 75% street driving and 25% track driving. Also, should I buy OEM rotors or replace them with something different?
In case it matters, on track days I use R-comps (Toyo R888), and for street driving use PZeros

Thanks all!

[gigharbor1]

I track my RS4 several times a month and can certainly relate to the fast wear of OEM pads (especially in the front with the front-heavy RS4). I am using Pagid Yellows currently on the front brakes and they work great. Stopping power is better feeling and longevity is much greater than OEM. By the way, the OEM pads on the R8 and RS4 are Pagids as well, but a softer compound. I would recommend the Pagid Yellows for your R8 for track and street. I was warned that they may squeal a lot, but the squealing has only occurred one time, for a 15 minute period on the track on the first day I tracked them, and since have not made any noticeable noise.

I am not sure about your rotor issue, but I wonder if you have slightly warped rotors from uneven cooling. Do you use the E-brake in between lapping runs? If so, you gotta stop doing that. If not, I'm not sure what's happening.

[MotherTucker]

Yes, that is a very common problem, especially when you get new rotors. Many people think they have warped rotors, but 99% of the time it's uneven pad material deposited on the surface, due to getting the brake rotors hot and then holding the pads firmly against them while stopped (done before the entire rotor surface has an even layer of pad material on it, which is normally done by a proper bedding procedure).

It can happen when you change out the rotors and less often the pads (especially if you use the same pad compound on the new pads). Changing from one pad compound to another can can make it happen.

The quickest solution is to get the rotors turned to remove the old surface. Then you need to do a very important bedding procedure. Here's a link to more info on the bedding procedure:

http://www.zeckhausen.com/bedding_in_brakes.htm

Note step 2 where it describes how you can get the uneven deposit of pad material.


If you don't get the rotors turned, it eventually will smooth out, but it takes a long time, and a lot of very firm braking in a race-track like environment.

When I buy track pads, they always come with printed bedding procedures.

Hope this helps.

mt

[satmarshall]

Thanks guys. I'll read the bedding link and be sure I do that next time.
I never using the emerg-brake and always do a cooldown period at the end of a lap session, although the cooldown is only a 1/4 lap at the track I go to. Maybe I'll extend that by driving the in the paddock area a bit too.

Are you using Pagid yellows on the rear as well or just the front?

[MotherTucker]

I use track pads on all 4 rotors. If you're new to tracking your car and are a proper cautious novice, just the fronts would probably be fine. If you're a more advanced driver, you should have them on all 4 corners. Haven't tried the Pagids yet, still using carbotech XP-10's myself.

[jr_spyder]

This is a timely post for me as I'm about to do my first replacement of the OEM pads on my car for my next track day. I decided to go with Carbotech XP8s. I'm still a novice track guy (two days so far) and running on the stock P-Zeros. I also hope not to switch back to other pads on the street so the XP8's seem a good bet and I really liked talking with the guys there.

My question is this - will I come across any surprises when I change the pads this weekend? Do I need any special tools? These things are usually straight forward and qucik, but sometimes not. Advice?

Thanks,

JR

[MotherTucker]

Well the calipers are stock Brembos. So you need the proper sized flat nosed punch and a hammer to remove the pins. You may have to retract the pistons if your new pads are thicker than the ones you are removing, and that can be a major pain for us with 8 pistons in a caliper. Here's a big and costly tool that I invested in, and it works great for pushing multiple pistons back (4 at a time):
http://www.zeckhausen.com/Brembo/Consumables.htm#Tools

The other possible problem may be that the front pads have trouble seating over the pin. My first set of carbotechs had that problem, it was the first set Danny there at carbotech had made. I had to grind the shoulders of the indentation there on the front pads back a bit to get them to fit, it was very very close (like the thickness of the paint that the pads are painted with). I reported that to Danny and he said he would correct it. He also said that he had the proper anti-squeal shims ordered, so hopefully you will get those although they work fine without them.

Other than that, you should replace the brake fluid with higher temperature stuff. Valvoline synthetic fluid is readily available and not expensive and boils at 530 F or so which is pretty good. Or really go for broke for the Motul 600, that's what I use. Did you see the thread here about how to get at the brake fluid reservoir?

mt

[jr_spyder]

MT - this is great, thanks.

Yes, I saw the thread about getting to the reservoir. Not exactly user friendly. I saw the one cover someone made up by using a PVC vent cap. Has anyone come up with other creative solutions to cover the hole?

[satmarshall]

Is it correct to assume that the stock rotors are fine with either the carbotech or pagid pads?
I'm going to look at both pad options. What do you think is better for 75% street use 25% track use by an intermediate/advanced driver

Thanks!

[MotherTucker]

Yes, the stock rotors are fine for any kind of pad. I have not yet heard of any non-Audi rotors that fit the R8, but they may be out there.

Both PAGID and Carbotech make pads that fit the R8 in several different compounds. So the real question is what compounds should you use. 3 different people may give you 3 different opinions, but here's mine. The stock pads are reported to be fine for novice/beginners on the track. If you're an intermediate to advanced driver, your rotors are going to get very hot. You need a good track pad so it won't glaze over and suffer from major fade or wear down very quickly. Pagid yellows or carbotech XP10s or XP12's are serious track pads that will do the job very well. They are a little aggressive on your rotors, so if that's very important to you, go with slightly softer compounds like Pagid blues or carbotech XP8s. But they will fade slightly when they get very hot, but will come back fine when cooler. All those pads will squeak when run on the street, but the softer ones will squeak less. You'll have to go back to street pads if you want silent braking on the street.

mt