[driverxdeutsch]

Just got back from my 6th track day in my V6 1LE (ran a 1:36.08 at Big Willow) and keep running into the same issue every time I'm at the track. For some reason the brake pedal feel changes drastically as soon as the brakes come up to temperature (within the first two laps at any track). It isn't fade but the bite point changes and moves about an inch or so lower and becomes much more gradual. I'd describe them as feeling squishy I guess, but all the stopping power is still there, I just have to get on the pedal harder and push it further.

I thought it was the stock ferodo pads just having a hard time coping with track temps, but I just threw on Carbotech XP12's and new rotors (just did the front for now) and the pedal feel changes in the exact same way. I also flushed the whole system with RBF660 before my first track day. The stock brakes and the new setup have both been fantastic at scrubbing off speed and I've never had more than very slight fade (at Laguna Seca while pushing hard) so it's a bit of an odd problem. I'm left wondering what could cause the pedal travel to change like that and loose feel?

[Roostie]

+1. I agree with this assessment of the V6 1LE brakes. Since they keep working well, I haven't worried about it, but I'd like to know why they act that way

[Deesiel678]

Sounds like hot brake fluid. Heat causes the viscosity to go down which necessitates the need to apply more pedal pressure for the same amount of friction than with cooler fluid.

Its not uncommon for rotor temps to go well beyond the boiling point of high temp racing brake fluid, especially at a track event. The heat from the rotor transfers into the pad material, which transfers into the backing plate, which transfers into the caliper pistons, which then transfers into the fluid (which cause the viscosity to decrease like described above).

I'd bet titanium shims would help.
https://hardbrakes.com/

[Move_Over]

Careful with TI shims too though as the heat is now retained in the pad and will cause faster wear, which is probably less catostrophic than a soft pedal but still can create some probs

[driverxdeutsch]

I would agree about it potentially being fluid if the difference only happened when hot, but strangely, once the pedal travel changes in the first lap or two, it stays different for the remainder of the day. After 2+ hours on the freeway, the pedal is still odd when I make it home. I also have garage therapy cooling ducts because I though heat was a big part of the issue. Big Willow is pretty easy on brakes and with the cooling ducts I would be surprised if heat alone is the culprit. I am going to be doing a fresh flush of the fluid since it's now been 6 days, I'll report back after my next outing in March if that helps.

One theory I have is that there is that maybe there is some weird air bubble somewhere in the lines or ABS module that only comes into play after the module cycles a few times, is that even something that is possible after doing a full bleed with a motive power bleeder?

[thescreensavers]

OP Try better fluid, this is also an "issue" on V8 1LEs as well. These cars have a lot of travel for modulation and are sensitive to temp of brake fluid.

I would look into Endless RF650 or Brembo HTC 64T which are better fluids and tout superior compress-ability vs temp.

I personally have the brembo fluid and I did feel a difference though the pedal still sinks, just something you have to get used too. The Car still stops with confidence.

Originally Posted by Move_Over

Careful with TI shims too though as the heat is now retained in the pad and will cause faster wear, which is probably less catostrophic than a soft pedal but still can create some probs

This is completely a non issue and fear mongering. Ti Shims add contact resistance so its harder for heat to flow into the calipers and thus heat up the fluid. Same reason we have two piece rotors (more contact resistance) for heat going into the wheel bearing.

Your OEM pads also already have fiber shims on them which probably do a better job than Ti shims imo.

[kropscamaro16]

my buddys all love the castrol stuff and maybe throw some ss brake lines on there also?

[Move_Over]

Originally Posted by thescreensavers

OP Try better fluid, this is also an "issue" on V8 1LEs as well. These cars have a lot of travel for modulation and are sensitive to temp of brake fluid.

I would look into Endless RF650 or Brembo HTC 64T which are better fluids and tout superior compress-ability vs temp.

I personally have the brembo fluid and I did feel a difference though the pedal still sinks, just something you have to get used too. The Car still stops with confidence.





This is completely a non issue and fear mongering. Ti Shims add contact resistance so its harder for heat to flow into the calipers and thus heat up the fluid. Same reason we have two piece rotors (more contact resistance) for heat going into the wheel bearing.

Your OEM pads also already have fiber shims on them which probably do a better job than Ti shims imo.

Fear mongering? Definitely not trying to scare anyone, just trying to inform. Think about it. You are correct that it will slow the conductivity of heat getting to the calipers/fluid but now you are just keeping that same heat in the pad. Raising the pad temp will eventually cause pad fade if you heat that pad to beyond it's thermal limits. In that case it WOULD be an issue.

The correct solution here (if he was already using one of your recommended fluids) would be to add additional cooling to the brakes to get rid of some of that heat. Unless the fiber shim has a lower thermal conductivity than titanium, which i doubt it does as titanium is very low, than it simply cannot do a better job than a TI shim of it's designed purpose. Can't say for sure unless we knew the exact material of the OE shim.

I use TI shims in the rear on aftermarket pads to slow the heat getting to my calipers, but really that's because there is no cooling in the rear. My pads are designed for a higher operating temp than stock pads. If you throw TI shims on stock pads without understanding what you are doing to the pads/calipers in the way of heat, you very well may have now created a temp issue within your pad, instead of your fluid.

I agree with your recommendation of going with a different fluid, maybe add SRF to that list.

[thescreensavers]

Originally Posted by Move_Over

Fear mongering? Definitely not trying to scare anyone, just trying to inform. Think about it. You are correct that it will slow the conductivity of heat getting to the calipers/fluid but now you are just keeping that same heat in the pad. Raising the pad temp will eventually cause pad fade if you heat that pad to beyond it's thermal limits. In that case it WOULD be an issue.

Unless the fiber shim has a lower thermal conductivity than titanium, which i doubt it does as titanium is very low, than it simply cannot do a better job than a TI shim of it's designed purpose. Can't say for sure unless we knew the exact material of the OE shim.


I agree with your recommendation of going with a different fluid, maybe add SRF to that list.

In terms of "Compressibility" Endless and Brembo fluids mentioned have an edge over SRF. Im sure SRF is a great fluid but, in this car with a "Squishy" brake pedal finding the best items for eliminating the squishyness is more important to me than a few deg F in fluid temp which is already in excess of the brake seals max temp.

About the shims holding in heat,

So lets say you have a Box(6 sides)(brake pads) and you are blowing air at all sides. You go an add a shim to one side of the box. Remember you are still keeping the 5 remaining sides open and blowing air at it, how exactly are you holding heat?

If some how you were holding heat in this box(pad) the OEM shim would do the same.

All OEM pads have shims. If your Track pads do not come with shims, the user should procure shims. If you can get the OEM fiber ones to work use em. The contact resistance alone is worth a relatively large % in cooler brake fluid, and longer brake caliper seal/rubber life.

If your pads over heat because you have shims on the back side, I can tell you its not because of the shims. Find better pads that can handle the heat range that you are subjecting them too, or add more cooling as you suggested.

Empirically(everyone on here that tracks their cars) better pads are all you need.

[driverxdeutsch]

Originally Posted by thescreensavers

In terms of "Compressibility" Endless and Brembo fluids mentioned have an edge over SRF. Im sure SRF is a great fluid but, in this car with a "Squishy" brake pedal finding the best items for eliminating the squishyness is more important to me than a few deg F in fluid temp which is already in excess of the brake seals max temp.

About the shims holding in heat,

So lets say you have a Box(6 sides)(brake pads) and you are blowing air at all sides. You go an add a shim to one side of the box. Remember you are still keeping the 5 remaining sides open and blowing air at it, how exactly are you holding heat?

If some how you were holding heat in this box(pad) the OEM shim would do the same.

All OEM pads have shims. If your Track pads do not come with shims, the user should procure shims. If you can get the OEM fiber ones to work use em. The contact resistance alone is worth a relatively large % in cooler brake fluid, and longer brake caliper seal/rubber life.

If your pads over heat because you have shims on the back side, I can tell you its not because of the shims. Find better pads that can handle the heat range that you are subjecting them too, or add more cooling as you suggested.

Empirically(everyone on here that tracks their cars) better pads are all you need.

Just reviewing everything here to try and figure out a likely cause. I'm on Motul RBF660 and I know I'm not boiling the fluid in one lap (when the feel changes), I can actually say with very high certainty that I am not boiling the fluid at any point. I'm not sure that I'm familiar with brake fluid "compressability" as a measured factor, I'd love to hear more about that (would that characteristic change with heat?). I suppose that air in the lines somewhere could be expanding and causing a change in feel. Could this also explain why the change in feel lasts at least 6+ hours after tracking the car? Is there a need to cycle the ABS pump while pressure bleeding the lines?

Brake fade has a specific feeling that I'm fairly familiar with, and is almost always accompanied by a lack of braking performance. Since the stopping power remain consistent and easily able to trigger ABS if you stand on the pedal (on both the stock Brembo/Ferodo pad and Carbotech XP12), I'm pretty sure I'm within operating temperature range for the pads. I also have brake ducting that pipes air directly into the rotor near the hub, again making me pretty confident that heat at the rotor/caliper/pad are not the cause of the change in feel.

I'd be curious to change fluid before the next day and see if RBF660 just doesn't work well in this instance. And if there is air, it seems likely that fresh fluid could solve that issue too. I'm still curious if there could be another cause or some strange factor that I'm not thinking about at all.

[ninetres]

Base model ZL1 here. SS lines and SRF fluid. Pedal firm AF, consistent, predictable.

[Stephen12ZL1]

Likely still air in the system and it is boiling due to moisture or improper bleed/flush procedure. Most of these Camaro systems will purge a few air bubbles after track action. I bled/flushed 5 different Camaros at VIR and they all developed a few bubbles in the system after a few sessions. I wouldn't worry too much if the pedal didn't drop more that what you mentioned. Get a Motive bleeder and a bleed bottle...watch it closely during the procedure. The inner bleeders always seem to have double the amount of bubbles compared to the outers. It is possible that this happens because I do the inner bleeders first. I have had the best luck using the Motive bleeder as a positive pressure device and not filling it with brake fluid.

Use a turkey baster and remove as much fluid as possible from the master cylinder. Refill the master cylinder with fresh Motul all the way to the top, connect the Motive unit, and proceed. Start passenger rear, driver's rear, passenger front, & driver's front. Refill as necessary during the procedure. Obviously, you will have to depressurize the system to refill. Hope this helps as this has been proven to work well!

[driverxdeutsch]

Originally Posted by Stephen12ZL1

Likely still air in the system and it is boiling due to moisture or improper bleed/flush procedure. Most of these Camaro systems will purge a few air bubbles after track action. I bled/flushed 5 different Camaros at VIR and they all developed a few bubbles in the system after a few sessions. I wouldn't worry too much if the pedal didn't drop more that what you mentioned. Get a Motive bleeder and a bleed bottle...watch it closely during the procedure. The inner bleeders always seem to have double the amount of bubbles compared to the outers. It is possible that this happens because I do the inner bleeders first. I have had the best luck using the Motive bleeder as a positive pressure device and not filling it with brake fluid.

Use a turkey baster and remove as much fluid as possible from the master cylinder. Refill the master cylinder with fresh Motul all the way to the top, connect the Motive unit, and proceed. Start passenger rear, driver's rear, passenger front, & driver's front. Refill as necessary during the procedure. Obviously, you will have to depressurize the system to refill. Hope this helps as this has been proven to work well!

Oh interesting, I have a Motive bleeder but I've only ever used it with the fluid in the pressure bottle. I guess I took the directions at face value and didn't consider just using it to pressurize the system. It sounds like flushing the whole system is my next step in any scenario, and it's due after 6 track days anyhow. I'll report back here in a couple weeks after my next event.

[TrackClub]

Originally Posted by driverxdeutsch

Just reviewing everything here to try and figure out a likely cause. I'm on Motul RBF660 and I know I'm not boiling the fluid in one lap (when the feel changes), I can actually say with very high certainty that I am not boiling the fluid at any point. I'm not sure that I'm familiar with brake fluid "compressability" as a measured factor, I'd love to hear more about that (would that characteristic change with heat?). I suppose that air in the lines somewhere could be expanding and causing a change in feel. Could this also explain why the change in feel lasts at least 6+ hours after tracking the car? Is there a need to cycle the ABS pump while pressure bleeding the lines?

Brake fade has a specific feeling that I'm fairly familiar with, and is almost always accompanied by a lack of braking performance. Since the stopping power remain consistent and easily able to trigger ABS if you stand on the pedal (on both the stock Brembo/Ferodo pad and Carbotech XP12), I'm pretty sure I'm within operating temperature range for the pads. I also have brake ducting that pipes air directly into the rotor near the hub, again making me pretty confident that heat at the rotor/caliper/pad are not the cause of the change in feel.

I'd be curious to change fluid before the next day and see if RBF660 just doesn't work well in this instance. And if there is air, it seems likely that fresh fluid could solve that issue too. I'm still curious if there could be another cause or some strange factor that I'm not thinking about at all.

Cant help with any specific tech ideas here, but if the condition persists for a few hrs after tracking the car and then goes away it aint pads or fluid (as they cool down much faster than that).

Also, stock Ferodos are great and run pretty cold. I run cheap Willwood Racing DOT3 fluid with absolutely ZERO issues with stock Ferodos regardless of the type of venue. OTOH if i ran ST43 pads with the Willwood fluid vs Castrol I'd get serious fade in a few laps. But even then it would take one cool down lap to restore them for a bit.

So there was a clear cause and effect here (insufficient rating of fluid for the high torque pads).

Your situation seems very different. Good luck getting to the bottom of it. Cheers!