ColinW

I wanted to dial 1/8" (0.125") of toe in per rear wheel, a number a lot of people recommend for autox, but my alignment shop does everything in degrees.

When I convert, should I use the outside tire diameter (vs the rim diameter)?

So radius = 26.1" tire/2 = 1

Tan-1 (.125/26.1) = .009578 radian

.009578 * 180/PI = .55 degrees

Does this sound about right?

Thanks!
Col

Bill Dearborn

You should use the rim diameter. The shop will set up their equipment on the rims not the tires.

Bill

jbauch357

+1 the alignment heads lock onto the outer diameter of the rims...

Road machine

Use the rim. The formula for translating degrees to inches over the wheel size is as follows.

Offset= rim size (18") X tan of the degrees you want to add(1 deg = 0 .0175) so 18 X .0175= .3142.

To go the opposite direction... Knowing the offset and looking for the angle.

Tan of the angle= .125 (offset amount)/ 18 (rim dia) So .125/18=.0069= angle of 24 minutes or .4 degrees or more precisely .3979 degrees.

Hope this helps.

ColinW

Thanks guys.

I guess that makes sense that you use the whole rim, rather than half, since toe is the difference from the front and the back.

So does 1/8" toe in in back sound like a good amount?

I was going to go with zero toe upfront and -0.9 camber.
Out back, -0.7 or -0.8 camber and 1/8 toe in per wheel. Just looking for something a little more aggressive, but just for street use.

Thanks!
Colin

ColinW

So I realized that I wanted 0.125" toe in at the edge of the tire (where I've been setting it so far), so that's arc tan (0.0625 (half total toe)/13.05 (half tire diameter)) * 180/pi = .27 degrees. (This is the same as 0.086" toe in at the rear wheel rim).

Anyways, did those alignment (last post) sound reasonable?

Thanks!
Col

vms4evr

I'd go 1/8" total toe-in in the rear. 1/8" per side is ok but don't go past that.

If you're setting this car up for AX then go with more front camber. My previous settings worked well for track/ax/street.

Front: Camber= -1.5 Caster: 7deg Toe=1/32" out per side
Rear: Camber= -1.0 Toe=1/16" in per side

You'll get a bit of tire wear on the street but not much. For AX it will work well and for track it works very well for me.

Remember that not everyone wants a car setup the same way. Some people like cars that feel loose. Some are ok with understeer and/or oversteer. The above numbers are good for aggressive driving. With FS WO tires for the street I don't get any tramlining issues. With the GY F1s you might get some as they wear. If you want to AX with race rubber then you'll need that camber on the front or you'll be cording the edges of the tires.

I'm a bit confused on your alignment shop and what equipment they use. All the newer Hunter alignment racks operate in either mode. I use inches for toe and degrees for camber and my alignment guy is just fine with it.