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After doing some research I had concluded that the C6 J55 rear brakes are not significantly better than the C4 rear brakes so I am going to leave my rear brakes stock.
That does bring up one other issue though. By adding more powerful front brakes I will essentially be shifting the brake bias more to the front of the car and C4's are already know to have a bit too much front brake bias to start with.
There are a few way to solve this. However, the way I decided to address the issue is to order a brake bias spring from DRM which will shift the braking bias a bit more towards the rear brakes and restore a proper front rear brake bias.
DRM sells 2 springs for the C4 I got the ABS version since my car has ABS.
Here's the DRM spring:
The spring goes in the brake master cylinder. To access the spring you remove the sensor on the side of the master, then both brake lines followed by the bolt on the front and then you remove the plunger assembly which contains the spring:
After removing the plunger I put it in my bench vise and used a allen key socket to compress the spring while I removed the retaining ring.
Next I gradually let the pressure off the spring and it came out, also take note that the spring is under pressure and if your not careful it can shoot out of the vise. Here's the spring ready to be removed:
Installation of the new spring is the reverse process.
Once the spring was back in I thoroughly bleed the brakes with Wilwood 570 brake fluid (6-7 containers).
Here's the master after the bleeding was complete, full of fresh fluid.
Here's some pictures of the brakes with the wheels back on:
I think the new brakes look at home behind the C5 Z06 wheels
I completed this brake upgrade at the very end of summer / start of fall and had a couple weeks of driving plus one last autocross so here are my impressions:
the C6 brakes definitely have a bit more bite than the C4 brakes. They definitely engage the ABS more easily. I was a bit worried about pedal travel but there is no noticeable difference. So overall I am happy with the brake system.
have you considered lowering? is it already lowered? would lowering be an advantage to autocross?
Its actually lowered already about 2-2.5 inches. It doesn't look like it in the pictures because I have it driven up on boards otherwise I can't get a jack underneath.
I link lowering helps a little by lowering the center of gravity and maybe allowing less air to get under the car so a little bit less lift at high speeds I would think, but imo looks is the main advantage to lowering.
Also I was careful not to go too low as you don't want to loose so much suspension travel that you either bottom out or have the suspension hitting the bump stops. It took me a while to find the right ride height but eventually I found the right balance between suspension travel and lowering.
Cool thread. I am going to check out your older one.
Are the brake brackets aluminum? Did you happen to weigh the whole C4 setup VS C6 w brackets and bolts?
Consider using the C4 fronts on the rear? IDK what is involved.
The bracket I think were made of powder coated steel and they didn't weight much (a little over 1lbs ea). I had to use 2 extra bolts per side to attach the adapter bracket but the bolts I used were shorter than the OEM bolts so that's a wash.
The C6 calipers and brackets were very close to that of the C4 components although the S/S pistons added a bit of extra weight to them, so maybe 1/2 -3/4 pound per side with the S/S pistons in the C6 calipers.
My old well worn 13in C4 rotors came in at slightly less than 20lbs per side and my new slotted 13.4 in C6 rotors were about 21lbs a side. (new full thickness C4 rotors might be a tad heavier than my used ones) So about 1lbs more per side. I could get lighter 2 piece C6 rotors in the future to cut a few pounds though...
So I probably picked up 2.5 lbs per side over the original C4 J55 setup. But I have gained a fair bit more braking power and 0.5lbs of that weight was the S/S pistons which lots of people add to the C4 calipers. Also my wheels are 4lbs lighter per corner than stock so I'm ok with adding a little weight to gain better braking and the difference is noticeable especially at a race.
The issue with 88-96 C4's for rear brake upgrades is the E-brake. With a manual car like mine an E-brake is a must, for me anyway.
If I put my front calipers on the rear I would lose the E-brake. Street Shop inc. and Vansteel sell a nice kit to convert the rear brakes to use C5/C6 style e-brake but that is $$$ and I don't think the C5/C6 rear brakes are much better than my stock rear brakes to make that conversion worth while. If i had choosen C6 Z06 brakes or high dollar aftermarket front brakes I might do the conversion but I think the with the use of the brake bias spring this brake system is pretty close to the system used by C6 Z51 corvette's for balance and performance which is good enough for my goals and... better rotors + ducting can add more performance if I need more. In my opinion the big issue with the C4 J55 system is the calipers aren't strong enough for heavy use and this was a cost effective way to remedy that.
Sorry for writing a novel, just wanted to give a through answer.
David, your car's awesome and your write-ups are fantastic! You should consider submitting them to the club website as tech articles.
Thank you for the kind words, There are lots of more knowledgeable people than me but I would be happy to contribute what I do know to the club website. So far I haven't been able to figure out how to do that on the club website. I'll give you a call later and maybe you can walk me through how the website works a far as posting goes.
Just read through your other thread, nice work. Wouldn't mind a write up and materials used for the battery relocation.
With the new suspension, with more articulation, do you notice a more compliant, smoother ride?
Thank you. I made my own battery relocation kit, I will have look at it tomorrow to remind myself exactly what I did and I'll give you some info then.
To answer your question about the suspension, there is a significant improvement in articulation which seems to give much better handling as well as a much smoother ride even though I have 'stiff springs' the ride is very smooth. Its really a night and day difference compared to stock.
I am very happy with the rear suspension now and will leave it as is, the front suspension is good but I don't like the general design of the sway bar as I think the endlink design causes binding, hopefully one day I will figure out how to fix that.
So on one of the last drives of the year before putting the Corvette away for storage I had a problem. I had gone on a long drive as part of a charity cruise and when I got on the highway to head home I pressed the O.D button and I turned on for a second then turned off, and I couldn't get it to stay in O.D
So I had to go in the slow lane with the engine at like 2,800 at cruising speed, thankfully we stopped for dinner on the way home. When I I back in the car a couple hours later the O.D worked fine until I was most of the way home and then it shut off again???
Anyway I talked to my friend who Is mechanic and he suggested that I might be my O.D relay going bad which caused the realy to work when cool but stop working when the car/relay got hot from engine heat. Since the fluid in the O.D seemed to look fine I decided to give it a shot.
New O.D relay from NAPA:
On my 88' the O.D relay is on the engine side of the driver's side front wheel well.
I took the car out for one more drive and the O.D seemed to work fine, but it wasn't a long drive and the car is now in storage for the winter so I'll have to see if the O.D issue truly solved or not next spring...
Now that the corvette was in winter storage I had a few more projects for it, More updates to come...
This is a little off topic but I thought I might share it.
I picked up an old 4in Wilton Bullet vise and decided to do a restoration on it. Did a full cleaning, media blasting and powder coated it now it looks and works great!
This is a little off topic but I thought I might share it. I picked up an old 4in Wilton Bullet vise and decided to do a restoration on it. Did a full cleaning, media blasting and powder coated it now it looks and works great! I won't go into to much detail here but if are interested I did a small thread on the Off Topic corvette forum which can be found here: https://www.corvetteforum.com/forums...storation.html Here's a couple pictures, what I started with: The finished product: Installed on my garage work bench: More Updates to come:
I been looking to do the same thing! The old vises are awesome. Pricey but you get what you pay for. I'll have to check out your thread. Brakes look great and I'm glad your OD relay is an easy swap.
12-30-2016, 10:54 AM
Brake Upgrade
