jpobrien

A couple of years ago, I started doing HDPEs at Mid-Ohio and Putnam with my 92 LT1.

I have recently upgraded my C4 to C5 front brakes (Vette Brakes and Products kit), and have been running the Hawk HP+ pads. I seem to have a problem with the fronts causing a "long" and "soft" pedal. I put the new pads on the morning of my last track event, bed them in, let them cool, and then the first time I really used the brakes at the end of the front straight at Putnam, the pedal went long and soft, and never came back until back home (slower street driving). They also (still) produce a grinding type of noise.

At the track, I noticed that the brake dust on both sides of the front seemed to be more like brake flakes.

Would the pad taper issue still put a lot of heat into the brakes? I am getting caliper temps between 450 and 500 F. I run ATE super blue fluid, which I flushed with my power bleeder at the track (no difference).

I don't think it is the master cylinder, as it tends to hold pressure pretty well, and the ABS seems to be working properly - mostly because the backs start to lock up, as the fronts are probably glazed over from the heat.

A friend suggested that the vacuum may be too much with my 383 engine conversion, but I tested that and no reading above 21 inHg vac.

I'm thinking of puting a vacuum relief valve on to limit the vacuum to 17-18 inHg for a more consistant feel to the power boost (I don't think that will solve the real problem though).

Any ideas?

Gray Ghost GS

Bill Dearborn

Can't comment on long and soft. Pad taper gave me a long pedal every time I went to the track with the stock calipers. Didn't matter what type of brake fluid as the fluid could be bled and the pedal would still be long. On the second day of an event the brake pedal would go almost all the way to the floor. However, a quick double pump of the pedal and I would have a high firm pedal. Just took a little more planning when approaching a turn. When I was using stock C5 pads the long pedal would gradually go away after a few weeks of easy driving on the street and highway.

Bill

STEVEN13

Hi,

Do you run the stock master? I have heard here on the forum that with the larger diameter pistons in the C5 calipers it may require a master to compensate. Makes sense as it all has to work together.

This is the reason (with my 1992) I upgraded with the GS calipers instead.

Steve

WNDOPDLR

My track car is an 88 with a 383 and C5 conversion on the front brakes. Pedal is short and rock solid. I run either ATE blue or Motul for fluid. Pads are Wilwood H. My stock MC and booster work well with the conversion. What kind of rotors are you running. I am concerned and confused by your description of "brake flakes". You swapped brake pads just before the event and may have had residual build up from the street pads on your rotors. I am not familiar with Hawk pads other than name, but could the harder pads be cleaning the old residue from the rotors causing diminished performance and the deposits you see on the wheels? Tell us more. Someone here should be able to help.

jpobrien

The rotors are the cryo'd sport rotors that came in the Vette Brakes and Products package. I'm not sure the actual brand. One of the problems that I had was that they were not labeled for L or R (like they were supposed to be). I have run them both ways, and it seems that maybe the slots could be going the wrong way now, and grinding off the pad material - hence the flakes. I personally think they are on backwards now - from my assumptions about how the air should flow in the vanes between the rotor surfaces. If anyone is familiar with fan wheels, I believe it should oriented as a backward inclined wheel - rather than a forward curved fan wheel.

I have only used the Hawk HP+ (only 2 sets at this point), no street pads.

One think that I've been thinking is HP+ is too low of a heat range for as hard as I'm braking (causing the soft pedal), and pad taper (causing the long pedal). I've thought about going up two grades to Hawk Blue pads, which have an operating temp from (I think) 250 - 1000 F. I don't know what the HP+ temp range is, but I know it is less than that. Maybe they are glazing over.

Is there anything I can do about the pad taper? If not, that really bothers me - on a new "upgrade".

TRACKMAN2

had the same problem with the car at left>>> went to c 5 callipers and wouldnt stop... there is a simple mod you can do to solve this .. it really works it breaks like a beast now... teck guys back me up on the details its been a long time
step one remove the 2 bolts holding the master on
step two there is a little hikie sticking out of the break boster grab it ..
step three with a needle nose vise grip grab the little hikkie amd unscrew the shaft that comes out of it @ 2 or three turns,
replace test and repeat .. i reaolize my tech talk is lacking but it really works in about 2 hours and suprizingly few cus words she works like a dream....... there was a more detailed post years ago mabe someone could find it for you,,, slots face bacwards like sawblades .. try willwood h doug @ ecs sells them best money you will ever spend.. btw keep those bolts tight on the adapter brackes check often they walk on you...

jpobrien

TRACKMAN2,

Thanks for the procedure. I'll look into that.

One question on your car - are you directly connected with ram air from your front license plate hole to the filter, or is it just letting more air into the engine compartment (right in front of the filter)? I'm thinking about doing something similar.

TRACKMAN2

at first it was kind of a ram air set up, but with constant overheating problems (even with a 3 thousand dollar ron davis rad setup) i ditched the air box for a three banger air filter from mid america and cut a huge hole in thr front of the rad cover i cut everything i could out of the front and added the big mouth front from aci. almost the entire front of the rad is expozed to race air and havent had an over heating issue scince .....get the aci big mout thingy its cool and works well but has suprizingly stupid air ducts i added my own for break ducts and love it plenty of preformance and lots of grownd clearence...

Aardwolf

Mine is similar with air. I cut the filter lid and bent it into a scoop shape for air coming in. I also cut the cowl seal and took the underhood lights out and drilled holes in the hood shroud at the windshield.

Good tip with the brake booster rod, it sounds to me like that may be the problem.

The rod sticks out from the booster and should have 1/16-1/8" or so clearance to the back of the M/C. I used a small L shaped piece of metal to measure this, witch I marked the depth of the M/C on the metal with a marker. Note you cannot measure the total depth of this as it is very narrow, the rod is blunt and does not go that far. So note this and measure up on the slope in the M/C. I ended up having the rod turned all the way in to get clearance. The pedal is now good! Did you have to double pump the brakes for pressure? That was one the symptoms mine.

jpobrien

Double pump does not seem to help. The more I think about it, the more I think the front pads get glazed and just stop working. I have noticed that, if I do engage the antilock, it is the back that is starting to lock up.

I have read some more about brake pads on other threads, and I think I'm going to try Carbotech 12s/10s with cheap $20 rotors and see what that gives me.

I will definitely see if the booster rod clearance is having any affect as well.

Aardwolf

Sounds good. You may be able to clear the glaze though with acetone and garnet paper (sand paper) as something to try. Is there any tread difference front to back? When the booster rod was to long with my car the back pads wore real fast to.

jpobrien

Back pad wear is relatively normal - considering most of the braking is being done with them - I don't think they are dragging.