For my 2014 GT... How much different can the overall tire diameters be between front and rear before the car's brain thinks there's a traction problem? Or does it not matter? TIA!

 

It's not an AWD car.... The rear wheels only apply in ratio with the speedo gear....fronts are only along for the ride.

 

Thanks. After posting my question, I read in another forum that the ABS would read the different wheel speed front to rear, think the car is in a skid, and react. Not true?

 

Simply put: Do not put different size diameter tires on the front and back. The ABS will go nutz, all the time.

You can, of course, get all the same, such as I did this go 'round for Awesome with the 275/40-18s on the 2010 GT500 'Vert wheels. Or you can get a staggered set, which would be the 255/45-18s in front, and the 285/40-18s in the back, which, provided you get the same manufacturer for both sizes, will ensure they are indeed the same diameter. As examples. But don't go putting a bigger tire on the backs, diameter-wise, than the fronts. Or vice versa.

I'd say that a 1/4-1/2" difference is enough. I've seen it in person. Guy had a Mark VIII (and at the time, so did I), complaining of this problem of the ABS always coming on. He had goodyears on the back, michelins in the front, same 'size', but the difference in manufacturing was causing the computer to read speed differences, and launch the ABS.

Now, apparently the Mark VIII had some weird rims or such, so while I was doing work there at that dealership, they asked if they could borrow my relatively fresh BFG Touring TA tires and wheels. Bemused, I said "Sure, why not? It'll teach the guy something."

Sure enough, they put 'em on his car, got him in it with a tech, and lo and behold... Problem solved. He had to go get another two matching tires, either the Goodyears or the Michelins. Don't know which he picked. I got my wheels and tires back, of course.

Dude didn't believe them until it was demonstrated. And I saw the car, it was no more than 1/2" inch of diameter difference between the two makes of tires, but there it was. Smaller ones were in the front, if it matters.

If that helps any.

 

Sure Thing. That's why the Shelby's have like 265/40/19 front and 285/35/20 rear... 27.35" front and 27.85" rear in diameter. Stock.

I was putting those on my car and never had any ABS issue.

LEXiiON

 

Interesting. I wonder if it's the nature of the car (and the suspected drivers that'd be drivin' them) that Ford maybe has a little less stringent ABS rules regarding the sensors. So we can do burnouts and stuff.

I say you put different size tires on it Vike and let us know when you get all the experimentin' done, k? Thanks!

 

Can verify for you that 19/20 combo on a non cobra produced no abnormal behaviour from ABS, have never seen it or known anyone to experience anything like that first hand. Lot of friend-of-a-friend hearsay, but nothing else. If rears turning faster than fronts caused an ABS freakout all your burnouts would really suck.






That said, your ABS does not react based on what the other wheels are doing. If you lost traction on left front how much sense does it make that your rears are going to trigger? No. Each corner is processed independently. If you stop to think about it, that's sort of the point.