RacePro Engineering

C4 Racers or Autocrossers, we need a little help here.

For those of you using the J55 front brake kit, what Hawk Blue part number pad are you using?

If using some other aggressive bite pad, what is it (brand and p/n) , and perhaps I can cross-reference.

Thank you,
Ed LoPresti

The Bus

Hawk DTC70's

Sidney004

I believe the Hawk Blues are part number HB111E-610

My all time favorite is the Raybestos ST-43 part number R412

Bill Dearborn

Ed, for track duty I would use the DTC70s. For autocross I would use the HP Plus or GM Pads. When I had my white 86 I put the J55 brakes on the front and ran PFC 83 compund in the front and 80 compound in the rear. However, that was 15 (amazing) years ago and those were about the best pads you could get then. At places like the Glen that old 230 HP car would run out of steam at 124 mph at about the 600 ft on the back straight so I didn't need anything more than those brakes gave me. Didn't need to scrub a lot of speed. The 97 with 345 HP would peak out at 137 at the same place. Not sure where you will end up with your LT1 but I would expect it to be 130 to 135 if the engine is still stock so you will need to scrub 40 to 50 mph for the turn into the bus stop.

Bill

RacePro Engineering

Thanks Sidney,

I know the 111E-610 will work with the Baer calipers on the 12" rotors, but I thought a different P/N (size) might be required for the 13" rotors.

Actually, we have some used 111E-610 around. I should stop being so lazy and simply try a corner.

Ed

RacePro Engineering

Well, two authoritative votes for DTC70s. I guess I had better do my homework and find out about these.

Bill - I think it is very telling that, even as long as "15 (amazing) years ago", you were fine-tuning your front-to-rear brake bias with differing compounds. See you at the track in about a month!

Thanks,
Ed

ScaryFast

The "hot ticket" for the C5Z's is DTC70 front and DTC60 rear. I personally run DTC60's front and rear, easier to modulate without ABS. But I also have 4 piston aftermarket calipers and not J55's so take my results with a grain of salt.

RacePro Engineering

Scary,

Along with the other gentlemen who have been good enough to reply with actual experience from the track, I would never take any of your posts with the proverbial grain of salt.

As a matter of fact, we have a couple of used, slotted Wilwood 13" rotors and hats in the shop right now, that I am attempting to fit with the J55 calipers. Since the car has not yet turned a wheel on the track, I am reluctant to make too many chassis changes before it has a chance to tell us what it wants and needs.

Ed

RacePro Engineering

OK, Gentlemen, I think I have refined my question -

It appears so far that the later C4 "stock" calipers, and the J55s, can use the exact same pad. I am puzzling on why that is so, since the rotors are different diameters.

Is it just that on the 13" rotor, the pad contacts less of the swept surface? And if so, then is there an alternative pad that more fully utilizes the larger rotor?

Just trying to understand this better.
Ed

Rag Top

The only difference in the calipers is that the J55 has more room between the sides to allow for a thicker rotor. The brackets move the caliper out to allow it to clear the larger diameter rotor. If anyone has ever found a different pad, I have not heard of it. The problem would be that the pad would not be supported evenly by the caliper.

BTW, if you decide not to use those Wilwoods, I am in the market.

RacePro Engineering

Michael,

That makes a lot of sense - thank you.

Ed