skdiablo

First off, I'd like avoid making this a discussion about the necessity of upgrading the calipers, BBK's, rotors, etc. I understand that would be the best solution. However, I'm reasonably happy with the Z51 brakes for my skill/pace level, just looking for a bit more heat-capacity for the duration of a session.

I have a 2014 Z51 7-speed manual with Mag Ride.

I'm using the Raybestos ST-43 pads, which I've previously used at the track with my C6 Z06 and a C6 Z51 before that. One thing I'd note...on my C6 Z51, these pads felt almost too good for the car. ABS would constantly engage if I didn't apply the pedal carefully. This is not happening on the C7.

Rotor cooling rings installed and Dot 4 Brake Fluid.

Brakes work great, but gradually overheat towards the end of each session. Not too bad...they don't fall off a cliff. Just a gradual fade until the pedal goes to the floor. Usually work well for about 15 minutes, then overheat the last 5 minuntes. I still finish each session, albeit with adjusted brake points to counter the fade. Brakes feel great again each time at the next session.

This was less evident at Sonoma/Sears Point, but happened in every session at Laguna (which is known to be tough on brakes).

PTM is set on the least intrusive mode (Race), so I don't think the AH or TC is intruding too much.

My pace right now is 1:57 at Sonoma and 1:48 at Laguna.

Short of upgrading the brakes, is it worth getting more aggressive pads? Anything else that I can do to get a bit more heat-resistance for a session?

If I do get more aggressive pads, is the problem likely to move on to another weak point? (such as brake fluid)?

There's also a chance that I'm just using them too much. I tend to ride the brakes a bit, get on them too early and drag. Maybe I should try to use them less, but more aggressively/shorter periods?

I believe a better driver than myself could achieve faster lap times while maintaining the braking performance over an entire session...

Poor-sha

I'm running the Ferodo DS 1.11 on my C7 Z06 and they have worked very well for me. Oh, and Castrol SRF fluid.

12zo

If your pedal is going to the floor and you are on a race track or highway, you need to get serious about it.
If it is a bleeding issue fine, I'd get after it.
If your car needs better front brakes, I'd do it soon.
Don't mean to come of harshly but a pedal to the floor is a real hazard and not just to you.
I'd read the AP Essex thread that is recent.
Sometimes pads and fluid won't cut it.

StreetSpeed

X2. Switch to Castrol SRF and see if that solves the pedal issue. I always added SS lines to my stock brake systems as well. Easy to do and cheap.

johnny c

Whoooo nelly!



If your overheating the system it’s not guaranteed to be the fluid’s shortcomings. The OP is running dot 4, if that’s generic auto-boys-parts-plus off the shelf stuff then yes switching over to some Castrol, PFC or motul fluid will help. The majority of times when I see fade it’s from a wrong pad selection. Using a low Tq pad that isn’t matched to the tire can lead to heat leaching into a system. Most of the time I can increase the Tq in a system and the pedal fell will return.

buying Brake fluid is like buying insurance.

Adam@Amp'dAutosport.com

What tires are you using?

k24556

Yea, sort out what is going on. Having lots of happy pedal is great, but having good brakes and lots of grip... even better!. Especially for those of us on the track with you.

Also make sure your reservoir is not over full. Last HPDE, a friend with a new C7 (Z51) had almost the same problem and removing a little fluid from the brake master reservoir cured his braking problem. Turned out with it was over full from the factory, when the fluid heated and expanded, it had no headspace in the reservoir, created a slight pressure on the brakes all the time and overheated the system. He also got some pad transfer on the rotor, so he had some pulsating when he braked.

StreetSpeed

Right. Which is why I said make a switch and see if it solves your issue. I didn't say "this is your issue, make a switch."

VThokies

I run PFC08 pads on the front, Carbotech XP10 rear. Motul RBF600 brake fluid. DBA 4000 slotted rotors front, stock on rear. No fade with my intermediate driving skill set.

Like others have posted, pedal to the floor is serious. What type of Dot 4 fluid are you running? Could you have accidentally introduced some air to the system when bleeding/flushing the brakes? Do the brakes feel any different during normal driving?

skdiablo

I'm running Motul 600. I believe it's the same temp as the Castrol SRF.

skdiablo

This is my thinking as well. I don't have proof obviously, but I doubt that I'm boiling the Motul. Pedal feel is solid and normal again at the start of the next session, so I'm not sure new fluid or bleeding would be the solution.

Regarding the pad choice...

the ST43's on my C6z51 would constantly trigger lock-up/ABS, but would never fade. Conversely, the same material on my C7z51 do not have that same lock-up tendency, but then overheat towards the end of the session. So you may be right about getting a more aggressive pad.

Is there a way to know if its the pads or the fluid overheating?

skdiablo

Tires are the OEM Michelin Pilot Supersports.

skdiablo

I'll definitely take a look at that. The fluid was flushed and filled with Motul 600, so its not the original fill from the factory. I'll check.

KNSBrakes

If pads fade - the pedal is still hard and the times I felt it it was as if the brakes stopped working. So hard pedal but no stopping

Fluid boiling is a pedal to the floor i.e. you cannot create pressure due to the fluid being a gas. The pads still work though

The hard part is if it's somewhat simultaneous.

skdiablo

I had the fluid flushed at a local shop. The pedal feels firm and braking is perfect for most of the session. Doesn't feel like it needs bleeding. Brakes also feel normal during city driving with OEM pads.

The pedal to the floor is not a sudden thing, but more of a gradual deterioration of the braking performance. With each lap, I'm forced to adjust my braking point earlier and earlier, but the car still stops and makes the apex.

skdiablo

I just spoke with Livermore Performance, and they told me the exact same thing about their experience. Pad fade would still maintain a hard pedal, whereas fluid fade would cause pedal to floor.

Sounds like that's the case for me.

I'm curious, if the fluid is overheating, how does it return to a firm pedal at the beginning of each session, without any bleeding?

skdiablo

Along those lines, what fluid do you guys recommend with a higher temperature rating than Motul RBF600?

KNSBrakes

It cools down and condenses back to a liquid. But that is bad for it and reduces it's temp range.

Castrol SRF is the gold standard of brake fluid.

Phillip123

Castrol SRF fluid works fine for me.

skdiablo

So the SRF and Motul have similar dry temp of 590. But the SRF has a waaaay better wet temp of 518 vs 420 for the Motul. I'll give it a try.