abs inop

[stevo5662]

Well just the day before yesterday i put a set of the C5 vette rims on my car. I got 18's int he back and 17's in the front and they were fine at first except for a lil tire rub on the inside fender in the back but a hammer fixed that. Then last night just randomly driving the abs inoperable light came on and the brake light came on. i made sure my e-brake wasnt engaged and even shut it off then turned it back on and the light went out then came back a few minutes later. also sometimes i get the low trac light on downshifts and im not downshifting hard. even my old skinnier tires wouldnt spin when i downshifted like that.

[Bad Andy]

I put my camaro on a dyno and they disconnected the traction control manually somehow on the car. They never reconnected it and it left mey abs inop light on. I actually had a dealer fix it for me, i should have called the dyno place. I'm not exactly sure were the sensor is, maybe your new rims nocked it loose. Hope i helped ya.

[Orcus79]

It is possible that that on the remote chance that your ABS pump has died. i doubt that changing the rims did anything. If you are getting both the ABS inop light and the brake light there are major issues some where and should be checked out right away. Check to make sure you don't have any leaks in all the hoses and any fittings.

[badazta]

check the wires that go to the back wheels. I jacked mine up one day and pinched the wire. abs came on so did the trac. light. Just an i
dea....

[2001NBMZ28]

Check the wheel sensor connections first, you have traction control? How much difference in the overall tire diameters front to back?

[stevo5662]

the total tire height isnt that much different. And it is not consistant. the light only comes on when i get on the brakes really hard. then i wont see it again for a while

[Orcus79]

the light coming on when you are hard on the brakes is normal, usually caused when they lose contact with the road, happened to me when the rear tires hit a crakc in the road under moderate breaking no TC. The tires could also be sliding due to lack of ABS causing the low traction light to come on, just my two cents. Get the sytem checked out should be a code being generated.

[98Camarod]

I just put on new wheels also and the same thing happened. It is because they are two different sizes. I am just trying to see how to fix it.

[2manycis]

if your tire diameters are different front and rear... or anywhere on the car, it'll make one or some wheels travel faster that the others, causing your abs to whack out. Put a doughnut on your car, the same thing should happen.

Try putting your old rims and tires back on the car and see if the problem goes away.

[98Camarod]

That is not the way that I want to fix it. I want to keep my NEW wheels on and get rid of the lights.

[2manycis]

I wasn't recommending it as a fix. Just saying try it out to see if that's actually it. If you know for sure that's the problem then maybe try a tire with a smaller sidewall?

[98Camarod]

My abs inop and brake light came on before when I started the car on the lift. I drove halfway down the street and they were off. I put these tires on and I go halfway down the street and the bitches come on.

[Steve Crowe]

Interesting problem, and a hard one to correct at that. You'd need an electronic device that could correct the output of the off-size wheels to match that the BCM expects to see.

This would be similar to the speed correctors they sell to correct for changing tire sizes all around; the one that goes in series with the VSS and corrects the pulse frequency per rotation so your speedometer reads correctly and your tranny will retain the proper shift points.

I could design and build such a monster, probably take about two weeks of research and another week or so to finalize it. To keep expenses down it would have to be a "cut and hardwire in" arrangement or I'd have to scrounge up some used connectors so it could plug inline with the connector going to the BCM. Cost? Probably around $150 for a single unit, less if done in volume.

[98Camarod]

The speedo calibrates from all four tires and not just the rear? I would think that it would only be necessary for the rear to be known because of all the different setups of gears you could have.

[Steve Crowe]

The speedo feeds from the VSS which is connected to a pont in the final drive of the tranny. It's not in any way associated with the wheel speed sensors that feed data to the antilock brakes and traction control monitored by the BCM

[98Camarod]

So then why when I changed the wheels the lights came on?

[Steve Crowe]

Obviously the diameter of the tire/wheel combination you put on the rears is different from that of the fronts.

What size tires are your running, front & rear?

[98Camarod]

Front 255/40/17 and rear 255/50/17

[tdking112]

vss and wheel speed data are read by the ebcm(electronic brake contol module). you may actually be able to recalibrate the ebcm to your new tire sizes using a tech 2 scan tool. I've done it before on an 01 blazer. check with a local general motors dealer.

[Steve Crowe]

The 255/40R17 have a diameter of 25.0" and rotate 833 times per mile.

The 255/50R17 have a diameter of 27.1" and rotate 769 times per mile.

The BCM thinks you've got flat rear tires or, since it assumes they're really not and that the tire sizes are as they came from the factory it thinks the wheel speed sensors are amuck.

I just chose a tire I like to get the data but it'll be virtually the same regardless of brand.

http://www.tirerack.com/tires/Spec.j...irePageLocQty=