BMW 5-Series E39 (1996 - 2003) - (96-03) 535i (Sport) Wonky chassis/monocoque ? | Technical matters | Back Room Forum

Thu 20 Dec 2007 17:02

(96-03) 535i (Sport) Wonky chassis/monocoque ? - Analyst

Bought a BMW 535i (Sport) from the first owner with 73k miles and FSH. It looked as if it was sagging a bit on the driver?s side and the tyres were worn unevenly. The answer was seemingly obvious and professional opinion concurred, so it was new shocks and springs all round (BMW MTech OEM factory spec), and while we were at it, I replaced the tyres and refurbed the wheels.

To cut a long story short, the cant is still there. A ?body audit? shows that the car is not sagging, but sitting up 30mm nearside rear and 10mm nearside front. Has the car had an accident ? Not to my knowledge and according to the bodyshop, ?If it has it?s had the best repair we?ve ever seen.?

None of the professionals in my neck of the woods seems to be able to suggest what might be causing the skew, or to cure it. Ransacking the web has not produced a solution either. The best anyone has come up with is ?It?s just one of those things?. Can you or any of your readers help ?

Edited by Dynamic Dave on 20/12/2007 at 17:54

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Thu 20 Dec 2007 17:12

Wonky chassis/monocoque ? - Screwloose

It doesn't need signs of body repairs to have a twisted shell. Jumping it over a hump-back bridge could cause the shell to distort without any panel damage at all.

All those [300?] Dodge Chargers that were used [abused] in the Dukes of Hazzard must have ended up sitting slightly askew after their return to earth.

Get a good bodyshop to put it on a laser jig. That will soon tell if the spring mounts are in the right places.

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Thu 20 Dec 2007 19:09

Wonky chassis/monocoque ? - Aprilia

I doubt it would have left the factory with that amount of chassis tweak - so its not 'just one of those things'. As Screwloose has said, its essential it goes on a jig so that measurements can be taken from all the critical chassis datum points and suspension mounting points.

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Thu 20 Dec 2007 19:10

Wonky chassis/monocoque ? - nick

Sell it quick!
More seriously, have you done an HPI check?

Edited by nick on 20/12/2007 at 19:11

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Fri 21 Dec 2007 10:03

Wonky chassis/monocoque ? - Analyst

Thanks guys - unfortunately selling it will only crystallise a loss - money spent sorting so far. Car is clean HPI wise and one expects to lay out some money getting a used car up to scratch (as indeed one often has to with a new one :-) and it seems to drive OK (in fact it is better than most 'luxury' cars still). Fascinating about twisting the body shell - and there are a few humpback bridges in my area !-) But even if that did turn out to be the answer, what effects would that have on performance/wear & tear - if any ? - and what chance of straighening it ?

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Fri 21 Dec 2007 13:12

Wonky chassis/monocoque ? - Aprilia

Analyst

You would have to determine why the chassis has this tweak. It could be localised to suspension/spring mounting points, in which case a pull on the jig would probably sort it out.
If the whole shell has a slight twist then the chances of satisfactory repair would be less. Each case is different though. First step is to get the data on what/where the problem is and then take it from there.

I would try to get it sorted out though, any chassis tweak has a negative effect on handling and can make the car behave assymetrically (i.e. it behave different on a LH curve than a RH curve).

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Fri 21 Dec 2007 18:53

Wonky chassis/monocoque ? - Analyst

Thanks for that. I will get into action and report back.

A Merry Xmas and HNY to all listers :-)

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