Contributed by John Aho Saturday, 31 December 2005
Ideally your local wheel alignment store will have these specs in their computer, but it wouldn't hurt to have these in hand when you bring your car in. If you are setting your toe by hand, be as accurate as possible as the specs are fairly fine and most likely within the margin of error of any hand-setting technique.
"Toe" is the setting of the front wheel alignment that specifies whether the two front wheels point inwards at each other at the front, or not. Toe-in is when the front wheels do point inwards at each other (slightly), and toe-out or negative toe is when they are splayed out from each other. Individual toe for each wheel is added together to get the total for the front axle.
On our racecars, for short & tight tracks we run a lot of negative toe (toe-out) to help turn in characteristics. But that won't work on the street, and massive toe-in won't help anywhere.
A little bit of toe-in on a street car is useful to ensure the wheels point straight when moving forward, as forces working on the bushings cause the wheels to splay out. If you have stiffer/less compliant bushings, then less toe-in is needed to counteract those driving forces.
BMW specs shown in the service manual & the owner's manual have slightly different values. These are "total toe" for the front axle, cut the number in half for individual toe.
Owner's Manual (1973)
1 mm (+/- 1 mm)
0*, 10' (+/- 10') or in decimal that's 0.166 degrees (+/- 0.166 deg)
1.5 mm (+1 / -.5 mm)
0*, 14" (+9' / -4') or in decimal that's 0.233 degrees (+0.15 / - 0.066)
If you are doing it yourself at home, then the distance (like 0 to 1 mm) is useful to read off the tape measure. Be aware that you will likely be measuring at the tire tread, and the factory distance value is from the rim. Won't really matter, as the difference is less than the presumed accuarcy of the method, and it's probably better to err on having less toe anyways.
Going to a Professional:
If you decide to take your car to a shop's alignment rack, the tech may not know how to change his machine's display units to read distance (1 mm) or degrees/minutes, so that's where the decimal angle spec is good to know.
For a reasonably tight street driven 02, I'd say ask for total front toe of around 0.15 to 0.20 degrees.
These values are typical for many BMW. For example, the E36 M3 has less toe specified for the sports suspension vs the stock (nominal angle of 10 minutes vs 20 minutes.)
I just had to set toe on my 98 Compact, after installing late E36 M3 lower control arms which have a different geometry. These M3 LCA's feature more caster, achieving that by placing the ball joint approx. 10 mm forward of the standard E36. I put the LCA's on with solid motorsport bushings (not offset), and the geometry pushed the toe out 38 mm ! I used longacre toe plates to reset that to near 1 mm toe-in before I could test drive it. I've checked it a again since the install, and the measurement is repeatable & the car feels good.
Still, there is no substitute for a computerized Hunter alignment machine for checking and setting the whole front & rear alignment specs accurately.