Alignment Question

[Rob M.]

Finished installing new trailing arms, new u-joints, new bushings in strut rods and then went to get the rear end aligned. I had installed shims (original style) approximating what was in it with the old t-arms.

I took my car down to an alignment shop that was recommeded by corvette restorer. When the alignment was done, I thought it strange that on the RH side they didn't use any shims on the inboard side to get the toe correct. All the the shims went on the outboard side. Does that sound normal? The LH side had shims both inboard and outboard as before.

BTW - I watched the process and they used original style shims that I provided, took the bolt out, took their time (over two hours) to get it right and obviously used a computer to get the numbers. They gave me the print out of before and after numbers but don't have them in front of me at this time.

Drove it home with no issues. Thoughts on the shims?

[Tom S.]

Re: Alignment Question

In my opinion if they took the time to use the original shims and kept taking the bolts in and out that alone say's alot. Then if they took two hours and gave you a print out afterwards you are good to go. kepp an eye on tire wear and make sure it handles good and I think you are fine. JMHO .Tom

[Joe L.]

Re: Alignment Question

Finished installing new trailing arms, new u-joints, new bushings in strut rods and then went to get the rear end aligned. I had installed shims (original style) approximating what was in it with the old t-arms.

I took my car down to an alignment shop that was recommeded by corvette restorer. When the alignment was done, I thought it strange that on the RH side they didn't use any shims on the inboard side to get the toe correct. All the the shims went on the outboard side. Does that sound normal? The LH side had shims both inboard and outboard as before.

BTW - I watched the process and they used original style shims that I provided, took the bolt out, took their time (over two hours) to get it right and obviously used a computer to get the numbers. They gave me the print out of before and after numbers but don't have them in front of me at this time.

Drove it home with no issues. Thoughts on the shims?

Rob------


I have never yet seen a case in which there were no shims on one side of the trailing arm forward bushing. I'm not saying it's impossible to occur, but, so far, I've never seen it occur.

Assuming that the car had a more-or-less "normal" shim pack on either side of both arms BEFORE you replaced the trailing arms AND assuming that the car had proper rear end alignment with the old arms, I'd say there is some problem with one of the new arms. Either it's not configured correctly OR the bushing was not properly installed.

If the car was like this BEFORE the installation of the new trailing arms OR if the alignment was way off before you replaced the arms, then I'd say that the frame suffered some damage at some point.

[Rob M.]

Re: Alignment Question

Joe,

When I pulled the original arm, the shims on that side had rusted enough that they were crumbling. I did keep them and there were what I would consider "normal" packs on each side of the old arm.

Regarding the new arms/bushings - the new trailing arms were built by Bairs, so I am assuming that they were done very well (they looked great), but I'm not an expert.

As for the frame - there has never been any indication that the car has been hit.

The car didn't seen to have any alignment issues before. As a matter of fact, I had taken it to the same alignment shop a couple of years ago and it was checked. IIRC, the rear was fine and front needed a minor adjustment then.

Thoughts on next steps? What to check?

[Joe L.]

Re: Alignment Question

Joe,

When I pulled the original arm, the shims on that side had rusted enough that they were crumbling. I did keep them and there were what I would consider "normal" packs on each side of the old arm.

Regarding the new arms/bushings - the new trailing arms were built by Bairs, so I am assuming that they were done very well (they looked great), but I'm not an expert.

As for the frame - there has never been any indication that the car has been hit.

The car didn't seen to have any alignment issues before. As a matter of fact, I had taken it to the same alignment shop a couple of years ago and it was checked. IIRC, the rear was fine and front needed a minor adjustment then.

Thoughts on next steps? What to check?

Rob------


While the arms were supplied by Bairs, if they are reproduction arms, I don't think they would really have had anything to do with them other than the vendor that supplied them to you. I don't know, offhand, if the reproduction arms are supplied with the bushings, or not. If not, then Bairs would have installed those. It's too bad the arms are on the car now. It would have been interesting to measure the thickness of the installed bushings.

[Steven S.]

Re: Alignment Question

One would like to think that Bairs knows what to check for with these arms, but either way it would have been interesting to see what the measurement from the spindle support surface to the bushing end was on the arm before they went back on the car. What was the before/after on the rear toe according to your printout?

Steve

[Timothy B.]

Re: Alignment Question

Rob,

If you indeed have a bent trailing arm and decide to replace it don't get crazy over the alignment. The camber will probably stay the same if you don't loosen the adjusting cam by the rear.

You can also measure the total toe before taking it apart and replace shims on the new trailing are accordingly. Shim the inside to the correct toe then stuff the outside to fill with shims.

I would call Bairs and see what they say about the problem. If it's bent they may offer to pay alignment shop to reset camber and toe..

What does the computer read out say about the toe at the wheel. Were they able to achieve the correct toe??

[Duke W.]

Re: Alignment Question

Post the camber and toe numbers for each side.

Did you have both ends aligned on a "four wheel alignment" machine, and if so, how does the machine determine true vehicle centerline?

It's all about the equipment used and measured numbers.

Duke

[Rob M.]

Re: Alignment Question

All,

Thanks for the support. I will post the before and after print out numbers tonight when I get home from work. I watched them use a four wheel machine to get the numbers/measurements. But, I don't know how the machine measures "true vehicle ceterline" when used - I'd have to ask the owner of the shop.

Bairs used new trailing arms, but original spindle supports and other parts (dust shields etc.). I don't know if bushings were installed already when Bairs put them together of if Bairs did it. I'll call them.

Again, I'll post numbers tonight.

[Steven S.]

Re: Alignment Question

The reproduction arms I've seen all had the bushing factory installed, I'd bet your arms were no different. I'd take the earlier advise and give Bairs a call and tell them what you are dealing with.

Steve

[Rob M.]

Re: Alignment Question

Alright, home and the kids are in bed!

I spoke to Ed at Bairs who told me the bushings were installed by them. He also thought something was strange about the shims. His thought was that the shop should have aligned the front and THEN aligned the rear. I am certain they did the other way around.

Here are the numbers from the alignment shop:

Left Front
Camber - Actual= 1.0 deg. Before=0.9 deg. Specified range= 0.3-1.3
Caster - Actual= 0.3 deg. Before= 0.3 deg. Specified range=0.5-1.5
Toe - Actual= 0.23 deg. Before= 0.43 deg. Specified range= .19-.31

Right Front
Camber - Actual= .4 deg. Before= .7 deg
Caster - Actual= 1.0 deg. Before= 1.0 deg.
Toe - Actual= .25 deg. Before= .39 deg.

Front
Cross Camber - Actual= .6 deg. Before= .2 deg. Spec. Range= -.5 - .5 deg.
Cross Caster - Actual= -.7 deg. Before=-.7 deg. Spec. Range= -.5 - .5 deg.
Total Toe - Actual= .48 deg. Before= .82 deg. Spec. Range= .37 - .63

Left Rear
Camber - Actual= -.7 deg. Before= 2.5 deg. Spec. Range= -1.0 - 0.0
Toe - Actual= .10 deg. Before= .45 deg. Spec. Range= .06 - .19

Right Rear
Camber - Actual= -.06 deg. Before= 2.1 deg.
Toe - Actual= .14 deg. Before= -0.01

Rear
Cross Camber - Actual= -0.1 deg. Before= 0.4 deg.


Sorry for all the numbers, but I don't have a scanner. At any rate, there's the specs from the shop.

Do I need to have the whole thing done AGAIN?

[Terry M.]

Re: Alignment Question

Alignment instructions are to align the rear first, then set the front to the center line established by the rear.

[Steven S.]

Re: Alignment Question

Alignment instructions are to align the rear first, then set the front to the center line established by the rear.

Thats the only way I've ever seen them done as well.

Just skimming over those numbers, it looks like your shop did a good job of putting everything close to nominal values. It sure sounds like that replacement RR arm is the culprit, now if it's worth the hassle to pursue it any more is the real issue. It's not as if the toe on that side is just barely in spec and you are out of adjustment, that would be different in my mind.

Steve

[Timothy B.]

Re: Alignment Question

I will check my 63 service manual but I always thought caster setting is +1.5* to +2.5* so the caster seems like it could be increased. This will give a better return to center feel for the steering wheel.

Also, I think I set my camber setting around 0* front and just slightly negitive on the rear..

How does the car drive, does it steer straight on a flat road??

[Duke W.]

Re: Alignment Question

Alright, home and the kids are in bed!

I spoke to Ed at Bairs who told me the bushings were installed by them. He also thought something was strange about the shims. His thought was that the shop should have aligned the front and THEN aligned the rear. I am certain they did the other way around.

Here are the numbers from the alignment shop:

Left Front
Camber - Actual= 1.0 deg. Before=0.9 deg. Specified range= 0.3-1.3
Caster - Actual= 0.3 deg. Before= 0.3 deg. Specified range=0.5-1.5
Toe - Actual= 0.23 deg. Before= 0.43 deg. Specified range= .19-.31

Right Front
Camber - Actual= .4 deg. Before= .7 deg
Caster - Actual= 1.0 deg. Before= 1.0 deg.
Toe - Actual= .25 deg. Before= .39 deg.

Front
Cross Camber - Actual= .6 deg. Before= .2 deg. Spec. Range= -.5 - .5 deg.
Cross Caster - Actual= -.7 deg. Before=-.7 deg. Spec. Range= -.5 - .5 deg.
Total Toe - Actual= .48 deg. Before= .82 deg. Spec. Range= .37 - .63

Left Rear
Camber - Actual= -.7 deg. Before= 2.5 deg. Spec. Range= -1.0 - 0.0
Toe - Actual= .10 deg. Before= .45 deg. Spec. Range= .06 - .19

Right Rear
Camber - Actual= -.06 deg. Before= 2.1 deg.
Toe - Actual= .14 deg. Before= -0.01

Rear
Cross Camber - Actual= -0.1 deg. Before= 0.4 deg.


Sorry for all the numbers, but I don't have a scanner. At any rate, there's the specs from the shop.

Do I need to have the whole thing done AGAIN?

If I'm reading the numbers correctly I don't like them. Front camber should be close to zero, with as much caster as possible up to1.5 deg. with manual steering and 2.0 with power steering, and cross camber, cross caster should be as close to zero as possible.

At the rear camber should be nominally -0.5 deg. with as close to zero cross camber as possible.

Toe readings should be about 1/32" per wheel on all four corners.

Toe per wheel in deg. = (toe, in.)(360)/2Pi(tire radius, in.)

Using a tire radius of 13.5", 1/32" toe in per wheel should be about .13 deg.

Alignment has been discussed many times, so before having your car aligned, look at the archives or ask. There are two recommended sets of specs for C2s with radial tires (by John Hinckley and me) - "touring" and "sport". The sport settings are a little more aggressive on negative camber and positive caster (half degree more camber in the neg. direction at both ends with as much positive caster as possible)

Give the shop WRITTEN INSTRUCTIONS with the target values and an instruction to keep cross readings as close to zero as possible.

Duke