Front end alignment '81
Melting Slicks
Joined: Jun 2011
Posts: 3,116
Likes: 598
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)
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 would use the driving to settle the suspension and validate actual camber.
As for wheel movement at the 12 & 6 oclock poistions it will come from 2 places.
1. wheel bearing
2. Diff side yokes.
Bearings setup factory are about ~ 0.005 - 0.008 play.
Diff side yokes usually in good is about 0.005-0.010 play.
You can see the yokes move in and out when you push / pull the wheel 12 &6 oclock.
Bad conditions usually are very noticable. But does require some force to lift the weight of the wheel & trainling arm.
If you are lightly pushing this may not be enough force. Try lifting the wheel and see what happens.
Last edited by cagotzmann; Oct 6, 2021 at 06:33 PM.
Thread Starter
Drifting
Joined: Aug 2017
Posts: 1,433
Likes: 351
Took it for a drive after the rear camber adjustment and it has settled exactly where I wanted it at 0.5 degrees negative camber both sides, so I'm happy I can now move on to final thrust measurements and adjustment,.
Melting Slicks
Joined: Jun 2011
Posts: 3,116
Likes: 598
I usually get the same reading or with-in +- .1 degrees.
When I add my skid plates you can see the wheels push outward as they settle. I use cutting sheets with grease between the plates. When my suspension was worn this would change the camber by .2 degrees (more camber) and change the toe to more toe out.
Last edited by cagotzmann; Oct 9, 2021 at 12:04 PM.
Thread Starter
Drifting
Joined: Aug 2017
Posts: 1,433
Likes: 351
Haven't tried the skid plates again, but will do, along with re-checking my toe/
No matter where the suspension is in it's travel (within reason) the thrust remains out of alignment by very similar amounts, so this is the area I'm keen to get in the ball park soon so I can test drive and see if this is the cause of it pulling to the right. If that solves the problem, I can then fine tune to my hearts content and replace all the bushes etc if I need to - I just want to get the bottom of what the key issue is.
No matter where the suspension is in it's travel (within reason) the thrust remains out of alignment by very similar amounts, so this is the area I'm keen to get in the ball park soon so I can test drive and see if this is the cause of it pulling to the right. If that solves the problem, I can then fine tune to my hearts content and replace all the bushes etc if I need to - I just want to get the bottom of what the key issue is.
Melting Slicks
Joined: Jun 2011
Posts: 3,116
Likes: 598
Haven't tried the skid plates again, but will do, along with re-checking my toe/
No matter where the suspension is in it's travel (within reason) the thrust remains out of alignment by very similar amounts, so this is the area I'm keen to get in the ball park soon so I can test drive and see if this is the cause of it pulling to the right. If that solves the problem, I can then fine tune to my hearts content and replace all the bushes etc if I need to - I just want to get the bottom of what the key issue is.
No matter where the suspension is in it's travel (within reason) the thrust remains out of alignment by very similar amounts, so this is the area I'm keen to get in the ball park soon so I can test drive and see if this is the cause of it pulling to the right. If that solves the problem, I can then fine tune to my hearts content and replace all the bushes etc if I need to - I just want to get the bottom of what the key issue is.
Align your steering wheel where you like it for straight driving. Then mark like this so you can repeat the position. I also have marks for caster positions . One full turn to mark for left or right caster angles.
Thread Starter
Drifting
Joined: Aug 2017
Posts: 1,433
Likes: 351
Great stuff - didn't think about the front thrust as just imagined the toe vs steering wheel angle would sort itself out by adjusting the arms in opposite directions to maintain toe but change the position of the steering wheel...... which is, I guess... setting the front thrust.
Can't wait to get my quick jacks so i can get my torque wrench on the camber bolts for 70 lbs, as currently, I've just set them by feel at 'FT' and took all of my will not to use copper grease on reassembly! LOL
Can't wait to get my quick jacks so i can get my torque wrench on the camber bolts for 70 lbs, as currently, I've just set them by feel at 'FT' and took all of my will not to use copper grease on reassembly! LOL
Thread Starter
Drifting
Joined: Aug 2017
Posts: 1,433
Likes: 351
Having now got the rear camber and toe where i want it, I rechecked the thrust so I have a more accurate target to aim for.
After multiple checks, the total thrust offset is 16mm, meaning I've got to shift both trailing arm bushes to the right by a certain amount,
I guess my next step is to work out how much of a shim adjustment at the bush will give me 8mm at the front axle.
For my own ease of calculation, and given that I'm a brit, I'll work in metric.
We know the wheelbase is 2,489mm and thanks to a measurement from my alignment guru and mentor cagotzmann, the effective length of the trailing arm is 17.5", or 444mm.
By my logic, if we need to shift the thrust er wheel by 8mm over a length of 2,489mm, then using the proportional factor of 2,489 divided by 444 equals a factor of 5.6, am I correct in deducing thst the work out the dimensionsl shift required at the trailing arm bushing is 8mm divided by 5.6 = 1.43mm each side?
If so, and we then convert that into available shims, 1.43mm in imperial is 0.0563", which fractionally is just less that 1/16".......
If all the above is correct, and given we know that the thinnest shims are 1/32", my task in the first instance is to swap a pair of 1/32 shims from the left, to the right of the bushings on both sides of the car?
After multiple checks, the total thrust offset is 16mm, meaning I've got to shift both trailing arm bushes to the right by a certain amount,
I guess my next step is to work out how much of a shim adjustment at the bush will give me 8mm at the front axle.
For my own ease of calculation, and given that I'm a brit, I'll work in metric.
We know the wheelbase is 2,489mm and thanks to a measurement from my alignment guru and mentor cagotzmann, the effective length of the trailing arm is 17.5", or 444mm.
By my logic, if we need to shift the thrust er wheel by 8mm over a length of 2,489mm, then using the proportional factor of 2,489 divided by 444 equals a factor of 5.6, am I correct in deducing thst the work out the dimensionsl shift required at the trailing arm bushing is 8mm divided by 5.6 = 1.43mm each side?
If so, and we then convert that into available shims, 1.43mm in imperial is 0.0563", which fractionally is just less that 1/16".......
If all the above is correct, and given we know that the thinnest shims are 1/32", my task in the first instance is to swap a pair of 1/32 shims from the left, to the right of the bushings on both sides of the car?
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Melting Slicks
Joined: Jun 2011
Posts: 3,116
Likes: 598
Having now got the rear camber and toe where i want it, I rechecked the thrust so I have a more accurate target to aim for.
After multiple checks, the total thrust offset is 16mm, meaning I've got to shift both trailing arm bushes to the right by a certain amount,
I guess my next step is to work out how much of a shim adjustment at the bush will give me 8mm at the front axle.
For my own ease of calculation, and given that I'm a brit, I'll work in metric.
We know the wheelbase is 2,489mm and thanks to a measurement from my alignment guru and mentor cagotzmann, the effective length of the trailing arm is 17.5", or 444mm.
By my logic, if we need to shift the thrust er wheel by 8mm over a length of 2,489mm, then using the proportional factor of 2,489 divided by 444 equals a factor of 5.6, am I correct in deducing thst the work out the dimensionsl shift required at the trailing arm bushing is 8mm divided by 5.6 = 1.43mm each side?
If so, and we then convert that into available shims, 1.43mm in imperial is 0.0563", which fractionally is just less that 1/16".......
If all the above is correct, and given we know that the thinnest shims are 1/32", my task in the first instance is to swap a pair of 1/32 shims from the left, to the right of the bushings on both sides of the car?
After multiple checks, the total thrust offset is 16mm, meaning I've got to shift both trailing arm bushes to the right by a certain amount,
I guess my next step is to work out how much of a shim adjustment at the bush will give me 8mm at the front axle.
For my own ease of calculation, and given that I'm a brit, I'll work in metric.
We know the wheelbase is 2,489mm and thanks to a measurement from my alignment guru and mentor cagotzmann, the effective length of the trailing arm is 17.5", or 444mm.
By my logic, if we need to shift the thrust er wheel by 8mm over a length of 2,489mm, then using the proportional factor of 2,489 divided by 444 equals a factor of 5.6, am I correct in deducing thst the work out the dimensionsl shift required at the trailing arm bushing is 8mm divided by 5.6 = 1.43mm each side?
If so, and we then convert that into available shims, 1.43mm in imperial is 0.0563", which fractionally is just less that 1/16".......
If all the above is correct, and given we know that the thinnest shims are 1/32", my task in the first instance is to swap a pair of 1/32 shims from the left, to the right of the bushings on both sides of the car?
8 mm may require 1.8 / 32nd shim where a 1/16th shim might get you closer. But I would move 1 side and see if this calculates as expected.
I used the angle change to get the calculation. 8mm change requires a 0.184 degree change over a 444mm trailing arm = 1.4369mm same as your number. Should be good.
Thread Starter
Drifting
Joined: Aug 2017
Posts: 1,433
Likes: 351
Before I dive into the rear trailing arms, and whilst I had it up on the jacks with the wheels off the floor, I ran the motor to see if the power steering remained stationary.
The jury is out.... near centre, it did, sometimes, not all of the time, turn the steering wheel to the right very slightly, like a few degrees, maybe half a spoke width over 10 seconds before stopping, but not all of the time and only very slight and tiny amount with next to no force - i.e if I barely touched the wheel, it would stop it moving. Once the car had warmed up and I'd cycled the wheel full left and right a good few times, it remained stationary with equal effort in both directions at all times.
Is this a red herring, as the very slight and tiny nature of this 'drift' I can't imagine giving anything like the pull to the right I'm experiencing.
Thoughts?
The jury is out.... near centre, it did, sometimes, not all of the time, turn the steering wheel to the right very slightly, like a few degrees, maybe half a spoke width over 10 seconds before stopping, but not all of the time and only very slight and tiny amount with next to no force - i.e if I barely touched the wheel, it would stop it moving. Once the car had warmed up and I'd cycled the wheel full left and right a good few times, it remained stationary with equal effort in both directions at all times.
Is this a red herring, as the very slight and tiny nature of this 'drift' I can't imagine giving anything like the pull to the right I'm experiencing.
Thoughts?
Melting Slicks
Joined: Jun 2011
Posts: 3,116
Likes: 598
Before I dive into the rear trailing arms, and whilst I had it up on the jacks with the wheels off the floor, I ran the motor to see if the power steering remained stationary.
The jury is out.... near centre, it did, sometimes, not all of the time, turn the steering wheel to the right very slightly, like a few degrees, maybe half a spoke width over 10 seconds before stopping, but not all of the time and only very slight and tiny amount with next to no force - i.e if I barely touched the wheel, it would stop it moving. Once the car had warmed up and I'd cycled the wheel full left and right a good few times, it remained stationary with equal effort in both directions at all times.
Is this a red herring, as the very slight and tiny nature of this 'drift' I can't imagine giving anything like the pull to the right I'm experiencing.
Thoughts?
The jury is out.... near centre, it did, sometimes, not all of the time, turn the steering wheel to the right very slightly, like a few degrees, maybe half a spoke width over 10 seconds before stopping, but not all of the time and only very slight and tiny amount with next to no force - i.e if I barely touched the wheel, it would stop it moving. Once the car had warmed up and I'd cycled the wheel full left and right a good few times, it remained stationary with equal effort in both directions at all times.
Is this a red herring, as the very slight and tiny nature of this 'drift' I can't imagine giving anything like the pull to the right I'm experiencing.
Thoughts?
6:30 section of this video.
C2 & C3 (1963-1982) Corvette Power Steering Control Valve - Corvette Parts Center - Bing video
He is showing with the rod disconnected (Best option) but I have adjusted this many times just with the wheels raised.
This way you eliminate the thoughts in your head.
Last edited by cagotzmann; Oct 23, 2021 at 10:45 AM.
Thread Starter
Drifting
Joined: Aug 2017
Posts: 1,433
Likes: 351
This is a easy adjustment to center, so while you are at it make the adjustment without disconnecting anything.
6:30 section of this video.
C2 & C3 (1963-1982) Corvette Power Steering Control Valve - Corvette Parts Center - Bing video
He is showing with the rod disconnected (Best option) but I have adjusted this many times just with the wheels raised.
This way you eliminate the thoughts in your head.
6:30 section of this video.
C2 & C3 (1963-1982) Corvette Power Steering Control Valve - Corvette Parts Center - Bing video
He is showing with the rod disconnected (Best option) but I have adjusted this many times just with the wheels raised.
This way you eliminate the thoughts in your head.
Thread Starter
Drifting
Joined: Aug 2017
Posts: 1,433
Likes: 351
So disconnected the steering ram from the frame mount and started the engine and it fully retracted, supporting the pulling to the right issue as mentioned up thread.
I popped the cap, experimented with some adjustment and got it to state still, then reassembled everything,
Took it for a quick drive and amazingly, its fixed - no longer wanting to drift right any more - the steering is straight, the wheel is straight and it doesn't pull.
it feels like a different car - I'm so pleased!
Thanks everyone.
I popped the cap, experimented with some adjustment and got it to state still, then reassembled everything,
Took it for a quick drive and amazingly, its fixed - no longer wanting to drift right any more - the steering is straight, the wheel is straight and it doesn't pull.
it feels like a different car - I'm so pleased!
Thanks everyone.
Burning Brakes
Joined: Jan 2001
Posts: 1,219
Likes: 448
From: Loir Valley Sarthe, France
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2024 C3 of the Year Finalist - Unmodified
2023 C3 of the Year Finalist - Unmodified
So disconnected the steering ram from the frame mount and started the engine and it fully retracted, supporting the pulling to the right issue as mentioned up thread.
I popped the cap, experimented with some adjustment and got it to state still, then reassembled everything,
Took it for a quick drive and amazingly, its fixed - no longer wanting to drift right any more - the steering is straight, the wheel is straight and it doesn't pull.
it feels like a different car - I'm so pleased!
Thanks everyone.
I popped the cap, experimented with some adjustment and got it to state still, then reassembled everything,
Took it for a quick drive and amazingly, its fixed - no longer wanting to drift right any more - the steering is straight, the wheel is straight and it doesn't pull.
it feels like a different car - I'm so pleased!
Thanks everyone.
I confess, I hadn't thought about the P/S valve adjustment, but as you say, its a simple adjustment, so a nice easy fix! Glad that you got it sorted!
Thread Starter
Drifting
Joined: Aug 2017
Posts: 1,433
Likes: 351
I actually wondered how you were progressing today, when I came across the details and the all important diagram for setting up the 4 wheel alignment using cross beams, and fishing line!
I confess, I hadn't thought about the P/S valve adjustment, but as you say, its a simple adjustment, so a nice easy fix! Glad that you got it sorted!
I confess, I hadn't thought about the P/S valve adjustment, but as you say, its a simple adjustment, so a nice easy fix! Glad that you got it sorted!
Melting Slicks
Joined: Jun 2011
Posts: 3,116
Likes: 598
At some point getting the rear thrust adjusted will only make things better. But won't be as noticable as fixing the steering balance issue. Rear thrust alignment now should be noticable as full throttle pushing steering.
The best part is the experience / knowledge you gain about "YOUR CAR"
Thread Starter
Drifting
Joined: Aug 2017
Posts: 1,433
Likes: 351
And it only gets better knowing your alignment is perfect, supporting the car can drive nice and straight in uneven road conditions. Get max tire life. Suspension is tight and not worn allowing steady steering.
At some point getting the rear thrust adjusted will only make things better. But won't be as noticable as fixing the steering balance issue. Rear thrust alignment now should be noticable as full throttle pushing steering.
The best part is the experience / knowledge you gain about "YOUR CAR"
At some point getting the rear thrust adjusted will only make things better. But won't be as noticable as fixing the steering balance issue. Rear thrust alignment now should be noticable as full throttle pushing steering.
The best part is the experience / knowledge you gain about "YOUR CAR"
Ironically, my self adhesive 3m tapes arrived this week which i attached to my cross pieces to help measure and check alignment - they can lean against the wall until the next time I need to make an adjustment.
My next dilema is when I'm under the car I can't help but notice the old, heavy, steel leaf spring...... ahem....
I'm an absolute sucker for originality..... but.....
Burning Brakes
Joined: Jan 2001
Posts: 1,219
Likes: 448
From: Loir Valley Sarthe, France
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2024 C3 of the Year Finalist - Unmodified
2023 C3 of the Year Finalist - Unmodified
But, I changed trailing arms recently - the car did not come with Gymkhana suspension, so when I ordered new arms I went for the "non drilled" option. Only to find that the originals were drilled and "gymkhana ready". Had I known, I'd have got the drilled arms because on our recent 1080 mile Alpine tour, a rear sway bar might have been nice!
Thread Starter
Drifting
Joined: Aug 2017
Posts: 1,433
Likes: 351
We changed the '78's original metal spring to a composite item back in about 1998 and it's one of the best things we ever did. A much nicer ride and the bonus that it makes future work on anything at the rear a whole lot easier We put Koni Adjustables all round, to go with the new spring. I'm not into racing it around a track etc, so that smoother ride when touring was important.
But, I changed trailing arms recently - the car did not come with Gymkhana suspension, so when I ordered new arms I went for the "non drilled" option. Only to find that the originals were drilled and "gymkhana ready". Had I known, I'd have got the drilled arms because on our recent 1080 mile Alpine tour, a rear sway bar might have been nice!
But, I changed trailing arms recently - the car did not come with Gymkhana suspension, so when I ordered new arms I went for the "non drilled" option. Only to find that the originals were drilled and "gymkhana ready". Had I known, I'd have got the drilled arms because on our recent 1080 mile Alpine tour, a rear sway bar might have been nice!
From what I read, a 330 VBP would be ideal?
I'm in no rush at all and might well leave it, but nice to know in advance if the mood takes me.
Burning Brakes
Joined: Jan 2001
Posts: 1,219
Likes: 448
From: Loir Valley Sarthe, France
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2024 C3 of the Year Finalist - Unmodified
2023 C3 of the Year Finalist - Unmodified