Not the 'offset' but the diameter of the tires. What tire sizes do you have on the 18 & 19 wheels. It could actually be the diameter difference of the 18 vs the 19 is so dramatic it's setting the ABS/ASR.

WHAT SIZE 18" and 19" TIRES ARE ON THE WHEELS?

Maybe only a speedometer correction is required to correct it if the diameters are dramatically different than the 17" tires but similar to one another.

It would be aggravating but you could put the 18 & 19 back on the car and compare the speedometer to a GPS and post back the differences.

Do a check at maybe 40 - 50 - 60 - 70 MPH from the speedometer and note the GPS value for each. We want to establish a % of error so we need multiple values.

It might be possible to do using tire sizes of the OE combination as a comparison. Involves more math.

It will require either speedometer correction or maybe a change in the tooth count on the ABS ring on the rear spindles. I know people that have done that.

 

The rear tires are 1.2 inches larger in diameter. The front tires are the same diameter as stock 25.7 rears are 26.9. IDK if module can sent off to be reprogrammed. It would be simpler to go with a different tire combination.

 

I have a 92 6speed, used to have this problem with stock wheels. If the lights come on after hard turns, acceleration, or braking. Try checking your brake fluid levels, i topped mine off and it solved the problem

 

Thanks for the reply. The tire size off of the 16 vette are 245/40R18 and 285/35R19. I hooked up myGPS and it appears the speedometer is 5mph on the high side.

 

Brake fluid is right full.

 

You need to decide how well you like the sizes that you have!! That will determine everything I'd think as to how you go about it. You need to do the speedo checks like I mentioned in post#2. NO GUESSING - do it 3 - 5 times.

The rears are 774 RPM and I've not compared them yet to the 285/17 that I'm guessing was there originally. I've never had a M6 with a PCM so I don't know how much of a tweak can/could be done in the PCM. Even after a speedo calibration you could have issues, that's why I mentioned the ABS rings.

If you liked the tires well ........ if you don't mind changing tires to something more comparable to the originals as far as RPM that might be the thing to do.

I don't like 19" on a C4 - 18" can be done to look very good.

*** Here's the thing maybe - often it's said that 4.5% will often be tolerated - your 18/19 (809/774) combo is right at that threshold and combined with the the difference when doing turns the ABS sees a difference(lateral acceleration) and the lights are maybe only an 'advise' warning. Do you actual feel anything? Were the car mine I'd certainly calibrate the speedometer first and reevaluate things after that. If the WSS sees a dramatic difference compared to the VSS (and yours certainly should) it also sets the warning sequence. I'd think a drive after calibration on a scanner might be the thing to do. Prepare for the worst!!

The fact that the original tires are both 799 RPM (advertised) maybe the 4.5% is a stretch.

These might be ideal but then you've wheel width issues I'd think, maybe 275/40/18 & 325/30/19