Suspension sag Front LHS

[Lafia]

Hi All

A question for those with a better understanding of the suspension geometry of a 1998 130 300tdi than me:

I've got a 50mm sag on the passenger side front (by comparison with the drivers side) which I've been meaning to do something about. I've also noticed that I seem to be getting more wear on the front left tyre. I've replaced the tie rod ends etc recently and it feels fine on road.

Will the 50mm sag cause a change in the caster angle(?) and result in greater wear on that tyre?

Is the solution to refit with new springs? (I don't want any extra lift - just the standard height suits me fine).

Cheers

[JDNSW]

Suspension sag in itself will not cause uneven tyre wear. I would look for something that is causing this rather than just sagged a spring. This would include a bent axle housing, worn or damaged swivel, and incorrect toeout (not unusual for wheel aligners to get this wrong!).

Caster angle will remain the same on both sides unless the axle housing is bent or twisted, but changes in suspension height will change it on both sides, averaged by the effect of the bushes at the front of the radius arms. In fact, these arms, the bushes, and the axle housing are, in effect, a sway bar, and it is possible that soft or worn bushes allow the vehicle to lean to left in a way that it would not otherwise do.

And it is worth noting that one corner cannot sag without either the other corner on that side sagging as well or the diagonally opposite corner rising, unless the chassis is twisted; which is, of course, possible. (This would be either damage or rust.)

John

[DeanoH]

50 mm is a fair bit of difference. When measuring sag measure from the bottom of the rim to the guard across the centre of the wheel, this takes variations in tyres etc out of the equation.
If you're looking at the front start with the back and jack up the lowest corner (jack under the body) till both rear heights are the same, then measure the front. As JD points out essentially 'change one change all', setting the rear equal lets you see what's really happening at the front, and vice versa for the rear.
Still 50 mm is a fair difference, I'd also look for a broken spring front LHS.

As for the tyre wear, with the vehicle parked on a flat surface looking at the front of the vehicle from say 10 metres or so, how does the camber look ?, a bent axle or crook swivel pin bearings, or even very crook wheel bearings will affect the camber. Jack up the front LHS and give the wheel a good shake, spin etc. Something not right here.

Also as JD says wheel alignment people often have a fixation about setting toe to 2mm toe in which is OK for rear wheel drive but no good for FWD or AWD like the Defender where it should be 2mm toe OUT (from memory), a very common problem.

Deano

[BigBlackDog]

Presumably the back end sits level? If not check your sway bar links are both dangling

[Lafia]

OK, thanks for your thoughts and sorry for the pause in responding. So took into account your suggestions and when remeasuring from the wheel centre (and being a little more accurate about it) it appears the difference is 38mm not 50.
Since then I have replaced the bushes in the front radius arms,sway bars, trailing arms,panhard rod - what a difference in the ride now!

No obvious list now but measuring it when parked on the street seems to show a bit less than 10mm, so that is a good result. My friendly mechanic up the road was happy to press the old bushes out, and in his opinion these were almost certainly the originals (315k).

I'll find a bit of level concrete soon and measure it properly (and with my specs on!) and see what it really is.
I'll be looking at the swivels next.

Many thanks for your thoughts.
Cheers