My digital angle box has confirmed I've got a rather large amount of rear neg camber - circa 2.5 degrees both sides, so either worn rod bushes, slipped camber nuts or someone liked neg camber.

I'm thinking it might not be a bad idea to replace all the suspension bushes.

 

Based on your 2667 measure bar distance.

Not sure what shim pack you have but I have shims that measure .02" .03" shim I move most offen, I would start with 1/32" and see how much it moves 1 wheel.

 

When you lift the rear wheels off the ground and push @ 12 / 6 oclock how much do the wheels move ? Don't need a lot of force to feel worn suspensions parts / bushings. They would move freely.

See if you can adjust camber back to Zero. If its not possible then you have worn suspension / bushings / other parts.

 

Thanks - will do some tinkering tomorrow.

No idea how easy or hard it is to remove, swap, replace rear shims on a '81?

 

No different than my 78, bigest problem is when were they last worked on.
If many many years you may have 2 problems.

Tailing arm bolt won't loosen, when you remove shims they are rusted and fall apart. I would spray some lub on the bolt a let it sit over night.

Good luck and hope things go well.

 

Is it a case of just jack up and disassemble? Any special techniques or procedures?

 

That entirely depends on whether they are rusted in place or not.The shims in an "81 will be slotted, so you remove the retaining split pin, remove the pivot bolt split pin and loosen the nut, you should then be able to prise the shims out. If it was shimmed correctly and the trailing arm bushes aren't knackered the shims should be an interference fit with the pivot bolt loose. If it was me I would make sure all of the shims are removable before I took the car to an alinement shop else they will hate youIf you need to replace shims its a good idea to get a set of the stainless steel ones and replace the lot to save hassles in future. If the trailing arm bushes are knackered that's a whole other mission!
FWIW I would suggest shooting for as much caster in the front as you can get, my vette is set up at 5 deg, this helps to tame the darty go kart feeling the steering has. Look at later model vettes they all run more caster than what a C3 came with from the factory.
Also. you don't mention whether you checked the power steering? Easy enough to do, make sure the wheels are pointing straight ahead, disconnect the steering assist ram from the bracket on the chassis rail then start the engine, if the ram moves in or out the valve needs adjusting.

 

Good tips. thanks.

Are you saying that the shims are only secured with friction and nothing mechanically locks them in place? I.e I don't need to remove the bolt?

What is the best way to grip them to pull them out?

 

Remove tire, Remove cotter pin on trailing arm bolt, Lossen the trailing arm bolt, remove cotter pin securing the shims, then you should be able to move shims, Before you tighten it all up, snug the bolt, quick short drive, remeasure & adjust. Once good , torque and re-instert cotter pin for shims.

 

When we changed the trailing arms last winter I found that they were pretty tight in the "pockets" and needed a good whack with a mallet to pull them out! I'd attempted to wrangle out one or two shims, to no avail! The bushes were well and truly "shot", so the arms were somewhat expendable! There is a long split pin (in UK parlance!) that holds the shims in place, but in reality they are held tightly by the trailing arm pivot bolt.

Here's an idea of what it looks like, with the split pin in place, so the shims dropped into the pocket:


This is a close up of the first attempt. That showed the toe-in to be "miles' out and took a bit of working out to determine which shims were needed where to get it right.



Incidentally, it's the inner shims on both arms that "control" the toe-in; the outers are there just to "fill the gap", so you need to calculate the inner requirement first. The new shim packs have a selection of shims, but they only come in three sizes, basically, thick. medium and thin, (I can't recall the actual thickness, but you'll need to know that to work out what you need!) And, they'll need to be tapped home with a "toffee hammer", they should not just slide in.

 

Thanks Stephen - I've elected against any further 'absolutely filthy' work on the car this week and I'm concentrating on soppy little cosmetic jobs here and there.... you know.... kicking the proverbial can down the road.

Given my total toe is correct, what are the chances of just relocating one or two sims from one side of the trailing arm to the other to chift the toe (if they're in re-useable condition). i.e I might not need to order a new set?

Or is that hugely, naively optimistic?

 

If you don't have stainless shims now, you will need them later. To change the bushings, I needed to cut the trailing arms out of the pocket with a carbide blade, and even then the shims didn't move until I pried them out.

 

Hope this isn't a silly question, but hot do you know if your bushings need replacing?

 

Use a pry bar to lever on the trailing in an up down movement underneath where the pivot bolt is. If the bushes are shot the trailing arm will jiggle up and down easily.

 

I had a pretty good idea by the amount that they moved in an arc when the car was jacked up, ie, the weight of the wheel etc pulled them down into a wild positive camber attitude! And, I could easily lift them back up, so clearly they were rocking and rolling on the expired bushes. I didn't get to the pry bar stage, but given how they looked when they came out I'm sure they'd have moved!

Based on mine, I suspect a "simple" swap of shims is unlikely. I'd suggest that if the numbers look good, and there's no signs of wear, I'd leave well alone!

 

Another quick question - did you buy and use the expensive and apparently essential installation tool for the trailing arm bushes permitting the correct flaring of the pin bush?

 

Tonight i made some home brew lateral rollers to enable quick measurement of camber between adjustments. Whilst the suspension will still need to settle, I can make the required adjustments all in one go from a known base line,

For the avoidance of doubt, there are stops screwed into the plates to prevent it rolling off the sides in either direction and the front end is fully chocked in both directions on both wheels.

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​​​​​​5unyFJ6.mp4

 

You can use this to check worn suspension parts.

Drive the car into the garage measure camber / toe. Then apply these (skid plates) and compare. If you notice a big change in camber / toe. Then you most likly have worn suspension joints / bushing somewhere.

 

That's interesting as after a good drive round the other weekend, I measured 2.5 degrees negative camber on both rear wheels.

After jacking the car up and putting on the rollers, they measure give or take zero camber, despite bouncing the rear end and shifting it on the rollers side to side. I would still expect some suspension settlement after further driving though as nothing is perfectly free to move like a rose joint would permit?

Incidentally, whilst up in the air, I checked for play in the rear wheels - no play in or out telescopically/axially, wheels turn smoothly and silently, absolutely nothing in the 3 - 9 o'clock left/right position and only a tiny bit of play in the 12 - 6 o'clock position - enough to feel and hear a very slight 'rock', but barely enough to see. It was perhaps 1/32 at the tyre edge, or 0.1 degree when using my angle box.

My own conclusion from that is that the bearings are fine, but possibly a tiny bit of wear in the camber control bush?

I welcome thoughts as I'm not sure what is normal or acceptable in this regard.

My plan was to dial in 2 degrees of positive camber from wherever they are now, so that once settled, it sits at 0,5 degrees negative camber,

Once set, I was then going to set the thrust with a slight shims swap on both sides to maintain the correct total toe, but correct the thrust.

Right track? (pardon the pun)

 

I'll keep today's update short and succinct.

The rear camber bolts were tight.

I think I just expelled a lung.