how to work out why car seems to not 'sit' properly... 1985 8V 900i

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Craig's Saab C900 Site - 28 Jan 2006 10:51 GMT

For ages I've been suspecting that my 1985 900i has a suspension problem in
that either both rear springs have shrunk from having too much load placed
on the rear of the car by previous owners (perhaps using trailers), or
something else.

Anyway, it 'seems' like the problem might be the right/rear of the car, but
I've jacked up the back of the car today and taken off both rear wheels yet
so far I can't see anything physically wrong.

How it came to light is that when driving (even slowly) on rough ground the
rear wheels rub on the wheel arches, and if I drive at speed on the road,
the car seems to handle badly and it 'bounces' a little on corners.

I've already had the front of the car under close scrutiny due to problems
with other things (mainly when I changed the right/front swivel member and
wheel hub), but it could well be a problem with something at the front.

Are there any tried and tested ways to explore rear suspension, etc. to work
out if there is a problem even if it's just that the springs are tired?

Craig.

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ShazWozza - 29 Jan 2006 00:03 GMT

> For ages I've been suspecting that my 1985 900i has a suspension problem
> in that either both rear springs have shrunk from having too much load
[quoted text clipped - 16 lines]
> work out if there is a problem even if it's just that the springs are
> tired?

Springs lose their set over time, but you say the car 'bounces' a little on
corners so this would point more to the dampers having gone to lunch.
Springs and dampers form a resonant circuit of sorts and their rates must
match.

You can roughly test the dampers by violently jouncing the car up and down
at each corner and noting how quickly the motion stops. A really bad
damper will be obvious this way.

If you park the car on level ground is one corner of the car lower (measure
it with a tape).

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Craig's Saab C900 Site - 31 Jan 2006 10:50 GMT

>Springs lose their set over time, but you say the car 'bounces' a little on
>corners so this would point more to the dampers having gone to lunch.
>Springs and dampers form a resonant circuit of sorts and their rates must
>match.

>You can roughly test the dampers by violently jouncing the car up and down
>at each corner and noting how quickly the motion stops. A really bad
>damper will be obvious this way.

Thanks for the tip - I'll see if this test gives anything tangible
result-wise.

>If you park the car on level ground is one corner of the car lower (measure
>it with a tape).

Don't really have anything level around here. We don't have a garage or any
flat concrete slab.

But if I get to such a spot I'll do some measuring.

I'm leading towards suspecting both rear springs since the car has a towbar
and it's quite an old towbar (going on how much rust it's bottom surface
has). So a previous owner may have hauled trailers around with the car,
and/or loaded up the boot space with far too much weight. 8-)

Craig.

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Richard Sutherland-Smith - 29 Jan 2006 20:54 GMT

> For ages I've been suspecting that my 1985 900i has a suspension problem in
> that either both rear springs have shrunk from having too much load placed
[quoted text clipped - 17 lines]
>
> Craig.

Have the rear bump-stops vanished. I had a 900 in the UK that had lost
these, and it used to bottom when coming back from France full of
wine... the car, that is!
They fail their MoT there if there is only one, but pass if both have
come off!

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Richard Sutherland-Smith
19 Webb Road, Wanganui 5001, NZ

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Craig's Saab C900 Site - 31 Jan 2006 10:51 GMT

>Have the rear bump-stops vanished. I had a 900 in the UK that had lost
>these, and it used to bottom when coming back from France full of
>wine... the car, that is!
>They fail their MoT there if there is only one, but pass if both have
>come off!

8-) No both of the rear bump-stops are in place. That was one of the first
things I looked at when I jacked up the back of the car the other day and
sat it on stands so I could take off both back wheels with the rear of the
car supported at the jacking points.

Craig.

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