utjmac

I just swapped my full tread Potenza's for a new set of Michelin Pilot Sport's, and what a difference that makes! My Potenzas were over 12 years old, and lots of cracking, so it was time to go.

I've never had a warning light come on until 5 minutes after leaving Costco today. The antilock warning light came on, I cleared out the "!", and the antilock light remained on. After a shutdown and restart, it came back on about 5 minutes later, both at highway speeds, 75-85mph.

Is this coincidence or are there sensitive ABS wires that could have been disconnected or knocked loose during a tire change?

FYI - Always take pictures of your wheels prior to getting new tires. I've always been happy with Costco, but today I swear they gauged my front two Cup replicas, but the manager swore that he saw the scrapes before hand. My wheels aren't perfect, but he said the guy called him over specifically to show him prior to dismounting

What should I check first?

Thanks in advance for the assistance!
John

worf928

What size tires did you put on? More than a 5% (IIRC) difference in overall rolling circumference will cause an ABS error.

Bob Rouleau

I agree with Worf928 - this is a common problem. Check the tire rack specs for rolling diameters of the old and the new tires. If the difference is more than 3 percent, ABS get "confused" because wheel speeds (front to rear) are different from what is expected. In the worst case I've seen, ABS kicks in and reduces brake pressure when you are hard on the brakes. That's a BAD thing!!

86'928S MeteorGrey

If the tire diameters are ok, I'd pull the wheels and check for sensor/wire damage. Box store monkeys can't be trusted.

jon928se

If your tyres are the correct size (or within X% rolling radius), the it could be complete coincidence and just happened to have a sensor that is failing or as you suggest it is possible that the ABS sensor wiring got dislodged - check all the barrel shaped connectors at each wheel - unplug and reconnect the ABS sensor plugs from the barrel shaped connectors a couple of times to clean the contacts. Also worth doing the same at the connector in the spare wheel well and under the hood on the drivers side near the ABS unit.

utjmac

Replaced with same size tire, Potenza S-02's to new Pilot Sports. I can't believe there would be a 5% difference in the same size tire.

Thanks for the suggestions, I'll pull the tires and investigate in the morning.

John

worf928

What size? Exactly? Front and rear?

Randy V

Model year of your 928?

utjmac

Sorry, I still haven't figured out how to customize my signature here. It's an early 86 928S.

Fronts are 225/45 17
Rears are 255/40 17

Replaced with like size, different model. I drove the car in medium paced traffic yesterday, and the warning didn't come back on. Thoughts?

Mrmerlin

check the tire pressure

worf928

Totally stock-sized (for 17") so, tires are not the problem.

utjmac

But my vehicle came with 16" wheels originally. I know the previous owner upgraded the wheels, and looks as if he's rolled the fenders out. The stance and offset looks correct, but again, I was replacing like tires with new ones. I'm just trying to put all the data on the table. I need to pull the wheels and inspect as suggested. Thanks guys!