I know a way to check toe-in. It requires two people, two straight pins
from the sewing room, one tape measure, and the ability to roll the car a
few feet.
Most of you can figure it out already. :-)
This method measures directly at the spindle, provided your wheel bearings
don't wobble. Bent wheel rims or crookedly-mounted tires have no effect
upon its accuracy.
Measure a distance off the ground at the back side of the tire where you
have a clear shot all the way across the car. For many cars, 3.5" will
work, so a couple of scraps of 2x4 can come in handy. Measure from this
point to an identical point at the front of the tire. Write this distance
down for later. DT = direction of travel
Stick a pin in the back side tire tread at your assigned height from the
floor. Have your assistant stick a pin in the back side tire tread at your
assigned height from the floor on the other tire. Have your assistant hold
the measuring tape on the base of the pin exactly at ten inches. Record the
exact measurement at your pin. Write this down (don't bother subtracting
the ten inches). LB = lateral back
Roll the car forward until the pins are exactly at your assigned height from
the floor on the front side. Have your assistant hold the measuring tape on
the base of the pin exactly at ten inches. Record the exact measurement at
your pin. Write this down (don't bother subtracting the ten inches). LF =
lateral front
A common way to express toe-in is the total measurement at the wheel
diameter (I'm calling this TI). To convert your numbers to this, you need
to use the ratio between your DT and the wheel size in the tow-in specs you
are reading (not the wheel size you have on the car now). WD = wheel
diameter.
(LB-LF) * WD / DT = TI
Obviously, a negative number for TI will be toe-out.
A little trig will give answers in degrees, which are less ambiguous than
the fractional distances that are usually quoted.
Since I run my autocross Lotus at zero front toe, I get to skip out on a lot
of arithmetic.
I'm sure if I have made an important typo in this, somebody will catch it
right away.
This tip was passed to me by autocrosser Akkana Peck. I have not heard from
her for some time. I hope she is well and happy.
Phil Ethier West Side Saint Paul Minnesota USA
1970 Lotus Europa, 1992 Saturn SL2, 1986 Suburban, 1962 TR4 CT2846L
pethier@isd.net http://www.mnautox.com/ http://www.vtr2002.org
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