Track Car Braking Woes

[ESD1711]

So...... looking for a little bit of advice in diagnosing some braking 'issues' i've found myself having.

Both discs and pads were new at the start of the track car season back in April and braking setup is as follows:

285mm MTEC discs
Carbon Lorraine RC5+ pads in Hispec 4 pots
AP Racing dot 5.1
Bigger master cylinder
Braided flexis front and back

Over the last few track days i've done, the braking efficiency has tailed right off - they are still stopping the car, just without the same level of bite as i'd come to expect from them. It seems to take a hell of a lot more effort to stop the thing than it should.

The pads are now passed their best and will need renewed for next year now regardless, but there is still a bit of material on them at this point so they are still in usable condition..... ie my issues shouldn't have come as a result of dead pads.

I know its not much to go on, but what are folks thoughts on the causes of the picture below?

Would this be as a result of glazing? Have I perhaps been asking too much of my brakes too soon? Did I perhaps make a mistake in bedding them in?

Have heard nothing but good things about the CL pads, so dont think they are the problem. Whilst the discs werent exactly 'expensive' - again, i'm not sure its those which are the issue. I suspect the most likely cause here is user error - but trying to understand why.

Any thoughts appreicated.....

Cheers,
Erik

[axsaxoman]

simple you cooked the fuckers
and melted the pads which then stuck to discs
bigger discs get your backs working right --car should squat --not dive
and wheels with more ventialtaion?
If you haven,t already got a bias valve +replumbed pipes then do so --ideal is backs just squirming on full braking into hairpin ,so you can turn in with foot still on brakes if needed----adjust bias every time you go out to suit track conditions

must be a brake set-up prob cos you still running close to std bhp
the problem with grooved discs is that when you get them hot the lacquers in the pad boil +slots allow this vapour to blow out --so eventually you end up with pads like weetabix
plain dics is all you need --but bigger

[ESD1711]

Bigger than the 285? Shouldn't that be plenty big enough?

I do feel like the car does nose dive a bit - under braking for the hairpin I think the inside back wheel is barely in contact with the ground, that corner has a tendancy to lock up a bit, however im not sure if that's partly due to me having to work the pedal even harder to compensate for the lack of braking as a result of the mess on the discs.

Bias valve and get the backs doing a bit more then?

[welshpug]

reface the discs if there's enough meat left and new pads time.

try the RC6 or RC6E

[Chipwizards]

Heavy resin transfer.
Improve your cooling and put some disk temp paint on the discs to see how hot they are getting so you know you're in the right operating window for the chosen pad material. I prefer to run the most cooling I can on the lowest mass of brake disc that allows the pads not to get too hot, because it's lightest that way. However, you have to be careful to keep the cooling tip-top, if you take a trip onto the grass at any point give the ducts a good blow out. Discs vented from the rear are easier to get cooling air into rather than 'hope' enough air finds its way in through the wheel, which is rotating so makes that more difficult....

[axsaxoman]

Originally Posted by ESD1711

Bigger than the 285? Shouldn't that be plenty big enough?

I do feel like the car does nose dive a bit - under braking for the hairpin I think the inside back wheel is barely in contact with the ground, that corner has a tendancy to lock up a bit, however im not sure if that's partly due to me having to work the pedal even harder to compensate for the lack of braking as a result of the mess on the discs.

Bias valve and get the backs doing a bit more then?

yes backs need to do a lot more --should not be a problem if you have 283mm discs on a car of that weight if set up right --its all we ever used
like i said before car should not dive at all--so its overheating and brake set-up problem
you certainly need to sort that before looking for more power --more power makes all your problems more apparent-
even a small quirk at std bhp becomes a real problem if you double the power in the chassis and are heading for the hairpin 20mph faster

[ESD1711]

Thanks as always guys - another thing on to the winter to-do list then

[KamRacing]

Ok. You have to remember the pads are metallic so not everything mentioned above applies.
First port of call. Fit plain discs. Grooves will wear out your pads faster and thats it.
They will not glaze, they are metal. If you are overheating the pads generally it will just increase the pad wear with the CL Brakes, but have a look at the pad to really tell. If they are melting as such then there will be material in between the two pad blocks. As the pads wear their thermal capacity will be reducing and heat will be transferred to the fluid.
Cooling will certainly keep fluid temperatures in check and lower pad temperatures will decrease the wear rate.

[axsaxoman]

what do think they stick the pads together with --not just compressed metal --the glue melts +vapourizes as its supposed to --but with no grooves when it cools down it goes back into pad and doesn,t get squirted out the slots--
yes you can get carbon pads which don,t have glue £100+--but no need

[welshpug]

those RC5's are £140+ depending on caliper.

[ESD1711]

Which is kinda why i'm a bit surprised I've managed to cook them tbh. I remember at the time having a bit of a dilemma over RC5 vs RC6. At the time i'd planned ot keep the car for road use as well, hence the decision to go with the RC5 - but i'd have thought that pad should still take everything I could chuck at it and then some?

I'm getting a bit confused about some of the comments above - If we're saying these pads wont glaze, then would that not mean I shouldn't really be seeing the material stuck to the disc as per the pic?

[axsaxoman]

dont, be confused -- its simply the only way material can be stuck to discs is by overheating -end of-

[KamRacing]

Can we see pictures of the pads please. Also maybe tell us how often your brake fluid has been changed and if the braking recovered afterwards..

The CL brake pads are formed by sintering the metal particles together. My understanding is that process bonds the pad together using pressure and heat rather than resins. Its one of the reasons these pads do not require a bedding in process with the disc. That pad material is brazed onto the backing plate as well.

I've been a CL Brakes dealer for a long time and really the only overheating issue we have seen is increased wear as the metals soften at high temperatures. The RC5 has been used on competition saxo's with standard discs and calipers without issue. You will be running cooler than they do, but most now use the RC6 as its more durable when extremely hot.

[ESD1711]

Thanks again for the input guys, it is appreciated.

Would stress that right from the first post, I did state I thought it was unlikely that my issues have come from the pads themselves. As I've said, heard nothing but good things about the CL pads, and the RC5 was chosen over the RC6 as recommended to me on the basis of the car being road usable at the time. That circumstance has changed now and I'd certainly be going RC6 when I replace them.

Not trying to point fingers at the pads or whatever, just trying to understand the issue and learn from it. As I said, if there's some user error in there somewhere, I'd rather learn from it than keep making the mistake again, cos at the moment I'm not sure where I coulda gone wrong - I always try to make a point of warming them up and cooling them down at either end of a session, and whilst I'm no pro driver, I'd like to think I'm fairly switched on when it comes to applying them.

I'll be more than happy to provide more pics of the pads and more detailed pics of the wear when I get around to stripping it, but given that it's now parked up for winter, that probably won't be any time soon - I'll maybe need to dig this back up again in a few months.

Regarding brake fluid..... car was bled up when it was all built up in April using ap racing dot 5.1. Hasn't been bled since, just level checked before each outing. Have done maybe 7 track days on it since first bleeding.

[sexy_gt]

I have used rc5 pads for about 4 years. Always been great pads, supplied by kamracing.co.uk

I had the same thing happen to my discs but ony when using slotted discs like you have. Ive not had this problem with plain discs.

I understand the loss of brake effort from unglazed to glazed having experienced it myself on several sets of slotted discs and pads.

My pads show no glazing just the discs.

My last two outings i have used a ds3000 pad on the same slotted disc with no glazing yet.

[ESD1711]

Thanks Stu,

So...... plain discs for sure then.

Out of interest how do you find the DS3000 stacks up in comparison to the RC5 (or even the 6 I suppose - I'm guessing eh RC5 might be closer to the DS2500?)

[AndySAXOp]

I would say after using them all ds3000 are close to rc5+ and rc6 are much more aggressive and give better stopping power. I am going back to rc6 from the rc5 for next year. Will never use ds3000 again, too many bad experience with them.

[Chipwizards]

Originally Posted by AndySAXO

Will never use ds3000 again, too many bad experience with them.

Such as?

[sexy_gt]

Originally Posted by ESD1711

Thanks Stu,

So...... plain discs for sure then.

Out of interest how do you find the DS3000 stacks up in comparison to the RC5 (or even the 6 I suppose - I'm guessing eh RC5 might be closer to the DS2500?)

No problem.

Plain discs also cheaper to replace.

[Jimmy-Boy]

As above really plain oem discs, and cooling should eliminate that problem. i run Rc6 on the front and rc5 on the back with rbf600 fluid and been using for 3 years or so and no bother what so ever