Alignment conversion:inches to degrees - help!

newms · 03-28-2005, 09:42 AM

What is the conversion for inches to degrees (minutes)? For example:
I want 1/32 inch of toe out each side for a total of 1/16inch toe out, what does that equal in degrees? (or more likely minutes).
Thanks!

Wil Ferch · 11:54 AM

It depends on the tire rolling diameter...

Craig Watkin's SmartRacing products web site has a conversion chart for this...be careful...it shows up on two different places on the site and it either shows TOTAL toe or PER SIDE toe....if you see the graph it will be obvious but you may easily end up 100% in error if you don't watch out....

here--->http://www.smartracingproducts.com/pdfdocs/toe_settings.pdf

Try also here, a "search" is your friend-->Hey, math guys (trig), help out an old carpenter

Wil

J Smith · 03-28-2005, 01:14 PM

I'm interested in this as I'm scheduled for an alignment on Friday (after a winter's worth of suspension work).

First let's disregard caster and camber settings. Most say run the most caster as possible while keeping both sides identical.
Camber is more or less personal preference (how aggressive a driver are you?), but the general rule is to run .5 degree more negative camber in the rear than the front.

Almost all previous threads with information about alignment settings deal with toe-in and out measurements in inches. Common settings are 0 to 1/32" toe in on the front, and 1/32" to 1/16" toe in on the rear.

From what I can put together from information I've gathered these numbers in inches cross over to these numbers in degrees: (this is based on a 25" diameter tire, which is pretty close to standard on a 911)

1/32" = .07 degrees = 4.2 minutes
1/16" = .14 degrees = 8.5 minutes
3/32" = .21 degrees = 12.6 minutes
1/8" = .28 degrees = 16.8 minutes

Are these numbers close?

The reason I'm asking? Well, I stopped by the garage today to schedule my alignment and he was saying (bragging) how good his alignments are. All his numbers for the car on the rack were in decimal figures (tenths, hundredths). So I'd like to go in with target numbers in decimal figure instead of measurements in inches.

So, if I want 1/32" toe in on the front, that's about 5 minutes each wheel or roughly .07-.08 degrees. (8-10 minutes total)

And if I want 1/16" toe in on the rear, that's about 8 minutes each wheel or roughly .13-.14 degrees. (about 15-17 minutes total)

Any opinions on these settings?

FWIW - He says he can get within .02 of target numbers.

Wil Ferch · 03-29-2005, 04:34 AM

Two things....

1.) I didn't check your math but please do re-check against the SmartRacing products chart...biut be careful as they quote "toe" and "total toe"....so you can be "off" by 100% if you mix up "per side" vs "total".

2.) Chasing Extremely small numbers ( 1/32") is ...IMHO...fruitless with our street suspensions that move in elastic rubber bushings. The whole idea is to get a "smidge" of toe-in so there is less tendency to "hunt" in a straight ahead position ( unless you're an autocross guy and want toe-out....but you see the point). If you end up at 1/16"...it won't kill ya.

...IMHO....

-Wil

masraum · 03-29-2005, 04:42 AM

To go along with what Wil said if you have that smidge of toe in for stability that will translate to toe out under braking due to the bushing deflection and front end compression.

J Smith · 03-29-2005, 01:08 PM

Thanks Wil. I used the Smart Racing chart. I'm pretty sure my numbers are right.

Also, I'm assuming that with new polybronze bearings/monoballs all around, small changes in alignment numbers will be more noticeable than with the factory rubber bushings.

So, if we want a "smidge" of toe-in on the front, do we want a "smidge more" on the rear. From what I understand, this will keep the car from being "tail happy".

Thanks.