Brakes overheating at the track

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Karim

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Joined
Jan 19, 2012
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43
Location
Canada
My car is an evo I GSR (CD9A).

New rotors, new brake pad (Carbotech XP10), new brake fluid (ATE Typ200).
Tires are Kumho XS 215/40R16. Almost finished. Brake lines are stock rubber.

Suspension is a set of Ground Control coilovers with 440FR (8kg/mm), 340RR (6kg/mm) spring rates.

I have -1.5 deg front camber, -1.9 rear camber. Stock toe and caster.

I run around 38-40 psi (hot) on all 4 tires.

On the track, I have been having brake fade issues after a few laps

My brother has the same car with a very similar setup. The only difference is that he has slightly softer springs front and rear (340/280). He does not experience brake fade as bad.

We did a couple sessions where I would follow him closely on the track.

I was extra careful with my braking technique, trying to brake hard but for as little time as possible.

At the end of the session I measured the surface temperature of our rotors with an IR pyrometer:

Me: front 400+ F, rear 300F
Brother: front 350F, rear 325F

(this is after a cool down lap for both of us)

First question: Why are my front discs getting much hotter?

It seems counter intuitive. With the stiffer springs, I would imagine my car would experience less weight transfer to the front. The greater temperature difference between front and rear on my car seem to indicate that the front brakes are doing more work. What can be the cause of this? Problem with the bias? Can bias valves fail? Can they get clogged? Easy to replace?

Any other ideas or suggestions as to what may be the cause of this?

Thanks for the input.

Karim
 
I can only think that with the stiffer springs comes less weight transfer, so the energy not being transferred to the springs is instead being transferred to your brakes. With all things being equal.

Otherwise, do you have the same rotor thickness? (previously machined?) Wheel type? Your wheel weight and design will make a difference.. The wheels can act as a large heatsink / fan pending design.

It would be interesting if you swapped a few parts to test....
 
technique can play a big part, wheel design may also be a factor.
and do both cars weigh the same? same power levels? exactly the same braking points? same tyres?
But as noted in your temps your brothers is using the rears a touch more by the looks of it,
temps are hard to translate front to rear though as the rear rotor is smaller and not vented
 
technique can play a big part, wheel design may also be a factor.
and do both cars weigh the same? same power levels? exactly the same braking points? same tyres?
But as noted in your temps your brothers is using the rears a touch more by the looks of it,
temps are hard to translate front to rear though as the rear rotor is smaller and not vented

Exactly what I was going to say: "Technique" You need to be progressive with your brake application and release.
Having said that though I did struggle a bit in the beginning with my standard Evo 3 brake set-up. I'm fairly sure the OEM units are more suited to a "Gravel" car more than a "Tarmac" car (?)
Anyway some better pads, braided lines, fluid and a bit of ducting did wonders
 
I can only think that with the stiffer springs comes less weight transfer, so the energy not being transferred to the springs is instead being transferred to your brakes. With all things being equal.

Otherwise, do you have the same rotor thickness? (previously machined?) Wheel type? Your wheel weight and design will make a difference.. The wheels can act as a large heatsink / fan pending design.

It would be interesting if you swapped a few parts to test....

We both replaced our rotors with brand new ones, same brand, same thickness, same everything.
We even have the exact same wheels. Only difference is the paint color on the wheels. ;)



technique can play a big part, wheel design may also be a factor.
and do both cars weigh the same? same power levels? exactly the same braking points? same tyres?
But as noted in your temps your brothers is using the rears a touch more by the looks of it,
temps are hard to translate front to rear though as the rear rotor is smaller and not vented


Same weight I assume since there was no major modifications. They are both 92 EVO I GSR with the same diffs. Same power level based on the mods but did not put them on a dyno. Exact braking point is hard to determine but we are pretty close.

I would agree 100% with the technique being the difference but I am puzzled by the difference front to rear on my car vs. his. Although... maybe a more brutal application of the brakes could be the cause. Harder breaking could mean more weight transfer which could explain the difference...

What type of fade is it? Hard fade (pedal still hard, but not stopping), or soft fade? (Pedal gone soft)

Soft fade. Boiled fluid. The pads are holding up.


Exactly what I was going to say: "Technique" You need to be progressive with your brake application and release.
Having said that though I did struggle a bit in the beginning with my standard Evo 3 brake set-up. I'm fairly sure the OEM units are more suited to a "Gravel" car more than a "Tarmac" car (?)
Anyway some better pads, braided lines, fluid and a bit of ducting did wonders

Braided lines and ducting are in the plans. Just wanted to figure out if anything else might be causing the problem.
 
A couple of things I just thought off:
Check for fluid leaks where the hard line joins the rubber hoses.
Also check your brake rotors to make sure the fins inside the rotor, if they are that design of rotor, are turning in the right direction. Air should be getting sucked from behind the hat (near the hub) up through the inside to the outer edge
 
No fluid leaks at all. I inspect the car before every track outing.

Rotors are installed properly.

I am thinking more and more that my braking technique might be the problem. I will experiment with that and see what happens.
 
I would say technique. If you brother is tapping strong on his brake as he reaches the corner appose to you slamming the brakes to the corner, it would spread the heat over the distance.

You could do a few drag runs both going the same speed then brake hard and record the temperature. The try another method - if both of you get the approx same number it aint the car but if its not then something is different between the two. If they are virtually the same.

Could be a factor of how you both pre-heat the pads/tires before the real laps. I know some pads/tires work alot better when heated up first.
 
That's... weird? Granted that there are other cars on the track, but at powercruise here in perth I've run my VR4 twice and both times punished the shit out of it and it's never faded. Well, maybe once a tiny bit after being out on the track for over an hour. It's weird, my pads get cracks in them like they are getting too hot, but I don't have any loss in braking performance.

Anyway, I run the RDA slotted rotors up front with a set of EBC red and pbr gold brake fluid. Rears are just standard discs with some lucas pads I got ages ago. I don't know if that's any help, just seems odd that you'd get noticeable fade on a lighter car with similar braking capacity.

The VR4's not making an abundance of power, but it's got all the usual supporting mods ready for a bigger turbo but still running the 14b @ 18PSI

Not sure what the actual temps were, but they got hot enough to slightly discolour the centre of the rim, turn the pads from red to yellow and melt/distort the plastic centre caps so they became loose and fell out =S Needless to say next time I'll be throwing in a few more cold laps to limit the heat...
 
remove your disc sone sheild if your still running them helped tonnes with my wagon on track work after I removed them
 
remove your disc sone sheild if your still running them helped tonnes with my wagon on track work after I removed them
:thumbsup: Beat me to it. was also thinking if one car was braking later and harder from a higher speed that may attribute to the difference in temps.I use Motul RBF 600 but i think they have produced a higher temperature fluid now.
 

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