I'm searching the forums but thought I's ask - front nearside suspension "banging"

[Julesprivate]

Just a quick question. My car (1994 LS400) has modified (lowered/stiffened) suspension and 20" rims fitted.. 3 corners are great, but the front nearside has a really bad habit of "crashing" loudly on potholes, I mean to say it sounds as though the front wheel is hitting the top of the wheelarch, it's really that bad. It only happens on larger potholes (so I am not drunk if you're following me, I'm avoiding them) and I know the modifications will make speed bumps etc a challenge, but the other 3 corners are 100% fine, so clearly something is wrong there.

The shocks are all 12 months old, as are the springs, the fronts are both set up the same (same ride height adjustment, same damping/rebound settings) and the driver's side is flawless. I had a cursory glance at the nearside and the spring is (a) fitted correctly (it's a progressive, dual rate spring, so if it was upside down I could understand it).The shock has no apparent damage or leaking, the damping adjuster is free...

Ignoring the shock/spring for the moment what else could it be? I cannot see how a faulty A-arm could cause the feeling of the wheel hitting the top, I could kinda see it causing the same "noise" but not the intensity.

Any thoughts? - I know the non-standard nature makes it a little harder to diagnose but thought I'd ask..

 

[runsgrateasanut]

Sorry I've no ideas to help. Front offside is less likely to hit extreme potholes so difficult to tell if its just the nearside corner. Over speed humps should be a consistent problem L and R if hit at speed which may emulate a bad pot hole, I'd have thought?

 

 

[steve2006]

There have been cases of the UCA hitting the inner wing if the car is extremely lowered, have you also checked the UCA and LBJ for excess play in the balljoints?

Also make sure the upper strut cushion is fitted.

[mikeyv]

Get under and have a good scout around, look for any wear marks, where components might be rubbing or knocking together.

Get a good grip and try to move any joints, to check for play, both with wheel on ground and off.

If you have a suspicion of where it's knocking (wheel arch you mentioned, for example) , stick a lump of blutac or similar there, reproduce the noise, then check the blutac for indentation.

Good luck.

[Malc]

..........  when the UCA suddenly goes, well mine anyway, I heard it actually go a dead clunk as I was traversing the Dolomites last year in Italy .......  but it still drove fine for a few months OK, until the car failed the MOT   .......  I didn't know what on earth the sudden clunk was, but it was just the once and the car drove fine for the remainder of my Grand Tour  ...........  yours might be the UCA but it sounds like something rather more progressive happening.

Malc