Dale002

What all i need to upgrade brakes on an 85 to JL9 brakes?
Do I need adapter bracket for front and rear? I've been told that JL9 are 12 rotors, same as I have now on the single piston set up.
Are adapters needed for both front and rear

Dale002

ttt due to updating the request after correcting errors.

Nowhere Man

why do you need to up grade the brakes? and if you really do why to them?

c4cruiser

Why not get better pads? There are a wide variety of good performance pads that will provide a big increase in braking.

The 85 has 11.5" rotors and the JL9 rotors are 12". 12" front rotors became standard in 1991. I believe that you would have to change the front spindles to the 91 and later versions so that the 12" rotors would bolt on.

There is no easy way to upgrade the rear brakes. The early C4 rear brakes use an internal parking brake; the later C4's used the rear calipers for the parking brake. The cables are slightly different for the caliper parking brakes.

The next "level" for a brake upgrade is to use C5 front brakes. There are kits available that have everything needed; adapter bracket, caliper mounting brackets, 13" rotors, and C5 calipers. But kits like these will easily run close to $900-$1000. And the C5 conversion will also require 17" wheels and tires. Better pads for the rear would be a good addition with the kit and installing a different rear brake bias spring in the master will be needed. Doug Rippie Motorsports has them for non-ABS cars for about $20.

What I would suggest to start is to replace the pads with something like Hawk HPS pads or one of the pad sets from CarboTech. Replace all of the flexible lines with the flexible stainless lines from Earl's or Goodridge. Then do a complete flush and refill of the brake fluid. You can go with a DOT3 fluid such as Castrol LMA, Valvoline, or even the Ford Motorsports HD fluid. These are all fluids that are at the upper end of the DOT3 Wet Boiling Point Range. For a DOT4 fluid, use ATE TYP200.

WVZR-1

I would think that if you actually wanted to use JL9 12" product all you would need is the adapter/bracket that is used to do early spindle/knuckles to J55 but use the calipers and the JL9 bracket. To do JL9 to J55 only requires calipers/brackets when you have appropriate spindles/knuckles so using the adapter/bracket for early seems like it would certainly work.

I do though think it would likely be less expensive to just confirm quality hydraulics and use "premium" brake pad product. Quality fully functional hydraulics I'd think might be the more important issue to correct along with a premium brake pad product OR if you've recent brakes just do the hydraulics first. The brakes might surprise you.

Dale002

The brake system was just completely overhauled to include new hard lines and Earl's flex. All four calipers were overhauled as well but the front passenger and the drivers rear have a small leak at the piston O'Ring. When I was overhauling the calipers, these two bad calipers bore are at their max od. I cleaned them up and install o'ring and dust seal but they leaked anyway. so I need two new one and thought it would be a good time to upgrade them. I also don't like the drum ebrake system. I'm not set on any type of brakes, I just listed the JL9 and J55 because they are the only ones I've heard of. This set up is going into a 62 resto mod that has the 85 front and suspension.

c4cruiser

Wht kind of weight will the resto mod have? The early C4's weighed around 3400 lbs so if the build car will be less than that, you may find that the '85 brakes will work very well in stock form.

As far as the J55 13" front brakes, that would require an adapter to be able to mount the caliper bracket to the spindle. Those would be hard to find and still require 17" front wheels.

For the internal drum parking brake, as long as it's adjusted properly and the shoes are in good condition, it should work fine. The issue would be finding the correct cables for the later caliper-style parking brake. The rear rotors may be different too, not just having the internal drum, but the height of the rotor hat may be different between the two types.

pologreen1

C5 brakes are cheaper and all you need are some extra brackets.

Dale002

Awhile back,I stumble into a thread that showed the dimension of the brackets. If I could find it again, I could have them made. I think eventually, I will put C5 calipers and big rotor so it look better,viewing through the wheel.
Are C5 rear calipers used as well?
Could I swap out my existing caliper mount plate and replace with a plate from an 89-96? Then, I would be able to use J55 in the rear or at least a caliper with emerge?

pologreen1

type in ebay, also c5 pads and rotors are cheaper and better

C5 brake adaptor brackets for C4 Corvettes 84-87

Dale002

OK. If I understand it correctly, I need adapter plates to use any calipers with emerge on the rear.

The same type plates are use for both the JL9 and J55 brakes set up.

Different plates are use for front C5 Calipers.

Are there plates to adapt C5 rear calipers to the rear of the 84-87 C4?

c4cruiser

There's no real reason to use C5 rear brakes on the C4. The rotors are the same diameter, the pads are very close to the same size, and I don't think there is a commerically-made bracket to adapt the C5 rear caliper abutment brackets to the C4 spindle.

C5 front brakes will make a difference in stopping power (I have them on my '87) but as I mentioned, the cost of the conversion for the brakes doesn't include the cost of new wheels and tires. You could be looking at something in the area of $2000 as a total cost for this conversion.

And again, what is the reason for bigger brakes? Paying a couple hundred for better pads that can easily improve braking performance is a much better way to start than jumping into a big brake conversion project.

WVZR-1

There's way more reasons to maybe improve what you've got vs. attempting to adapt something else to the build. Not all of the adapters/brackets are created equal, you could end up in a way worse situation that's going to cost again to recover.

If you really wanted to alter the brakes it needed to have been done before you spent on these. There's many options for you and maybe using "none" of the C4 product requiring adapters should be considered. Depending on e-brake requirements there's product for the rear also. Not inexpensive but quite likely a much better build.

Depending on the suspension in the rear the change from "shoe in rotor" to "caliper activated" is likely very difficult and maybe easier/more efficient if after-market product used.

The master, pedal ratio etc needs to be considered I'd think before you do anything. Depending on the build it could be way more difficult than doing just an early C4 or maybe even easier.

Have you ever driven this build?

Dale002

Yes, I have driven these type of build on different chassis,different powertrains and brakes. I've also owned C4s in the pass and was happy with the way the brakes worked, I've had many issues with the shoe type set up for e brakes to the point of taking them out.
My last C4 was donated for this build.

As I posted before I want to make the change because :

1.) I need to buy two calipers for the set up I have now and rather spend the money doing the change.

2. It's a resto mod so I will be purchasing 17" or larger wheels anyway.

3. I want to get rid of the rear shoe e brake set up.

4. Being that it's a resto with newer type of wheel, they will show the brakes more, I want something that will fit better with the larger more open wheels. I don't want to have 11.5 rotors and a tiny calipers behind 17" or 18" wheels.

In summary, the upgrade is not necessarily for a better stopping brakes system but more as a better looking fit with the build set up.

What I need to know, is what is needed to change the rear, What are my options? If going aftermarket is a better answer, then can someone suggest a vendor or product?

Are the same adapter brackets used for JL9 or J55 brakes or C5?

I understand that better pads, new fluid will makes a big difference, that doesn't apply here!

WVZR-1

Contact this eBay seller "1976ls1" I've never used his product myself BUT I know those that have. He can fix you up with everything for all four corners of an early C4 with nearly all 13" or 14" product. 13" for sure. I understand how it's done and I believe you'd be much better off with his product rather than attempting to "copy" anything. You need to understand though that nearly every "big brake" vendor out there relies on a "shoe 'n rotor" for the e-brake. It works for everyone else I can't understand your problems with it.

His I believe would be effortless, if you want after-market Baer "Big Brakes" again for 13" or 14" BUT AGAIN "shoe 'n rotor" for e-brake.

Make the eBay contact --------------

His packages are sometimes on eBay if he's got product fabricated and on the shelf.

Dale002

I've had many issues with shoes hanging inside the rotor and making noises, Having that issues right now with my 99, The reason I would prefer a set up like the JL9 or J55 for the rear.
The front either of the one I mention would work for me or possibly a C5 set I will give197ls16 a text and see if he could help.

I though the rear brakes were upgraded as well but, looks like most guys only do the fronts and makes sense as they are doing it for best performance.
I'm surprise no one has a drawing for these brackets.

0BDE-Systems

Keep in mind that if you opt to go with a much larger brake setup (up front) a DRM brake bias spring will help rebalance the bias of the system - the cost isn't necessarily a big factor but sometimes install can be tricky (search drm install).

WVZR-1

If you think you've issues with the "shoe 'n rotor" wait until you have an issue with a caliper actuated e-brake. Parts or an experienced tech OR BOTH maybe can correct your '99 situation I'd think. For a project like yours where you control the cable routing and the application device there's no reason NOT to assume a "shoe 'n rotor" wouldn't be the preferred and better choice. Like I mentioned, I haven't used the product I mentioned myself but I know some that have and they've miles on their builds. That I believe is the "tale of the tape" -

Drawings? Well I believe that anyone with quality product has checked the product using fixtures and the like. There's many drawings out there but how many actually work well? If I had quality product I wouldn't offer my hours of fabrication and tooling up for "nothing" either. Generally you get "what you pay for". Pay little or nothing and get likely nothing or very little.

Do the fabrication yourself and market it?

PLRX

The first thing you need is money.

The second is buying, and installing 17" wheels

Options

C4 95-96 J55 brakes

C5 1997-2004 Brake kit

Wilwood Front brake kit

0Todd TCE

C4 Cars present serious challenges and decisions.

There are but two forms: Drum in Disc like that of the later (and earlier) C5 and C6 platform. These offer you the option to do true "big brake kits" with multi piston calipers on 13 (or maybe even 14") rotors wheel size depending.

The later C4 however does not offer this. Due to the dual action or combo caliper design the parking brake is part of that caliper. You cannot change the rotor size due to the mounting height of the caliper, at least not in stock form or from any major brake manufactures.

The options on the later car are more limited. Not by default but market. Few want 13" or larger brakes without the parking brake feature. Shops such as myself can produce such kits but the price will rival what we can sell a front kit for very quickly. Few yet want $15-1700 rear kits (but they'd math the fronts) and thus there is not a strong market here.

Fitting the C5 in place...never tried it but I suspect you'll find many difference that make it all but impossible to do so. If it was truly that easy you can be sure now some 20yrs later you'd find a quick link to it and someone showing it in service. I don't know of any such cross fit. But I confess I'm not a Vette expert either.