Mr D.

Well this weekend was spent running around the car doing a wheel alignment and taking measurement after measurement, re-checking not once, not twice but at least four times. I have read just about everything on the subject here on the forum so I'm pretty sure I was doing all this correctly.

The tool I’m using is a FasTrax Wheel Alignment tool.

http://www.eastwood.com/fasttrax-cam...ter-gauge.html

The car is my 65 that I’m completing a frame off restoration and have not driven yet. Everything is new or reconditioned. The upper Arms are installed correctly and the alignment preliminary steps (ride height/coil spring sag) are within specs.

Here is what I ended up with;

Left Front
Camber 0 deg
Caster +.5 deg
Toe In 1/16”
A-Arm Shims – FWD .118 x 5 (5 Total) / AFT .118 X 4 (4 total)

Right Front
Camber 0 deg
Caster -.5 deg
Toe In 1/16”
A-Arm Shims – FWD .118 x 4 + .060 x 1 (5 Total) / AFT .118 x 4 + .060 x 1 (5 Total)

Left Rear
Camber 0 deg
Toe In 1/2” Toe Out
T/A-Shims – OTBD 1/4” and 1/32” (2 total) / INBD 1/4” and 1/8” (2 total)

Right Rear
Camber 0 deg
Toe In 5/8” Toe Out
T/A-Shims – OTBD 1/4” and 1/32” (2 total) / INBD 1/4” and 1/8” (2 total)

One of my concerns is why I can’t get the desired caster of 2.0 to 2.75 deg? My shim stack is already pretty thick after setting Camber and there is no way I’m going from .5 to 2.0 without running out of threads on the adjustment bolts.

Second is the toe out in the rear, I was surprised to see these readings and re-verified them 4-5 times. Given the current shim stack I’m not sure I can correct that much toe out? Could I be looking at bent T/A’s? These were not replaced just sand blasted and repainted.

Goal is to get the car close as I can before I hand it off to an alignment shop and ensure there are no issues with the mechanics of them doing the alignment. Also have to factor in that most if not all shops in my area seem to be scared of touching the rear toe in.

Should I just leave everything where it is and get a couple of miles on the car and let everything fine its happy spot and re-measure?

Thanks, just scratching my head a little here today as usual.

pop23235

Mr D. just opened for new posts and there you were.
May I offer:
Move some shims from the rear of the A arms to the front. That will increase caster and also change camber. Once you get the caster, try to shim equally front and back of the A arm to find camber. Set toe last.
Rear, let me think that one over. Is your data on rear showing toe in or toe out?
Let me assume you are toed out. Adding negative caster will help. I don't have specs avail right now, but I think the set up calls for negative camber in rear.

Mr D.

Yes, toe out. Everyone here seems to say 0 Camber all the way around for Radial Tires.

DansYellow66

Off hand I would say you might have to replace the upper control arm shafts with Moog offset shafts to reduce the shim pack at 0% camber. However, I'm wondering if you are getting good results with the camber gage. Are you on level pavement? Are you turning the wheels in and out the precise amount per the instructions - I think mine specifies 20 degrees? Have you run the settings multiple times to make sure they repeat?

As Pop23235 said, basically you need to pull some shims from the front bolt and shift to the rear to increase caster but if you have run out of bolt travel on the rear bolt - the off set shafts may be the only answer.

On the rear how, or what are you using to measure toe in? What I have done is pretty Rube Goldberg but seems to work OK as my IRS Corvette and Cobra Rep both track perfectly straight. I straighten out the front wheels dead ahead and stretch fishing line from front wheel to rear wheel - knock offs make this pretty easy as you have something to wrap the line around. The minor difference in track width doesn't really manner as the line is only to provide a uniform reference point on both sides. I do a little geometry and math to figure out how much deviation I need from that string line to a straight edge laid across the tire sidewalls - to obtain specified toe in at a specific distance from the wheel center. I used a distance that roughly is from the center of the wheel hub to where the trailing arm bolt is. I shim both sides to where I have equal deviation matching my calculation from the string line when I lay my straight edge across the tire at mid-height (or as close as I can get with the spinners). Then I use my toe gage to run a standard toe check to make sure it's overall in spec. If not meeting spec, then I repeat as necessary and wiggle everything in. Like I said, kind of Rube Goldberg but seems to work.

One last thought on the front - are you sure you got the right upper a-arm installed back on the right side and the left - well you know? They are not interchangeable.

pop23235

First off, Dans is correct and I misstated:
From the shop manual, "The addition of shims at the front bolt, or the removal of shims from the rear bolt will decrease camber". You want to remove from the front and add to the rear so you can increase - 65 manual states +3/4* +/-1/2* (obviously for bias tires). Interestingly that is 1* less than the 63 manual.

I was looking for a chart found in newer GM manuals than C2's that told exactly how much shim change gave how much caster/camber change, but it's not in the older manuals, at least not 63, 64, 65.

Mr D.

Thanks Dan for the input. The A-Arms are installed correctly, checked that twice today. I also did the string pull from the back wheel to the front wheel and took a measurement at the spindle grease cup, left side was 3" and the right side was 1 1/2".

For measuring rear toe I used the Fastrax toe adapter (let you hook tape measure in it) and measured to the outer tread line on the tire front and back. Also measured with a 3' level against the tire and came up with the same final toe out reading. I did this four times because I didn't believe the readings.

Mr D.

Here is a question, what would cause this caster problem when using OEM parts?

Mr D.

Pop, I will dig around the search function I think I read somewhere today about shim thickness vs degrees.

DansYellow66

I think your caster problem is mostly being caused by your camber problem and not having enough room to play with shims. Without looking I can't remember the recommended camber with radial tires - I suspect somewhere from 0 to neg 1/2 degree. So no help there with your shim pack. On older cars the engine cradle can spread from suspension loads. Not sure why it spreads - you would think with the upper spring pockets taking the load, that it would close up. But anyway spreading of the engine cradle is fairly common or of course a prior wreck can warp it too. Since yours seems to be uniform on both sides, I would suspect the cradle is spread. A frame shop can correct this but you are past that point probably. Unless there is something we are missing your best beet may be the off set a-arm shafts to reduce the shim count so you can adjust it properly.

I'm not sure I understand your 3 " and 1-1/2" measurements at the "spindle grease cup"? Is that the difference from vertical in the upper and lower ball joints?

On the rear, I think you are just going to have to shift a number of shims to the outside and see if it looks like the total toe is going to come into specs. If it does then you can try to wiggle it in to where it's tracking with the front.

BD104X

FWIW - you may not be able to get the desired amount of caster. My alignment shop (very Corvette literate) was only able to get me 1.9-2.0 degrees. As he explained it, these older cars didn't run that much caster back then (these cars were designed with bias-ply tires & manual steering in mind) so its hard to achieve with the factory suspension and if he shimmed it too much more he would have a hard time keeping camber in spec. This made sense to me and my car handles fine.

Mr D.

Dan

Here is the link to the string pull from the back wheel to the front wheel I did.

For the rear I'm going to pull all the shims back out and get my track set than work the toe in.

As for the front, I'm going to let that marble roll around my brain for a couple of days and revisit this.

http://www.duntovmotors.com/tech-alignment.php

Dennis

Mike Geary

Dennis:

When I went through all this fun with the '65 convertible, I came up with this relationship between shim thickness and toe angle on the rear:

1/16" shim results in 0.15* angle change.

I would try this on the rear: set the camber at 0.5*neg and use equal shim packs INBD & OTBD as an initial SWAG.

On the front, it will be interesting to see what happens to the camber when you move shims aft to increase caster. Might need to drive it for a while to let the front suspension settle in.


Mike

DansYellow66

Wow - those instructions are almost exactly the process I used about 20 years ago on my car before I even had a computer. Maybe it's not so Rube Goldberg after all.

Here's another off the wall thought for the brain - since this is a newly restored car were the upper a-arm bolts replaced? If so, any chance they have never been torqued down enough to fully seat the splined bolts in the frame? My thinking is that could be why they are not giving you enough room for shims.

mrg

Similar to the Duntov Motors article on setting rear toe:

A la 'Rube' 2x4's were used to make make a framework to support a fishing line strung taught from front to rear wheels.
I think the frame measured 11' long with 14" uprights at either end. The strung fishing line height was set to pass through the centerline of front and rear wheel diameter.
The framework was slid in place so that it didn't butt up against the front and rear tires. Measurements were taken at 3 points with a tape measure to set the fishing line in place - at the front and rear rim edge of the front wheel and the rear edge of the rear wheel.
The idea was to have these 3 measurements exactly the same. With the fishing line set in place the front edge of the rear wheel rim was measured. The difference between front and rear wheel rim edge established the toe.
John

66RBS

But the front track is 56.8" and the rear track is 57.6". How can you get all three measurements exactly the same? Seems to me the rear wheel will stick out .4" more than the front reference line

Randy

DansYellow66

Yes, you are correct, but the purpose of the string line is to provide a reference line on both sides that is consistent with the centerline of the chassis - even though it's slightly toed in. Once the "total" toe for the rear is dialed in with a common toe gage, the idea is to wiggle it in to where a straightedge laid along the sidewalls is equal distance from the string line at a fixed point on both sides. The wiggling in involves swapping a set amount of shims from one side of the trailing arm to the other side and an equal change in shims on the other trailing arm. Once the straightedge has equal deviation from the string line on both sides and the proper overall toe in is present - the rear suspension is aligned with the front suspension and will track straight.

Or, you can take it to your local alignment shop and let him deal with all of this. It's rather a tedious process but some of us will do anything to avoid taking our car to a stranger to work on it.

mrg

Drum brake C2's carry a bit narrower track - 57" rear, 56.3" front. Track was considered. The angular difference with respect to track in roughly 100 inches between front and rear wheels didn't amount to much. I felt the difference was neglegible.
John