Just what the subject line says.

Watcha got?


Larry

he has a site, just check it out.

Rob

Fieroguru doesn't sell a 12" c4 rotor version of that swap on 88 cars. Shoot me a PM, I carry those adapters.

Guru has the 13" brake upgrade for the 88's.

Great upgrade for the 88 - with none of the problems associated with the 12" Corvette rotors.

quote Originally posted by olejoedad: Guru has the 13" brake upgrade for the 88's. Great upgrade for the 88 - with none of the problems associated with the 12" Corvette rotors.

What are the problems with the 12" Corvette rotors. WCF claims there are no problems

quote Originally posted by Lurate: What are the problems with the 12" Corvette rotors. WCF claims there are no problems

There is a large probability that the tips of the lower control arms may contact the backs of the rotors. It is pretty much a certainty if the car has been lowered at all, or even when the stock suspension is compressed.
Also, due to geometry, it is not compatible with lowering ball joints of any sort. (Can't grind the LCAs enough to provide enough clearance.)

Edit - With all of that said, I have Corvette rotors on one of my 88s. I just "clearanced" the tips of the control arms.
Since they were already off the car, to have bushings and balljoints replaced, it was not a big deal.

[This message has been edited by Raydar (edited 10-02-2020).]

I am definitely having problems with mine. I have some lowering springs from Fiero Store (which they no longer list for sale) and the WCF Corvette brake setup. I lost substantial amount of turning radius and getting some unholy sounding impingement in the front. WCF suggested switching the left and right calipers to get more clearance. Do you think some adapters to put the stock 88 calipers on the 12" rotors would solve the problem? I really like the lightweight 2 piece 12" rotors.

There are 2 known areas of interference. One applies to all C4 rotors kit on the 88s (lower A-arm issue), the second one is specific the the WCF bracket design:

Nose of Lower A-arm to backside of rotor:



Caliper sliders to upper a-arm:

I agree that lowering ball joints and C4 rear rotors do have an interference issue. Be sure to check the clearances before you re-install the springs. Mount the A-arms and use a jack to push the arm up to the upper stop. Then rotate the steering to full limits. I found that the largest interference was on the rear part of the lower arm when the tire is turned in at the back.

It took considerable grinding to make it all go away. I also spaced the hubs out 1/16" from the trunnion. Any more and the brake pads don't want to fit when new. Rodney Dickman suggests that the lowering BJs be welded and I agree since they are taller and create more bending force on the press fitting. And removing metal from the arm does not help with strength either.

But in the end it all worked out well.

[QUOTE]Originally posted by fieroguru:

There are 2 known areas of interference. One applies to all C4 rotors kit on the 88s (lower A-arm issue)

Those are GREAT pics of the issue. Can you possibly estimate the maximum horizontal length of the interference: 1/4", 3/8", 1/2"?

Muchly appreciated if you can make that estimate!


Larry

Or just buy the 13" kit from guru and don't worry about fitment issues.

The 12" corvette rotor upgrade is obsolete.

Time Marches On.

quote Originally posted by imacflier: Can you possibly estimate the maximum horizontal length of the interference: 1/4", 3/8", 1/2"? Muchly appreciated if you can make that estimate! Larry

Not really sure what you are asking about?

The amount of interference depends on ride height (angle of lower a-arm), camber setting, toe setting, rack being properly centered, and production tolerances of the lower a-arm. There is no set amount that works for every application as you need to leave as much material in the nose of the lower a-arm as possible. The entire weight of the front of the Fiero is transmitted through the nose/lower ball joint area, so you don't want to remove too much.

As Joe mentions, this is a non-issue with my 13" brake kit as the nose of the lower a-arm is inside the rotor hat area of the rotor.

[This message has been edited by fieroguru (edited 10-04-2020).]

Well they may be obsolete but they do work and fit 16" wheels and are really cheap. My total cost of 4 rotors was $110. I made the adapters myself for $5 each. Oh and one more thing with the drop ball joints and the caliper brackets you may need to lengthen your front brake lines by 1". So there's another $60.
With my original 88 brakes it was almost impossible to lock up the brakes intentionally and the pedal force was higher. Now they can be locked up and the pedal effort is lower. The 13" rotors would give even more leverage, lowering the pedal force for sure.

The brackets are simple. Get some 3/8" x 2" flat stock.
Mark out a rectangle of 20mm x 67mm in the center of the flat stock
Drill 2 holes for 12x1.75 pilot and countersink (finding a 1" countersink was difficult, I re-cut a 1" HSS drill).
Drill other 2 holes to 12mm.
Round off the corners and relieve the top and bottom to avoid the calipers
Clean up rough edges
Get 2 x 12x1.75 FH x 25mm 10.9 or stronger allen head or torx bolts per wheel.
Mount the brackets in the old caliper position. Torque to 70 Ft-Lb.
Mount the calipers to the bracket. Torque to 70 Ft-Lb.

The calipers are a bit more difficult because the centering ringd don't exist in the exact size needed. Not that the hub diameter has two measurements. the diameter of the hub to mount the disc is larger than the diameter where the wheel mounts. And the discs are not 71mm exactly.
Find some spacer rings for the discs 70.5mm to hub 57. mm. to center the disc (finally found some 71 x 57 from autoanything.com and needed to trim them a bit to fit).
Measure and drill the rotors for 100mm PCD x 5 and carefully drill for 12mm (or a little larger since getting the hole placement exact was challenging for me).
Install the parts and make certain the rings do not prevent the rotors from seating.

quote Originally posted by olejoedad: Or just buy the 13" kit from guru and don't worry about fitment issues. The 12" corvette rotor upgrade is obsolete. Time Marches On.

Actually, this makes the most sense.
I own the kit. I've done the install. It's quite painless. Absolutely bolt-in. You don't have to source... anything. No nickel-and-dime stuff. Nothing. It bolts in. And it works. And there is no interference (no matter how "minor") with any existing hardware.

I thought I posted an install thread, but I cannot find it.
Regardless... Do it.