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

http://i1326.photobucket.com/albums/u649/ESD1711/F0BCE660-8875-4CD0-B053-6E3922DE8B5D_zpsahqg3ghe.jpg

[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]

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?)

[AndySAXO]

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]

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

Such as?

[sexy_gt]

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 :)

[axsaxoman]

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.

I don,t think its a pad/make /material problem --just front brakes being over worked due to set -up --every pad will melt if over heated-- thats why F1 use carbon discs etc -but 5k for front brakes is not the cure --get it set -up right

[KamRacing]

The fluid is usually the first to fail though so I think its that vs the pads. The CL Brakes compounds are rated to well beyond the fluid boil points and will cope with hard race use beyond what the Saxo should be getting to temperature wise.

[AndySAXO]

Such as?

They gave me extremely bad brake judder I try three ds3000 pads with my ap cp5040 and every set gave me judder to the point I didn't feel safe. Also got uneven pad wear. Changed back to CL rc5+ and rc6 pads and been totally fine on the same disc. Then i did some research and seem common with the ds3000 pads to judder. Honestly didn't think much of them at all. This is just my experience. Never had any issues with CL pads on my setup.

[Chipwizards]

The only time I've had judder with DS3000+ was when I used them on discs previously used with other pads and the resin that had previously transferred 'clumped' and caused judder.

Besides that I've found them to be excellent. I have the lap record at every circuit I've raced at with the exception of Cadwell, so the performance is there.

My brakes run at typically around 750 degrees peak and I never get fade, ever. If the temps go much higher the wear rate increases greatly, but I've only had that once when the brake duct became dislodged and in a twenty-minute race one side wore 8mm more than the other. Still had no fade though.

[axsaxoman]

I have never seen brake judder caused by pad material
has always been warped discs and or calipers not swinging freely and or pads binding in carriers not allowing free movement to conform to slight run out of disc or fitment of disc to hub flange
race car pads certainly need to be a "rattling good fit "--cos things get hotter and clearances close up due to expansion of all parts
even seen calipers which were a tight fit under wheels --say 3-4mm clearance --when hot expand such that they touch the inside of the rim --everything grows as it gets warm different metals expand at different rates .eg alloy caliper and iron disc + iron pad backings

[KamRacing]

The only time I've had judder with DS3000+ was when I used them on discs previously used with other pads and the resin that had previously transferred 'clumped' and caused judder.

Besides that I've found them to be excellent. I have the lap record at every circuit I've raced at with the exception of Cadwell, so the performance is there.

My brakes run at typically around 750 degrees peak and I never get fade, ever. If the temps go much higher the wear rate increases greatly, but I've only had that once when the brake duct became dislodged and in a twenty-minute race one side wore 8mm more than the other. Still had no fade though.

If you can get them up to temperature they are very good.

[AndySAXO]

The only time I've had judder with DS3000+ was when I used them on discs previously used with other pads and the resin that had previously transferred 'clumped' and caused judder.

Besides that I've found them to be excellent. I have the lap record at every circuit I've raced at with the exception of Cadwell, so the performance is there.

My brakes run at typically around 750 degrees peak and I never get fade, ever. If the temps go much higher the wear rate increases greatly, but I've only had that once when the brake duct became dislodged and in a twenty-minute race one side wore 8mm more than the other. Still had no fade though.

Like I said I was going from experience. The ds3000 where used on brand new rotors. And still use the same rotor now on the CL pads no problem with CL pads but 3 sets of ds3000 pads all had issues.

I wanted to use ds3000 as they are cheaper but just had issues so changed to CL pads. I knew cl pads after using them with hi spec billet 4. When I got AP brakes got ds3000 had issues so went back to cl pads.

It all comes down to personal preference. I had issues so will not go back to ds3000.

But after using ds3000, rc5+, rc6 the ds3000 and 5+ feel about the same in terms of stopping power. The rc6 feel a lot better for me, which is why I am goimg back to them for next year. It all comes down to testing only way you truly know what best for yourself I was just offering my opinion from experience.

[Chipwizards]

I'd like to understand how pads cause judder myself.

[welshpug]

by leaving deposits on the disc.

[AndySAXO]

I'd like to understand how pads cause judder myself.

Well I only changed the pads and fixed my problem with judder. I changed after researching and reading many others with ds3000 seem to have this problem. I then went back to CL pads and haven't had the problem since. Again same rotors the whole time.

[Chipwizards]

I've been in and around racing my whole life and things that rotate cause judder, not static things. Judder is a reciprocal motion and can only be caused by another reciprocal motion or a rotational one.

As I already said, when changing types of pad material you can get judder because of resin clumping on the disc surface, but it's still the disc that causes the judder, it can't possibly be the pad because it doesn't move so it can't cause any other motion.

If your judder was with pads and NEW discs as you say, they must not have been true.

Every time you fit discs, without exception, you should get the DTI out and check they are true. In my book, entry fees are too expensive to risk throwing a race meeting away due to duff parts fitted. On top of that, if they are duff you can return unused parts for replacement, you can't replace used ones generally- not in the motorsport world you can't.

There are lots and lots of garbage brake parts manufacturers now, much of it made cheaply in China. I ONLY buy AP Racing, Alcon or Brembo when it comes to hardware; because I've had issues with everything else at one time or another. Most cheap aftermarket stuff is much worse than stock stuff.

[welshpug]

without those pads you wouldn't have had deposits on the braking surface.

so yeah, the pads caused the judder.

[Chipwizards]

I already said that in an earlier post, but he said he had fitted new discs each time with new pads, so his symptoms doesn't make any sense.

[Chipwizards]

And in any case it's still the uneven disc mu value/thickness that causes the judder, not the pad itself.

[AndySAXO]

I already said that in an earlier post, but he said he had fitted new discs each time with new pads, so his symptoms doesn't make any sense.

Are you talking about me here? As I stated I have used the same rotors the whole time. Only changed the pads.

[Chipwizards]

Are you talking about me here? As I stated I have used the same rotors the whole time. Only changed the pads.


Like I said I was going from experience. The ds3000 where used on brand new rotors. And still use the same rotor now on the CL pads no problem with CL pads but 3 sets of ds3000 pads all had issues.



Sorry, my bad, I assumed you fitted new discs with pads when you changed the pad type, because that is what you really should do to avoid resin transfer problems.

So, to clarify, you had juddering brakes and DIDN'T change the discs and the juddering stopped with just a pad change?

If so, that is totally, utterly unbelievable. How a pad change could change the localised mu values of the disc form being uneven to being even, defies physics.

[axsaxoman]

we are back to what i suggested -
-calipers sticking or pads tight in carriers as things warm up -not allowing them to move free enough +causing judder

[AndySAXO]

Sorry, my bad, I assumed you fitted new discs with pads when you changed the pad type, because that is what you really should do to avoid resin transfer problems.

So, to clarify, you had juddering brakes and DIDN'T change the discs and the juddering stopped with just a pad change?

If so, that is totally, utterly unbelievable. How a pad change could change the localised mu values of the disc form being uneven to being even, defies physics.

It fine you don't believe me but that what happened, as below it could be the pad tight, which is the pad issues and been badly made from manufacturers. So again I blame the pad. The pad size shape ect is the one recommend for my cp5040 and used the same shape ect CL pads without an issue.

If I could afford to change the rotors everytime I would but I don't have unlimited money. I am trying to have some fun and just do some form of motorsport which is a little more than track days.

we are back to what i suggested -
-calipers sticking or pads tight in carriers as things warm up -not allowing them to move free enough +causing

The ap are always cleanEd and checked after every race meeting. You could be right on the pads been too tight, So again I would then blame the pad. All I can say is I wouldn't use the ds3000 again on my setup and offering my advice on experience I had with them. I didn't want to get into these debates. I am not going to say I know everything I just going off my experience.

[KamRacing]

Two things. The CL Brakes are undersized to not stick in the caliper when hot. That does not mean it will solve a problem with the caliper itself

The other is as its sintered metal it does not transfer pad material to the disc surface. I've always pondered whether it could clean a disc surface of old pad deposits so Andy may well have experienced that situation.

[ESD1711]

The other is as its sintered metal it does not transfer pad material to the disc surface.

Is it not pad deposit shown on my disc pic earlier in the thread though?

[axsaxoman]

Is it not pad deposit shown on my disc pic earlier in the thread though?
yes that will cause judder --but it is the reason for the overheating that needs sorting

[KamRacing]

Is it not pad deposit shown on my disc pic earlier in the thread though?
Brake dust could easily stick to a hot disc. Until you look at the pad surface we only can see half the picture.