ZoneM

Hello to all.
Well I am new to the forum and new to cars, I bought my 85 vette back in may for my 18th birthday.

This is my first post, sorry if i **** anyone off with stupid questions.

OK so, this is my situation, i have an 85 corvette all stock, I plan on upgrading my wheels and tires to c5 thin spoke wheels. But I've been told they wont fit due to offset and lug pattern. So, i decided to upgrade the whole brake and rotor and lug assembly (so the wheels look good with bigger rotors and for safety, (since i plan to upgrade to an ls1 shortly) AND My question is: How hard is this? I dont have much mechanic experience but i've managed to do a few projects with my friends. What parts do i need? And will the c5 z06 brakes fit my c4? will there be a problem since i dont have antilock brakes? any pictures and instructions will be appreciated. Thanks everyone

gerardvg

There are a lot of bolt on kits available
I put the J55 88-96 heavy duty 13 inch discs and twin piston calliper's to fill the wheels they needed a bracket to fit them to 84-87 corvettes.
Of course there are issues with putting bigger calliper's on you may lock your rear brakes before the front which is bad but you can fit an adjustable brake proportioning valve to fix that... look on corvette centrals website for that also.

http://www.parts123.com/parts123/yb....Z5Z5Z50000050F

or these expensive ones

http://www.parts123.com/parts123/yb....Z5Z5Z50000050F

Here are the adapters you need to fit the later model wheels

http://www.parts123.com/parts123/yb....Z5Z5Z50000050F

vetteoz

Most consider upgraded rears of little use ( esp on the street ) so you are only doing them for the bling value

With the price of those off the shelf front kits listed above you would be better doing a C5 front brake swap
putting new rotors on the rear and powder coating the stock rear calipers to match the C5 front ones

http://forums.corvetteforum.com/c4-t...-for-85-a.html
http://forums.corvetteforum.com/c4-t...ally-done.html

ZoneM

[QUOTE=gerardvg;1582128568]
I put the J55 88-96 heavy duty 13 inch discs and twin piston calliper's to fill the wheels they needed a bracket to fit them to 84-87 corvettes.
Of course there are issues with putting bigger calliper's on you may lock your rear brakes before the front which is bad but you can fit an adjustable brake proportioning valve to fix that... look on corvette centrals website for that also.

http://www.parts123.com/parts123/yb....Z5Z5Z50000050F

I saw your pictures gererdvg, You car looks badass. I Love it, so you only upgraded the front brakes and not the rears?

ZoneM

hey vetteoz, so i am considering the c5 front swap. Do you know exactly the parts ill need? i found a c5 parting out ad on craigslist, or ill just buy them all new.

76LS1BIRD

http://forums.corvetteforum.com/c4-t...ally-done.html

Only 84s have smaller bolts for spindle to cal. bracket (12mm)
85-87 & 88-96 all use 14mm

leesvet

calipers, rotors, adaptor brackets, abutment brackets, all bolt hardware, all seals, guide pins set, self bleeder screws, pads, (for caliper clearence) braided stainless lines.
Probably something else I forgot. I've got a box full of all that stuff that I'll go look at later...(waiting to be installed)
Thats getting close to $1000 if you assy all the stuff yourself from different vendors.

Then you need your 17" min wheels, and 1" wheel spacer/adaptors

jsinga

Adapter bracket rotor and pad is only new you have to have. Sometimes you can get the adapters used. C5 parts are less epensive. Only difference in C5 Z06 is color. Not sure 85 might have smaller holes for caliper bracket in spindle. Get bias spring for MC from Rippie.

JS

JrRifleCoach

Link saved

SouthCoaster

You don't "need" any of it.

The stock 85 brakes with a few cheap upgrades like high temp pads and a DRM bias spring will hold even that LS1 back for most driving.

But the easiest upgrade for looks will be the C5 upgrade in front. If you do anything up front to increase piston sizes or rotor diameter, you will actually make your braking worse unless you bring the bias back to normal with a bias spring. Don't worry about ABS, you don't have it and it won't effect your brake options.

In back, you are reinventing the wheel. There are no bolt on upgrades for the back. The few rear upgrades that I have seen involve losing the ebrake and fabricating caliper brackets from scratch.

SouthCoaster

[QUOTE=ZoneM;1582129175]Actually bigger fronts will cause the fronts to lock up prematurely. With the same ol' amount of line pressure they generate more braking torque due to larger diameter (mechanical advantage) and increased piston area ( = more pad clamping force). Meanwhile the rears are just barely waking up. The bias spring puts equal pressure to the rears longer before it finally starts to reduce rear pressure.

vetteoz

Many on here would disagree with that

coupeguy2001

pads help, but when I went to C5 brakes on my 86, NOW it stops.

I made my own adapter plates out of 3/16" flat steel, bought front brakes calipers and abutment brackets from a C5 for $100, bought new rotors for $50, and the calipers came with hoses that were 20 years newer than mine, so I used them.

I used C5 thinspokes, and added 1" adapters to each wheel. This setup has been on my car for 6 years, 40,000 miles,so forget what everybody else tells you about adapters, brakes, wheels. It works. I did not change master cylinder, or mess with it.
Upgrading to 17" tires in front with treadwear of 300 or less will give you a much better ride, and helps the car in corners and traction. The backs are going to be 18". Do not use runflat tires.
The expensive part of the swap is tires. Tires will cost you about $800, wheels anywhere from $200-$500, Adapters are $50 each, brakes are $150-$250, and you can do it in about 2 hours.
Making the adapter brackets will take you about 4 hours. You will have to buy bolts, so get grade 8 bolts.
After you assemble this, drive it and make a few panic stops. If you need an adjustable proportioning valve, They sell them on Ebay for around $40. Auto Zone sells short pieces of brake line with double flare and nuts for about $8. NAPA also sells them, and fittings, but NAPA won't let you root through their stock like Auto Zone will.

85vet

Quote:
Originally Posted by SouthCoaster View Post
The stock 85 brakes with a few cheap upgrades like high temp pads and a DRM bias spring will hold even that LS1 back for most driving.

And many will also agree.

mako41

Here's a complete list of those parts, not including the C4 ~ C5 aftermarket non OEM brackets you will need to do the front C5 swap;

https://www.superchevyperformance.co...les.asp?ID=124

I believe forum member 76LS1BIRD makes and sells the aftermarket brackets you'll need to mount the C5 calipers to your spindles. Keep in mind there are two different types one for '84~'87 C4's and one for '88~'96 C4's.

Doug Rippie sells a bias spring that will correct your braking bias after installing the larger C5 setup; Don't skip this part!

http://dougrippie.com/featured/drm-brake-bias-spring-3/

c4cruiser

There are two different DRM brake bias springs; one for ABS-equipped cars and one for non-ABS cars. You will need the non-ABS spring!

VBP also has a kit for installing the C5 front brake system. One thing to note is that if you start to acquire the C5 parts individually, the C5 caliper abutment brackets may be hard to find. Also, look for C5 Z06 calipers. The only difference between them and the "regular" C5 calipers is the color! With a little searching, you can find them for the same price!.

I have the C5 front calipers on my '87. IIRC, I paid about $650 for the C5 pieces and $105 for the custom brackets. You can use the existing C4 front brake hoses if they are in good shape, but I would recommend replacing all the hoses at the same time.

I use Z06-specific front pads and Hawk HP+ pads in the rear. This combo work fine for street, autocross, and I have also done tracks days with this combo. Before I installed the bias spring, the ABS would engage with not much more than 40% braking effort. With the spring, braking is balanced much better for front to rear and the car brakes very hard.

One thing about the C5 front brakes is that you must use a 17" or 18" wheel that clears the calipers. The ZR-1 style wheel with the correct 38mm offset works and the front C5 thin-spoke or even the Z06 front wheels should work when using a 3/4" to 1" adapter.

For tires, 275/40-17 tires have very close to the same diameter and tread width as the OEM 255/50-16 tire. This size would work great on a Z06 front wheel as it's a 17x9.5"

SouthCoaster

I'm not sure how the proportioning valve would work in conjunction with the stock master cylinder which is already reducing rear pressure.

But again, depends what you're using the car for. The main performance benefit of the larger front brakes is they can dissipate heat better, so they won't reach as high a temperature under heavy repetitive braking. If you aren't doing that, like on a road course or have otherwise faded the stock brakes with high temp pads, then you are really upgrading it for looks, so maybe you have some other performance stuff to spend that money on first.

You could improve your stock braking noticeably with just the bias spring alone and better pads.

gerardvg

I have an adjustable proportioning valve under the back of the vette (inline to the rear brakes), with a simple turn o0f the **** you can adjust the rear brakes so they do not lock up before the fronts.

Even with abs you want the brake balance to be spot on, remove the abs fuse and do some hard stops and adjust to suit. Iff the rear brakes lock up first it can send you into a crash backwards.

SouthCoaster

I've never heard of the rear brakes locking first. The factory is way too conservative with them, the bias springs are designed to put more pressure to them, and the front brake kits only increase the front braking.

So I'm not sure what sort of brake mods would ever warrant reducing your rear pressure more than GM did already.

gerardvg

The reason i fitted an adjustable brake proportional valve is due to upgrading the stock single piston caliper and 12 inch discs to twin piston calipers and 13 inch discs on the front.


That results in more brake fluid required to make the front brakes work, hence the rears tend to lock first especially in the wet while the front are only just starting to work. Although abs works when this is done the braking will not be effective as the rears will be doing 90% of the braking.

My 85 master cylinder has an extra brake pipe at the base compared to the 88-91 type, the 88 brake master cylinder i got for the twin piston calipers that would have had the correct bias spring didn't fit
although i used the bias spring from that i still had the odd lock up of the rear brakes on wet roads....

Standard i never had an issue as the bias spring in the master cylinder was made to suit the standard brakes, i agree there is a slight improvement in stock with some aftermarket bias springs to help the rear do more work.

By having a adjustable bias valve in a modified brake system as in fitting large calipers in the front, it allowed me to dial in the perfect balance. I do a lot of track work and it has made a tremendous improvement in track times and overall stability, she would lock the rears in wet weather or sharp sudden brake applications.

If you were to install C6 front and rear brakes a C6 master cylinder and its proportioning valve may work but the C4 and C6 front rear weight balance is different so you may still need to fine tune it.

Hope that helps explain the reason for the adjustable bias valve under the car to the rear brakes, only needed if modifying the brakes from standard.