quote:Originally posted by JFB #05177:
question...Isn't toe measure at the OD of the tire?
The chart I copied from "somewhere", I am not getting equivalent values when I try to go back and forth from angle to inches
Yes. Toe in is the difference of the "track" between front and back of the tire.
It isn't measured in degrees to my knowledge. I've only seen it stated in inches.
That chart could be for a specific machine but frankly you can do toe in with a tape measure on the floor.
It is an approximation. It will change on the same car by just changing from a bias tire to a radial since the wall of the radial tire is softer and the only way that you can standardize the measurements is off of the wall of the tire, not the tread.
Trying to read it from the tread is inaccurate.
I do it by clamping plywood plates to the tire with a bungee cord. The plates sit on the floor and measure the distance between them along the floor.
Computerized alignment machines are WAY over rated. They are most useful for adjusting the camber since the front plates are easily moved in and out with the car weight sitting fully on them.
You set the camber off of the rim of the wheel though.
Every club racer that I know of does their own alignment on the garage floor unless they own their own shop with an alignment machine.
Every car is going to be different. Those charts are just a guide. They don't need to be set to a 1/10th of a degree.
My Pantera is set at 5/8 of a degree negative BUT that's because that's where the tread of the tire sits flat and equally loaded.
My 92 SHO Taurus was set at -2 degrees to get the tire flat on it's treads. Factory specs were for the stock tire. When I went from a 215-60-16 to a 245-55-16 the change became mandatory. Stock settings would no longer work.
The type of tread pattern that the tire has CAN also effect the exact toe in setting. 3/16 might feather edge the blocks in the tread while 1/8 might not. A race tire with a "slick" pattern no longer cares about that consideration.
You may in fact need to "play" with the settings until the car is right?
You also need to standardize the air pressure in the tires. Too low of a setting and things like the toe-in will change too much in hard cornering.
More is better then less. Just for the sake of discussion if say you usually run 32psi, go to 40 psi and go drive the car. You will more then notice the change in handling.