toe in alignment question

[Randy S.]

I took my 66 in for alignment at the local "chain" tire retailer. They use a Hunter machine. Advice on this forum suggested 1/32" toe per side as radial tires do not require as much toe in as the original belted tire.

The alignment machine showed the degree symbol on toe in, we got .03 per side but I am wondering now if that was inches or degrees?. Can someone give me the degree equivalent of 1/32" toe in. Factory spec is 1/4" + or - 1/16"

If I remember my high school trig I want the angle whose tangent is .03/14.0"

Randy

[Michael H.]

Re: toe in alignment question

Randy,

I believe the .03 would be inches, not degrees. If 1 deg (sin)= .01745 per inch, times the R, 14, times .03, that would only give a toe setting of about .007 per wheel. Hope I have this right.

[Duke W.]

Re: toe in alignment question

The distance of an arc, which is effectively the linear toe measurment can be determined by multiplying the radius of the arc (half the tire OD) by the angle expressed in radians. (You really want the secant length, but for small angles the arc and secant are very nearly equal. The calculation can also be done using tangent or sin, but then you need a table or a scientific calculator with tan or sin functions. For very small angles tan and sin are nearly equal) There are 2pi radians in a 360 degree circle, so the calculation is as follows:

Linear toe = .03(6.28/360)13.5 = .007"

If the toe measurement IS degrees, then your toe is essentially zero toe-in, which is okay.

Most modern alignment equipment DOES report toe as an angle (in decimal degrees rather than degrees, arc minutes and arc seconds) rather than a linear measurment, but double check the report and verify with the service provider.

You can also check yourself with a tape measure.

The formula can be rearranged to determine the toe angle with 1/32" (about .031") toe:

Toe angle = .031/(6.28/360)13.5 = .01 degree

The standard convention is positive toe angle for toe-in and negative toe angle for toe-out.

Duke

[Randy S.]

Re: toe in alignment question

Duke,
So .03 deg is about .007" toe per side (and OK )and .01 deg is my target of .031" per side. I must be not reading the above correctly. More toe in inches has to increase degrees and the above is inverse.

I have to go back to the shop anyway for the rear. I recall you also suggested 1/32" per side toe in on the rear. The car was on the rack for an 1.5 hr and they could not get the LR in spec because there were not enough thin shims. Shop foreman said "no charge" and to bring it back with some more thin shims.

So one more time kindly give me your recommendation for front and rear toe in both inches and degrees.

Thanks

Randy

[Duke W.]

Re: toe in alignment question

Sorry, the numbers in the formula are correct, and if you run the arithmetic through your calculator result is 0.13, not 0.01, so 1/32" toe per wheel is a toe angle of approximately 0.13 degree.

Since the trailing arm pivot point is about 4" longer than the tire radius a 1/32" shim from the inside to outside position or vice versa will change toe by the ratio of about 13.5/17.5 times shim thickness, which would be about .024" or 0.10 degree for a 1/32" shim.

If you want finer adjustment you will need 1/64" shims.

Duke

[Randy S.]

Re: toe in alignment question

Thanks Duke. I got it now.

Randy