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I've been working on street tuning my vette and found my brakes to be rather underwhelming. I've spent alot of time searching this subject but it seems all the threads with vendor links are broken, and don't work. Ive been working on piecing together my own kit so that I can finally fix the brakes, but I've seen very different responses as to whether or not an adapter bracket is needed for the 85 to run J55 brakes. Ive got new rotors, calipers, and their caliper brackets all ready in my cart, but can anyone confirm whether or not J55s require a bracket and where I can get them?
I would skip the C4 J55 brakes and go right into a C5/C6 brake upgrade. The parts can still be found new, and cheaper than a lot of the asking prices for used J55 calipers and abutment brackets.
Go with the C5 adapter bracket, then you need all C5 parts, except for the brake lines which would be for your year car.
Going to C5 on my 86 was a night and day difference at the time.
Brake pad availability alone is worth it.
I have C5 brakes and rotors on the front, and C6 brakes and rotors on the rear (retained original parking brake setup by adding 1/4in to the brake shoe material thickness).
IMO it looks amazing with the C5 thin spoke wheels i have, and i there are a plethora of decent pad choices that include a lifetime warranty!
Stopping is amazing, right now i'm a wee biased towards the rear but i was sorta hoping for that.
Original 84 brakes, i could get brake fade pretty quickly when coming to a "quick" stop while going down a steep canyon road...
While it was probably the pos AutoZone pads I had (they had one option), the eye opener was when the freeway came to a sudden stop, and i needed to really step on the pedal to get the car to stop.
Now it's effortless, and I have yet to experience any sort of brake fade/overheating.
I do have to remind my self that the car does not have antilock brakes when taking her for a spin...
All of the claims that the C5 and C6 brakes will stop you quicker is a load of crap. Stopping quicker is related to the grip of your tire to the pavement. The better the grip, the quicker you can stop. Big brakes will only kick in the abs quicker, or in your case , lock up the wheels since you don’t have abs. There are a lot of good options for J55 pads and the rear calipers are the same as a Camaro so there are options there too.
I do have 1 set of J55 adapters left. They are my design and I CNC machined them from billet 1020 steel if you are interested.
PM Sent, thanks for all the info, I'm leaning towards the J55s because they're cheap, all in minus the adapters is $200, im gonna start looking into the C5 brake pricing, I know those brackets are around $185, if I can get them for a decent price thats definelty the way I'll go. I think there's air in my system but I've tried locking the wheels up and they just won't, might try a flush and bleed but the brakes are rusty as hell so might as well.
Last edited by ThatOneKid; Nov 22, 2020 at 12:59 PM.
Sorry to those that claim the C6/5 brakes are not better, they ARE better!
I had C4 J55 brakes with hawk pads, then I switched to c6 J55 brakes with the same compound pads and it made a BIG difference. I tested braking on the same piece of road before and after. Trust me the C6 J55/Z51 brakes are better than the C4 J55 brakes.
Also C6 calipers, rotors and pads are inexpensive. You really can't lose doing the upgrade vs the C4 J55.
I decided to step up the bakes once again this year and went to a C6 Z06 setup, it should be even better.
Sorry to those that claim the C6/5 brakes are not better, they ARE better!
I had C4 J55 brakes with hawk pads, then I switched to c6 J55 brakes with the same compound pads and it made a BIG difference. I tested braking on the same piece of road before and after. Trust me the C6 J55/Z51 brakes are better than the C4 J55 brakes.
Also C6 calipers, rotors and pads are inexpensive. You really can't lose doing the upgrade vs the C4 J55.
I decided to step up the bakes once again this year and went to a C6 Z06 setup, it should be even better.
If you applied both sets of brakes to the same point where the wheel was on the verge of locking up with the same tire grip, how did one stop quicker than the other? They didn’t. You are equating pedal pressure with better braking and that is not the case. Any corvette braking system in good condition is capable of locking the wheels. Or activating the abs.
If you applied both sets of brakes to the same point where the wheel was on the verge of locking up with the same tire grip, how did one stop quicker than the other? They didn’t. You are equating pedal pressure with better braking and that is not the case. Any corvette braking system in good condition is capable of locking the wheels. Or activating the abs.
Yes, but your not factoring in caliper flex that takes place as the brakes heat up (C6 caliper is stiffer) or brake fade, C6 Z51/J55 rotors are thicker and have larger diameter 13.4in rotors and larger pads, meaning they have a larger thermal capacity.
Also my car has 315 rival S tires all the way around it it has more grip than stock, so the brake difference was more notable.
And your correct, if your only talking about one single stop on 'hard' Street tires, than even the base C4 brakes will be as good as the best aftermarket system out there since both will engage the ABS. AND by that logic any brake upgrade is a total waste. Taking that view is kind of like saying why even consider upgrading the engine power when even a 205hp crossfire can spin the tires in 1st gear and get up to highway speeds...yet we all know there are better engines out there
You have to look at brake fade, caliper flex, pad size and thermal capacity on repeated stops to see the advantage of better braking systems and if you do that you will see that C6 J55/Z51 brakes (or even better systems) have advantages over C4 base or J55 brakes.
Yes, but your not factoring in caliper flex that takes place as the brakes heat up (C6 caliper is stiffer) or brake fade, C6 Z51/J55 rotors are thicker and have larger diameter 13.4in rotors and larger pads, meaning they have a larger thermal capacity.
Also my car has 315 rival S tires all the way around it it has more grip than stock, so the brake difference was more notable.
And your correct, if your only talking about one single stop on 'hard' Street tires, than even the base C4 brakes will be as good as the best aftermarket system out there since both will engage the ABS. AND by that logic any brake upgrade is a total waste. Taking that view is kind of like saying why even consider upgrading the engine power when even a 205hp crossfire can spin the tires in 1st gear and get up to highway speeds...yet we all know there are better engines out there
You have to look at brake fade, caliper flex, pad size and thermal capacity on repeated stops to see the advantage of better braking systems and if you do that you will see that C6 J55/Z51 brakes (or even better systems) have advantages over C4 base or J55 brakes.
When you talk about tracking the car , yes, bigger brakes are better because the larger surface area dissipates heat faster. But the OP doesn’t track his car. I put j55 on my 86 track car for that reason. But they still won’t make a difference for a daily driver grocery getter .
When you talk about tracking the car , yes, bigger brakes are better because the larger surface area dissipates heat faster. But the OP doesn’t track his car. I put j55 on my 86 track car for that reason. But they still won’t make a difference for a daily driver grocery getter .
That's a fair comment, if the op just has regular street tires in stock sizes such like all seasons and doesn't use his car agressively or do any track type events, auto-X etc... then yes, a brake upgrade won't provide any meaningful improvment for mild street driving. I totally agree with that.
He did however say he found the brakes underwhelming so I figured he must be doing something that is showing the limits of the stock brakes, and if he's going to spent the money to upgrade, for about the same cost why not get the better C5/C6 or C6 Z51 setup?
I should add while he's at it he should pick up the DRM brake bias spring too, which will allow the car to make better use of the avaliable rear brakes and will help compensate for adding stronger brakes up front.
C5 brakes are absolutely better. Using tires as an argument/excuse that they aren't better than the J55 is absurd. They ARE better, stop using shitty tires.
You can't use the grip of your tires as an excuse to demerit the better brakes.
You might as well be arguing that its stupid to add horsepower because your tires won't get traction.
Pricing and availability? C5 stuff wins there too.
I went through this whole thing with a few people here already, and the ONLY arguments anyone had in the favor of the J55 stuff were:
-They already had the J55 stuff.
-If your tires are garbage, you'll never see the benefits of C5 stuff.
That's a fair comment, if the op just has regular street tires in stock sizes such like all seasons and doesn't use his car agressively or do any track type events, auto-X etc... then yes, a brake upgrade won't provide any meaningful improvment for mild street driving. I totally agree with that.
He did however say he found the brakes underwhelming so I figured he must be doing something that is showing the limits of the stock brakes, and if he's going to spent the money to upgrade, for about the same cost why not get the better C5/C6 or C6 Z51 setup?
I should add while he's at it he should pick up the DRM brake bias spring too, which will allow the car to make better use of the avaliable rear brakes and will help compensate for adding stronger brakes up front.
The OP also didn’t say what size wheels he is running. The C6 big brakes would require at least an 18” wheel I believe.
The bias spring is a good investment. It made a difference in the braking on my car. The c4 doesn’t use much rear brake.
I would skip the C4 J55 brakes and go right into a C5/C6 brake upgrade. The parts can still be found new, and cheaper than a lot of the asking prices for used J55 calipers and abutment brackets.
Will C5 fit under 17" A Molds and is there someone who sells a front/rear package ready to bolt on? I hate trying to piece parts.
Hi
have been there and done that while the standard brakes can be made to work, with high friction brake pads like hawk.
There is no doubt bigger rotors and callipers assist with heat dissipation, my J55 setup works great however you really only notice the difference on a track day, the pedal stays hard and the brake effectiveness doesn't change.
On the road if you need to stand on the brake pedal to slow your car, you are not using the correct high friction brake pads. Friction does the braking and affects pedal effort, too little friction and you need another car or object to stop you.
I had used std 84-87 brakes with hawk pads, minimal effort to stop or slow the car , lap after lap. They can be made to work with fresh brake fluid and the right brake pads.
Thanks for all the thoughts, I'm running 285s in the back and 275s in the front, Nitto NT555s on 17x9.5 replicas I believe. I know the bias spring is all but required with the bigger brakes but is there a bias spring or shim kit or anything to get better rear performance?
The car doesn't have ABS and I live in the mountains so I don't want the brakes to be overly sensitive because of road conditions in my area. My goal is to get this car trackable but in the timeline and with the budget of a college student, and within that timeline, I plan on dailying it. I may try replacing rotors and pads first as just in traffic I had to stand on the pedal to slow from 50, systems bled and has a great pedal feel but the brakes are just utterly useless, PO looks to have replaced the booster previously, and from what I can tell its not cracked, pedal is a little bit on the stiff side, but not too bad.
Out of curiosity, has anyone attempted to fit HD truck brakes onto a C4? I have a set in my garage and from what I've researched, they're equivalent in diameter to the C6 ZR1 rotors, just minus four pistons in the caliper and with a different bolt pattern. I'm currently halfway across the country from my car so can't mock it up, but it seems like they'll fit alright, just need a custom bracket.
I think for something like C5/C6 brakes up front the DRM bias spring will work well as is.
I'm not familar with anyone that has put this 'HD truck' brakes on a C4. The C6 ZR1 has carbon ceramic 15in rotors (very pricey) they are very also lite weight.
If your going with a 15im front rotor upfront, you need to be concerned with unsprung weight, adding too much hurts handling, you'd want a 2 piece rotor at a min. Also you'll likely need minimum 19im wheels. Additionally, you will have a terrible front brake bias if only doing the front brakes, the DRM spring won't be able to conpensate for that much of a front brake upgrade, you'd be looking at having to install an adjustable brake bias system and maybe a new master cylinder.
I think using something like C6 ZR1 brakes is going to total overkill for what you need and will be a lot of $$$.
I'd suggest you look into Wilwood or bear brake kits, if you want or need a REALLY good braking system, you will be happier. If that is to pricey, then the C6 Z06 upgrade like I just did an option, below that would be the C5/C6 upgrade.
I honestly think for what your doing the C5/C6 or C6 Z51 front brakes with A DRM spring will be the best bet.
85 J55 Brake Upgrade
