MongoZ06

My car is 2004 Z06 with a little over 100K miles on it. I do a handful of HPDE/DE's a year and have noticed a slight deterioration in the quality of brakes both on the track and on the street. Even after putting fresh seals in and completely fresh fluid the pedal feels a bit soft and has a little longer travel than years past. On the track it doesn't seem to stop as good as it did just a couple years ago even with track pads, the soft pedal and longer travel become more noticeable or worse with each run.

I can't find any leaks anywhere and all bolts/nuts are tight.

As these are the original calipers could I be looking at fatigue from track use and possible spreading? Could the Master Cylinder need replacing?

moose.b3

Have you changed your rubber brake lines yet? Maybe they have deteriorated.

ScaryFast

While the C5 calipers are known to start spreading, this sounds a bit more like a MC issue to me. Lucky for you, both are cheap and easy to change...I have heard a lot of people use the Raybestos OEM replacement MC with good results.

If you get calipers, upgrade to C6 as they are slightly stiffer and no more expensive.

I am never a proponent of throwing new parts at an issue until I have determined with high confidence what the cause is, but in this case, not only will it be difficult to determine if you calipers are spreading when hot or your MC seals are deteriorating, but anything braking related is paramount on a race track and changing a 100k mile MC is a smart move either way.

mgarfias

Yes. It is time to replace the stock calipers. But it was time when the car rolled off the line.

MongoZ06

Rubber lines were changed to Russell Braided steel lines about 4 or 5 years ago and I see no cuts, tears or bulges either.

Joshboody

I'm in the same situation with 100k... pedal just doesn't seem to be as hard as it should be. Bleed often, no leaks, some slight longitudinal taper. Mostly a track car with limit street driving, so just thought that I don't give it enough time to eliminate the taper.

Wouldn't hurt to change the MC at $100.

Edit: if do change calipers good option seems to be new WW bolt-ons at $620ish for the pair. Just noticed these.

MongoZ06

I noticed those Wiilwoods too and wondered how well they might hold up as an "upgrade" from stock.

0Anthony @ LGMotorsports

Typically when the pedal doesn't "stay" firm then it is time. You can have a buddy check to see if the caliper is speading a lot when you depress the pedal too. There will be some movement there but if it is excessive then it is going to lead to a soft pedal.

Of course with that mileage on it and that time, if the master has that much time on it...you can't rule anything out.

CHJ In Virginia

Two things to consider 1) caliper spread and 2) wheel bearing / hub wear.
Check caliper spread with an inside dial micrometer. Measure at the top and bottom of the caliper opening. Any difference more than 20 - 30/1000's and they are trash.
Worn wheel bearings / hubs will allow the rotor to move back and forth pushing the pistons back into the bores causing a long pedal. At 100K, if you are tracking the car, you are way beyond the point that the hubs should be replaced. Spend the extra $ and get the SKF race hubs. Your brakes will appreciate it.

johnny c

things to check.
- a old worn rotor can get hot, distort and make the pedal feel "long", worn hubs can do the same.

- how old is your fluid? old fluid that goes threw heat cycles will loose it's compress-ability. race fluid get "old" faster then dot 3

- as you start to drive faster you transfer from WOT to braking faster. make a mental note and think if what your feeling is the vacuum assist starting to work.

Generally it's time to replace the caliper when it's damaged or when it can no longer retract pistons fully. this makes a lot of drag and you can tell with rotor temps.

LateBreak

This was my guess, the wheel bearings are probably shot. You'd be surprised at how much a single bad bearing can affect the pedal too, I had brand new bearings on the front but my RR was bad and the pedal went almost all the way to the floor on the track. Pretty spooky. As was suggested, get the SKF racing bearings when you replace hubs.

Joshboody

My soft-ish pedal (very slight) is when sitting. I think it's pad taper, which I'm starting to track thickness. Measuring the caliper is a good idea, but suspect hot vs cold may have a diff.

I think with bad MC you would have a leak... has to go somewhere unless can get back to res.

I also use speed bleeders (cheap ones) and may change to pressure to see any diff.

StreetSpeed

How about you're now going too fast for the stock system? I had nothing but problems with the brakes when I first got my car. Switched to an AP kit, not a single brake related issue in the last 3 years.

MongoZ06

I may just go ahead and replace the MC since i can do that for $100 and see how it feels then. A few of you may be right and its just the seals are worn out in it.

After that we'll look at the higher dollar fixes.

I'll check the hubs for play as well this weekend to see if 1 or more is bad.

As much as i would like to upgrade to a bbk its just outside of my budget at the moment especially with the fact that i would have to most likely get new wheels or run spacers. It is on the list of to-dos at some point but if im going go spend that kind of money Id rather do a Skip Barber or Bondurant school first before spending that kind of money on parts

FASTFATBOY

If the pads are taper wearing the calipers are spread.

If you put in a new set of pads, can you grab to top of the caliper with your hand and slip it back and forth easily? If so, the caliper is spread open.

REVHARD

I went about 25 HPDE days before I finally switched to the newer C6 base units with DRM pistons. I had soft pedal issues even with fresh pads and bleed. The new calipers fixed all my issues and the DRM pistons keep the pedal firm to nearly the end of the second day of my HPDE weekend without bleeding.

Supercharged111

Has anyone ever gotten a soft/long pedal from the ABS pump? It's notorious for such a thing in my truck, which is nice and dumb, so I removed it.

johnny c

i can get a stock system to perform like a BBK for one stop. that means balance it and get the tires to the limit. What a BBK gives you is consistency and longevity.
so you never really get too fast for one system or another. it's more like your tired of replacing cracked rotors and blowing threw pads all the time. a BBK should have a better caliper for more feel.

cliff notes. investing in a brake kit should bring operating costs down.

check the run out on the rotors first. hate to see you go threw all the trouble and spend money replacing good parts. a line pressure gauge would be a good idea too.

Joshboody

What if air was introduced upstream of ABS... like res running dry or even removing MC. Would you need a Tech 2?

FASTFATBOY

No,

Bleed like any old system, start at the the wheel furthest away from master cylinder(RR) and work your way to it.

If I replace the MC, I always bench bleed first. Then bleed the lines at the master cylinder just like you do the wheels. Crack the line at the MC have someone push the pedal down SLOOOOW, when the pedal is on the floor, close the line and repeat.

I use a bleed bottle, open the bleeder at the wheels and pump the pedal slooooow, even let it up sloooow until the fluid is clear, close the bleeder and move on.

I never pump the pedal fast, or pump it then crack a line or bleeder. It turns nice big air bubbles that are easy to get out into thousands of little bubbles that are hard to get out.