Perplexed - self steering 2.5si roadster

J

jnwright71

Member
All,

Help please ! I have had my 2.5si roadster since May and have always found the steering to between somewhere between imprecise and scary ! No problem, I thought, follow the great advice on the Z4 forum and ditch the run flats - Done.

The issue was reduced but still not resolved, so today I paid out for a full Hunter alignment (yes they weighted down the car and yes it had a full tank of fuel). Of the 12 readings, 9 were in the red, but they appear to have done a good job and now all are green.

Great I thought, problem solved, however not so. The steering is much improved and certainly no longer scary, but it does still appear to self steer on poor roads (i.e. it needs constant correction, and when you take your hands off the wheel the car can gradually veer to the right, cross the centre line of the road, then snap back to the left).

This is really beginning to annoy me. The suspension all seems OK with minimal wear (only done 53K) and the rear springs have been replaced.

I was thinking of replacing the lollipops next, but would appreciate any thoughts / advice on this. Are the lollipops likely to cause this type of issue ?


Thanks, James
 
I know I'm stating the obvious but you haven't mentioned tyre pressures. When my car gets a little wayward I usually find the pressures are a bit low and it doesn't take much to make it tram line more. I have 18" non run flats and I run at 33 front 39 rear which is what BMW reccomend. Had some new rears and wheel alignment a few weeks ago and they hadnt done the right pressures and it felt slightly vague and wandering. Did the tyre pressure and it was rock solid. The rears were down to 32 and the fronts were 31. Could be worth a try experimenting with tyre pressures before investing in new bushes.
 
I would say its possibly bushes. I changed the lollipop bushes and lower control arms problem solved. The lollipops where shot. The control arms looked fine. I did these after and they made the biggest improvement. And they looked fine. I would suggest if your doing all the above change the drop links and ARB bushes also.
 
Zeld4 said:
I know I'm stating the obvious but you haven't mentioned tyre pressures. When my car gets a little wayward I usually find the pressures are a bit low and it doesn't take much to make it tram line more. I have 18" non run flats and I run at 33 front 39 rear which is what BMW reccomend. Had some new rears and wheel alignment a few weeks ago and they hadnt done the right pressures and it felt slightly vague and wandering. Did the tyre pressure and it was rock solid. The rears were down to 32 and the fronts were 31. Could be worth a try experimenting with tyre pressures before investing in new bushes.
Click to expand...

39 rear? Sticker on my door sill says 33 front 36 rear (in bar, of course).
 
Thanks all.

I will definitely try increased tyre pressures as I am running 32 F 34 R. I hadn't seen the 33 F 39 R figure from BMW for non run flats, as I thought they only published data for the approved run flats.

I am happy doing the lollipop bushes and ARB bushes as these seem fairly easy. What about drop links etc are these easy too ? When changed, will I need to get a new alignment done ?

Cheers, James
 
Yes you will need to do the alignment after. Drop links are dead easy. The control arms are doable I did I am know expert!! You will need a ball joint splitter though. Where in the country are you? Someone might be able to help offer a second set of hands and eyes??
 
Interesting thread, Im thinking of dumping the RF's soon....and as James has stated mine is a handful too. But just have got used to it, it's a sports car so we need to have a fair bit of feel for the road.
 
ben g said:
Zeld4 said:
I know I'm stating the obvious but you haven't mentioned tyre pressures. When my car gets a little wayward I usually find the pressures are a bit low and it doesn't take much to make it tram line more. I have 18" non run flats and I run at 33 front 39 rear which is what BMW reccomend. Had some new rears and wheel alignment a few weeks ago and they hadnt done the right pressures and it felt slightly vague and wandering. Did the tyre pressure and it was rock solid. The rears were down to 32 and the fronts were 31. Could be worth a try experimenting with tyre pressures before investing in new bushes.
Click to expand...

39 rear? Sticker on my door sill says 33 front 36 rear (in bar, of course).
Click to expand...
Not in my car it doesn't. It says 2.7 bar which is just over 39 psi.
 
Right, tried an increase in tyre pressure to 34 F and 37 R. Much better, but not perfect. I have just checked my sticker on the door shut and it states 2.1 bar F and 2.4 bar R. This converts to 31 psi F and 34 psi R, so now I am confused. Obviously 31 / 34 is for RFT, so should non RFT have a higher or lower pressure (I assume higher to compensate for the lower side wall stiffness)?

Zeld4 advises 33 / 39 for non RFT as published by BMW. Can anyone else confirm this, as if so, I still need to up,the rear tyre pressure.

Many thanks, James
 
jnwright71 said:
Obviously 31 / 34 is for RFT, so should non RFT have a higher or lower pressure (I assume higher to compensate for the lower side wall stiffness)
Click to expand...

Not necessarily. If they are extra load (XL) tyres you will end up roughly in the same place.

I'm with monkey on the bushes theory. Can you jack it up and check?
 
jnwright71 said:
Right, tried an increase in tyre pressure to 34 F and 37 R. Much better, but not perfect. I have just checked my sticker on the door shut and it states 2.1 bar F and 2.4 bar R. This converts to 31 psi F and 34 psi R, so now I am confused. Obviously 31 / 34 is for RFT, so should non RFT have a higher or lower pressure (I assume higher to compensate for the lower side wall stiffness)?

Zeld4 advises 33 / 39 for non RFT as published by BMW. Can anyone else confirm this, as if so, I still need to up,the rear tyre pressure.

Many thanks, James
Click to expand...
Hello!:) Sorry I hope I'm not misleading. My coupe says 2.4 front and 2.7 rear inside the door. This isn't specified as non run flats.
When I first went to non run flats I had a very unusual steering wobble, it would nibble from side to side and wouldn't settle at certain speeds. That's was after a full hunter alignment. I just want to make you aware that the problem totally disappeared with just tyre pressure changes. Cheers
 
Thanks Zeld4, that may explain the difference as your coupe with the extra weight probably needs higher tyre pressures than the lighter roadster.

Does anyone else have any opinions on this, especially the correct tyre pressures for non RFT (standard widths, 18" extra load).

Cheers, James
 
Zeld4 said:
ben g said:
Zeld4 said:
I know I'm stating the obvious but you haven't mentioned tyre pressures. When my car gets a little wayward I usually find the pressures are a bit low and it doesn't take much to make it tram line more. I have 18" non run flats and I run at 33 front 39 rear which is what BMW reccomend. Had some new rears and wheel alignment a few weeks ago and they hadnt done the right pressures and it felt slightly vague and wandering. Did the tyre pressure and it was rock solid. The rears were down to 32 and the fronts were 31. Could be worth a try experimenting with tyre pressures before investing in new bushes.
Click to expand...

39 rear? Sticker on my door sill says 33 front 36 rear (in bar, of course).
Click to expand...
Not in my car it doesn't. It says 2.7 bar which is just over 39 psi.
Click to expand...

Very odd. Perhaps the coupe has different tyre pressure on the rear compared to the roadster?

All that extra unnecessary weight most likely :lol:
 
I think this is now solved. Took the Z to my local trusted BMW Indie today and within 2 minutes on the ramp, they had diagnosed badly worn front wishbone rear bushes. The play was staggering considering the car has just passed an MOT. New Meyle HD ones being fitted Monday AM - £108 all in.

I will post the results on Monday PM.


Thanks, James
 
Get her to a pro with the proper kit, bloody sure an alignment and a decent set of rubber will sort it. Admittedly vast amounts of ££££ but it really is worth it.
 
When I bought my Zed I was informed that the rears were non rft and fronts were still rft. Car was bloody awful!!! Upon investigation only 1 of the fronts was rft the other was non rft. Changed to non rft all round now, P Zero's. And bloody hell!!!!!!! What a transformation its like a new car, far more pleasant ride and although does tramline a little, well it's sports car with rubber bands for tyres...... I love it.. :D :D :D :thumbsup:
 
Happy :D :D :D

Front wishbone rear bushes replaced today and car transformed. £108 fitted inc VAT. Meyle HD with 4 year warranty and only took my trusted indie 40 minutes to fit. Just need to get the tyre pressures optimised to bets the best trade off between ride and performance, but looks like 31F/33R is the way to go.

My car only had 53K on the clock, has just passed an MOT, but the bushes were really shot. I would recommend anyone with a tramlining / twitchy steering issue to get these bushes checked ASAP. From what I have read, these seem to be a weak point and for £108 replacement has made the handling / steering way way better.

Enjoy.

James
 
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