W123 oversteer

[stever]

Hi All

I have a handling problem with my '79 280 CE - it oversteers far too easily. I never push it particularly hard, but the back end will step out without warning on bends (i.e. no understeer first), especially in the wet. Tyres are ok - different brands, but a similar tread pattern, and pressure is correct. Anti-roll bar links appear to be attached ok, but I haven't checked anything else.

I'm going to book it into the garage next week, but does anyone have experience or tips I can pass on to the mechanic?

 

[Sprint'n'Go]

What condition are the dampers in? if the wheels are bouncing around all over the place it would induce the oversteer you are experiencing.

Alternatively, is it leaf springs on the rear axle? If so it is worth checking all the U bolts are tight as the axle could be moving in relation to the springs.

Just a few ideas to get you started.

 

[Sprint'n'Go]

Hi All

I have a handling problem with my '79 280 CE - it oversteers far too easily.
Tyres are ok - different brands, but a similar tread pattern,

Check all your tyre sizes carefully, you could have an odd sized tyre which wouldn't be very helpful. Check all four as you may find there are skinnier tyres on the back than on the front?

 

[stever]

Tyres are all the same size, shocks seem ok as they don't keep bouncing if I press the back of the car down. The suspension design is a wishbone/ semi-trailing arm arrangement, it's all on a sub-frame

 

[clive williams]

Tyres are all the same size, shocks seem ok as they don't keep bouncing if I press the back of the car down. The suspension design is a wishbone/ semi-trailing arm arrangement, it's all on a sub-frame

Stever,

Whats the turn-in like? Does it lurch in? That would indicate that the front end needs looking at first if not then the rear is the culprit.
If it oversteers then I bet the back end is not properly nailed down and is probably steering on its own accord. Check out shockers first and get somebody to follow you over a bumpy road and watch the rear wheels - you will see if they are not properly controlled and don't follow the surface accurately. The bounce test is next to useless unless the shockers are so bad that they don't work at all. Next, make sure that the mounting points and/or bushes are acceptable. If you're unsure about this get your local MOT man to do a (cheap) rear end check. He ought not to charge more than £10 for the honour.
After all the above have been cleared we are into a setup issue, which will occupy many more column inches.

Clive

500E
E320CDIT210

 

[kth286]

Stever

Tracking can cause your problem.

Do you have even wear on ALL your tyres ????

If the tyres are fairly new, were they changed because of uneven wear ??

Have you had the tracking checked recently ??

Is the steering wheel aligned properly in the straight ahead position when travelling along a straight road. ?????

Let us know the answers to above.

Regards

 

[stever]

Yep the front feels absolutely fine - turns in fine and steering is straight ahead. I've replaced the damper and adjusted the steering box which made a huge difference. It's the back which seems to "lurch" say when pulling out to overtake.

I had a look at my last MOT report - there was an advisory for wear to "rear axle beam mounts"

The tyres appear to be evenly worn, but it's not be aligned/ tracked recently - I've only had the car a year so it could have been some time since it was done.

Actually I rather hope Clive is right - if all it takes is a set of new shocks to fix it I'll be pleased.

 

[clive williams]

I had a look at my last MOT report - there was an advisory for wear to "rear axle beam mounts"

The tyres appear to be evenly worn, but it's not be aligned/ tracked recently - I've only had the car a year so it could have been some time since it was done.

Actually I rather hope Clive is right - if all it takes is a set of new shocks to fix it I'll be pleased.

Stever,

Sorry to disillusion you but I would definitely change the "rear axle beam mounts". I suspect whats happening is that the rear beam is squirming around - hence the rear end lurch. When you turn the beam is moving thus steering the rear end. The lurch is the transition from one state to the other on the turn.
It can't do any harm to change the shockers though whilst your at it?

Clive

500E
E320CDIT210

 

[stever]

Good point, hadn't thought of that. I'll have the mechanic look at the beam mounts next week. Frankly, the car is scary in the wet and it needs to be fixed asap.

 

[kth286]

stever

Agreed - get the axle mounts done first and judge the results before any further work, to see the effect.

Regards

 

[stever]

It's in the garage now and I've asked the mechanic to replace the axle mounts, I'll let you know the result.

 

[stever]

Now done and the car feels much sharper turning in. I think I'll find a quiet car park the next time it rains for a proper test though.

 

[Sprint'n'Go]

Alternatively, is it leaf springs on the rear axle? If so it is worth checking all the U bolts are tight as the axle could be moving in relation to the springs.

So I was not so far out with my initial diagnosis, the back axle was steering the car. I just need to swot up on modern car suspension design, I've done all my learning on vans and Landrovers.

 

[stever]

I'm reviving this thread to update on progress. As well as the main rear subframe mounts, I've now replaced all four shocks. The ride is much improved, as is stability at speed. Handling in the dry is very secure, although it does roll a fair bit - but then I think that's inherent to this model. However, there is still a tendency for the back end to step out in the wet (and only the wet) at moderate speeds. So should I look to replace the tyres, or maybe is there an alignment issue?

Thanks
Steve

 

[stever]

bump - any ideas?