suspension,handling
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bdolin
- Posts: 1
- Joined: Wed Mar 19, 2014 5:51 pm
suspension,handling
i have a vintage 356 speedster replicar on a 65 VW chassis the car bangs and bumps like crazy What should I be looking for to correct the problem Bruce Dolin
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Marc
- Moderator
- Posts: 23741
- Joined: Thu May 23, 2002 12:01 am
Re: suspension,handling
Check all of the shock absorber bushings; it's OK to remove a suspect shock for a test-drive to confirm the diagnosis. The front upper shock bolts can work loose and damage the threads in the towers of the beam.
`65 was the last year for the king & link front end so check the condition of the kingpins/linkpins (jack it up, grab each tire top & bottom and see if it clunks when you wrestle it back & forth). If there's play in the kingpin, the only fix is to rebush/replace. The linkpins have an adjustment for endplay, although they too need rebushing/replacement when they run out of adjustment and/or develop excessive radial play). Check side-to-side also, in case you have excess play in the steering linkage.
Rear end, look for loose transmission mount hardware or gooshy mounts. Does the shifter move to & fro by itself when you romp on & off the throttle in the lower gears? -that's a classic tell for a front mount problem. Look for rust trails at the bolts which secure the axles to the springplates, around the end of the axles against the brake backing plates, etc. Also where the rear axle nuts contact the brake drum snouts, a loose drum can knock loudly and eventually the splines will strip out (tow-truck time). The rubber bushings which center the rear torsion bars in the outboard ends of the tube may be so worn that there's metal-to-metal contact happening over bumps (that'll take some surgery to repair which is outside the comfort zone of most casual shadetree mechanics).
Also, with a kit car it's always possible that the body itself is rattling against the chassis somewhere - either from inadequate mounting or insufficient clearance. Look for any signs of rubbing where the fiberglass comes close to steel. Most kit car bodies leave a lot to be desired when it comes to the shape & fit of the engine opening; if the builder sealed it up using rigid materials the engine may be banging the body when the drivetrain moves in its mounts. The builder may have had some "clever" way of softening the springrate to accommodate the lighter body, too (such as leaving out some of the leaves in the front torsion bar stacks, positively lethal if it isn't done correctly - if the noise is coming from broken leaves be glad that you caught it before the suspension collapsed).
`65 was the last year for the king & link front end so check the condition of the kingpins/linkpins (jack it up, grab each tire top & bottom and see if it clunks when you wrestle it back & forth). If there's play in the kingpin, the only fix is to rebush/replace. The linkpins have an adjustment for endplay, although they too need rebushing/replacement when they run out of adjustment and/or develop excessive radial play). Check side-to-side also, in case you have excess play in the steering linkage.
Rear end, look for loose transmission mount hardware or gooshy mounts. Does the shifter move to & fro by itself when you romp on & off the throttle in the lower gears? -that's a classic tell for a front mount problem. Look for rust trails at the bolts which secure the axles to the springplates, around the end of the axles against the brake backing plates, etc. Also where the rear axle nuts contact the brake drum snouts, a loose drum can knock loudly and eventually the splines will strip out (tow-truck time). The rubber bushings which center the rear torsion bars in the outboard ends of the tube may be so worn that there's metal-to-metal contact happening over bumps (that'll take some surgery to repair which is outside the comfort zone of most casual shadetree mechanics).
Also, with a kit car it's always possible that the body itself is rattling against the chassis somewhere - either from inadequate mounting or insufficient clearance. Look for any signs of rubbing where the fiberglass comes close to steel. Most kit car bodies leave a lot to be desired when it comes to the shape & fit of the engine opening; if the builder sealed it up using rigid materials the engine may be banging the body when the drivetrain moves in its mounts. The builder may have had some "clever" way of softening the springrate to accommodate the lighter body, too (such as leaving out some of the leaves in the front torsion bar stacks, positively lethal if it isn't done correctly - if the noise is coming from broken leaves be glad that you caught it before the suspension collapsed).