How many trailing arm shims is "normal?"
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Joined: Dec 2012
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How many trailing arm shims is "normal?"
I just replaced the trailing arms on my 80 (bad wheel bearings.)
Once the car goes in for it's safety (tomorrow) I'm going to resume doing the home 4 wheel alignment.
What I was wondering is: how many shims does everyone else have in the back of their car? I know they are mass produced, thus the shims, just wondering what's normal - I know they should be snug, but how snug is snug? When do I stop adding the thin shims? It's not like I can stick my feeler gauge in there and measure clearance.
I think it was/is a bit toed out (just a visual, I ran out of time adjusting the camber.)
My car had (factory I think based on the rust)
Driver's outer: 1 big
Driver's inner: 1 big, 2 medium
Passenger inner: 1 big, 1 medium, 1 thin
Passenger outer: 1 big, 1 medium, 1 thin
adding/removing shims - does anyone know how much a shim change works out to at the wheel? If I moved one medium (1/8" ?) from the inside to the outside, that'll add toe-in, but is that 1/8" at the wheel? 1/4? 1/16? Trying to know before I move them, they're just a bit of a pain to put in.
I see also that changing one setting affects the others... it's not hard to do a driveway alignment, it's just a lot of time. Jack it up, adjust, lower, back up, drive forward, slip slurpee, rinse, repeat.
Once the car goes in for it's safety (tomorrow) I'm going to resume doing the home 4 wheel alignment.
What I was wondering is: how many shims does everyone else have in the back of their car? I know they are mass produced, thus the shims, just wondering what's normal - I know they should be snug, but how snug is snug? When do I stop adding the thin shims? It's not like I can stick my feeler gauge in there and measure clearance.
I think it was/is a bit toed out (just a visual, I ran out of time adjusting the camber.)
My car had (factory I think based on the rust)
Driver's outer: 1 big
Driver's inner: 1 big, 2 medium
Passenger inner: 1 big, 1 medium, 1 thin
Passenger outer: 1 big, 1 medium, 1 thin
adding/removing shims - does anyone know how much a shim change works out to at the wheel? If I moved one medium (1/8" ?) from the inside to the outside, that'll add toe-in, but is that 1/8" at the wheel? 1/4? 1/16? Trying to know before I move them, they're just a bit of a pain to put in.
I see also that changing one setting affects the others... it's not hard to do a driveway alignment, it's just a lot of time. Jack it up, adjust, lower, back up, drive forward, slip slurpee, rinse, repeat.
Pro
Joined: Nov 2012
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From: Chesapeake Virginia
I doubt you will get any kind of answer to your first question, the frame and suspensions on these cars all vary in small amounts, just because you have a certain amount doesn't mean everyone will have the same amount.
I would keep putting shims in until you can't get anymore in without prying the frame apart, then when you tighten up the pivot bolt it will pull the frame together enough to tighten them up good.
I'm not sure how much each shim changes things at the wheel, it may be trial-and-error to figure that out.
if you don't want to keep jacking up the car to adjust the alignment, try using a set of (4) four wheel car dollies from harbor freight, I found they raise the car just enough to get to most things (it is tight though), that way the weight it still on the suspension and the wheels can move and "settle in".
I would keep putting shims in until you can't get anymore in without prying the frame apart, then when you tighten up the pivot bolt it will pull the frame together enough to tighten them up good.
I'm not sure how much each shim changes things at the wheel, it may be trial-and-error to figure that out.
if you don't want to keep jacking up the car to adjust the alignment, try using a set of (4) four wheel car dollies from harbor freight, I found they raise the car just enough to get to most things (it is tight though), that way the weight it still on the suspension and the wheels can move and "settle in".
Thread Starter
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Joined: Dec 2012
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I doubt you will get any kind of answer to your first question, the frame and suspensions on these cars all vary in small amounts, just because you have a certain amount doesn't mean everyone will have the same amount.
I would keep putting shims in until you can't get anymore in without prying the frame apart, then when you tighten up the pivot bolt it will pull the frame together enough to tighten them up good.
I would keep putting shims in until you can't get anymore in without prying the frame apart, then when you tighten up the pivot bolt it will pull the frame together enough to tighten them up good.
I did "paint" the shims with anti-seize to make removal less torturous.
Melting Slicks
Joined: Dec 1999
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From: Mid West
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They do make stainless steel shims if your so inclined. They do make aligning the car a bit easier just because of less rust to deal with. I put as many shims in as I can. The last ones usually need a light persuasion with a rubber mallet to tap them in. Shouldn't be hard, just snug. Like Jig A Low said, once you tighten the bolt, the frame should clamp down on them so there is NO movement of the shims.
Race Director
Joined: Apr 2009
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From: Charlotte NC
You do not have to put shims in to the point that you have to beat them in. This is due to when the nut is tightened to 45 lbs/ft (plus additional turn to align cotter pin hole) The frame will close in on them and tighten them in place. AND with the use of the long cotter pin...the shims will not be able to fall out as you know.
OPINION:
AS for doing a driveway alignment in regards to the shims for setting the toe. I would not do this only because I have seen what changes occur on the computer screen to the alignment specs even when a thin shim is changed from one side to the other. To each his or her own....unless you have the "old school" measuring devices to get it set correctly. I prefer using a laser alignment machine. But that is just me.
DUB
OPINION:
AS for doing a driveway alignment in regards to the shims for setting the toe. I would not do this only because I have seen what changes occur on the computer screen to the alignment specs even when a thin shim is changed from one side to the other. To each his or her own....unless you have the "old school" measuring devices to get it set correctly. I prefer using a laser alignment machine. But that is just me.
DUB
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Joined: Dec 2012
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You do not have to put shims in to the point that you have to beat them in. This is due to when the nut is tightened to 45 lbs/ft (plus additional turn to align cotter pin hole) The frame will close in on them and tighten them in place. AND with the use of the long cotter pin...the shims will not be able to fall out as you know.
OPINION:
AS for doing a driveway alignment in regards to the shims for setting the toe. I would not do this only because I have seen what changes occur on the computer screen to the alignment specs even when a thin shim is changed from one side to the other. To each his or her own....unless you have the "old school" measuring devices to get it set correctly. I prefer using a laser alignment machine. But that is just me.
DUB
OPINION:
AS for doing a driveway alignment in regards to the shims for setting the toe. I would not do this only because I have seen what changes occur on the computer screen to the alignment specs even when a thin shim is changed from one side to the other. To each his or her own....unless you have the "old school" measuring devices to get it set correctly. I prefer using a laser alignment machine. But that is just me.
DUB
Then I start doing the math in my head of how many man-hours are involved and I start thinking: I can do it and save me a lot of money.
Combination of stubborn and stupid I guess.
I just wanted to make sure I wasn't forcing too many shims in, or not enough. First Vette. (Had many cars, first Vette.)
I had a dirt track Camaro, and my buddy has a Formula V, so I know how to measure everything, it just takes a long time, especially because yes, I suspect moving a shim from one side to the other changes the toe-in, and probably also the camber a bit too. Plus changing the rear ride height affects the front, etc. It's like timing and idle - you go back and forth.
I guess I just go: every dollar I don't have to give to a mechanic is one more dollar to spend on the car. Yeah, that's it.
My name is Ray and I have a car problem.
Race Director
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GM made the frames with the inside of the trailing arm pocket controlled to a specified dimension +/- a little bit. They also made the trailing arm bushing outer diameter the same way. This means that the total thickness of the shim pack would be constant from car to car +/- a little bit.
The final shim was intended to be helped into place with a hammer meaning that there was very little compression of the trailing arm pocket walls when the bolt was torqued.
If an owner finds that they have lots of shims left over from a new set, it usually means that someone before them didn't install enough shims and the pocket is partially crushed.
The final shim was intended to be helped into place with a hammer meaning that there was very little compression of the trailing arm pocket walls when the bolt was torqued.
If an owner finds that they have lots of shims left over from a new set, it usually means that someone before them didn't install enough shims and the pocket is partially crushed.
