Brakes aren't the same..

[j0oftheworld]

I've noticed over the last few track days my breaks constantly need to be pumped up before the pedal is firm.
This is cold and hot.
Fluid is fresh, pins were just lubed, pads are 50%, ABS was still kicking in @ last nights event..
Not sure why my pedal won't firm up top unless I pump it...

Ideas?

Thanks!

[MR 325]

Sounds like a failing master cylinder to me. Unless something is leaking fluid.

[j0oftheworld]

No fluid loss and it's bled 10+ pumps/wheel between each event..
It's an M50 swapped car.

[lateracer]

Failing MC won't necessarily leak fluid. Mine had same symptoms. Dead.

[nando]

50% pads could be toast too (glazed/overheated).

poor pads can make the pedal feel vague and very mushy.

[j0oftheworld]

I'll take a look at the pads.. they're HT-10's and didnt think I could overheat them. I ran Blues on my SpecMiata but seems like they were a little more "serious" so I may have overheated them!? Good point!
The PO did the swap and was my understanding all the brake components were new.
Guess I should get a new one. Was just running our track that has a drag strip as the main straight.. almost 2/3 mile and I was hitting 120+ :o :)

[nando]

you can definitely overheat them. I lost my brakes right after I got a point by from a Skyline.. I was so happy to have passed him, then I cooked my HT-10s coming off a 100mph straight, and had to let them pass me again. they came back but I went easier on them afterwards.

then again, if you are tracking a car with a 20 year old MC you should probably replace it anyway. But I thought mine was bad, bought a new one, then swapped pads and found out it was my shitty pads (Hawk HPS, never again!).

[jlevie]

If you have brakes, but just a slightly low pedal, and a single pump on the brakes brings the pedal back to normal, you may be seeing knock-back of the caliper pistons. On a track car that can be caused by worn track pads and/or slightly warped rotors, etc. When I experience that my first action is to make sure that there's not a leak at the lines or calipers and then to replace the pads and rotors. If I still have the problem I'll rebuild all of the calipers and install fresh guide bushings. If the problem persists after that, replace the master cylinder with a new (not rebuilt) unit.