Setting camber/caster (help)

[HP2]

I learned all this stuff just out of high school and probably a bit rusty on it. Camber is essentially the vertical alignment of a tire from 90 degrees off the road. If the top of the tire leans in our out, that will put more pressure on one edge of the tire and cause wear. Caster has to do with the angle of the of the pivot points. This affects stability and turning. Think sports bike(steep angle) vs a chopper (shallow angle). Also, a shopping cart front wheel has castor behind the center of the wheel. Castor doesn't affect tire wear since it doesn't change any angle off of the rotation direction.

Castor is often not adjustable. I THOUGHT we couldn't do this on the Challenger. So I am learning something here. I worked very briefly at a tire shop doing alignments, but that didn't last long and was 30 years ago. I did my challenger back then and for some reason I have it in my mind I couldn't adjust castor. The eccentric cammed bolts up top move the upper control arm around. I think in a circular position as you rotate the bolt. Turning the bolt would push out the upper control arm or pull it back in thus effecting camber. I am confused how this would adjust castor though. Maybe I am missing something.

Not sure if this adds to the discussion, but thought I'd through it out.

tparker, you are right on angles, incorrect about adjustment. Yes, turning the cams adjusts the arm in/out. Turn them both the same way and the arm moves in/out. So if you adjust one set in and the other out, you now have relocated the position of the upper ball joint.  Do this, grab a square box/paper/sticky note/whatever is next to your computer, set it down in front of you with a corner facing you, grab the opposing corners on each side of the corner facing you. Now move both corner forward and backward and you can see this move the arm in and out, camber.  Next move only one of those corners in and out and observe what happens to the point facing you. Then move the opposing corner the opposite way and see where the point facing you has moved. This is adjusting caster with a fixed upper arm on a mopar.

While caster is adjustable on an old mopar, its range of adjustment is limited as it is adjusted by the same cams doing camber adjustment.  Look at the diagram posted by Bullitt - this shows how you install the cam bolt to achieve maximum caster. At this max caster point, camber may be positive or negative. To get the camber back in range, adjust only one cam per side to bring camber in to where you want it. However, because you are turning the same cams that gave the max caster setting, you will loose caster while getting to the camber number.

There are two alternatives to this.  1) Moog makes an offset upper arm bushing that you can install to enhance the Bullitt diagram even further. If you can get 2-3* stock, then put in offset bushings and get another 2-3* This is a nice range of caster.  Then you sacrifice less caster while chasing camber.  2) install hardened washers on the bolt between the lower ball joint and spindle. I usually start with .100. This gives more static camber. Then when you install the upper arm for max caster, you have to move it less to get negative camber. Combine this with offset bushings and you can really get some good numbers.

I can't think of a reason to have positive camber at all in a restored car with radials. Even with bias plys. Well, maybe with manual steering, negative caster and positive camber will make it easier to steer, but it also gives up a lot of road holding capability. Stock specs where designed for tall, skinny, bias ply tires.  An E75 tire is something like 195 metric sized tires in modern equivalents. Even the larger performance  F60 tires are still only a 235 metric equivalent.

[CHL2T]

Hi @CHL2T, How do you see alignment giving you clearance? This isn't something I would normally think would give you any extra clearance. Adjusting torsion bars to raise the car up a bit might do it, but there are trade offs.

I'm not real sure that it will help out, I'm just hoping that adjusting the castor to send the tires toward the back will give my tire to fender clearance that little bit.

The thing is of it is is that the tires only rub when I'm turning in reverse and not going forward so whatever clearance I can gain will be a net positive as I don't want to go with a smaller tire in the front.

[tparker]

@HP2 that was a great explanation. I wasn't quite thinking of it that way. I saw bullitt's post but it didn't click. Thanks for posting that

[HP2]

Hi @CHL2T, How do you see alignment giving you clearance? This isn't something I would normally think would give you any extra clearance. Adjusting torsion bars to raise the car up a bit might do it, but there are trade offs.

I'm not real sure that it will help out, I'm just hoping that adjusting the castor to send the tires toward the back will give my tire to fender clearance that little bit.

The thing is of it is is that the tires only rub when I'm turning in reverse and not going forward so whatever clearance I can gain will be a net positive as I don't want to go with a smaller tire in the front.

Alignment can provide clearance because it changes the position of the tire relative to the body components. Close contact at the upper wheel opening can be improved with more negative camber.  Positive caster could reduce an interference at the front fender lip . Negative caster could help with interference in the back. Even less toe might help, but there is a danger in creating undesirable angles when using alignment to improve body clearance.

Contact that only occurs in reverse and not going forward would motivate me to look at loose or worn components. Unfortunately, if it is this minor, it will be really difficult to detect.