1999 EXPEDITION AWD
 

Hello, New to forum have question concerning awd bypass, I was wandering if pulling the fuse do I still have to worry about tire dimensions like I do if I don't bypass as in keeping the tires all within 3/32 of each other as well as tread pattern. Thanks as i have 8/32 in back and need 2 front tires asap, 255/70/16

What about your ABS?

Not sure of he abs system and if that would effect the tires size

No you do not, and to answer the other good question that came up, no the ABS will not be affected since that works by counting the passage of the tone ring teeth per wheel.

Except that the ABS might kick in while braking if there is too much variation in tire demensions.
I’m not sure on how much variation you can get away with.

I can’t remember, but does the ‘99 have a 2H position on the selector switch?

99 does not have 2h, if it did he wouldn’t be pulling the fuse.

No it does not work that way. The ABS continually counts the tone ring pulses and will only interfere if it sees a gap in the pulse count because it thinks the wheel has locked up and stopped turning. The size of the tires or any variety in the size of tires on the vehicle has no affect on how the ABS works.

Okay. What your saying is that the wheel tone ring signal must go to zero in order for the ABS to kick in while braking. I didn’t know that. Thanks for the correction.

No not necessarily zero, it just has to break the evenly spaced pattern the sensor counts as the tone ring teeth pass it. It's really fast, the pattern is counted in hundreds of a second, if not thousands. See the crack in the tone ring in this image, that additional gap is enough of a break in the pattern for the ABS to kick in when applying the brakes even though the wheel really isn't locking up.

https://cimg7.ibsrv.net/gimg/www.for...a510026fbb.jpg