[TR] Rear Toe - Spitfire

[Jim Muller]

On 11 Oct 2007 at 6:31, Bob Berger wrote:

> Do the degree numbers relate to/match the inches?
> How do I convert Degrees of toe-in/out to Inches?

Someone can correct me if I'm wrong, but as I understand it:

Toe-in is usually given in distance, not angle.  The distance is the 
difference between the track measured at the front of the rim and the 
track measured at the back of the rim.  So the relationship to angle 
is that toe-in = 2 * wheel diameter * sin(angle).  The factor of 2 is 
because measuring the track wheel to wheel gives the sum of the two 
wheels, whereas if you measured it from the car's centerline it would 
be just one wheel.

A curious thing is that if you had one wheel toed in and one toed 
out, you could still end up with a correct distance value.  Of 
course, at the front the wheels do turn together but at the back they 
aren't supposed to.  Measuring w.r.t. the centerline would seem to be 
necessary for the rear.  And of course, at the front toe-in changes 
with steering angle so you need to have the wheels point forward, 
more or less.

I confess I'm unsure of that factor of 2.  I'm sure of the 
calculation, just not sure whether quoted toe-in values take it 
account or are meant to be interpreted as for just one wheel.

-- 
Jim Muller
jimmuller at rcn.com
'80 Spitfire, '70 GT6+



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