Bottoming out

[Jimkounter]

I'm slowly getting through the jobs on my newly acquired C3 and probably the most pressing is the bottoming out when hitting a depression or pothole at speed.

Having fixed the cat converter hangers which had perished the exhaust now hangs a little higher than it did. However, the back roads around me are bumpy as hell and the car is bottoming out with the cat and the bottom of the pipes making contact with the tarmac. All of the dampers look to have been replaced recently and this would likely affect bouncing rather than initial travel?

The rear suspension does seem soft but I don't know if it's supposed to be like that or whether my rear spring has gone.

It's sporting what I assume to be the original fiberglass spring. Do these deteriorate over time? How can I tell if it requires replacement other than changing it and seeing what if any change there is?

Alternatively perhaps my exhaust system is just too low? I've attached photos showing the rather terrible clearance. Is this all due to having to accommodate the catalytic converter? Anyone else running a late model C3 with stock cat having these issues?

As always, help is greatly appreciated.

 

[Forrest Gump]

Fibreglass / composite springs supposedly do not deteriorate with regard to losing their spring rate (steel springs do though).
The factory option composite spring was in fact the "comfort" option (steel was the stiffer sports option) so you will get quite a bit of suspension movement over bumps. You may be able to gain a bit of extra clearance by raising the ride height by adjusting the drop bolts at each end of the spring.

 

[Mad4slalom]

I'm slowly getting through the jobs on my newly acquired C3 and probably the most pressing is the bottoming out when hitting a depression or pothole at speed.

Having fixed the cat converter hangers which had perished the exhaust now hangs a little higher than it did. However, the back roads around me are bumpy as hell and the car is bottoming out with the cat and the bottom of the pipes making contact with the tarmac. All of the dampers look to have been replaced recently and this would likely affect bouncing rather than initial travel?

The rear suspension does seem soft but I don't know if it's supposed to be like that or whether my rear spring has gone.

It's sporting what I assume to be the original fiberglass spring. Do these deteriorate over time? How can I tell if it requires replacement other than changing it and seeing what if any change there is?

Alternatively perhaps my exhaust system is just too low? I've attached photos showing the rather terrible clearance. Is this all due to having to accommodate the catalytic converter? Anyone else running a late model C3 with stock cat having these issues?

As always, help is greatly appreciated.

hmmmaybe time for a set of side pipes

 

[Oneball]

The left hand pipe looks like it’s sitting a bit low. Worth checking your bump stops are still there, rubber blocks on the chassis where the end of the swing arm would hit.

If you get a copy of the AIM (assembly information manual) for your car it details where and how to measure the ride height so you can check it’s correct.

Also check your shocks for leaks and age.

Do the fibreglass springs have a heat shield to protect from the exhaust?

 

[teamzr1]

I would measure each corner's height and adjust as needed as at least from image is the right side is sagging down
Also looks like left mid-pipe hanging further down
Have to do a 4-wheel alignment when done.



See what GM specs is, I think I have posted before the GM engineering PDF for your MY, would show corner heights

IF the car was lowered then what stock was, then the stock shocks designed for taller travel will no longer work as well due to the valving
was designed for longer travel, but less travel and the shocks just do not work correctly

 

[antijam]

The specification for your '81 gives the stock minimum ground clearance - measured at the catalytic converter - as 4.1 inches.

 

[teamzr1]