odxr

I bought a 86 c4 for $1500 to use for a track day car.86 was the first year for abs.Did these systems work or should the car by changed to an 85 master cylinder and a adjustable proportioning valve?I am stripping about 400 lbs of weight out of the car and suspect the abs will be confused.

TurbineSurgine

My car is a 85 and I was considering adding abs when I flat spotted a slick. Subscribed

Aardwolf

I removed it from my '88 here is the thread:

https://www.corvetteforum.com/forums...bs-thread.html

eogel

I bought an '86 in 2000 and have been road racing it ever since in NASA and SCCA with the stock ABS with no problems. Your weight removal will have no effect on the ABS, but will improve the braking. I have also upgraded the front calipers to Wilwood 4 piston and racing brake pads with no effect on the ABS, but greatly improved braking. My rear brakes are stock.

Rob31

I have an 86 , I have experienced some issues . but only on a 10/10s pace . Stab the brake ,the car seems to load the front wheels ,then pressure seems to release with no effect on the brake pedal . Almost like an overheated pad .If you ease on the brake ,no problem .Hit them hard it becomes a problem .

Bill Dearborn

I tracked and autocrossed my 86 for 6 seasons until I took delivery of a 97. The ABS worked fine for me. I used it all of the time when autocrossing but don't remember any situations where I actually got into it at the track.

The biggest problem with the 86 brakes is the small brake system. 3 Laps at the Glen and I was out of brakes (not boiled, just no friction) and had to do a couple of cool down laps to get them back. I had a friend who worked for a company that got me a couple of brackets to fit the 88 and up Z51 system (large caliper/rotor) on the car and the brake problems went away although you really can't push them that hard with only 230 HP and a top speed of 125 mph in 4th gear. Those calipers fit under the Stock 8.5x16 wheels and the 9.5x16 inch Enkei wheels. The other brand of 9.5x16 wheels used in 84 and 85 had to be individually fitted because of large amounts of casting flash inside the wheel where the spoke joined the barrel which sometimes wouldn't clear the caliper. Sometimes you could grind the fins on the caliper and other times the wheel had so much variability in the backside that you couldn't use it.

The hot ticket now is to throw some C5 calipers on the front.

Rear calipers/pads from the 88 and up cars will fit in the 84-87 rear calipers. The only difference is the 88 and up pads had notches in them for the 88 and up parking brake linkage. Other than the notch the pads are identical.

Fix the lack of brakes and add some more power/rpm and the car will be a track monster.

If you have the 4+3 tranny see if you can swap it for a newer 6 speed. It is too difficult trying to figure out where to put the shifter when you try to use the 3 overdrive gears besides the overdrive unit can have problems due to leakage from the main transmission. The 86 through 88 overdrive activation can be tuned to some extent by adjusting the TPS sensor so it swings through its full voltage range from .5 volts to 4.5 volts at closed and wide open throttle settings. The O/D tries to shift in when speed exceeds 107 mph in 4th but over time and lots of WOT operation the ECM will learn that it shouldn't shift into O/D automatically.

Bill

BrianCunningham

Brake ducts are a must

I've boiled my J55's and they're a lot bigger

TurbineSurgine

Which Willwood calipers do you use? The only kit I know of uses the 6 pot dynalight narrows. Do you use the 2PC rotors also? I would like to run a 4pot caliper with stock 13" rotors.

eogel

They are Wilwood Forged Superlite 4 piston calipers. Part 120-8465. I do not recall if a special bracket was required for mounting. This is a brake mod approved for racing in the Touring Challenge for Corvettes (TCC) several years ago. If a bracket was required, we got them from Robert Finlayson, AFX Performance. Front rotors are stock.

Ed

odxr

The j55 brakes are from what year of vette?Sounds like some more shopping at Rock Auto.

theseal

The only abs system on any vette since 87 is the 01-04 z06 setup. I don't know if the base model tuning is the same as z06 but I doubt it.

All the later stuff is complete garbage because it's not abs it's active handling.

Agreed on the pitiful hardware though. I'm thinking of trying the wilwood Bolton

BrianCunningham

They were standard 1995 & up, before then they were an option on certain years.

You need the brackets to go with it.

I was helping someone upgrade their brakes when I took the photo.

I'd go with the Wilwoods suggested.

Bill Dearborn

Not sure I understand this comment. C4s had ABS from 86 through 96 with no active handling. C5s had ABS in 97 and in 98 and 99 AH was an option. I think they made it standard in 2000. In 01 they changed the system to add DRP and it wasn't much different until 2010 when they added the Launch Control function to the EBCM and ECM. Active handling just rides on the base ABS as AH can't work without an ABS to work it on. AH can be totally disabled by disconnecting the steering sensor while ABS remains functional so it definitely doesn't impact ABS.

Bill

theseal

I guess I should have been more precise. Ah is a traction control routine which can be turned off...but the overall 'active handling' also includes the vehicle stability enhancement system and dynamic rear proportioning -- which are baked into the abs and which can't be turned off.


The 86-87 abs was pretty good. It was simple. Basically preventing whatever wheel was locking. That's what you want unless the car is mechanically/hydraulically wrong to start with.

I haven't raced 88-89 but my 90 had a lateral accelerometer and some routines in it that seemed to pull rear bias at over .5 lateral g. In other words, between that lat accell routine and the excessive kingpin and poor Ackerman GM baked into the later cars, it was a pig compared to the earlier cars. The 96 was about the same. Not terrible, but not as good as the 86-7. Ice mode was a regular problem in auto cross, in those late c4's too

My 99 just had way to much front hydraulic bias and so it was difficult to
Get the most out of. But I didn't notice it actively fighting me with drp. I've never studied the early c5 manuals so I don't know how much drp/vses was incorporated.


The 02-4 z06's had drp but it was tuned brilliantly. It was obvious that those cars were tuned and programmed by real drivers.

The c6 was most certainly not. At least the 08's I have had. When I say active handling I guess I really mean the drp and vses routines in the abs


Bottom line before the c6, the c5z had very well tuned suspension and brake proportioning. The drp routine was tuned to keep the car working correctly when driven by good drivers.

The c6z, at least the 08s I am very familiar with, were hydraulically barely in the ballpark. The cars suspension was tuned to feel 'crisp' on the street, and just lean on the electronics to keep the butt behind the nose. So if you are a good driver, the vses and drp will prevent you from ever really getting the most out of the car on corner entry.

Further, on the 08's the computer won't even allow Rear hydraulic pressure until you are several tenths of a second into your braking, and never allow any yaw angle, so the cars can never be anything but pigs when trail braking.


It's funny, you can really tell which generations of GM cars were tuned by drivers and which weren't. 82-92 camaro and 84-87 vette - drivers. C5 vette? Drivers.

C6. It was a software engineers convention.

Ps. Sorry if this rambles, tired and not much time. I'll be back to clean it up.

theseal

Ps, I know they had different tunes on the c6 and I think 2 completely different abs units on different years. One Bosch, the other I think Delco but am not sure. The Bosch is tuned to be complete garbage on the 08's.