Front Wheel alignment

[cwerve74]

Just got back from the alignment shop after finishing my total suspention re-work. The rear wheels came in just fine. They had trouble on the front. The left from camber is .2 negative and they had no more shims to take out. The right is set to .3 positive camber. I thnk my real issue is with the caster Left side is +1 and right is +.6. I think these need to be around +2.5. Toe is just fine.

When I started to ask questions they acted like they wanted me out of the shop. So my real question is "How bad is this? Is the left front camber issue preventing the left caster to be adjusted? Last question, Do I want both front wheel caster set near the same or do I want to adjust the right wheel (lots shims to work with) to spec?

This is a reputable shop and I think they tried hard but not sure if where to go from here. It was not cheap and I think I should be happy and I might be just not sure.

 

[JohnZ]

The inability to set LF camber is indicative of either worn bushings or frame damage; if your bushings are OK, you may need a Moog offset upper control arm shaft in order to set it. You shouldn't have more than 1/2-degree difference in camber from side to side, but I don't like negative on one side and positive on the other side. Radials like zero front camber, or up to 1/2-degree negative.

Factory spec for caster is 1 degree positive for manual steering, or 2 to 2-1/2 for power steering (2-1/2 is better for tracking and returnability, but will increase manual steering effort).

If you have radials, they want zero-to-1/16" TOTAL front toe-in, not the 1/4"-5/16" in the Shop Manual (that spec is for bias-ply tires).

 

[tomsgota724spd]

Hey cwerve74,
I think you need to take your car back and insist that they align the front end properly. Has a auto tech myself I do many alignments. They should have the camber within .5 degrees side to side. Same for the caster. Or else it will pull. You don't have enough caster. You are correct about needing 2.5 degrees of caster or more. I like about .5 negative camber on each side. Most cars today don't use shims any more so they may not have had enough to make the adjustments correctly. Or they just gave up because they had spent half the day on it and were loosing money.

 

[cwerve74]

Thanks for the feed back. For the front, they can get .5 negative camber on both sides and that will give enough room to set a better Caster number. Good point on the radial vs belted tires they were trying to set positive camber on the front. Also they had spent 3 hours setting the back and Your right the clock had run out when they got to the front. Not that they had trouble on the back just they had a small experience base. I will go back and negotiate something a little better.

 

[norvalwilhelm]

I ran into the same problem. I wanted less negative camber and their were no shims to remove and I wanted more positive caster.

I machined my own offset cross shafts. I offset the ends and at the same time I drilled the holes for caster 1/4 inch further towards the rear.
Double click to enlarge

 

[norvalwilhelm]

If you remove all the shims and you still don't have enough positive camber you can not expect the alignment shop to fix this. It is out of adjustment. What can they do? As for caster it involves adding shims which takes away from positive camber at the same time. What more can they do?
Before you jump on me I have worked through these problems many time and they always involve custom machined either stock cross shafts or custom made.
The alignment guys only have so much time and knowledge on how to fix these problems and it is beyond all of them to make the proper settings if shims are not enough.
To you alignement guys how do you add more positive camber to a car that is totally out of shims???
I do alignements in my shop and have a lathe and mill and blank stock to start from scratch and make shafts with the proper setting built right in but how many shops can do this???

I feel sorry for the alignement guys who are asked to do the impossible.

 

[cwerve74]

I understand the point on not being able to do the imposible. I did some more research. I have convinced myself the left front frame is 1/2 inch high. This generates the out of shim condition for camber. I have a plan to fix this but that will be next winter.

On the other hand the .2 neagtive camber is not that bad. Looks like 0 to .5 neagative is OK. The left to right side are with in the .5 limit. It is the caster that is keeping me up at night. The car drives pretty good but above 70 MPH it feels real light. More positive caster should fix this. (car has power steering) I looked at the geometry of the front suspention http://www.corvettefaq.com/suspdim/index.htm
and did some calculating. I come up with add an 1/8 inch shim to the rear of the upper control arm this will give 1.15 degrees more positive caster and put me close to the 2.5 degrees. It will add a little negative camber but not much. If I do the same to both side I should keep the left to right measuremnets. Does this sound reasonable? I don't have any pratical experience here. This is just me with a calculator and geometery book.

 

[norvalwilhelm]

The solution I found for increasing caster is pulling the upper A arms and this is alot easier then most think. I did both today in under an hour including reinstall.
Anyway I pull the upper A arms and put them fully assembled in the milling machine and machine the existing 7/16 holes into slots 1/4 inch towards the rear longer then stock. This give 5 degrees positive caster and no shimming that causes a problem with camber.
I realize you don't have a mill but if you pulled them and took them to any machine shop they would take about 5 minutes each side to slot the existing holes by 1/4 inch.
Adding shims to increase caster takes away from camber.
I also do not agree with .5 camber being within range. I try for NO change side to side. While .5 might be within factory specs the factory has too wide a spec range.
You can order offset cross shafts and I could get the part number on Monday if you wanted it. The shafts are $65 CDN each and are in stock. They have the holes moved 1/4 inch already.
To replace cross shafts is nothing and with a little coaching it would take you no time at all. Redoing A arm bushings is another of those things that is really simple if you know what you are doing.

 

[cwerve74]

norvalwilhelm, Thanks that is all good input. I am very comfortable with the parts involved. Not sure I could get the upper CR out in 30 minutes but you are correct it is an easy job. Over this last winter I removed every suspention part front & rear and put in all new rubber parts, bead blasted all the metal & painted. It all looks like new. I did not pick up on the frame issue durring this. (Left front 1/2 inch high).

I guess my real issues was do I need to get a different result from the professional alignment. I could get them to add in negative camber and a little more caster but I am still out of alignment just by a different amount. I think my strategy will be getting a good rate on putting my car on the rack & getting the current measurements. I think the solution will be a multi step process. 1st I was going to add 1/2 inch to the spring on the left front. Some sort of spacer on the bottomof the spring in the pocket. That will get the ride height correct. Then see if that gives me enough adjustability. If not then an offset upper CR would be my next step. Followed by the sloted holes. The part you have pictured looks like it would do what I need. Thanks for the help thinking thur this.

One thing I would like is some sort of feel for how much a given amout of shims changes the alignment. You gave me one. 1/4 inch slot is 5 degerees of caster. Do you have a generalization about lets say 1/16 inch shim added to both sides of the upper CR changes the camber by ---? or 1/16 inch shim moved from the front to the back changes the caster by ----?

 

[6speeder]

http://vettenet.org/susp_chart.html

 

[norvalwilhelm]

Why don't you buy your own caster camber gage. They are only about $130 and other then removing your dust caps snap on the spindle with a large magnetic base. They are very accurate and read both camber and caster. I also have a homemade toe gage.
Often after returning from a drive I will roll up the driveway without touching the steering wheel and get out my gages and take a quick rearing, toe in particular and try something else.
I got my gage from Coleman racing but summit should have something similiar.

 

[cwerve74]

Way cool. I love to be self sufficent. My wife is making some noise over my shoulder about the one time use aspect but I just reminded her of how I used the sand blaster on the patio furniture. I will get me one of these and get to where I need to be. May not be a laser but it will get me close enough and I maybe then follow up with the guy and his laser rack. Thanks

 

[norvalwilhelm]

I thought the same as you about one time usage but find and seems to be always checking and trying something new. I will have to take a few pictures of my homemade toe gage. It is another very useful tool.
I really watch for side to side changes in camber and caster. I certainly would not accept .5 difference.
I have even started to question toe OUT of Toe IN. Old settings were for bias tires and postive caster. Radial ties reduced this to 1/2 the old toe settings and I have started to test zero toe and slight toe out.
I also found that changing the camber shims by .100 changes the camber setting by less then .5 so it takes a fair amount of adjustment to move camber.
It is raining here to day and I will make another cross shaft with another 1/2 degree less camber to try.
When I want to change settings I machine blank cross shafts for camber and caster. I can change a cross shaft in the A arm in about 5 minutes on the bench.