Sorry again Joe, 0 for 2!
ABS systems do not work on acceleration principles, which is dynamic,
but on static principles, the rate of speed. The abs sensors on each
wheel feed the computer that wheels speed, and the computer compares the
speeds given at each sensor to each other, and if the brakes are on, it
releases and pulses brake fluid pressure to the wheel/wheels with the
slowest speed, ie. locked up. Traction control works on the reverse, it
limits throttle when it sees wheels spinning faster that other wheels.
Tire diameter can affect this. If 2 different size wheels are on a
vehicle, this will have tremendous effect. If the vehicle has the wrong
size tire on the right size wheel, it can also set a code. And even if
the wheels and tires are correct size, if the tire diameter is large
enough and some of the tires are new and the other ones are completely
bald, this can change the circumference of the tire enough to adversely
affect the abs system.
Some systems take readings off the vehicle speed sensor mounted on the
transmission, and changing wheel sizes requires recalibrating something
if possible, so the computer has new parameters to go by. Not all
systems are like this, but beware if you plan on changing wheels. Dont
forget, changing wheels also can affect the accuracy of the speedometer.
For you 4X4 guys, you can seriously damage your transfer case by
running different size tires from the other ones on your truck. So if
you went to 30X9.50's from 215/75's, you better get a spare to match,
dont dare put your factory spare on! If any one questions this, go see
how many 4X4's come with matching spares, and how many 2X4's come with
matching size or a smaller "donut" spare (yes, manufacturers even use
the donuts spares on pickups!)
Patrick J. Engram
ASE Certified Tech
This archive was generated by hypermail 2b29 : Fri Jun 20 2003 - 12:08:37 EDT