Converting Toe from Inches to Degrees?

[black_em2]

So since most alignment shops measure toe in degrees and its easier to think of toe in inches, how do you convert inches to degrees??

http://img710.imageshack.us/img710/3194/toex.jpg
The way I see it, toe in degrees would be equal to
aTan(Toe in Inches/Tire Diameter) per wheel


Is this a correct assumption??

Another question.... is there an appropriate way to store tires?? Like should they be deflated slightly, stood up or laid down etc.??

Edit:
Conversion should be considered at the edge of the rim where the measurement is taken.

http://img818.imageshack.us/img818/3194/toex.jpg

Toe in Degrees = aTan(Toe in Inches/Rim Diameter), per wheel
Toe in Inches = Rim Diameter * Tan(Toe in Degrees), per wheel

[psychostang]

Sounds good except I believe it should be radius instead of diameter

[dbratten]

So since most alignment shops measure toe in degrees and its easier to think of toe in inches, how do you convert inches to degrees??

http://img710.imageshack.us/img710/3194/toex.jpg
The way I see it, toe in degrees would be equal to
aTan(Toe in Inches/Tire Diameter) per wheel


Is this a correct assumption??

Another question.... is there an appropriate way to store tires?? Like should they be deflated slightly, stood up or laid down etc.??

Degrees will always be degrees but for toe measurements expressed in inches it will always depend on where (how far out from centerline) the measurement is taken.

With toe I believe 1/32" is equal to 0.1 degree when the measurement is taken at the 9" radius point of the rim/tire. This corresponds close enough to the outer edge for most rims.

You can do the math to check that -- 0.1deg is about 1/32". Take the inverse Sin of (1/32)/18 and you get 0.1deg. 18 is the wheel diameter, which is where I make my measurements or actually directly below on the tire with a tape measure front and rear of each.

Here's a chart I found online showing 18" wheels calculated but you can create your own spreadsheet referencing the radius point where you measure. For instance, the front edge of the tire may be at 12" vs. 9" which changes the conversion.

http://i152.photobucket.com/albums/s177/bse53/18inchwheels.jpg -- by Brian (bse53).


--Dan

[glieb]

Degrees will always be degrees but for toe measurements expressed in inches it will always depend on where (how far out from centerline) the measurement is taken.

With toe I believe 1/32" is equal to 0.1 degree when the measurement is taken at the 9" radius point of the rim/tire. This corresponds close enough to the outer edge for most rims.

You can do the math to check that -- 0.1deg is about 1/32". Take the inverse Sin of (1/32)/18 and you get 0.1deg. 18 is the wheel diameter, which is where I make my measurements or actually directly below on the tire with a tape measure front and rear of each.

Here's a chart I found online showing 18" wheels calculated but you can create your own spreadsheet referencing the radius point where you measure. For instance, the front edge of the tire may be at 12" vs. 9" which changes the conversion.

http://i152.photobucket.com/albums/s177/bse53/18inchwheels.jpg -- by Brian (bse53).


--Dan

I dub thee Mr Wizard. :D

[dbratten]

I dub thee Mr Wizard. :D

No, I am the Googler! :D

OK, so you're actually smarter so I'll ask you -- I want to replicate the chart I posted in Excel to calculate a given inch diameter (replacing the 18"). That part is easy but what is the formula to get radians in column B and inches in column D? From there I can get columns E & F with a VLOOKUP.

I'm finding SIN and TAN as functions in Excel but pitifully don't know what to do with them without far more Googling than I have time for right now.

--Dan

[dbratten]

I Googled it some more and have created an Excel file (27kb) (http://www.bratten.org/C6/Toe-Degree-Inch.xls) to use to calculate degree to inch conversions while allowing for where on the wheel you take your measurements.

In cell C3 enter (in inches) the point in front of (and also behind) the wheel centerline where you place your tape measure to check toe. Use the same distance in front and behind for accuracy. If measuring off the face of a 26" diameter tire you will enter 13". If measuring using the leading and trailing edge of an 18" rim then you will enter 9". Adjust it for what works on your car.

--Dan

[bgriggs]

Just to throw a curve ball at y'all... trig experts.

Has anyone else ran into alignment specs as minutes and seconds? A few years ago when I bought the GTI, I felt pretty ignorant when I looked up the alignment specs.

I remember it taking me a few days off and on to convert everything from minutes and seconds to degrees. Then I had to correct for the time difference between Wolfsburg and Fresno :P

[glieb]

Just to throw a curve ball at y'all... trig experts.

Has anyone else ran into alignment specs as minutes and seconds? A few years ago when I bought the GTI, I felt pretty ignorant when I looked up the alignment specs.

I remember it taking me a few days off and on to convert everything from minutes and seconds to degrees. Then I had to correct for the time difference between Wolfsburg and Fresno :P


That's just gutt German precision minutes instead of tenth of a degree ok, but seconds might be excessive. :eek:

[black_em2]

Degrees will always be degrees but for toe measurements expressed in inches it will always depend on where (how far out from centerline) the measurement is taken.

With toe I believe 1/32" is equal to 0.1 degree when the measurement is taken at the 9" radius point of the rim/tire. This corresponds close enough to the outer edge for most rims.
--Dan

Hmm ok so I need to think of it as being taken from the edge of the rim not the tire. I did find some document to back up the formula I saw though. For one, if you use the rim diameter instead of tire diameter, the result will be the same as the table you posted. I also found this link to a graph of toe settings from inches to degrees per given tire diameter
http://www.smartracingproducts.com/pdfdocs/toe_settings.pdf
basically I think we are saying the same thing but in different languages lol


Has anyone else ran into alignment specs as minutes and seconds?

Honda posts there specs in degrees & minutes, which you just take the minutes value over 60. But wouldn't think that they would get as precise as seconds for a stock car lol. That's usually where they set their range of spec
ie. Degrees +/- (Minutes/60) + (Seconds/120) = Degree value in decimal

[SmokeyBear]

You-all folks sho' nuff talk funny!

[thad]

I keep a cheat sheet in my wallet.