Page 1 of 2 12 LastLast
Results 1 to 10 of 11

Thread: Converting Toe from Inches to Degrees?

  1. #1

    Join Date
    Feb 2009
    Location
    Kingsburg, CA
    Posts
    436
    Real Name
    Daniel

    Default Converting Toe from Inches to Degrees?

    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??


    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.



    Toe in Degrees = aTan(Toe in Inches/Rim Diameter), per wheel
    Toe in Inches = Rim Diameter * Tan(Toe in Degrees), per wheel
    Last edited by black_em2; 07-11-2011 at 08:48 AM.
    Daniel Perez
    91 Miata (Work in Progress)
    05 Honda Civic #82 HS (RIP)
    SCCA Member #408775

    Photo by Bryan Heitkotter

  2. #2
    psychostang's Avatar
    Join Date
    Jan 2009
    Posts
    361
    Real Name
    Corky & Pam Schroeder

    Default

    Sounds good except I believe it should be radius instead of diameter
    Pam Schroeder
    06 Mustang, FSL #16
    SCCA# 389083

    Corky Schroeder
    06 Mustang, FS #116
    SCCA# 389084

  3. #3
    dbratten's Avatar
    Join Date
    Jan 2009
    Location
    Turlock, CA
    Posts
    883
    Real Name
    Dan Bratten

    Default

    Quote Originally Posted by black_em2 View Post
    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??


    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.

    -- by Brian (bse53).


    --Dan
    Dan Bratten
    OSP - C6 Corvette

  4. #4
    2014 Treasurer glieb's Avatar
    Join Date
    Jan 2009
    Location
    Fresburg
    Posts
    643
    Blog Entries
    21
    Real Name
    Gary Lieb

    Default

    Quote Originally Posted by dbratten View Post
    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.

    -- by Brian (bse53).


    --Dan
    I dub thee Mr Wizard.
    1994 Mazda Miata M #36 ES Auto crosser
    1991 Toyota MR2 "Mickey" #170 2010 BABE, GRM 2010 Challenge, 24 hrs of LeMons "Failrrari"
    1983 Ford Mustang 5.0 GT "Sally Prime" #17 ESP Auto crosser, 2012 BABE Rally Car. GRM $2013 Chalenge
    1971 Super Beetle "Haabu" Plan A 2013 BABE Rally car
    Forgive me father for I have sinned, it has been 6 years since I have changed my password.

  5. #5
    dbratten's Avatar
    Join Date
    Jan 2009
    Location
    Turlock, CA
    Posts
    883
    Real Name
    Dan Bratten

    Default

    Quote Originally Posted by glieb View Post
    I dub thee Mr Wizard.
    No, I am the Googler!

    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
    Dan Bratten
    OSP - C6 Corvette

  6. #6
    dbratten's Avatar
    Join Date
    Jan 2009
    Location
    Turlock, CA
    Posts
    883
    Real Name
    Dan Bratten

    Default

    I Googled it some more and have created an Excel file (27kb) 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
    Dan Bratten
    OSP - C6 Corvette

  7. #7
    2013 President bgriggs's Avatar
    Join Date
    Nov 2008
    Location
    Fresno, CA
    Posts
    718
    Real Name
    Brandon Griggs

    Default

    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
    Brandon Griggs
    2013 President

    STR #21 - '92 / '01 Mazda Miata
    DSP #21 - '06 VW GTI MkV

  8. #8
    2014 Treasurer glieb's Avatar
    Join Date
    Jan 2009
    Location
    Fresburg
    Posts
    643
    Blog Entries
    21
    Real Name
    Gary Lieb

    Default

    Quote Originally Posted by bgriggs View Post
    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.
    1994 Mazda Miata M #36 ES Auto crosser
    1991 Toyota MR2 "Mickey" #170 2010 BABE, GRM 2010 Challenge, 24 hrs of LeMons "Failrrari"
    1983 Ford Mustang 5.0 GT "Sally Prime" #17 ESP Auto crosser, 2012 BABE Rally Car. GRM $2013 Chalenge
    1971 Super Beetle "Haabu" Plan A 2013 BABE Rally car
    Forgive me father for I have sinned, it has been 6 years since I have changed my password.

  9. #9

    Join Date
    Feb 2009
    Location
    Kingsburg, CA
    Posts
    436
    Real Name
    Daniel

    Default

    Quote Originally Posted by dbratten View Post
    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/p...e_settings.pdf
    basically I think we are saying the same thing but in different languages lol

    Quote Originally Posted by bgriggs View Post
    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
    Daniel Perez
    91 Miata (Work in Progress)
    05 Honda Civic #82 HS (RIP)
    SCCA Member #408775

    Photo by Bryan Heitkotter

  10. #10
    SmokeyBear's Avatar
    Join Date
    Jan 2009
    Location
    Clovis, CA
    Posts
    1,412
    Blog Entries
    2
    Real Name
    Ron Branam

    Default

    You-all folks sho' nuff talk funny!

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •