How Do I Correctly Setup The Trailing Arm Shims
Old Pro Solo Guy
Joined: Dec 2017
Posts: 8,094
Likes: 4,449
From: Marlton NJ
I use old coffee cans. Maxwell House works the best! LOL
Seriously they just need to be big enough to get the straight edge over the radial tire bulge. And still let the tape measures fit under the car. I have measured off the sidewalls like this for decades and it is remarkedly accurate. Stand-offs to the rim edge do not really help as much as it seems they would. Just be sure you miss any raised white letters and touch bare sidewall.
Regarding the thrust angle, just eyeball down the straightedge toward the back tire. Make sure it lines up in the same spot on each side, touching tire, 1st tread block, 1/2 " outside etc. If it eyeballs the same it's close enough. I used to go crazy measuring that distance with a ruler, but it didn't matter. The will keep the car straight and not crab walk.
Re: toe-in, I use the same setup on both tires at once. Run the tape measures under the car, and hook them on one side. I use locking tapes, and lock them off the ground, so the tension in both tapes is the same. Look close in my pic and the tape housing is swinging in the air putting equal tension on the tapes. The should not touch car parts under the car. I have a black sharpie line on the Home Depot angle iron edge. If you use 2 ft beams the difference in the 2 tapes is your toe in. I use 4 ft beams for much greater accuracy. Cut the reading in half. A difference of 1/16" becomes a 1/32" toe in. Extremely accurate that way.
I have double checked these settings against an expensive Hunter alignment machine, and this method has the same accuracy.
And this is MUCH faster.
Seriously they just need to be big enough to get the straight edge over the radial tire bulge. And still let the tape measures fit under the car. I have measured off the sidewalls like this for decades and it is remarkedly accurate. Stand-offs to the rim edge do not really help as much as it seems they would. Just be sure you miss any raised white letters and touch bare sidewall.
Regarding the thrust angle, just eyeball down the straightedge toward the back tire. Make sure it lines up in the same spot on each side, touching tire, 1st tread block, 1/2 " outside etc. If it eyeballs the same it's close enough. I used to go crazy measuring that distance with a ruler, but it didn't matter. The will keep the car straight and not crab walk.
Re: toe-in, I use the same setup on both tires at once. Run the tape measures under the car, and hook them on one side. I use locking tapes, and lock them off the ground, so the tension in both tapes is the same. Look close in my pic and the tape housing is swinging in the air putting equal tension on the tapes. The should not touch car parts under the car. I have a black sharpie line on the Home Depot angle iron edge. If you use 2 ft beams the difference in the 2 tapes is your toe in. I use 4 ft beams for much greater accuracy. Cut the reading in half. A difference of 1/16" becomes a 1/32" toe in. Extremely accurate that way.
I have double checked these settings against an expensive Hunter alignment machine, and this method has the same accuracy.
And this is MUCH faster.
Last edited by leigh1322; Mar 7, 2025 at 02:09 PM.
