low speed shimmy - can't ignore it any more!! ideas please.

[tim]

The White One is high mileage and over the past year I've noticed a slight 'wobble' on the steering wheel at low speed. I remember reading here that this was most likely due to a knacked FDV and maybe a pump also. ( I have tried to find it again on the 'search' but to no avail). As it happens, I have a rebuild kit, a spare FDV to fit it to, and the pump off the scrappy which has done just under 200,000 miles which has to be better than the other one which is nearly 300,000 on it.
The plan was to rebuild the FDV, and do a full swap. However, over the past three or four weeks things have got a bit odder. The car has now started 'shimmying' at low speed, almost as if a wheel bearing is going. It is noticeable in any seat but more so in the back. I've had a look at the back and although it 'feels' like a lh rear wheel I can't find anything wrong with it; the rear arm bearings look OK without actually stripping them; we thought this might be the problem but now I'm not so sure. So wtf is this? I don't want to prat around doing the full hydraulic fix as above if there is something else I should be attending to. The car is needed for daily use so I need to get on with it, especially as the weather is closing in for winter. Andy, wife and I have pondered a lot, but I can't see how spheres could produce this effect (at cruising speeds the feeling disappears, though daughter did think it was rolling rather a lot a couple of days ago). Nor can I tie in knacked taper rollers in the rear arm to this one. If it was just 'rolling' I'd say hydraulics, but this shimmy has got me stumped. As a guide, when driving down to Andy's I had a big toolbox in the back, and you could hear the spanners going 'chink, chink, chink' in the tooltrays as the car wobbled. Almost as if you were going over a series of little speed bumps. (Can anyone give me a source of that bumper sticker, "squirrels - natures' little speed bumps".....) And I did swap the wheel for the spare just in case. No change.

[Geoffrey Gould]

Hi, OK in no particular order then:-
buckled wheel.
tread/sidewall defect in tyre. Check on the inside tyre wall, it may look OK from the outside but I have seen some almost tennis ball sized lumps in the inside wall.
wheel bearing bad, very.
Easy to check, jack up, spin wheel.
Worn track rod end, loose steering rack, bottom ball joint ( modern ones don't seem to last long now a days.) Wishbone bushes shot. Top suspension mount cracked/worn. Tracking a mile out.
General check round really, sounds as if it really would be a Good idea to be sorted out. ( Thinking defective tyre exploding.)
Cheers.
G.

[Dollywobbler]

Second shout for a tyre fault. I remember my dad having a Sierra with a distorting tyre. That caused a noticeable shimmy at low speeds. It's a quick, simple and cheap check!

[KevR]

And another for a deformed tyre. Not necessarily immediately obvious when you're looking at it either - sometimes need to look very carefully. And don't assume it's the wheel you think it is!

[MULLEY]

Could it be a flat sphere?

[KevR]

Dunno - the ones on the back of the grey one are so flat it's like driving a leaf-sprung Land Rover, but it doesn't seem to cause any of those symptoms.

[tim]

Cool - thanks for ideas. However, I did say that I swapped the tyre for a spare which I know is OK. No change. I have also checked out the back end; there is nothing wrong with the bearing. Andy and I did think about rear arm bearings but the arm looks OK and I have never heard that this was a symptom of knackered bearings.(Though someone out there may know different....) The obvious solution would be to recon the one off the scrappy and fit it, but this is a morning's work and time is a bit of a factor this week - if I need to be working on hydraulics instead then that's cool, but I won't have time to do everything.
Spheres - not flat - I know what that feels like. Kango on wheels! In fact the ride on the White One is slightly softer than mine, obviously whoever replaced them a few years back (no, they are not that new) used slightly different ones to the AEP ones on mine. I prefer those, mine handles better on corners.
Ball joints - all OK, mostly new, and whenever ones's going it goes from 'OK' to clickety-clunk in a very few miles. This ain't happened, there's no noise. Nor did the ones that failed ever produce a wiggle.
As far as tyres go, it certainly feels (and these things can be VERY deceptive) like it's under the rear left seat. But if that tyre is OK, would the other ones cause this effect? I have looked over them all briefly (small dose of flu leading to day off, not much energy for jacking things up all round....) However, the effect can be felt in ANY seat including the drivers.

[KevR]

Like I say, don't assume the problem's where the symptom apparently is, as it can be deceptive. I had a deformed front tyre once which managed to convince me it was on the other side. In fact I initially blamed it on driveshafts, then front wheel bearings and it was only when the damn thing went pop that the penny dropped...

[tim]

OK - problem solved, I think. Having read all the above I popped down to my local garage at 5.30 and got the car up on the bed where we could look underneath with a decent light. And behold, the RIGHT hand rear tyre was quietly shredding its sidewall just on the edge of the rim. Very hard to spot but definitely about to fail. The front one had also scrubbed out on the edge which must be related to the wiggle cos it was OK a month ago. So hopefully a couple of new tyres will cure the problem. If not, watch this thread!

[Mothman]

Bugger me Tim, dont know why we didnt spot this on Saturday. Probably the best and easiest fix, although not cheap but certainly better than removing and replacing the rear arm bearing.
Fingers crossed this sorts it. Wheel span ok when jacked up, no grumblings or wobbles but we were looking at the outside.

Andy

[KevR]

And behold, the RIGHT hand rear tyre was quietly shredding its sidewall

Aha! I win!

[Geoffrey Gould]

Dont forget the tracking while you are there. If its out it can destroy a tyre/s very very quickly. I did have a slight wonder when you said you had replaced ONE tyre, it's 4 t0 1 its the wrong one if you see what I mean.
G

[Tim Leech]

Nice cheap fix, ftw!