Got all my new suspension installed and was wondering how everybody checks toe and what specs I should be shooting for with autocross duty for my 2011 coming up.

 

Best shown with a few pictures - this is how I do it: Measuring Toe. For road course I aim for zero toe to very slightly toe'd out (less than 1/16"). Generally for AX I think most guys like a little toe out (fronts of tires futher apart than rears) in the neighborhood of 1/16". But keep in mind adding toe out makes the car more 'darty' on the street (standard alignments typically have toe in to make the steering more stable).

If you have adjustable camber and/or caster make sure you get those adjustments done first...toe should be the final adjustment. And make sure you measure on level ground with the suspension fully settled.

 

There are several ways to check toe.

For dirt cheap if you've got a little patience and a wind-less day, just set up parallel strings, one on each side of the car, and measure from them to the wheel flanges ahead of and behind the axle centerline.

However you choose to do this, it's far better to work off the wheels rather than the tire sidewalls. Molded information and other tire nonuniformities will make it difficult to actually get what you think you're setting. A bent wheel will mess things up even doing it this way, but it would anyway.


Norm

 

Last night I took a string tied to 2 jack stands and ran it along the passenger side of the car. I had the string pass through the center line of each wheel. I squared up the string to the back wheel and then took measurements from the front and back of the rim on the front wheel. How do you know that the steering wheel is exactly straight before taking measurements? My car lowered almost exactly 1" with the Steeda sport springs and Steeda HD upper strut mounts.

Another question: how much camber should I dial in for Autocross this weekend?

 

You may not really know this until afterward and you drive it a bit. If the steering wheel is only off a little bit, total toe is good, and you made your initial toe adjustments equally on both sides, just adjust the toe on one side inward and the toe on the other side outward in equal amounts.


If you're relatively new to auto-X, just set them to -1.25° or so and don't worry about it until you've got more seat time under your belt. The biggest gains come early just from learning how to drive the various course features and how they might be strung together.

Otherwise, it depends on how serious you are, what the rest of your driving is like, and whether you're willing to work with two sets of camber specs (swapping back and forth between them at the auto-X lot).


Norm

 

If I am adjusting camber for daily driving and weekend racing, do I have to also adjust toe back and forth?

 

Probably not. The S197 toe change as a function of camber change done at the strut top is apparently pretty slow. Most front steer cars tend to go toward toe out as camber goes more negative when camber is adjusted at the strut tops, which at least would be in the direction that you'd like it to go in.


Norm

 

Car looks great. What size wheels and tires did you go with?

 

Wheels are SVT Shelby 9.5"x19 with 255 and 285 Goodyear F1 Supercar tires. Checked toe and it measures 1/8" toe out on each side. Looks like I need to move it in. Is there a ratio of turns on the tie rod to movement of toe?

 

Yes, but I don't know what it is.

If you know the pitch of the tierod thread and the length of the steering arm measured to the steering axis, you've got enough information to calculate it close enough to put the toes in the ballpark.

FWIW, 1/8" at the tire tread will be about 0.08" at the wheel flanges, which are much more reliable surfaces to take measurements from/to than the tires.

FWIW #2, it may be easier to deal with toe as angles (1/8" toe given in inch specs on a 27" OD tire is very close to 0.25° in degrees)


Or you could turn both the left and right tierod adjustments exactly one turn in the direction you need to go, roll the car a few feet back and forth, and see how much toe change occurred. Chalk-marking the tierods will make it easier to make "exactly one turn".


Norm