[thescreensavers]

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.

If your pedal did feel did not come back after heating the fluid than yes something is wrong. With good fluid the pedal should return back 100%. Endless, Brembo and Castrol fluids do that.

I did Sebring full track(2:29 Pace)with St43s and HCT64T and its amazing how the pedal felt compared to ATE Type 200 that I had used previously. As I turned laps in my 1hr session I did allow for a lap here and their for cool down (when I hit traffic..etc)

"Compressibility" suffers at higher temperatures, and how the fluid performs at elevated temperatures is what I am after. On Paper a fluid can list good dry/wet boiling points but I care more about usability.




Chart shows HCT64t has less Compressibility at elevated temperatures but, can you feel it well thats up to you

Empirically(from what I read on many forums) Endless/Brembo > Castrol for brake feel.

I have used Motul RBF in the past it isnt that all impressive while it had good numbers the pedal feel isnt there.


Id upgrade to Endless,SRF and or Brembo fluid for your next track day and see how you like it.

Good Conversation on fluid choices here https://rennlist.com/forums/racing-a...ake-fluid.html



Also a general comment, when people recommend "X pads and X fluid" try to find how fast they drive(why I put my time as a frame of ref), if they are slow then take what they say with a grain of salt

[thescreensavers]

Originally Posted by TrackClub

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.

Where you running shims on the ST43s? OEM pads have a fiber shim if you were not running Shims on the ST43s then its puts higher demand on your fluid. Obviously the ST43s operate hotter than OEM pads but the shims can help alot.

[TrackClub]

Originally Posted by thescreensavers

Where you running shims on the ST43s? OEM pads have a fiber shim if you were not running Shims on the ST43s then its puts higher demand on your fluid. Obviously the ST43s operate hotter than OEM pads but the shims can help alot.

Thanks for making this point: indeed i am aware of it.
Nope didnt have shims on st43s. Just making a point that higher torque pads will lead to fade when mismatched with inadequate fluid to manage temps.

PS Not sure if the above post was a dig wrt my pads to fluids pairing observations, but my times are posted on the forum should anyone be curious as far as my pace is concerned.

[thescreensavers]

Originally Posted by TrackClub

Thanks for making this point: indeed i am aware of it.
Nope didnt have shims on st43s. Just making a point that higher torque pads will lead to fade when mismatched with inadequate fluid to manage temps.

PS Not sure if the above post was a dig wrt my pads to fluids pairing observations, but my times are posted on the forum should anyone be curious as far as my pace is concerned.

Fair enough.

That comment is not directed at anyone specifically, I just wanted to put it out there to give a frame of reference for when you do read reviews on "x pads x fluid"

[TrackClub]

Originally Posted by thescreensavers

Fair enough.

That comment is not directed at anyone specifically, I just wanted to put it out there to give a frame of reference for when you do read reviews on "x pads x fluid"

Fair enough.

Edit: to your pace reference comment you may wish to post your Sebring time in Best Lap Times sticky.

[driverxdeutsch]

Well, just ran Chuckwalla this weekend with a fresh full bleed of SRF and there was no difference in the problem. I'm really curious as to what is happening here. Again, the brakes performed just fine, stopping remained consistent, just a totally different engagement point and feel all day. Even after the track at the end of my 4 hour drive home, the pedal still felt totally different than normal. Morning after it was back to how it usually feels.

[Roostie]

Thanks for the update.

[Kairles]

Just did a track day In my V6 1LE and it did fill "softer" while on track. Mine didn't take a couple laps, 1st time I got on the brakes good it was noticeably different. But as soon as i hit the paddock it was back to "normal", high and firm.