anybody upgrade their early c-4 with the later 13 in j-55s / good or bad idea

 

Five years ago I went from the standard 12" on my '94 coupe to a 13" rotor and the GS Calipers up front. I did the S/S brake lines and Hawk HPS pads. It was amazing to me the difference. However, I also had gone a long time before that without a brake fluid flush and from what I understand a flush alone will make a significant change in the pedal feel too. I love the GS calipers they look cool with just enought bling in black to stand out as different but not too bold. They stop the car great during spirited driving.

Although I might add, that you can do a C5 brake swap much cheaper than a J55 or GS change over. Plus I think the C5 rotors are cheaper too.

 

Did you do the brake bias sping change? Did the factory do one? I have been less than happy with the exact same brakes you mentioned with the bias spring change all done in one swoop with SS lines andfluid flush. They are not bang your head on the steering wheel right there by any means. I changed booster as well and that helped some but nothing has gotten me what I want to date. I am not going to mod an eninge in a car that will not point or stop world class to me fast without those traits is still pointless so my hood remains shut until that happens. I did read a bunch about bedding in pads and the need to redo that from time to time so maybe i just need some pads that are less sensitive to that or maybe the bias has sent too much pressure to the tiny rear pads cheating the fronts that do 80% of the real work. Long story short sold a really nice Fiero set up for auto X that could corner at 1 G and not stop for a C4 that can not corner at 1 G and still not stop.. sigh.. Sure the C4 has more go but once both a 80+ mph not a more capable car yet. The Fiero at 700 less lbs sure had more nimble going for it for sure and within 7% hp to weight ratio so the go part not that wildly different either. Not complaining as the C4 has way more cool factor and certainly generates more cool car comments compared to thats interesting choice sort of comments.

How critical is the bedding in deal and how do you redo that if done wrong? Did the factory J55 have the same or different bias spring the other comment. I want they are here right now brakes.. Maybe C5 brakes are the answer but not ready for new wheels and tires for that just not in my budget right now.. I want to stop better than my 2002 Pontiac GP so far has not happened..Possibly factory pads better for me as most of my use is dead cold pads going to full on without heating them up in any way.

Dave

 

If you use Hawk HP+ or Carbotech Bobcat (autox) pads you have to bed them in.

I like the Carbotech, I run xp12/xp10 with a bias spring on the road course. I have used lots of other pads on this car and I like the Carbotech for its rotor friendlyness. A set of rotors last me more than a season and the pads last me a season +

 

ttt

 

Either way (C5 or later C4 J55 brakes), you are going to need a custom adapter to attach the new caliper abutment bracket to the knuckle.

With C5 front brakes, you will have to go with a ZR-1 style wheel to clear the caliper. Later C4 "sawblades" won't work with C5 calipers. Going with the J55 setup still requires 17" wheels and later sawblades will work but you have to use 3/4" adapters to properly mount the later wheels because of the difference in offsets.

For parts, the C5 rotors are less than the J55 rotors, and the calipers should be about the same. Pads will be about the same price too.

When I did my C5 brake upgrade on my 87, I tested the brakes before I installed the Doug Rippie brake bias spring. Without the spring, I would get the ABS to engage at something like 40-60% brake effort. After the spring was installed, ABS engagement was back to where it was before the upgrade. Note that DRM has two springs; one for 84-85 (non-ABS) and the other for 86-later ABS cars.

Because of the increased braking capability of the C5 brakes or even the J55 brakes and the larger front rotors, the bias spring will be a necessity to return the bias to near-stock. Without it, the chances are that the front brakes will do 80%+ of the braking.

Bedding street-use Hawk pads like the HPS is not really necessary if you are just doing street driving. But if you intend to jump right into autocross or track use, it is much better to follow their bedding procedure to transfer pad material to the rotors. Going from an HPS to a HP+ pad without changing rotors won't need bedding as the pad material is very similar.

Getting a C4 to stop like you tossed out an anchor will be a function of finding the right pads for what you are doing. Right now on my 87, I have OEM Z06 pads in front and HP+ out back. Stock C5 rotors in front and Centric drilled rear rotors. This combo works great for autocross and seems to work fine for the track days I do at Portland International Raceway (flat track and fairly easy on brakes)

 

I had these for a 86, but had to sell the car. They are powdercoated & 5/8 thick @ the tapped hole. They are brand new &
never bolted on. Comes with all grade 12.8 hardware. Selling for $140 shipped priority mail.
You will need 17" or bigger wheels to run these. These are for the C5/C6 brakes!!!!!!!!!
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