kermooni

I was training with the Porsche club on Fri. During the morning brake excercises, my brakes started to fade - bad - to the floor bad

Background: My car was back from the shop on Wed, brand new Z51 pads - fully bedded and flushed with 2 quarts of Castrol SRF. The BSS line were installed in April. Had no fading issues before - that I know of.

Any ideas why the brakes were fading? I have an event coming up on Oct 13 - 14 and want to avoid the fades.

AU N EGL

Your driving harder and braking harder, yet your still using the STOCK Z51 brake pads. They are aggressive street pads, not race pads.

You will need Race brake pads, PFC-01s, Wilwood H, Carbotech XP12 7 XP10 plus re flush your brake lines.

Cooling ( ZO6 brake duct extensions) will help too.

HTH
Tom

63Corvette

While I agree with Tom that you need a "race" pad, I think you have other issues here.

!) Fluid boiling issues usually result in "to the floor pedal" type fade.

2) Pad temperature fade usually results in a firm (hard) pedal, but the car doesn't stop because the temperature of the pad material is exceeded, and the result is a falling coefficient of friction for the pad material.

Complicating this is the fact that Castrol SRF is the best brake fluid made, and I have "never" heard of it boiling. Look for air in your lines, foreign material contamination (water) or something that has to do with the recent changes that you have made to your brake system.

Miaugi

I must agree with 63Corvette, there seems to be another issue. Did the shop remove your calipers for some reason, if so could they have re-installed them with the bleed screw down instead of up?

kermooni

Thanks for all the tips.

The guys at my shop are experienced "trackers". I doubt they would make such big mistakes. My brake pedals were rock hard after I got the car, so air is not an option. I am concerned about water in the fluid or having some old fluid left over. We did go through almost 2 containers (1.8 Liters to be specific). I can not imagine any other reason why the brake would become so "cushy".

Regarding brake cooling, LG's were ordered and delivered and supposed to be installed. Except they were a poor fit and needed cutting up of my car. My shop would not do it. When contacted, LG mentioned they were the C5 cooling ducts and their new C6 ones with a perfect fit for C6 will ship in a week - let's all hope.

Best.

John Shiels

z51 pads wouldn't take 4 hard stops in a row.

AU N EGL

I agree with John. We do believe you melted your stock Z51 brake pads, thus no stopping. and mushy brake feel

Bill Dearborn

You could have just tapered the pads. The caliper is the same one used on the C5 and pad taper definitely will lead to a pedal to the floor syndrome. I personally think it is more likely that you tapered the pads than boiled the fluid as the stock pad temps don't get hot enough to boil the fluid. On my 97 I ran stock pads for several years. Never boiled the fluid but tapered the hell out of the pads and usually had a long pedal by the end of the first day of an HPDE. Never got more than two days of track time from a set of stock pads due to the tapering.

Bill

0Randy@DRM

A z51 pad after 4 hard stops is making more heat then any race pad out there. SRF will boil in the caliper and cause a low or no pedal at all. It takes time to get the heat to transfer to the rest of the fuild.

Randy

Bill Dearborn

Randy,
My experience just didn't go that way. Before I realized pad taper was the problem I bled the brakes several times and the pedal never came back until the pads were replaced with new pads. The taper was so bad the dealer warrantied the pads as I only had 2500 miles on the car.

Bill

kermooni

Thanks for all the feedback guys.

This morning - first day of driving my car after the Fri event, I could press the brake pedal all the way to the floor

She is going to the shop next week to have the brakes inspected to determine what has caused the failure. I am headed to the track on Sat 13th, and Sun 14th so the brakes will have to be working.

Does anyone recommend a different pad to put on? Please note I have to drive this thing to the event and then back.

kermooni

How can I tell if the fluid has boiled in the caliper? When bled out, does the fluid have a different color? Texture?

02impactblue

When you say the pedal goes to the floor please explain in more detail. I find the c6 brake pedal will go to the floor with significant pressure when sitting with the car idling, but if you turn the car off and hit the brake pedal a few times to remove the boost does it go to the floor or is it solid? The corvette brake system is decent for the street and ok for the track until you really push the car on a heavy braking track. I have ran carbotech pads and have had good success until this past event at watkins glen. I went thru a brand new set of xp12's in 5 25 min sessions and the pedal felt good at the beginning of the session but as the heat built the pedal was getting longer and longer but would still stop good. Once it cooled down the pedal was normal again. Bleeding the system did nothing to fix this issue. BBK is in my future!

snitz

Above posts come from a number of members with extensive track experience; more so than myself. That said, having been in your shoes here's my experience.

Eventually, as you spend more time on the track your stock brake set up, even with proper fluid and pads starts to show it's limitations.

I finally bit the bullet and bought a set of Brembo GTs with Hawk Black pads this past Spring. The difference is huge. I don't get fade, drive with much more confidence, I don't blow through pads as frequently.....

Brembo's aren't cheap, but having the stopping power when you need it and keeping your ride on the track is worth something. Or put another way, road racing your car without having confidence in your brake set up can be an expensive proposition if/when something goes wrong.

Good luck which ever way you decide to go.

kermooni

Thanks. I tested the brake as you asked - engine off. The pedal was hard at first and rock hard after a couple of pumps.

- What brake fluid do you use at the track?
- Do you have cooling ducts? If so, which one?

02impactblue

I use motul 600 fluid flushed several times a year and bled prior to each event. I'm running the stock ducts at this point. I think cooling ducts should help reduce the heat soak fading that I'm experiencing. I haven't done to much to the car because I was planning on replacing it soon with a z06 and it will have a high quality brake kit on it before I hit the track.

99 C5 Coupe

Kermooni
A lesson learned with my C5 is if you plan to keep your car and track it for a few years bite the bullet and buy a good brake kit like the Brembo GT kit for your car. Brake cooling ducts, good brake pads and good brake fluid are still important. The OE brakes are only good up to a point and it sounds like you've crossed that line. If I would have upgraded my brakes right away when I started noticing problems, they would have paid for themselves once or twice by now.

AU N EGL

I have driven 25-30 some cars with BBKs. Most were one particular very popular model. Now remember braking ability has to more to do with the front tires, rubber compound for grip and width. Consistency of the braking ability is more related to experience of the driver and braking style not the brakes themselves.

That being said, I will stick with the stock PBR calipers, race pads, SRF and NAPA rotors for now.

I have liked the Wilwood and Stoptech set ups.

ghoffman

What budget can you allocate for this? I would also add the DRM stainless steel pistons in the calipers in addition to the SS lines, Wilwood H pads (for example) and good fluid. Eventually though, the slide rail cailpers have to go in favor of a "BBK". There are many choices, it depends on wheel clearance, budget, intended use, etc. I am happy to run through the options if you want, 603-682-8073.
Gary

John Shiels

Stock PBR calipers just don't cut it if you run the car hard for 20 minutes on most every track. There is no way they feel the same in the end of a session as the beginning unless you nurse them through, but what fun is that. Few sessions and you have pad taper which feels crappy and is costly in pads. JMHO