vt951

In a DE this weekend, my front driver side caliper was sticking (not immediately retracting when I took my foot off the pedal). It was intermittent, but it happened enough that it was a bit disconcerting when it locked up going 120 mph and getting ready to turn-in!

Another symptom (not sure if it's related): After one of the sessions, when I was pulling into my parking spot, the brake pedal went completely to the floor, but brake pressure returned after I pumped the pedal a few times. This only happened once all weekend, and I didn't notice any change in braking in later sessions (pretty sure the front left caliper was still sticking intermittently).

Does this typically mean the caliper needs to be rebuilt? Or just cleaned/flushed? Or replaced? Or could it be something goofy like uneven tire pressures causing it?

rlm328

You got ABS?

vt951

No ABS. It's an 86 with stock 951 calipers. I was running Hawk HP+ pads all around.

jerome951

Did you verify the sticking by observing more pad wear on 1 caliper or 1 pad within the caliper? If so, sounds like either the calipers need to be rebuilt or you have some gunk in there partially clogging one of the lines.

vt951

Nope, haven't checked that yet. That's a good idea. So, just to clarify, if both pads are "over-worn" equally, then it could be something in the line. If only one pad is "over-worn", then it is more likely a stuck piston. I'll swap out the pads and see if I can tell.

Trucho-951

I would recommend rebuilding the calipers, it would be a great way to ensure thorough cleaning out the insides. Hopefully you can get away with only replacing the piston seals, that is, if the pistons are nice and smooth. I rebuilt my calipers earlier this year and did not touch the "scraper rings" left those in place. I just cleaned them up with brake fluid. As I'm sure you are aware, with age and high temps, the piston seals loose some of their elasticity and the pistons do not retract as much as they should after releasing the brake pedal. Even if the seals are not as stiff as to cause the calipers to stick, they still tend to overheat the pads. So from that perspective, it's a good idea to get fresh seals in there and help keep your brakes from overheating.

Say on the brake pads, I've used Hawk HT-10's up front and Hawk Blue for the rear with good success. This past weekend I was using the Hawk (Dynamic Torque Control) DTC-70's. This is Hawk's newest racing compound, easy on rotors and awesome stopping power. But they are too grabby, so I'm thinking of dropping down to DTC-60's next time. Of course. it goes without saying that with aggressive brakes you need wide sticky tires, otherwise you may not have the grip to prevent locking up.

vt951

Good point about the wide sticky tires. I'm only running 225 width Falken Azenis RT-615 up front, so maybe if I had wider r-compounds, this wouldn't be an issue. However, this was my 6th track day on those tires, and I never had a problem with locking up before.

Phil R

you found the dtc-70 easy to modulate? I remember those things being an on off switch much like the hawk ht-10

vt951

Sorry, I'm not sure what the dtc-70 is. Is that a model number for the Hawk HP Plus? If so, yes, they feel great to me. Very good modulation and no fade whatsoever (at my novice to intermediate level of driving). I have never used full race pads, though.

EDIT: never mind... I'm getting lost in my own thread... looks like you were asking trucho, not me.

hp18racer

Last track event last year I was having problems with boiling fluid. Rebuilt my brakes with seals only from Stop Tech. 1st track event this year the car was wildly unstable on the brakes. Pulled to one side or another, lock ups at random. Rebuilt my brakes again with a brembo kit that included pistons, rings and grease for assembly. Brakes work perfect now.

Trucho-951

Nope, i did not say that. I found the DTC-70 are too grabby on my '86. The HT-10 pads, however, I found very easy to modulate.

xsboost90

sounds like

1. - you need to re-flush your brake fluid its prob. boiled from the track

2. - you need some new brake lines if they are not new already- they get old and collapse on the inside, causing them to act like a check valve- high pressure from the master cylinder pushes the fluid to the brake caliper but then does not have enough pressure to push itself back and causes one caliper or more to stick.

vt951

Thanks Dan. I'll start there (new lines and flush).