One way to align a hot rod

Once you build a car you need to make sure the front and rear axles are perfectly square to the centerline of the frame. If you don't, the car will never track correctly.

Last night we decided to align Don's car. I always just triangulated them with a tape measure and string, but someone posted on another forum how the circle track guys do it, so I decided to give that a try.


What it involves is taping or painting a perfectly square box on the floor of the garage that is slightly longer and wider than the car. I used masking tape and we laid out a very square box pattern, and then ran one more piece of tape down the very center of the box. This is the centerline, and you position the centerline of the car directly over this line. To do it, we measured the exact center of the rear, and the exact center of the front and used a plumb bob to move the car right over the tape centerline.


Now the car is square to the box. Next, you simply drop the plumb bob down from the exact center of each rear axle and mark where it touches the tape on the sides. You then measure how far each side is from the back edge of the box, and it will tell you if you are in alignment or not. By adjusting the radius rods in and out you can get the rear axle square to the frame.


Then we moved on to the front, after blocking the rear wheels so they couldn't move. First we corrected his caster from the initial 10 degrees to a more acceptable 6 degrees. After that we did the same plumb bob routine from the kingpins down and adjusted the radius rods to get the front axle square to the frame. Finally, we ran a tape measure between each kingpin to the rear axle housing and got exactly 97 inches on each side. Toe in was set next at 1/16, and we were done.


I know the explanation is a little confusing, but this method really works well. I am going to put my T on the box to make sure it is square too. The picture below shows his car sitting squarely on the taped box pattern.

I thought this might be helpful to anyone who has never done this.


Don

Looks like a great way to get 4 wheel alignment. Thanks for posting.

Great tip Don, thanks.

Jeff

Thats what I am talking about.
Technical stuff, yeah.
Thanks for posting.

BTW Don, thats one outstanding piece of work.
You have nicer paint on that frame than I will have anywhere on the entire car.

Thanks for the tip Don, I'll try that. I do it slightly different using the same basic principle.

Great post Don , the visual aid is great. We basicly did just that as we were building Ratzilla.We had to try to get it right from the start because of the rear engine frame thingie that was totaly new to us and we were winging it a lot of the time.So after riding for a while I bit the money bullet and took it to a rod friendly alignment shop.There was less than an 1/16 of an inch difference between the front and rear axles.Guy couldnt believe we got it almost perfect with a plumb bob and marks on the floor. We are now finishing up a new design for the rear struts and goil springs to get a better ride.The guys over on a Fiero board have been real friendly and helpful. Hope to be test driving it by monday.LFE

Ummm hey Don, what do you do if your garage floor has multiple pitches to each of the four squares?????

Seriously, thanks for the tech. I've had to come up with my own weird ways to align axles. I will give this one a try and see what happens.
I typically have mine on jack stands with shims between the axles and stand to make up for the compound angles. Then triangulate. Try setting caster with as much as 6* slope to the side and 4* back and that is only one of the squares of concrete.

This works well and is easy to do

I have also done the triangulation thing, where you pick the exact center of the frame in the back and then measure from that point to the exact center of each king pin. Then you do the opposite by measuring from the center of the front crossmember to the same spot on each side of the rear axle housing. Problem with that is once the engine and tranny are in place there is stuff in the way of getting your tape measure or string in a straight line. By using this method, it doesn't matter what is in the way as you are working on the outside of the car chassis.

All you are doing is drawing a perfectly square rectangle on the floor and the squaring the car up to that rectangle. I think it worked, my car goes pretty straight down the road.

Don