Rear ride hight

[Mad4slalom]

Morning All. I see that a lot fit longer bolts to lower the rear ride hight. A lot of c3’s seem to sit down a bit more on on side or the other. Min seems to on the drivers side. My bolts are 6 or 7 “ from memory . The nuts where they sit are nearly at the end of the threads. If I wound Up the nut on the drivers side, that should raise that side ? . Anyone else had similar and corrected or improve it in this way.? (Vette has newer composite spring , newer rear shocks and the chassis was re jigged at a frame shop in the usa when the body was off) any thoughts appreciated

 

[Corvetteville]

My 78 was leaning on the drivers side. Longer bolts were fitted and adjusted, which leveled it up. However it still felt somewhat soggy, due to it most likely being the original spring. A NOS one with the correct number of leaves was fitted. All good now.

 

[Forrest Gump]

How much difference are you talking about? Have you checked the ride height at the front side to side?
There are so many factors that can affect the ride height at each corner of the car.
The first things to check though is that the floor is absolutely level and tyre pressures are even side to side.
As you have a composite spring you can be fairly sure that that is okay. Supposedly they won’t ever sag (instead just snap completely!!) Your bolts are set the same so the problem lies elsewhere.
Try disconnecting one end of the sway bars front and back (if there is one at the back) These could be bent or not set correctly, and will affect the ride height if wrong. Check there’s nothing amiss with the front springs too, the front affects the back.
Really, a cars ride height is taken as a chassis to the ground measurement at each corner. Then if it’s a competition car, corner weights come into the equation too. This might all be correct but the car still looks wrong when viewing the wheel arch gaps or wheel arch to ground measurements. So it’s down to how the body and panels are aligned and sitting on the chassis and if any areas have ever been repaired etc.. Adjustment to these things is difficult or impractical, so rightly or wrongly……most people end up adjusting those rear bolts if there’s nothing else obviously wrong on the car! I would’t want to see too much difference in the bolt lengths though - you’re hiding a problem elsewhere.

 

[Mad4slalom]

How much difference are you talking about? Have you checked the ride height at the front side to side?
There are so many factors that can affect the ride height at each corner of the car.
The first things to check though is that the floor is absolutely level and tyre pressures are even side to side.
As you have a composite spring you can be fairly sure that that is okay. Supposedly they won’t ever sag (instead just snap completely!!) Your bolts are set the same so the problem lies elsewhere.
Try disconnecting one end of the sway bars front and back (if there is one at the back) These could be bent or not set correctly, and will affect the ride height if wrong. Check there’s nothing amiss with the front springs too, the front affects the back.
Really, a cars ride height is taken as a chassis to the ground measurement at each corner. Then if it’s a competition car, corner weights come into the equation too. This might all be correct but the car still looks wrong when viewing the wheel arch gaps or wheel arch to ground measurements. So it’s down to how the body and panels are aligned and sitting on the chassis and if any areas have ever been repaired etc.. Adjustment to these things is difficult or impractical, so rightly or wrongly……most people end up adjusting those rear bolts if there’s nothing else obviously wrong on the car! I would’t want to see too much difference in the bolt lengths though - you’re hiding a problem elsewhere.

Thanks forest , i will check what I can , floor is pretty level, bolts set pretty much the same. Wheel arch to floor is an inch lower on drivers side rear, ie 28 v 29 inches. And 1/2 an inch lower on the drivers side front .
I dont have much thread left to lengthen the passenger side but I can shorten the drivers side by winding nut up some threads. Can I wind up with vehicle on ground?

 

[Forrest Gump]

I would Jack the car up before adjusting those bolts - it’s asking a lot of the threads otherwise.

 

[Mad4slalom]

I would Jack the car up before adjusting those bolts - it’s asking a lot of the threads otherwise.

That makes sense, will have a go this week

 

[Mad4slalom]

That makes sense, will have a go this week

Hi forest. Just reading your original reply to my bolt query, I have now got some 8” bolts , but as you say my existing bolts are the same height off the ground so chassis my be riding level and it is indeed a separate body fit issue.
I notice my body mounts have been shimmed mor on the drivers side in an attempt to pos raise that side.
I slso spoke to the po in the usa who did the body off on the car ,(or “cah” as they say in Buffalo ny!)
He said that when he stripped the paint he saw that the drivers side rear fender had at some time previously been
replaced.
He also said he has seen this on many vettes and some came out of the factory down on one side. I have posted pic of both rear body mounts, whether it is worth loosening drivers side one and seeing if the body will move up a bit . It Seems wrong to mess with the chassis set up to correct a panel or body alignment issue. May have to do as many say and live with it. Ps , the bolts I purchased are a metric equivalent and could only get 8 “ with an allen socket head. Interested in people ‘s thoughts on bolts and body mount /s shims etc .
Thank you all.

 

[Chuffer]

My car has always had a slight list to the the drivers side when viewed from the front . There is half inch difference in floor to underside of front wheel arch and the passenger side even though floor to chassis rail dimensions are the same . Interesting to hear that they often left the factory like that . I thought it might be down to the aftermarket flared arch panels on the car although the rear arch measurements are almost spot on . I spent ages taking before and after measurements and fine tuning the adjustments on the rear suspension when I replaced the bolts together with new bushes about 4 years ago to get the ride height just right as mine sits lower than standard .I still have run the steel spring rather than composite .

 

[teamzr1]

Keep in mind since we drive on the correct/right side of the road and most roads here
have a crown in the center of road for runoff of water for street drainage so American cars
are designed a bit to overcome car pulling to the right by a bias of height to the left
so pulling out or adding shims is common when we race on flat tracks or when the track has banking

 

[Chuffer]

Keep in mind since we drive on the correct/right side of the road and most roads here
have a crown in the center of road for runoff of water for street drainage so American cars
are designed a bit to overcome car pulling to the right by a bias of height to the left
so pulling out or adding shims is common when we race on flat tracks or when the track has banking

 

[Chuffer]

An interesting point . However , here the UK we have bends in our roads , lots of them ! Sweeping bends , tight bends , S bends and hairpin bends with surface cambers constantly changing one way to the other . We don`t do straight over here .

 

[Forrest Gump]

Hi forest. Just reading your original reply to my bolt query, I have now got some 8” bolts , but as you say my existing bolts are the same height off the ground so chassis my be riding level and it is indeed a separate body fit issue.
I notice my body mounts have been shimmed mor on the drivers side in an attempt to pos raise that side.
I slso spoke to the po in the usa who did the body off on the car ,(or “cah” as they say in Buffalo ny!)
He said that when he stripped the paint he saw that the drivers side rear fender had at some time previously been
replaced.
He also said he has seen this on many vettes and some came out of the factory down on one side. I have posted pic of both rear body mounts, whether it is worth loosening drivers side one and seeing if the body will move up a bit . It Seems wrong to mess with the chassis set up to correct a panel or body alignment issue. May have to do as many say and live with it. Ps , the bolts I purchased are a metric equivalent and could only get 8 “ with an allen socket head. Interested in people ‘s thoughts on bolts and body mount /s shims etc .
Thank you all.

Exactly as Chuffer has done..........If you check the chassis to ground height side to side and they are the same, then any differences in the wheel arch to ground height (side to side) must be either the fit of the panels or the way the whole body is sitting on the chassis. If your chassis was jig checked during it's re-build that is good to know at least.

Note also though that a slightly lower ride height at the front of the car compared to the rear is a good thing for not only appearance but aero stability at speed.

 

[Forrest Gump]

Keep in mind since we drive on the correct/right side of the road and most roads here
have a crown in the center of road for runoff of water for street drainage so American cars
are designed a bit to overcome car pulling to the right by a bias of height to the left
so pulling out or adding shims is common when we race on flat tracks or when the track has banking

I've never heard that before. Learnt something there!

 

[teamzr1]

An interesting point . However , here the UK we have bends in our roads , lots of them ! Sweeping bends , tight bends , S bends and hairpin bends with surface cambers constantly changing one way to the other . We don`t do straight over here .

We have lots of them here

 

[Roscobbc]

I've never heard that before. Learnt something there!

My understanding (of old admittedly) was that American vehicles (and certainly shoeboxes) were set-up suspension wise in the 50's, 60's and 70's specifically allowing for the 'Septics and their 'cack-handed' and really bizarre habit of driving on wrong side of the road.......idea being that driving on a road with adverse camber you'd be able to take your hands off the wheel and the car would still 'track' in a straight line.
That logic (if true) would potentially mean significant straight-line stabilty issues if the tracking etc wasn't later adjusted for the UK?

 

[Chuffer]

We have lots of them here

View attachment 26700

That`s one way of slowing traffic down I guess !!!

 

[Forrest Gump]

Thanks forest , i will check what I can , floor is pretty level, bolts set pretty much the same. Wheel arch to floor is an inch lower on drivers side rear, ie 28 v 29 inches. And 1/2 an inch lower on the drivers side front .
I dont have much thread left to lengthen the passenger side but I can shorten the drivers side by winding nut up some threads. Can I wind up with vehicle on ground?

Just looking back on your post and your current measurements - You could in theory make suspension adjustments to set the front passenger side 1/4' lower than drivers side then the effect diagonally across the car would be the drivers side rear is then raised 3/4". That would get you to within 1/4" on all corners. This would assume the chassis is perfectly rigid to aid this (they're almost certainly not).

But if the chassis to ground measurements are good/even at the moment (?) it would be a shame and obviously not technically correct to alter the suspension settings in order to correct an error on the body/panels.

Without looking it up, I've got no knowledge of the procedure for setting body mount shims. I don't think later C3's even have shims? I'm not sure how rigid the body structure is but imagine its a case of shimming the mounts to take up any gaps between the chassis and the body when they're brought together. I'm not wether you can alter the way the body "drapes" itself on the chassis by shimming (not very much I wouldn't think, and not as much as you're looking for).
Maybe others on here who have done a body-off can advise.

Assuming your car is for just cruising around and looking right aesthetically then perhaps suspension adjustments are your only practical option.

 

[Forrest Gump]

My understanding (of old admittedly) was that American vehicles (and certainly shoeboxes) were set-up suspension wise in the 50's, 60's and 70's specifically allowing for the 'Septics and their 'cack-handed' and really bizarre habit of driving on wrong side of the road.......idea being that driving on a road with adverse camber you'd be able to take your hands off the wheel and the car would still 'track' in a straight line.
That logic (if true) would potentially mean significant straight-line stabilty issues if the tracking etc wasn't later adjusted for the UK?

Exactly - a US car in the UK the car would be noticeably pulling into the ditch. I can't see how ride height could be used, but perhaps some other suspension geometry bias could, ie slightly more castor on one side to counter the effect? Luckily most C3s are all-over the place when driving so road camber is not actually an issue!

 

[Mad4slalom]

Exactly as Chuffer has done..........If you check the chassis to ground height side to side and they are the same, then any differences in the wheel arch to ground height (side to side) must be either the fit of the panels or the way the whole body is sitting on the chassis. If your chassis was jig checked during it's re-build that is good to know at least.

Note also though that a slightly lower ride height at the front of the car compared to the rear is a good thing for not only appearance but aero stability at speed.

I will have another look in a week when we get back from hols in spain

Just looking back on your post and your current measurements - You could in theory make suspension adjustments to set the front passenger side 1/4' lower than drivers side then the effect diagonally across the car would be the drivers side rear is then raised 3/4". That would get you to within 1/4" on all corners. This would assume the chassis is perfectly rigid to aid this (they're almost certainly not).

But if the chassis to ground measurements are good/even at the moment (?) it would be a shame and obviously not technically correct to alter the suspension settings in order to correct an error on the body/panels.

Without looking it up, I've got no knowledge of the procedure for setting body mount shims. I don't think later C3's even have shims? I'm not sure how rigid the body structure is but imagine its a case of shimming the mounts to take up any gaps between the chassis and the body when they're brought together. I'm not wether you can alter the way the body "drapes" itself on the chassis by shimming (not very much I wouldn't think, and not as much as you're looking for).
Maybe others on here who have done a body-off can advise.

Assuming your car is for just cruising around and looking right aesthetically then perhaps suspension adjustments are your only practical option.

I will double check frame to floor measurements and wheelarch to floor again before deciding whether to move any thing. It is pretty easy to raise the drivers side and lower the passenger side by adjusting rear spring bolts now I have longer ones. So I can try that and see if it looks better , I can always return it to where it is now.

 

[Mad4slalom]

Just looking back on your post and your current measurements - You could in theory make suspension adjustments to set the front passenger side 1/4' lower than drivers side then the effect diagonally across the car would be the drivers side rear is then raised 3/4". That would get you to within 1/4" on all corners. This would assume the chassis is perfectly rigid to aid this (they're almost certainly not).

But if the chassis to ground measurements are good/even at the moment (?) it would be a shame and obviously not technically correct to alter the suspension settings in order to correct an error on the body/panels.

Without looking it up, I've got no knowledge of the procedure for setting body mount shims. I don't think later C3's even have shims? I'm not sure how rigid the body structure is but imagine its a case of shimming the mounts to take up any gaps between the chassis and the body when they're brought together. I'm not wether you can alter the way the body "drapes" itself on the chassis by shimming (not very much I wouldn't think, and not as much as you're looking for).
Maybe others on here who have done a body-off can advise.

Assuming your car is for just cruising around and looking right aesthetically then perhaps suspension adjustments are your only practical option.

I dont know if it is possible to adjust front ride hieght without cutting springs is it? Dont fancy cutting just one side, maybe will try playing with rear bolt adjustments first after accurate measuring as that is easy to return to current state if no better. thanks all for your thoughts and suggestions .