109 death wobble.....got me stumped!

[ejparrott]

Twice today I've experienced a fearsome wobble in my 109 - on the way to work this morning and then again on the way to MoT this afternoon....got me stumped as to what it could be.

The 109 is sitting on an ex-mil 1-ton chassis, with the front springs riding in the bottom hole with matching long shackles. The rear axle is sitting on the same long shackles but the front eye is in a standard spring mount - unfortunatly when someone changed the outriggers they didn't refit the 2-hole hangers....thats a job on the to-do list.

I've had this problem before...

changed the relay = made no difference

changed the droparm = made no difference

rebuilt both swivels = made no difference

got the feeling it was knackered chassis around the relay, so cut it out and fitted PAS from a 90....there's a thread of mine somewhere...

Steering box is 4-bolt from 90, seems to have no wear, she drives in a straight enough line

Steering column and UJ's from 90, with brand new UJ's

Gwyn Lewis steering rod from drop arm to n/s series swivel housing

Series drag link.

There is no Panhard rod, and no steering damper. I know other people run Series with no Panhard rod, and to me fitting a damper would mask the symptoms rather than cure a problem.

She's been for MoT this afternoon, I'm assuming they will have checked all TRE's and all spring bushes, and of course chassis for corrosion. Tyres were all inflated yesterday lunchtime to 38psi all round. I do have advisories on tyres perished on outer sidewalls and a leak on the steering box.

This morning I tried acclerating out of it, but that seemed to have no effect, and then this afternoon I tried dragging the brakes, and that didn't do anything either, I had to slow right down for it to stop.

What have I missed??

[Gremlin]

I feel your pain....... here is my experiance over the years............

I had the same problem for a while when i made an experiment by fitting bearings at the top and bottom of the swivels!! (looking for a lighter steering) It was a bad move!! death wobbles all the time (no preload). I cured it slightly by putting on standard narrow wheels (no offset), then i put castor correcting shims and gave it negative castor which did stop the wobbles, but it cornered horribly!!. That was with the old axle. I then went back to railko bushes and set the preload as it should be and it cured it.

I then got the stage one bits fitted to my housing and again the wobble came back, put the castor shims back on and that cured it but it never felt good.

Then i fitted the PS and removed the shims.......joy drives like it should with no wobbles

Last time it happened again was due to worn spring bushes at the chassis end in the front. Changed those and it was fine, i have the same setup like you do, 4 bolt PS with disco drop arm, military chassis front and civvy rear hangers, with military shackles. No steering damper! But i have wide rims and tyres with some offset.

My suggestion would be to check your spring bushes, castor, and try different tyres.

G

[Team Idris]

Honestly to me 38psi sounds too much pressure. That's more like my old twin wheel 3.5 tonne transit on 14" rims sort of pressure? On 7.50x16 I'd think 28?

My S1 88" is a mare on 7.50x16 crossply above 22psi.

I have to throw in the obvious one though; is the nut tight that holds the drop arm to the steering box?

[ejparrott]

Just been out and tried the drop arm nut, its certainly too tight for me to move by hand. To be honest, I'd be suprised if it was related to the steering box, as the problem was there before the PAS conversion, though bearing the green oval as she does, I'd not rule it out! I hadn't thought to check that either.

I'll check the spring bushes tomorrow, I'd have expected the MoT man to check them, but not being a tester I wouldn't know if that was standard proceedure.

I'll get the front end up in the air on saturday and check the preload on the swivels, just in case they've worked loose. How would I check castor angle?

She did it to me again tonight, got up to about 45 and off she went..not sure if I hit a pothole to start it off, don't remember there being any there.

Forgot to add, she has 11-leaf nearly new front springs, and nearly new 10-leaf rears of the type with the two massive bottom leaves and the U straps around them...although the front o/s one fell off a little while ago.... Tyres are 235/85/16 MT's, and fitted to grey modulars...7x16's I think they are.

Thanks for the thoughts guys

[Snagger]

The tyres could cause it if they have any bulges or uneven-ness, as I had once on a Saab. Check them carefully for roundness by jacking up an axle and turning the wheels slowly with something really close to the tyre tread to use as an indexer.

Castor can only be adjusted by slotting the mounting holes in the swivel housing or axle flanges, using mismatched spring hangers and shackles (like at the back of yours) or wedging between the spring and axle saddle. Small variations may occur from production tolerances and the play between the bolts and their holes.

Your wheels, having greater offset than standard, won;t be helping and could be exacerbating the problem, but unless one or more of them is bent, then they are not the cause.

Try tightening the pinch bolts on the relay arms and check the swivel arms for play relative to their housings (the studs and wear at their wastes). If none of that is at fault and the rod ends are all good, have a look to see if the stub axles are worn where the wheel bearing sit on them - I think that is the cause of the vibration my RR's front axle gets at about 60mph.

The rear suspension may cause premature UJ wear and vibration at around 60mph - it did on my 109 when I ran a standard chassis with 1-ton rear shackles on parabolics.

[lexi]

<br />To add to all of that ,set the tracking as it may be way out.

[Gremlin]

Yes and lower the tyre pressures, with PS you can run low as 25psi, that's what mine are at.

G

[FridgeFreezer]

I wouldn't start p*ssing about with modifying caster etc., you want to undo any changes / remove possibilities not add more stuff to the mix. I'd put money on the kingpins / swivel preload, that's what's given me wobble before.

38psi is a little high for 7.50's, from memory the book says 25-30ish for normal use, 35 for towing / heavy load. If your tyres are actually 235/85 or whatever then they are wider and you can go a bit lower. ISTR people running 35's at 15psi on the road.

[mickeyw]

I'd put money on the kingpins / swivel preload, that's what's given me wobble before.

Got to agree here.

38psi is a little high for 7.50's, from memory the book says 25-30ish for normal use, 35 for towing / heavy load. If your tyres are actually 235/85 or whatever then they are wider and you can go a bit lower. ISTR people running 35's at 15psi on the road.

I didn't think load affected the front tyre pressures so much, more applicable on the rears.

[CwazyWabbit]

I had a death wobble on my 110 (yes I know you have a series) that would almost rip the steering wheel out of your hands ...... turned out to be as simple as having the wheels balanced.

Might be worth getting them checked first as it's a quickie

[Tanuki]

How old are the shock-absorbers? The MoT 'bounce test' doesn't really test for function of shock-absorbers - it only looks to see that they're there, they're not leaking oil and they're not about to fall off.

My Defender-90 developed a major steering wobble a while back: a pothole could trigger a spectacular accident-looking-for-somewhere-to-happen event over the next 100 yards or so. Replaced the 80,000-mile-old original shock-absorbers with a set of yellow gas-pressure Bilsteins and the problem was solved.

Remember if the vehicle itself is heavier or there's more un-spring weight (bigger wheels/tyres) on the axle then the shock-absorbers will be doing extra work and wear out faster. Stiffer springs cause more shock-absorber wear too.

[lexi]

<br />Yeah but shockers don't do much on a standard leaf spring set up. A bit more on Paras.

[mickeyw]

If you've ever driven a leafer with no shocks fitted, you will appreciate that they do in fact do quite a bit

[Daan]

I would swap the wheels front to back or change the fronts for a known pair. I would imagine the wheels giving the problem. Maybe your kingpin pre load is too low, but if your wheels would be balanced and straight it still wouldn't happen in the fist place.

Daan

[ejparrott]

I was going to tackle it today, but I'd forgotten we're taking the Guides to the Think Tank in Brum today I'll make a start in the morning..

I'll also check wheel nuts are tight, although I doubt its that somehow..... Now that the 88 also has 235/85R16's I'll swap them over to the front of The 109 - I had them balanced when they were fitted only a few weeks ago.

[ejparrott]

I did get a start on looking at various things but got called away....front spring bushes on both sides seem fine.

Rear of front o/s though is a bit interesting, though I'm not convinced may be the cause....

Re-cap, Series leaf sprung 1-ton chassis, 11 leaf springs, running on bottom hole and military extended shackles. It appears that the rubber hasn't broken down in the bush, however the inner sleeve does seem to be able to slide inside it. Also, it seems there is a gap between the shackle and the inner sleeve, of about 2mm, both at the spring end and the chassis end. If I stick the prybar in, I can get it to slide across, so I'm wondering if that might be a problem. Slight downside though, is that the PO said it used to do it to him, and he cured it by fitting the steering damper which I've removed for now. The Kingpins were worn out though, and he did change the springs just before he sold it to me...

[CwazyWabbit]

Have you tried the wheel swap yet?

[Gremlin]

Seems that is your problem then, change the bushes, there should be no movement whatsoever, do both sides. I use the standard bushes in the chassis as i found that the poly bushes tend to do what you are saying, move around, making it steer like jelly. Polybushes in the springs seem fine.

What i have noticed that with PS the bushes get a beating, in fact my chassis ones need changing already after 2 years! PS tends to move the axle from side to side ever so slightly, but i have noticed this is with the wide wheels, as the wheels have some scrub while turning. On standard wheels it does not do it.

G

[ejparrott]

Have you tried the wheel swap yet?

Not yet - too many calls on my time!

[Orgasmic Farmer]

Another vote for getting the tracking checked. On my Disco (and then the 110 when I changed the front axle over) I had tried everything. Every nut bolt bearing bush shim component etc had been changed, repbuilt or reconditioned and all set up by the book. Shimmy was still there. I decided to experiment with the tracking (using the taut string method!) and noted quite a lot of toe out. I had had it set professionally a year or so earlier. Anyway, I decided to try it with a few degrees of toe in and voila! Has been fine ever since.

[Snagger]

Seems that is your problem then, change the bushes, there should be no movement whatsoever, do both sides. I use the standard bushes in the chassis as i found that the poly bushes tend to do what you are saying, move around, making it steer like jelly. Polybushes in the springs seem fine.

I agree, and I also do the same - standard bushes in the chassis and poly in the springs - that way, failure of the bush does not result in chassis damage, but the spring bushes which need more rotation are free to do so.

[ejparrott]

Hmm..hadn't thought of mixing poly and OEM.... I'm guessing I should replace the spring bushes in the front if I change to Poly's as well as the rears (of the front springs that is)

[Snagger]

Might as well if you buy a kit, but as long as you work symmetrically, it shouldn't matter if you mix and match. Its the rear spring eye bush that has the most rotation - the eye rotates like the front end, but the bush also has to deal with the shackle rotation in the opposite direction.

I have had no trouble since fitting the polys to the springs four years ago, and the chassis bushes are the original metalastic ones fitted by Marsland in 2005, and are still fine.

[ejparrott]

Kettle's drivers seatbelt just died, so I've ordered that and a full set of Flo~Flex bushes for The 109.

I am right in thinking that the shackles should be hard up against the middle sleeve of the bush aren't I?

[Gremlin]

Yes correct.

G