The ABS on the 1986 car seems to work great on the street, but it greatly reduces braking effectiveness... especially as an example where I brake hard coming out of a corner that had some wheel spin or differential between speed f/r just prior..... brake foot to the floor with everything I have and still very little braking. Happened twice on the autocross courses, once two weeks ago and then every time this weekend. Unplugged the ABS after that and no more issues, but prefer to to somewhat neuter the current aggressively controlled ABS strategy.

 

Not that I know of. I own one of the Kent-Moore ABS test tools that were used by dealers to repair the systems and can verify there is no programmability via that route.

 

There's a recent thread on here showing a video where a guy opens the ports and is able to clean a couple of screen/filters pretty easily. Yours may be getting clogged.

 

I have the Kent Moore ABS Tester and Pinout box for 1986-1989 Corvette ABS. It allows you to diagnose, but no way to program. If you get an ABS error (ABS lights up) the only way to read the code is with this tool.

 

I wonder if it could work to retro fit a later year system? On my '88 I removed the ABS because of those and other issues. I would like to add in a racing abs system at some point.

 

The Gent I bought the Kent Moore dealer tool was a Porsche guy. Remember, this is a Bosch system and was used on several makes/models. I believe he used the tool on his Porsche 924 or 944s. Another source of info for this question might be some of those forums. You never know what others have figured out.

 

This sounds like the infamous GM "ice mode." My 96 definitely did it a lot during autocross runs, where brake and throttle inputs are close together and pretty abrupt and some tires aren't always very stuck down. No, nobody has come up with a way to reprogram them - if they did, there would be over 30 years' worth of GM owners lining up to hand them money! Those ABS module is separate from the ECM/PCM, and it's not flashable or blessed with replaceable PROMs. I went down a rabbit hole with someone on this forum a while back, who thought he might be able to trick the late C4 system into not doing it, but it never came to anything. Ice mode sucks because the C4 is an inherently good-braking car, but it's hard to rely on the brakes. If I were doing a full-on CAM-S or Optima build, I'd chuck the whole ABS system and either do fully manual brakes with a balance bar or spend the big money for a race-oriented ABS system. That's the only real solution.

You can mitigate it with pads that are less grabby. If you are a left-foot braker in competition, stop that and go to right foot only. It helps avoid overlapping pedal inputs, which seems to invite ice mode. Probably some tires are worse than others. I used Rival S tires, which weren't very good for launching or braking. Now I'd use either the Yokohama A052 or Falken RT660, which are better for longitudinal traction. I never got to try those on my C4 before I sold it.

FWIW, in 2019 GM finally got the Camaro brake system to hit ice mode a lot less frequently: my 2020 1LE barely ever gets it, even during autocross runs. I would consider that to be fixed. Not sure if any C7s got that improvement, but I'm guessing the C8 does.

 

^THIS

I've actually never got ice mode in my 93 C4. That being said, J55 system with Ferodo DS2500 front pads and Hawk HPS rear. I use the brakes quite hard in auto-x or track days. The DS2500 is a great brake pad. Your 86 fundamentally has a older ABS system and the suspension has a much different design (positive scrub radius) instead of the zero scrub in the 89 and up cars.