Brake options for Corvette C4 85-87 Hubs

#1
Been looking at upgrading the brakes on my DRB GT40 which runs standard 85-87 Corvette hubs. It's running stock Corvette brakes at the moment. Looking for reasonably economical ways to do this.

Lots of kits only seem to fit C4 models from 88 onwards.

Would like to do front and rear. Would like handbrake to still work, even though I don't use it.

Using new Ford GT as guide to determine proportions of front brake to back brake system. Although I don't know thicknesses of rotors, I expect the rear rotors will be thinner than the front. If anyone knows any more details like piston sizes, caliper area, rotor thickness/design, it would be interesting to know. Ford GT brake specs as I know them: 4 piston monoblock Brembo calipers, 356mm front, 335mm rear cross-drilled/slotted vented rotors.


My requirements:

1. If I'm going to do upgrade, might as well get serious.
2. Want something that can be DOT(engineer) approved. Well hopefully.
3. Must fit under 17" or 18" wheels.
4. Will be adding Tilton or Wilwood pedal box so I can get adjustable bias and master cyl. size correct for calipers.
5. Will be club raced and perform in a variety of events - Sprints, Motorkhanas, Go-To-Whoa, Drags etc.
6. Looks are also important. And to fill the Bling, Bling wheels. Some of sizes below are more for looks anyway. (Hey, I'll admin to that)
7. Wheel offset change isn't important as I haven't ordered my new wheels yet.
8. Budget limit is US$2500 for each end, would prefer less. Lots of other choices after US$2500 for serious brake upgrades.


This is what I've been able to come up with for front for bolt on kit(pads included):

1. Around US$800. There are lots of upgrades to Corvette C5 spec. 2 piston PBR Caliper, 300mm x 32mm rotors. Baer seems to be the biggest brand with this offering. (I really want more than this)

2. US$2400. Brembo Big Brake Kit. Brembo Lotus 4 Piston Caliper(2x36/40mm pistons), 2 piece 328mm x 28mm directional curve vein rotors. 54.2cm squared pad area. Stuck with Brembo for replacement parts, not available local. More info here.

3. US$2170. Porsche 993 turbo brake conversion. Brembo 993 Calipers(2x36/44mm pistons), 2 piece 322mm x 32mm directional curve vein rotors. 76.6cm suared pad area. Expensive replacement parts, but available local. More info here.

4. US$1100-$2200. (I expect not approvable, but good value) Wilwood 4 piston calipers, 1 piece 330mm x 28mm rotors. Through to Wilwood 6 piston calipers, 2 piece 355mm x 35mm rotors. Replacement Wilwood parts available cheaply here as well. More info here.

5. US$??? I can pick up new Porsche 996 GT3 calipers and rotors here in Aus for a good price. Need to manufacture/obtain hat & caliper adaptors though. Calipers are 4 piston monoblock(36/44mm) US$479. Rotors are 330mm x 34mm directional curve vein rotors US$147ea. OEM pads are $US111 This would leave US$1200 for manufacturing hats/adaptors and kit would cost the same as landed 993 kit above. All replacement parts would be cheaper. Gee I wonder how close those 993 hat adaptors are to fitting 996 and I can buy them separately.


For rear I don't have many bolt on options(pads included).

1. US$1949-$2369. (I expect not approvable, but good value) Wilwood 4 piston calipers, 1 piece 330mm x 22mm rotors through to 2 piece 355mm x 32mm. All kits include emergency brake(some sort of mechanical spot caliper I assume) More info here.

2. US$2170??? + handbrake cost. Porsche 993 turbo brake conversion. I would have to source or get fabricated caliper adaptors. Brembo 993 Calipers(2x36/44mm pistons), 2 piece 322mm x 32mm directional curve vein rotors. 76.6cm suared pad area. Expensive replacement parts, but available local. Have to work out handbrake??? More info here.

3. US$??? + handbrake cost. I can pick up new Porsche 996 GT3 calipers and rotors here in Aus for a good price. Need to manufacture/obtain hat & caliper adaptors though. Calipers are 4 piston monoblock(36/44mm) US$479. Rotors are 330mm x 34mm directional curve vein rotors US$147ea. OEM pads are $US111 This would leave US$1200 for manufacturing hats/adaptors and kit would cost the same as landed 993 kit above. All replacement parts would be cheaper. Gee I wonder how close those 993 hat adaptors are to fitting 996 and I can buy them separately. And I have to work out a handbrake.

4. Oops, ran out of choices already. /ubbthreads/images/graemlins/frown.gif


I'm really tending towards using either Porsche 993 or 996 calipers and rotors. I can even get custom caliper decals made for them. /ubbthreads/images/graemlins/smile.gif

Decisions, decisions... Any advice guys? /ubbthreads/images/graemlins/confused.gif /ubbthreads/images/graemlins/confused.gif /ubbthreads/images/graemlins/confused.gif
 
#3
Thanks Mike, I did check out SSBC. They only list 2 piston PBR option for fronts to suit 85-87. They have a good value 4 piston option with 330x28mm 1 piece rotors for 88 onwards...hmm...US$1360 Even DOT approved. /ubbthreads/images/graemlins/smile.gif Maybe I should contact them to see if they can do something for me on older C4 gear. /ubbthreads/images/graemlins/smile.gif
 
#4
Craig if you wish to have a little bit of creative enginering and source calipers from a porsche etc there is a 330 dia rotor listed for C4 Corvettes listed in the DBA website. I have a pair of these for my DRB under construction but I found the lest expensive were from Rotors & Drums Australia. These are directional curved and almost two thirds the price of DBA rotors. Part Number RDA 7736 and RDA 7737.
For the rear I am using BMW E46 330I coupe rotor these are 320 dia and 22 mm thich and have a internal handbrake drum with the same wheel stud pattern as a corvette. I am machining my own hub but I would be worth the look to se if this rotor will fit on a Corvette rear hub assembly, these were only about $80 each from my local BMW dealer. I have not decided on a front capiper but am concidering using R32 front Skyline calipers on the rear, can be picked up for about $200 a pair grom importers.

Hope this may help
Darrell DRB chassis no 46
 
#5
Thanks Darrell, some great info there. I think I might owe you a beer or two. /ubbthreads/images/graemlins/smile.gif

Checked out DBA 330mm rotors but were pretty expensive from memory(AU$300+). I've heard of RDA, but didn't think they would be much cheaper and wouldn't dream they would be curved vein. Wow. /ubbthreads/images/graemlins/shocked.gif

Searched the net looking for larger rotors that might fit the rear drum handbrake. No luck. And I thought that it was just going to be too hard. I'll look into BMW ones as they are cheap as. Not too worried about adapting something for handbrake.

This sort of engineering is beyond me, but have a good Cobra guy here with great engineering skills and plenty of experience with custom brake conversions.

Not sure how much you know about Skyline stuff, so I'll put down what I know and maybe it will be useful. Used R32 Skyline GTR rotors & calipers on last Cobra kit(track car). It even runs the factory Nissan directional curved vein drilled rotors. Just be careful as there is different types of calipers, even within R32 family. R32 GTST/GTS-4 run 280mm rotors and are thinner, 28mm from memory. GTST/GTS-4 front calipers have shallow ribs over them, so easy to spot. R32 GTR have 296mm x 32mm rotors, these calipers have a smooth finish(no ribs) and can fit over 320mm rotors. You will just need to make some shims up for behind the pads for thinner BMW 22mm rotors. Guys have grooved GTST calpers though to fit up to 330mm rotors. R33 calipers are same as R32 GTR calipers. Also from memory the DBA webite is confusing in it's rotor sizes for Skylines.
 
#9
Ian, Baer only list 2 piston upgrades for 85-87 Corvette. The bigger kits are for later 88-. I emailed Baer a few months back about any larger kits available for 85-87 and they didn't get back to me. Anyone know any more than this? I'm still sitting at Porsche 993 setup and now being tempted by making a system up using cheap 1 piece rotors that Darrell pointed out.
 
#10
Be careful fitting spacers behind pads as the pad can sometimes come out of the keeper slots when the pads are almost worn out (very bad). I would split the caliper and mill them to be the correct with for the pads I am using, just a thought. If you need some more info on BMW rear rotors or anything else I could email you a cross sectional veiw of them with dimentions.

Darrell
 
#11
Craig

The 84/87 and 88+ Vettes use the same ball joints and
bearings. The A-arms and spindles are slightly different,
but you MAY be able to use 1988+ spindles with your 84/87
A-arms to mount the kits designed around the 1988+ Vette.
Baer should be able to answer that question.

Converting the rear from 84/87 to 88+ is super simple....
just need a small spacer ring and the 88+ brake parts.

MikeD
 
#12
Thanks Mike, I searched here and on the web, but wasn't able to find out what the differences were between early C4 and later C4 models.

No simple job for me to get the vette parts in Aussie land. But it is another option. Rear is the most tempting to convert. Some companies offer C5 conversion as well, not sure if that will be a problem to fit to GT40 uprights though.

Now I've got more options. /ubbthreads/images/graemlins/confused.gif
 
#13
Craig

If you decide to pursue C4 stuff further, let me know and
I'll see what 88+ spindles will cost. They shouldn't be
hard to find in the US.
Regards

MikeD
 
#15
Hi Craig - any further progress on the upgraded Vette brakes decision ?

Bill Bayard is starting to think along similar lines & I might also do it in the future.

Kind Regards,

Peter D.
 
#16
Can't help on any 'vette stuff, but I am using Brembo monobloc calipers and porsche GT3 380x32mm steel disks on an Audi, and they fit under 18" wheels /ubbthreads/images/graemlins/smile.gif
The offset is the thing to watch, as the clearance to the wheel spokes is very tight.

The disks are bolted to alloy bells using porsche T nuts and bolts, so presumably you could simply get the bells machined locally to fit your bolt pattern and desired offset.

For the Audi guys, these come from a company called 'Movit' in Germany. They are somehow affiliated to Porsche & Audi, not quite sure how though.

I have the part numbers for the disks, T nuts, bolts, and calipers somewhere if your interested.

Also, other Audi owners are now using the 6 pot calipers with 360mm disks, which Movit claim are just as good.

Cheers,
John.
 
#17
Wilwood does make a rear rotor with hat that is made to fit a corvette. They also make a two piece rotor/hat combo to fit a corvette. These use the corvette e-brake parts and has a drum brake inside the hat just like the corvette.

This way you would be able to run any 7inch diameter X 8 hole rotor bolt pattern. This will allow you to run a lot of different rotors. You could then select a different brand caliper if you don't like wilwoods. If I was doing mine again I would use the forged superlight 3 caliper from wilwood on all four corners and 13" X 1 1/4" up front and 11 3/4" X 1" on the rears.

I left the e brake off my car. Not worth the extra hassel and cost. Also the little spot calipers have been known to slip on sloped driveways. Beware these little go cart calpiers.
 

New Member
#18
Craig,

""7. Wheel offset change isn't important as I haven't ordered my new wheels yet.""

Concur with John on this point.

""The offset is the thing to watch, as the clearance to the wheel spokes is very tight.""

More specifically the clearance from the outboard side of the caliper to the backside of the wheel center. Technically though this isn't directly related to wheel offset. Typically the Vette stuff has little clearance in this area because they use floating calipers with no outboard pistons.

I compromised with smaller calipers than originally desired (Wilwood's). There's only two ways to gain clearance. Find a wheel which has some offset between the wheel hub face and the wheel center section. Or use a rotor that's offset more to the inboard side. This runs into clearance issues to the upright depending how close it already is with the stock Vette rotor. You could use a spacer at the wheel hub but I don't thing this is DOT legal.
 
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