brakes knackered?

[Guest]

I did my first trackday in my C2 last week at Bedford. Although the day was great and the car behaved perfectly I have subsequently noticed a nasty juddering from the brakes.
I'm no mechanical expert but I'm guessing I've warped the discs after possibly cooking the brakes on track. (maybe I stayed out too long?)
They were fairly new OEM discs and pads (3 month old) so I'm a little dissappointed that this might have occurred so soon.
Can anybody shed any light on what I might have done and a possible remedy?

Do I need to upgrade the front discs/pads, fluid and braided hoses for future trackdays? I use my car regularly on the road so racing pads aren't practical.

I'm sure my driving skill (or lack of it) will come into question so I should say I've done quite a few trackdays over the years in Caterhams and Lotus's and never had this problem.

Please help!

 

[OllieW]

The first thing to look at is cooling, are you getting cold airflow to the brakes whilst driving the car (in-takes in the front bumper area), if not then you need to let the whole braking system cool down between sessions.

I run my RS on the road a lot and have found a good compromise with running Pagid blue pads on standard discs. I also changed the fluid for Castrol SRF and swapped the brake lines for steel ones.

I don't think you would have a problem running with Pagid blues as they are more bias towards fast road use and occasional track use rather than the other way round.

 

[964rh]

I run with pagid blues and castrol srf as well, mainly road use (fastish) and occasional track use. Find their great on the road when warmed up a bit (squeal like a pig sometimes tho') and even better on the track.
Stainless hoses and srf only help with brake fade (I think) not cooling.

I bedded my new discs and pads in at a trackday about three days and 100 miles after having them done. I noticed no warping after the day despite steam/smoke after a hard run (Thanks Jason!!!)

You didn't lose a wheel balance weight did you?

Rob

 

[Yoda]

Definitely sounds like they are warped and probably the easiest solution is to restrict the number of fast laps you do in one go ie you stayed out too long. I would suggest you get the discs changed (there is no cure that I am aware of) and at your next track day do 3 or 4 fast laps and then a slow "cooling" lap then a few more fast laps.

The other thing to think about is, as you suggested, your driving. Brake short and hard to avoid heating the discs and pads up, I think it all helps.

Regards

 

[Guest]

Annoyingly I did do a cool down lap after each session but perhaps I did stay out too long.
Not sure I can brake much harder and shorter than I did!

 

[SimonExtreme]

Finally, my pet subject. Warped disks! The first thing is that even without seeing the disks concerned, I would bet a lot of money that they aren't warped. In fact, I have yet to see a disk truly warp.

There has been lots of research on this subject (warping disks). Most of it has been carried out on race tracks, mainly in the US . So, the major finding is that disks don't warp. What causes the judder isn't warping but uneven deposits of pad material getting embedded in the disk. Disks that are made of metal are porous. Under the microscope you can see that the surface isn't smooth but that there are little craters in the surface. Depending on the material used, these can be better or worse. On some disks these craters allow pad material to get embedded in the disk in an uneven manner. This leads to high and low spots which cause judder.

The main material that gets trapped is the binder (glue) that holds the pad material together. As it heats, it sets more solidly and the disk begins to wear around it and the build up continues.

Skimming doesn't really help as the fissions (craters) are too deep to be cleared or new craters are opened. It becomes only a matter of time before the vibrations resume. I have never heard of a disk that has been skimmed and that this has been a perminent cure.

Another factor is pad material. It seems that both the friction material and binder can make a big difference. Some pads, usually the most abrasive, seem to be very much self cleaning while some binders seem less likely to "set" into the disks.

With some disk manufacturers the problem is known. Brembo use really poor material for Evo disks and combined with very hot brake temps, it is a problem waiting to happen.

It should be noted that disks made from the same material might work on one make/model but not another. It is the combination of disk material, cooling or heating and the pad material that causes the problems.

All of the above is distilled from many articles and research papers.

So what does that mean for you? Well, I am fairly sure that the problem has been caused in this case by heat and that ducts will help a lot. The next thing I would do is change pads and Pagid Blues are good as a "cleaning" pad. Some do experience squeel but with good bedding in, it is normally avoided. I would try these or something even more abrasive and see whether it cleans up the disks. This often works.

Whatever happens, I would not use OEM pads for trackdays again. A good trackday tip is to finish your laps with a cooldown lap (I am sure you do) and then bring the car in, parking on flat ground with neither handbrake or main brakes on. Somethimes, just the act of keeping your foot on the pedal for a short while when stationary when the disks are still hot can lead to problems.

I hope all this helps and please feel free to ask any questions.

 

[jimmyslr]

There is a very fast 993rs driver who, until recently, used OEM pads over dozens of track days and was happy. He changed to pagids on advice of mates, but hasn't seen perceptible difference. Point is, I think OEM pads can work, but most of us (or at least seems that way) run pagids.

I had horrible judder after my seconf track day with my car last year. New front discs and swapped from pagid oranges to yellows. Seems ok so far since then. No good explanation!

 

[Guest]

wow!

thanks for the details replies.

I tend to agree that warped discs are unlikely given how new they were.

I've already ordered some Pagid blue pads and it looks like I'll just have to bite the bullet and replace the discs. Hey ho, you live and learn.

I'll let you know how I get on.

thanks again

 

[SimonExtreme]

ORIGINAL: jimmyslr

There is a very fast 993rs driver who, until recently, used OEM pads over dozens of track days and was happy. He changed to pagids on advice of mates, but hasn't seen perceptible difference. Point is, I think OEM pads can work, but most of us (or at least seems that way) run pagids.

I had horrible judder after my seconf track day with my car last year. New front discs and swapped from pagid oranges to yellows. Seems ok so far since then. No good explanation!

I don't know if this is a good explinationation, but it is at least an explination!

Orange are old technology! They are carbon based pads and the "glue" or binder that holds them together is an old technology as well. The yellows are a ceramic pad which uses a very different binder. While the overall braking isn't quite as good when hot, the yellow pads are rated to a slightly higher temperature and it is because of the binder. Therefore, if your brakes were getting anywhere near maximum temperature, you could have had the problems I describe above.

The other possibility is that the earlier disks were, at a molecular level, more pitted than the new disks (see above). Or it could be a combination of the 2.

One handy tip is to get some heat sensitive paint and check what temperature your disks get to. It is very useful in understanding whether more cooling is needed and also which pads to choose.

 

[Guest]

I know it's a different car, but a friend of mine has a Skyline & has a monster Brembo set up, up front. He bought a brand new pair of discs for it & when he braked they were all over the place, judder ect.
Turns out they were out of true from the factory, & he doesn't brake hard.

 

[paul howells]

Guys the solution for warped front discs,which 964 are prone to,so is 993rs and cup etc,is to use the 2 part turbo disc and bell.This allows the disc to distort through its heat cycle and then cool back to its original shape with out warping.
Solved my problem on my 993 cup car,at donnington i would knacker a set of front discs with a test day,qualifying and 2 x20 min races.
Part no 99335104510 & 99335104610,left and right hand discs.
Price for 64& 93 rs register members are £97 + vat each.
Top tip,also to keep the cross drilled holes cleaned out,not only does the dust cause judder through being out of balance,it also hinders brake cooling,as the dust packs into the cooling slots inside the discs.

 

[boydyrs]

Hi Paul
Is that price from any OPC?
regards
Boydy

 

[paul howells]

No,its a price i have arranged for some racers and the register boys.
Can get them sent any where,i think the postage is around £12 ish

 

[OllieW]

Paul

Is there any chance of a pic of the brake setup?

This might be the answer I am looking for.

Cheers

 

[Guest]

Hi Paul,

The two piece turbo discs sound ideal.
My car is only a humble C2 not an RS, so will my standard calipers etc. fit?
Is it a fairly simple swap (by simple I mean inexpensive as I'll be getting a specialist to do the work).
If so I'd like to take the plunge and order a set asap.

cheers

Kristian