Odd Handling Issues

Tue Jun 21, 2011 11:14 pm

I've borrowed my brothers E30 318iS, and have been giving it a bit of a shakedown after it been laid up all winter.

At the end of last summer, the car was fitted with new shocks all round, with new top mounts, new front wishbones, track rod ends and poly wishbone mountings. It had the front alignment done and a fresh MOT applied. Shortly thereafter it was parked up for winter.

There are two issues with the car that i'm a bit puzzled about which may or may not be related.

The first i noticed coming off the motorway doing ~60mph into a long banked motorway offramp. Upon turning into the corner, it felt like the rear end of the car stepped sideways a little bit and the cornering angle tightened up requiring me to reduce steering angle to maintain course.(IE what felt like the rear end did something odd which seemed to make the car steer itself tighter into the corner)
Slightly reducing the steering angle seemed to remove whatever oddness happened, meaning the cornering angle became too shallow again, and it seemed to oscillate between these two extremes by just moving the steering a small amount.

As you can imagine it felt properly nasty, I backed off the throttle and the effect seemed to lessen/vanish as the car slowed.

There was plenty of grip, it wasnt oversteer. It felt more like something on the rear end suspension moved when it was put under load changing the rear toe angle, and hence altering the arc the car was travelling thru. Backing off the steering seemed to reduce the load by enough that the geometry moved back, ending up with the odd oscillation.

The second effect is that when driving on rough roads (like most of them around here!) theres a vibration or knocking that can be felt thru the steering wheel itself. The track rod ends etc are all new, so i'm wondering if it might be the column UJ's or perhaps the rack itself. The steering also seems to change between being nicely weighted with lots of feel, to being very light and floatey with not much feel at all. Most of the time its fine, but now and then it just feels horrible.

Any ideas?

Cheers

Tue Jun 21, 2011 11:16 pm

The first problems makes me think that it could be worn rear beam bushes

Tue Jun 21, 2011 11:53 pm

Had similar symptoms with a dodgy rear wheel bearing. It was as if when you changed lanes, the car wanted to change lanes again and wobble over.

Tue Jun 21, 2011 11:57 pm

Yeh thats kinda what i was leaning towards. Most of front end is in effect new, but the rear i have no idea about, so can probably assume its old!

What sort of a job is replacing the rear beam bushes?

Wed Jun 22, 2011 12:01 am

Beam bushes and wheel bearings are both a pain to be honest.

It's worth having a good look at the car and making sure everything is tight and there's enough air in the tyres and all that (not trying to teach yo to suck eggs) just thinking of the simple things first.

Wed Jun 22, 2011 9:37 am

Yeh i'll have a good look over it at the weekend.

I dont think its a bearing, as if it were i recon i'd feel the effect on every change of direction as the wheel moves back and forward. They're quick and easy to check though, so i'll do that.

If its the rear beam whats involved. I've never actually looked under the rear end yet so i've no idea what it consists of.

Wed Jun 22, 2011 10:30 am

I had a similar problem when I first bought mine, drove down to the southwest from london on rear tyres that were ovallated from being stored in garage by a previous owner, noticed that it wouldn't hold a line on long sweeping bends, constant corrections needed (arse twitchy moments!). Picked up a set of BBS with fair set of tyres on them whilst I was down there which seemed to cure it. Is it possibly the same thing due to it be garaged over winter?

Wed Jun 22, 2011 3:54 pm

I would check the rear beam bushes,lift the car slowly using the sill jacking point and have an assistant watch as the weight comes off the beam,there should be no visible movement.You can expect a touch of 'rear wheel steer',that's normal and is built into the rear suspension to help slow down rear end breakaway....it could be eliminated by fitting polybushes,but this is not recommended for a road only car.
Plenty of threads about swapping these bushes,I am sure a search will turn a few up.

Steering;
I would suggest that you raise the bonnent and locate the steering shaft,then get your assistant to waggle the wheel for you,look particularly at the rubber guibo just above the u/j's,these have a cunning habit of breaking up,giving vague steering.Replacement is easy compared to rear beam bushes,and a repair kit can be bought from your local dealer,make sure he gets you the correct shouldered bolts to replace the rivets used on original ones.

Wed Jun 22, 2011 5:05 pm

The first i noticed coming off the motorway doing ~60mph into a long banked motorway offramp. Upon turning into the corner, it felt like the rear end of the car stepped sideways a little bit and the cornering angle tightened up requiring me to reduce steering angle to maintain course.(IE what felt like the rear end did something odd which seemed to make the car steer itself tighter into the corner)

This does sound exactly like my first 325i which fooled me into thinking I was a drift hero and then cost me £250 when my mechanic mate got it on a lift and burst out laughing when he saw the state of the rear bushes.
It could be something else but it's well worth checking since they're an MOT failure anyway.

Wed Jun 22, 2011 9:00 pm

Thanks guys.

The rear tyres are brand new T1R's, so i'd hope they're fine.

I'll check the steering bits over the weekend, sounds like that could be the culprit if its not the rack itself. Got some other bits under the bonnet to take care of anyway.

Good tip on watching the beam bushes moving while jacking the car, will do that for sure.

Wed Jun 22, 2011 10:08 pm

I'll be watching this one - I've got a similar problem with mine except the rear bushes were done less than 1k miles ago. There is a lot of whining coming from the back that gets worse when turning in both directions so either the diff is going and I've got a suspension problem, or one or both bearings have failed but don't have any play when I lift the car and shake the wheels

Those rear bushes are a pig to do... If you can afford to get a garage to do the work do that. Those are a few hours of my life I'm not getting back...and I had the bushes already pressed in another beam!