Jedi-Jurist

While I love my 2015 Z51, especially at the track, its one Achilles heel has always been the brakes. I've tried three different kinds of rotors, different pads, different fluid, but I have never been able to go a full session without a soft pedal and sometimes no pedal I've run the stock rotors with Carbotech pads (10/8s, then 12/10s), I ran (and cracked in one session) a pair of RaceBrake front rotors, then seemed to have more success with DBAs up front and stock rear rotos using the Carbotechs, but I still experienced a soft pedal after about 10-12 minutes. I was never actually able to complete a full HPDE session without having to take a cool down at some point to bring back the brakes.

So, I decided to try something new before throwing in the towel and upgrading to the larger Z06 brakes (which would require me to find new wheels to clear those calipers as the 18" Nurburgring wheels touch). I first rebuilt the front calipers (dust boots were completely toast), then changed the front rotors to KNS' private label version (called "4K") of the DBA T3 Club Spec 4000 Rotors I had been running up front. The 4Ks went at all 4 corners. They are the same as the 4000 Rotors but without any slots. Then I switched pads to Raybestos ST45's up front and ST43's in the rear. After installing everything, I flushed and replaced the Castrol SRF fluid.

This past Monday I had my chance to try out the setup at Mid-Ohio in about 95 degree heat. Finally, for the first time EVER, I never once had a hint of fade, and those pads grabbed HARD. I could go deeper into brake zones and shed speed like never before. The rotors held up great, and the max temp I read after each session was 450 up front and 350 in the rears, which for me is very cool. Ken was a big help over at KNS, and so was a guy over at Zeckhausen where I picked up the caliper repair kits.

And since , here you go.

BrunoTheMellow

So the rotors or the brake pads fixed it?

X25

For those who plan to use their cars for serious track, I'd still highly recommend the Z06 brakes instead. It costs about $1200, and works great with ample heat capacity; just make sure you have wheels that can clear it.

Jedi-Jurist

I'd say it was a combination of all the things mentioned, but probably the biggest factor was the pads, followed by the new rotors, fresh fluids and rebuilding the front calipers.

Jedi-Jurist

I had read your thread many times and was very tempted to go that route, but this was my last ditched attempt to solve the problem without also having to buy new track wheels. Do you happen to know if any TSW 18s clear without spacers? I like your CCW wheels, but they're pricey in comparison. I tried fitting mine over some Grand Sport brakes and that's how I know they don't clear (they are the Nürburgring style wheels). I still may eventually get there, but for now this seems to be doing the job.

X25

I think there are forum members who use TSW Interlagos at 18"x10.5" ET65 on all corners for their C7 Z06. I haven't tried it myself, so I can't guarantee it, but you can search for it. They're incredibly cheap, yet good quality!

BEZ06

There are two common brake problems at the track when you run OE brakes at the track and overheat them:

• Pad fade
  
• Soft brake pedal

Pad fade is firm pedal but little/no braking due to glazed pads - i.e., the pads are probably street pads that are operating way above their temperature zone when used at the track. The street brake compound is getting soft from overheating and not giving you any effective braking even though the pedal may be firm.

You say you are getting a "soft pedal and sometimes no pedal" - that's from boiling your brake fluid!!!

If your brake pedal is going to the floor, you need to flush in a good DOT 4 brake fluid with a high boiling point to solve that problem!!

Bottom line - a soft pedal is not pad fade, it's due to your brake fluid boiling. I recommend Motul RBF 600, or if you want what's arguably the best fluid out there (and about the most expensive) get what I've been using for the last couple years - Castrol SRF.

.

BrunoTheMellow

I run stock pads, stock rotors with rbf 600 and never get soft pedal. Just lose bite 10 minutes in and need to length my braking zone near the end of a 20 minute session going 9/10ths. My track is pretty light on brakes. No straights above 120 mph and plenty of no brake zones in between. I'll start doing track pads soon. But tracking 1 time a month and having to swap pads in and out each time is not attractive. I hate the squeal.

Jedi-Jurist

Yes, I had been using the Motul, but I still ended up boiling the fluid. Ever since switching to Castrol, no more fluid boiling, but until these last changes, I was getting a soft pedal on some of the more demanding tracks (Road America, Blackhawk).

I've since traded the Z51 for a Grand Sport, and those brakes are just SO much better than the Z51's, mostly because of the size of the rotor and front pads. Even with stock fluid at Gingerman, no fade whatsoever (only change was ST43 pads all around). Anyone else leave the stock brake fluid in on a Grand Sport? I was going to change to SRF for Road America, but kinda tempted to see what would happen with the stock stuff...

BEZ06

I recommend - CHANGE THE FLUID!!!!!!!

The stock DOT 3 is just NOT GOOD ENOUGH for serious track driving.

Flush in a good high boiling point fluid.

I've been looking for the specs on the stock GM DOT 3 used in our C7 Vettes, but haven't been able to find it.

However, DOT 3 specs require a minimum dry boiling point of 401°F and a wet boiling point of 284°F. The GM stuff meets at least those specs, and may have slightly higher boiling points, but it certainly isn't up to DOT 4 specs!!

Minimum DOT 4 boiling points are dry 446°F and wet 311°F.

That's still far below what you want when you're running a track event.

Take a look at the list on this website page:

https://www.lelandwest.com/brake-flu...ison-chart.cfm


The Motul RBF 600 that I used to use has a dry of 594° and a wet of 401°.

The Castrol SRF I've been using for the last few years has a dry of 608° and a wet of 518°.

You can see that the Motul RBF 600 has a wet point that's the same as the DOT 3 dry point spec.

And the Castrol SRF wet point is WAY above even DOT 4 min dry point spec!!!

So....DO NOT RUN A TRACK EVENT WITH STOCK GM DOT 3 FLUID!!!!

You might get away with it if it's your first ever HPDE, and you're just learning how to brake on a road course track, but I STRONGLY recommend that even first-timers flush in a good DOT 4 (or a DOT 3 with high boiling points).

Same with pads. The stock pads that come with Vettes that have cast iron rotors just can't handle the temps they'll see when braking hard and aggressively on the track. I strongly recommend that even first time track drivers slap in some good track pads when going to their first HPDE type track event.

There's not much worse than coming into the brake zone after a nice high speed run up a long straight and getting very little braking or none at all!!!

• Soft pedal, long pedal, or brake pedal that goes to the floor - you've boiled your fluid
  
  
• Firm brake pedal but little or no braking - pad "fade" from a street pad compound essentially melting from the high temp from braking at high speed and numerous times every lap

You don't want either of those things at the track, and stock fluid and pads just won't stand up to the braking you'll be doing on the track.

.

lv2jmp

I have a GS, brakes allow me to go deeeep into the corners, but I'm running SRF and stock pads. Thinking about Carbotechs for track day, but the OEM pads on the GS stop me as urgently as I want -- and the Carbotechs cost more than the OEM replacements. But as my lap times improve, I'm certain I'll change my tune.

Present best is a 2:37.xx at CoTA, with a consistent < 2:40 absent traffic. I'm working on bringing this down, but that is not too bad for a completely stock ride with only a fluid upgrade, and zero brake fade. I was getting a *touch* of pedal softness this last time (not something you want to feel as you're approaching the corner with some serious momentum); I'm told that stainless brake lines may fix this.

I be learnin'.

But the GS is a serious track beast. If only it had a bit more grunt on the straights....

BEZ06

Stainless brake hoses are WAY overrated!!! There's no problem at all with the stock hoses.

I don't know what you mean by "softness".

If your pedal is not firm, then you're boiling the fluid - but I don't suspect that if you're running SRF.

If your pedal is firm but you're getting "soft" braking, you're getting pad fade because you're overheating street pads with the temperatures they experience on the track. You essentially melt the compound and smear it on the rotor. Take a look at your rotors for uneven transfer layers of pad material - a good indication that you're probably over-temping the pads.

Like you said, little to no braking when you hit the brake zone is "not something you want to feel".


10 or 11 years ago I put SS brake hoses on my C6 Z06, and I never noticed any difference at all from the stock hoses.

Since then I just run the stock hoses on my C6 ZR1 and now my C7 Z06. They are excellent hoses and give me great braking effectiveness with excellent ability to modulate the brakes with absolutely no "softness".

Just MHO, but I like the stock hoses. YMMV!!

Bottom line - if you're running SRF and stock pads, the weak point in your brake system is the stock pads. I highly recommend you get some good track pads when running the track.

Dane@LGmotorsports

3 inch hose to the rotor 2 inch to the caliper. LG Motorsports parts are primarily products developed from the track, and Lou likes to brake late. This system along with better fluid/pads/rotors has been LG proof so far.

MitchAlsup

Are the air hoses delivering a cooling blast of air to the calipers and rotors?

Dane@LGmotorsports

Yes sir, carbon fiber duct attaches to factory inlet or replaces, plastic plastic duct on z51's and routes air directly to caliper/rotor.

G-ForceJunkie

Did you remove the rotor dust shields?

Dane@LGmotorsports

Yes we do.

LSRX

Very useful thread. Thanks guys!