I had my 1978 C3 to the alignment shop today after replacing the TA bushings and the shop measured that the rear was a little out of spec.
They don't have any shims for my car so I just left the shop with the print out.
Left side toe is + 0°04'
Right side toe is -0°06'
I have tried to Google how thick shims I need to get to spec?
My shop manual says total toe to be 1/16" to 3/16" but how do I relate that to degrees?

Many thanks in advance

Christian

 

Normally, you simply move a shim from one side of the TA to the other. Did you not want the alignment shop to adjust it for you?

 

I'm sure they didn't know how.....

That amount of error is very small. If you don't feel any problem with the vehicle's ability to track 'true' and you don't see any abnormal weal on the rear tires (inner or outer edges wear 'differently'), leave it as-is. If the rear has never been re-aligned since it left the factory, it's probably the same as when it came off the assembly line.

 

Locate a center groove in the rear tire tread approx at the 9:00 oclock position/put a dab of white-out in the groove for a reference point
Do the same to the rear tread of the other rear tire.
Measure the distance between the two grooves with a metal tape measure and write down the measurement.

Use the same procedure to measure the groove distance across the front of the rear tires and write the measurement down.
The difference should be about 1/16". The larger measurement should be the distance between the grooves on the rear of the tires.

Tell us what you discover.

 

Rear camber will affect toe readings, so make sure it's on a level surface from side to side. Did they tell you what the rear camber readings were?

 

Roughly (calculated)
0.05" shim would equal 0.16 degrees
0.1" shim would equal 0.33 degrees

Not sure why they gave toe in degrees on an old car.... Sure it wasn't thrust angle they gave you?
M

 

If I'm not mistaken thrust angle only refers to solid axle cars.

 

Ours as well.
You can get the toe correct but have them pointed almost anywhere.
I finially tackled my alignment last year and that was one of the issues I needed to pull back in. (thanks to cagotzmann for help on that)
M

There was a pretty detailed thread going on a while back
https://www.corvetteforum.com/forums...r-bubba-s.html

 

Like mentioned, you normally just take one shim out from one side and install in the other but your specs are close just negative.02 combined

 

Wow. Those numbers are a mess to convert. Toe in in minutes WT?!?!
4 minutes in degrees turns into .067 decimal degrees. That turns into .031" or 31 thousandths in inches (toe-out) Also 1/32" toe-out.
The other side turns into .047" in inches. (toe-in) or 2/32" toe-in
Since one is toe-out and one is toe-in you wind up with 1/32" toe-in.

Which is the lower than your spec. (1/16-3/16')
Personally the middle of the spec would be better, but the difference is pretty minor.
However the rear of a C3 tends to go into toe-out in a turn during suspension compression..
If it feels "twitchy" to you go have it fixed.

So basically I think maybe you are good, as-is.

There is a very slight difference in toe from right to left, all that is going to do is make your thrust angle change a little and make the rear of the car swing left until the toe in is equal on both sides.

I could probably calculate how far off it would be, but not sure it is worth the effort, or worth a new alignment to fix it.
If you are curious you could drive absolutely straight in some sand and see how far to the left the rear tires are, vs the fronts.
If it is only an inch I would not worry about it.

So I guess the rear of the car would swing 4 degree minutes to the left, or .067 decimal degrees.
Over a 98 inch wheelbase it is not going to be far. Less than 1/4" ?

I would worry far more about any possible twitchiness in a turn.

 

I would move one 1/32” shim from the inside of the left trailing arm to the outside of the left trailing arm and take it for a drive. Or if you prefer, make the change and take it back to the shop. Before you do that get a set of these:

https://www.zip-corvette.com/63-82-t...stainless.html

They are cheap and last forever.

One other thing you may want to verify is that the TA bushings are tightly shimmed. Take a large screwdriver and pry the TA over to one side and see if you can fit a 1/32” shim. If you can, your TAs are loose or at least that one. Try the same on the other side.

 

All that detailed discussion about the data provided by the alignment shop ASSUMES that the data are absolutely correct. Since ALL such devices have some amount of error, changing what little offset the OP is 'said' to have could make things somewhat "better" or, actually, make them somewhat "worse". Why make ANY change if the OP can't detect any problem with the 'seat of his pants'?

 

I bought an alignment tool that attaches to the outside of the rim and uses 2 tape measures to get the tires square. from there I got them to the proper toe. Then i used the outside beam of the tool as a straight edge to run string to the front of the car. I then used that to find a common spot behind the front tire to the frame and measured out to the string from there. It gave me the toe in and told me where it was pointing. JUst adjusted each side in or out equally to get the measurements equal so it was pointing to the centerline of the car. Been good for over 5 years

 

The alignment shop haven't got the shims for Corvette's.
Thanks for the upload of references. I will try to swap suitable shim.
I attach the read out from the shop - please disregard front end as I haven't worked on that yet.
I ordered complete set of front end suspension parts and will work on that after this season.

Thanks all

Christian

HUNTER Hawkeye print out

 

Your rear alignment is fine along with the camber. Why try to fix something that isn't broke? Just monitor tire wear and how the car handles.

 

Thanks for sharing the detail. I stick with my original perspective that moving a 1/32” shim from the inside of the left TA to the outside. For the record, I’ve been aligning my own vehicles in my garage by myself. Periodically I’ll take them to a friend here in San Antonio who has a rack and he will check them. Never needed to be touched. Your print out shows that while the total tow is within spec, it is tracking towards the left. Probably an insignificant amount unless you were wringing every last bit out of the car, but why not address it since you know about it? Perhaps just my ocd talking!

Not sure why the rear camber is red, looks good to me! If anything I would want a bit more negative for slightly more aggressive street driving.

 

Thanks for all the input. I'll probably drive it as is for this summer and do the front next winter.
Now that I know about the difference I will probably make the small correction.
In any case i will take to the alignment shop after doing the front.

Thanks
Christian

 

Yes that printout helps.

• I see you are overseas, that makes C3 parts an order-in-advance proposition.
• I agree with moving the one TA shim. It should not affect anything else.
• You will never notice it with that much toe-out in the front anyway. That should give you some twitchiness by itself.
• I see the rear camber is red, but I like the 0.2 degree negative setting than the book setting of almost 1 degree anyway. Leave that alone.
• Your front camber is good too.
• The front toe out may be an indication of worn bushings or joints in the front. You said you were going to work on it. Just replace it all. Especially Ball joints and a arm bushings. They always seem to be the worst. If the rubber bushings look loose or flaking, they're bad. Then check the tie rods ends, and idler arm, for shake/looseness, and see if any of that stuff needs to be changed as while, "while you are in there".

"While I was at it" is a common disease among C3 owners! LOL

 

I bought this kit - Its called the Front suspension Deluxe kit. Anyway it appear to have what I need to do the job.
I'd be happy for suggestions for other parts I would need while I am at it as you say
I changed the steering box to a Borgeson last year but it still is a bit lively so I could adjust the front toe or replace the tie rods and joints now and do the big job after the season.
I appreciate the input very much.

 

I don't know who the manufacturer might be, but I hope they are quality parts...especially the rubber bushings. Steering and suspension are two of the critical areas involving passenger safety. Good luck with your repairs.