carreracoupe997

I have the luxury of and alignment rack at where I work but the toe settings are only in degrees/minutes. The car is an '86 951 race car and I want to run a litttle toe out in front and a little toe in at the rear. Recomendations for settings in degrees /minutes would greatly be appreciated.

TheOtherEric

It's a good question, and I've seen a lot of conflicting answers on this. To convert inches to degrees, use the equation: (Toe per side) = Diameter * sin(angle)

But the question is: what diameter to use? Is it the wheel diameter or outside tire diameter? There's surely a "correct" answer but search and you'll see lots of disagreement on that, but most seem to use wheel diameter. Which, BTW, is ridiculous that toe would depend on wheel size, since toe should be a measure of angle not distance.

SundayDriver

A couple of things. Your equation should use radius, not diameter. You are measuring the toe at only one end of the wheel or tire and that is relative to the center of the wheel.

The correct measurement point is whatever you decide to use, or what others use who are giving you a spec. It will either be the outer edge of the wheel or the bulge at the tire - it is not likely going to be outside diameter.

Toe is not degrees and very much depends on where you measure it. It you go out enough miles, that 1mm of toe becomes a mile of toe, so it is not ridiculous. This is because most race cars are aligned with strings and all you can measure is distance, not toe angle.

Jarez Mifkin

You're doing too much work. Go here: http://www.smartracingproducts.com/i...ions/index.htm and look at the pdf's under Set up Sheets.

You're welcome.

himself

Probably won't help with the 86, but here is my conversion chart for 18" wheels.
I have a spreadsheet that calculates and auto-populates a chart - all you have to do is insert rim size. PM me your email and I'll send it over. But, I make no guarantees WRT accuracy

Here are some suggested settings for a 996 GT3. Not sure they translate 1:1 to your car, but they might be helpful in any event. Up front GT3's run between 0º0' and 0º3' toe-out on each side. Currently I'm runing 0º0' as I use the car on the street. In the rear, recommnded is between 0º10'-0º15'. Currently, I am set at 0º13'. You can use the chart below to convert that to any format you want (MM, decimal degrees, inches). If you want 13', just add 10' and 3'.

-td

mark kibort

toe is most certainly in degrees.

Just measure the front of the tire , or better the rim and the rear of the rim and make marks on the ground. measure the distance between the two fronts and then the two rears of the front marks. thats the "distance of toe" , from the tire or rim radius or diameter.

IT doesnt matter if you use the radius or diameter, thats the beauty of trig. you use radius, and the delta between the two points will be different and the angle will remail the same.

Now, take the distance of the tire points, probably 19" or so. take the toe difference. say, 1/4". you divide 1/4 by 19" and get a number (.013)

take the INV TAN of this number (inverse tangent) this gives you degrees.

.74 degrees

degrees is what toe is.

you can do the same thing with a bubble level and your rim for camber.

19" and .25 from vertical, would equal the same, .75 degrees of camber.

I knew we could use our 7th grade trig someday for useful purposes!

mark kibort

to answer your question, there are best settings for wear and handling, but generally, close to 0 degrees is good, with a slight hint toward toe-in. most use 1/16" or 1/8" . (based on front and rear of tire measuring positions)
basically, .1 degree to about .3 degrees max .

oh, and minutes is just the degrees x 60. so, in this case, .3 degrees would be 18mins or 18'

mark kibort

There should be NO disagreement here. It doesnt matter if you have a 40" diameter truck wheel. angle is angle. it will all trig out the same.

the toe result, does depend, but doesnt change, on wheel size as it would change the factor to arrive at the angle.

Oddjob

Any rubber left in the rear suspension, or all solid bushings?

944s need to run quite a bit of rear toe-in to keep from getting dynamic toe out under hard braking - which tends to make the rear end dance during high speed braking.

I would shoot for 0.10 deg or a little more per side, 0.20+ deg total.

carreracoupe997

Mark, was your .1 to .3 degrees total toe? I assume it is but want to make sure.

carreracoupe997

Oddjob. all solid in the front and rear (spherical) . I also would like someone thoughts about slight toe out in the front and if so how much? Thanks guys.

Veloce Raptor

You will find a number of track-only race cars will run a tiny bit of front toe out for better turn in, and a tiny bit of rear toe-in, for stability under high speed braking and trail braking.









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carreracoupe997

[QUOTE=Veloce Raptor;8285483]You will find a number of track-only race cars will run a tiny bit of front toe out for better turn in, and a tiny bit of rear toe-in, for stability under high speed braking and trail braking.



VR, yes, and this is what I want but I need to know how much in degrees (total), not fractions because of the alignment machine I have access to.

Oddjob

With all solid rear bushings you might be able to run a little less rear toe-in and still maintain high speed braking stability.

I run slight toe-in on the front too (maybe around 0.03-0.05 deg per side), due to my local track configurations. Long high speed tracks, so the slight toe-in helps for straight line stability. Toe-out will create a little more wandering and tramlining. I dont think I would recommend more than -0.05 deg, toe-out per side.

Veloce Raptor

[QUOTE=carreracoupe997;8285562]
Why not contact Autometrics? One of its owners, Cory Friedman, posts here regularly, and knows his stuff.









Professional Racing and Driving Coach