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JBOYLE
05-01-2007, 12:55 PM
My Avanti bottoms out over parking lot speed bumps. The last owner did a good deal of suspenion work (bushing, mounts, etc) so I'm wondering if it's the shocks or springs.

What brand of shocks did the Avanti come with?
Gabriel? Monroe?

63 Avanti R1 2788
1914 Stutz Bearcat
(George Barris replica)

Washington State

bige
05-01-2007, 01:53 PM
Do you mean the suspension compresses completely and hits the snubbers or is the frame or exhaust hitting the bumps? Either way shocks wouldn't help bottoming unless they were air or coil over style.

I believe the original shocks were Gabriel...

ErnieR

http://i146.photobucket.com/albums/r241/AvantiR2/avnatiglamour007.jpg

JBOYLE
05-01-2007, 02:57 PM
The frame is hitting bumps...I should have been more precise.

63 Avanti R1 2788
1914 Stutz Bearcat
(George Barris replica)

Washington State

bige
05-01-2007, 03:41 PM
Could be that springs have sagged some. I know the leafs on my car were causing the rear to drop at least 3 inches. Are you running a low profile tire or a 195 or 205, they are a little shorter than the 6.70 original equipments bias ply.

I have to be careful over speed bumps because my exhaust has to hang below the frame but generally if I'm alone in the car it won't hit if the bumps are negotiated slowly. So, I would say your symptoms aren't normal.

If it hits more toward the rear you may need to replace the leaf springs. It's not that difficult and the improvement in the ride is well worth the effort.

ErnieR

http://i146.photobucket.com/albums/r241/AvantiR2/avnatiglamour007.jpg

Dick Steinkamp
05-01-2007, 06:08 PM
quote:Originally posted by JBOYLE

The frame is hitting bumps...I should have been more precise.



Are you sure it's the frame? Generally it's some part of the exhaust system that will hit before the frame does. Usually this can be fixed by "adjusting" the low point of the exhaust. My '54 is fairly low and the frame has never touched the ground...only the exhaust cut outs which are the lowest part of my exhaust system.



http://thenobot.org/images/s2d/s2d_01.jpg

John Kirchhoff
05-01-2007, 10:07 PM
Actually worn shocks will let the springs bottom out more easily. The compression resistance of a shock is much less than the extension dampening is, but none the less a good shock will help prevent bottoming. The old bouncing bumper trick is an easy way to see if the shocks are getting worn.

Don't always think "heavy duty" shocks are better. The stiffer the spring and the higher the speed traveled, the more shock dampening needed. However, put a shock with very heavy extension dampening on a vehicle with soft springs and when running over a washboard surface, the suspension finally ends up being fully compression. That's because the spring isn't strong enough to extend the shock back to it's orginal position before the next bump comes along and compresses it some more. It acts kind of like one of those ratcheting fence stretchers. If you have stiff springs and drive aggressively, heavy duty shocks may be for you but for most of us they'll just make the car ride rougher.

bams50
05-02-2007, 05:32 AM
Just remember this general principle:

Springs are designed for holding up the vehicle, and providing "give" over bumps; shocks are only for dampening (controlling) the action of the spring!

This is a bit of an over-simplification; we all know about air shocks and coil overs. But using those are merely band-aids- use the springs to fix ride height, then select shocks. Over all my years in racing, whenever we put the car on the scales, the first thing we did was disconnect the shocks till we were done...

If you separate the shocks and springs into two categories and address them individually, you'll end up with properly working suspension! [^]

Applying this to your bottoming out: the problem is either 1. Ride height too low (springs) or 2. Suspension bouncing/rebounding (traveling) too far (shocks).

Robert K. Andrews Owner- IoMT (Island of Misfit Toys!)
Parish, central NY 13131
http://www.cardomain.com/ride/2358680/1

John Kirchhoff
05-02-2007, 03:40 PM
Just for a bit of trivia, many large trucks don't have shocks on the rear axles. Stiff springs make for limited travel and lots of leaves makes for quite a bit of friction which acts like a shock absorber. It's not just over the road tractors, my Dodge 1 ton never has had rear shocks. But then again I think it has 7 leaves on the main spring and 5 more on the overload.