Help with Alignment

[Michael B.]

I'm just completing a body off restoration on a 72 coupe and am having trouble "roughing in" the rear wheel alignment. The rear camber cams are both at their maximum positive camber position and I've still got negative camber on the passenger side rear wheel. The driver's side is at a slightly positive angle but as I said, the cam is in the max position and I suspect there should be more adjustment available.

Everything has been rebuilt or is new with all new bushings.

Wheel alignment is kind of like "magic with a little Voodoo" to me so I could sure use some ideas from anyone who might have experienced this.

Something is definitely wrong here.

Any ideas?

Thanks.

[Richard G.]

Re: Help with Alignment

All it takes is one incorrect length on the half shaft. If they were reused this isn't likely.
Also are the wheels free to move on the floor or did you roll the car after the adjustment.
Body is on the chassis?
I was amazed how difficult they are to roll before an wheel alignment.

[Michael B.]

Re: Help with Alignment

Richard,
Thanks for the response and the ideas. I'm going to disassemble today and double check everything.

The body is on the chassis and I've got the tires on "grease tiles" so they are free to move. I bounce the rear suspension after each adjustment to ensure the suspension settles. The half shafts are the same that came out of the car prior to the restoration. It's probably something simple but so far I'm stumped.

[Dan P.]

Re: Help with Alignment

Ride height has a LOT to do with it.So if you have not put all the parts on yet you will not get a accurate reading .Some cars have to have weight put in the drivers seat to get a accurate reading . If you just let the car down from a jack or hoist the wheels can not settle in .The wheels camber in and out during there travel .So the tire is pinched. That is why alignment machines have plates that move around under each wheel .So when you let car down the tire can settle.You can take a floor jack and put it under each wheel as close to the tire as you can get jack it off the ground and then let it down. You can also roll the car back a couple of car lengths and then forward to let the tire settle.I would wait till i was done with the car and then take it to alignment shop.

[Dan B.]

Re: Help with Alignment

It's no wonder you are getting negative camber at the rear wheels even fully adjusted positive, they are supposed to have negative camber, you are looking for 7/8 " negative on your C-3. As viewed from the rear of the car, the top of your tires should tilt INWARDS. Try again going in the other direction and I think you will find it will adjust to spec as long as nothing is bent. Good luck. Dan

[Michael B.]

Re: Help with Alignment

Dan,

Thank you for the response. I'm embarrassed I didn't realize that before reading your post. My service manual states 7/8 degree, +/- 1/4 degree; so without a negative sign in front I just assumed it was positive camber. After reading your post I checked my manual again and noticed everything with positive camber or caster had a + sign in front, other values had no sign.

Thank you again.

Mike

[Dan B.]

Re: Help with Alignment

7/8 * negative camber IN Degrees .

Toe in (total) 1/16 to 3/16 in Inches.

[Michael B.]

Re: Help with Alignment

Dan,

I just finished setting the camber (properly this time) and was going to post another "Thank You" to you when I saw your last post. I doubled checked both the Chevrolet Service Manual and the Motor's manual and both agree the setting is minus 7/8 degree, not inches. That setting gave about a 3/8 inch inward tilt at the top of the rim.

Incidentally, the Motor's manual included the minus sign in front of the 7/8, the Chevrolet Service Manual does not, and it is up to the reader to know that means a negative setting. GM sucked me right into that trap.

This reminds me of another trap I fell into a few years ago checking the manual timing advance on a distributor. I thought my distributor was really screwed up until I realized the advance curve in the book was using distributor rpm, not engine rpm. Once I doubled all the rpm amounts shown in the book I found my distributor was right on target.

Again, I appreciate your response to my thread and I learned a valuable lesson. Thank you.

Mike

[Tim G.]

Re: Help with Alignment

It sounds like you're past this, but for other folks it's important to reinstall the half shafts on the same side. Ask me how I know :-)

[Dan B.]

Re: Help with Alignment

Dan,

I just finished setting the camber (properly this time) and was going to post another "Thank You" to you when I saw your last post. I doubled checked both the Chevrolet Service Manual and the Motor's manual and both agree the setting is minus 7/8 degree, not inches. That setting gave about a 3/8 inch inward tilt at the top of the rim.

Incidentally, the Motor's manual included the minus sign in front of the 7/8, the Chevrolet Service Manual does not, and it is up to the reader to know that means a negative setting. GM sucked me right into that trap.

This reminds me of another trap I fell into a few years ago checking the manual timing advance on a distributor. I thought my distributor was really screwed up until I realized the advance curve in the book was using distributor rpm, not engine rpm. Once I doubled all the rpm amounts shown in the book I found my distributor was right on target.

Again, I appreciate your response to my thread and I learned a valuable lesson. Thank you.

Mike

Mike, Sorry I was thinking about toe in for some reason which is in INCHES . Sounds like you got it now, so alls well.

One last thing about camber, after you get it set, roll the car a couple of feet so the rear can "unwind" and then check it again to be sure it's still where you want it. I like to put a witness mark on the strut bolt with a sharpie in case you have to disassemble it again or as sometimes happens the bolt loosens and the adjustment goes off. That way you can just look at it and know if it has moved.

[Michael B.]

Re: Help with Alignment

Hi Tim,

I didn't know that either. I won't be attending the National but will be at Frisco in October. I'd like to hear about that.

Mike

[Tim G.]

Re: Help with Alignment

Mike, since the half shafts are part of the geometry for the alignment, if one of the half shafts varies from the other at all it will change the alignment when you mix them up.
See you in Frisco.