just started doing some track days and my brakes are getting spongy and getting alot of vibration on high speed braking. i recently did a brake job, new rotors, pagid blue pads and new fluid. i already have ss lines. any ideas on how i can improve braking without braking the bank?

 

your pagid blues are good..... but you can do a lot better..

Pagid Yellow kick ****... now your vibration hmmmm... time to go back to the shop who did your brake work....

 

Vibration....pads are not bedded in fully yet.

I like Pagid but Hawk HT-10 are the bomb at the track but VERY noisy on the street.

 

A few questions:
Can you describe what you mean by "spongy" and "alot of vibration"?
Are the brakes spongy at the same time you get vibration? Or do you get sponge at a different time than vibration?
What tires are you running?
Do you engage ABS when you get the vibration?
Does PSM/PASM kick in (if you have it)?
Do you only get the vibration under "high speed braking" - which I interpret to mean threshold braking?
Are you getting vibration in the steering wheel, or vibration of the chassis? Is the back end shaking? Can you tell if it's all 4 corners, or just the front, or just the back?

Thanks,

-td

 

yes, the cheapest way is to change the way you apply the brakes; also the vibrations you feel may be due to the pickup (rubber and stuff) from the track that lands in the barrel of the wheel and stays there.

think additional wheel weights all over your wheels at random places.

try washing the wheels with a good brush; then drive the car again -- much of the vibration should go away -- if you are talking about wheel and tire vibration

 

by spongy i mean that they do not feel as firm as usual. the vibration comes through the wheel, didnt notice any vibration in the rear. seems to get worse as the brakes get hotter. not noticable during regular driving.

 

cleaned the wheels off, even had the fronts re- balanced just in case i had lost a weight. didnt help. the instuctor riding with me said that either the disks were warped or i was getting pad transfer. never heard of pad transfer before...

 

I'd bet the vibration is due ton uneven pad transfer.

You can try sanding them down a little with some garnet paper and then re-bed the pads.

Soft/spongy pedal sounds like you still have some air bubles in the lines/calipers.

 

uneven pad transfer is when material from the pads unevenly attaches to the disc in clumps -- it actually fuses to the disc material.

all of the suggestions could work, also you could just work through it next time you are at the track. really hard brake applications should help the problem correct itself somewhat.

how do you apply the brakes; hard and sudden with short pressure duration or do you apply less pressure for a longer duration?

the second method puts more heat into the brakes; if you are finding you are consistently having brake concerns, change the way you use the brakes - its the cheapest :-)

what group where you running with; where you had an instructor riding with you?

cheers!

 

i apply the brakes hard for a shorter period of time. i have been riding with an instuctor in the blue group, moving up to the green group next time. i've only done 2 de's. i have a friend that rents the track every oct so i have driven the track a few times without an instructor. never had an issue with brakes before the last 2 times.

 

What rotors are you using? I've seen people cook new OEM rotors in 1 track session. What brake fluid are you using? You should step up to Super Blue if you are using OEM. I also agree with the air bubble comment. Any vibration is almost always rotor related. Also, check the installation of the pads. It sounds like they may have been put on backwards. FYI...you should put between 100-200 easy-braking miles on the pads before tracking.

 

i have oem rotors. had about 1500 miles on them before the track, never had any vibration. rotors are under warranty so i can swap them out. my mechanic has a set of gt3 calipers i can buy cheap. i would need to buy gt3 rotors, maybe i should go that route?

 

You don't need GT3 rotors, even for the track. The stock 996 brakes are more than enough to lock up R-compound tires, much less streeties. Once you sort out your vibration, your car will be fine. IMO, upgrading brakes is one of the last things you do - after safety, seats, suspension, tires, diet, exhaust, and engine. [probably in that order as well].

-td

 

i re-read your posts and it sounds like you get the vibration through the wheel after the brakes/wheels/etc. get hot and this happens when you brake from high speed.

i had exactly the same issue; its a function of needing the pads to bed into the rotors -- as people have mentioned.

i thought I would need new rotors because the vibration was so bad it upset the car; I didn't get new rotors and the vibrations are gone for the most part -- definitely not as bad as they were.

keep driving with the set-up you have; over time pads/rotors should marry/bed to each other and your problems should diminish.

also if you can find a private road where you can do some higher speed stops, you might be able to help with the bedding process. i wouldn't recommend doing that on the street though.

let us know if that helps.

cheers!

 

i actually tried that on a couple of 100mph + runs, no luck. getting frustrated. getting back on the track in about 10 days so i need to resolve the problem. i'm actually getting some vibration now without the brakes even getting hot.