Vague/light steering

[Rldee007]

Hi all,
As the subject suggests I have a steering issue at 50/60mph. Can feel scarey and skittest. Not an issue at lower speeds. I see this seems like a well documented issues but I am more of home mechicanic newbie.

Background:
- Passed MOT with no advisories
- Did mentions front ARB bushes look a little tired
- Tuned the steering for the sticky steering, got the wheel were it felt tight and direct but I could feel knocking/intermiien vibration when driving through the steering wheel so I back it off but I still have vague steering again
- Non run flats on the car, different brands on the front to rea
- New tyres on rear only done 100 miles
- Front tyres have approx. 5/6mm

Plan
- New ARB bushes and drop links to be fitted
- Going to check tyre pressures, any particular non OEM setting any recommended for 17's?
- Then get the car wheel alignment and balance done

Is there anything else I should do at first?

I am home DIY guy, so don't mind having a crack if needed though I don't have the tools to push out bushes if needed. Any advics on this front let me know too would be very much appreciated.

Thanks

 

[sw4nny]

Dont know if this is really related but just extra info.
I replaced the wishbones and bushes a while ago and the steering didnt feel bad after that and was fine for me,but just this week i changed front springs shocks and outer tie rods and it feels a lot tighter and direct about the same difference again like sport button being on but without it.
Feels a lot more planted and sure .
How many miles has the car done on original parts?

 

[MKZ4000]

It’s possible that the different brands of tyre are causing it and tyre pressure. Experiment around 30-32psi.

I had a mix and match, switched them out for eagle f1s and the tram lining went completely without any alignment.

Prior to that, as soon as I hit 60+ the car was tugging like crazy

 

[Rldee007]

Thanks for the advice.
I don't really want to change the tyres as the rears a brand new. Are they really sensitive to different tyres even if they are paired from new?

Some one did suggestion changing the rear bushes too. I need to look into this. Is it easy to do?

 

[Scooba_Steve]

Going to check tyre pressures, any particular non OEM setting any recommended for 17's?

33 psi front, 35 psi rear work well for me on 17 and 18 non-RFT.

 

[Scooba_Steve]

Some one did suggestion changing the rear bushes too. I need to look into this. Is it easy to do?

You will need some pressing tools. Definitely do the RTABs, either poly or new OEM with limiters (poly are easier to fit). Consider upgrading the rear lower bushing (where the camber arm goes) to the same as the upper.

 

[Rldee007]

Hi all,

Just a quick update.

Reducing the tire pressure to 32 psi made a massive difference on the rear (as suggested by another a source). When driving above 50mph the steering is much more steady.

I checked the rear bushes by jacking up each corner off the ground and gave it a good shake. I am not mechanic but I have watched enough Wheel dealers to know that my wheels don't have access movement. The car has just had a MOT and they should test this too if this was an issue.

When driving along the motorway I do still feel slight intermittent tugging which you can see as you do minor adjustments as you drive along. I would describe it feeling like running two magnets over one another trying to pull them apart.

My thoughts for my next steps would be:
- Would further adjustment of the steering column fix this or is this as good as it gets?
- Waiting for the new front ARB powerflex and front drop links to fit
- Would wheel alignment and balance be next?

 

[brillomaster]

Thanks for the advice.
I don't really want to change the tyres as the rears a brand new. Are they really sensitive to different tyres even if they are paired from new?

Some one did suggestion changing the rear bushes too. I need to look into this. Is it easy to do?

what tyres do you have front and rear, exactly?

 

[Rldee007]

Michelins front and Falkens rear.

Where are you in Leamington? I live in Leamington!

 

[brillomaster]

ok that should be ok... falkens are a perfectly decent tyre, though not quite as good as michelins. i'd have concerns if it was michelins front and proper budget tyres on the rear, but a premium and a mid range should be ok.

in that case, i'd be looking at alignment and pressures, and then bushings. was the alignment done both toe and camber, and done by a reputable place? and pressures you've already checked.

i once had a really skittish car when the RTAB went... but that was really really bad, felt like the rear wasn't even connected to the rest of the car (which i guess technically it wasnt!)

edit: indeed i am - well - a couple of miles south of leamington to be precise. but you wont see me in a z4 cos i sold mine last year... i just stick around on the forum cos i like it, and haven't bought my replacement yet...

 

[Rldee007]

ok that should be ok... falkens are a perfectly decent tyre, though not quite as good as michelins. i'd have concerns if it was michelins front and proper budget tyres on the rear, but a premium and a mid range should be ok.

in that case, i'd be looking at alignment and pressures, and then bushings. was the alignment done both toe and camber, and done by a reputable place? and pressures you've already checked.

i once had a really skittish car when the RTAB went... but that was really really bad, felt like the rear wasn't even connected to the rest of the car (which i guess technically it wasnt!)

edit: indeed i am - well - a couple of miles south of leamington to be precise. but you wont see me in a z4 cos i sold mine last year... i just stick around on the forum cos i like it, and haven't bought my replacement yet...

Do you recommend any where in Leamington to do the alignment?

Also can any show me which rear trailing arm bush could need replacing please?

Regarding pressing tool surely some stubbed bar, a matching nut and a selection of sockets could do the trick??

 

[brillomaster]

I would heartily recommend Spires Technologies on the Heathcote Industrial estate - very knowledgeable chap who knows his way around BMWs, and setting up suspension and geometry. If you tell him what you want the car to do he'll set it up for you.

https://www.spires-st.com/

 

[Rldee007]

I would heartily recommend Spires Technologies on the Heathcote Industrial estate - very knowledgeable chap who knows his way around BMWs, and setting up suspension and geometry. If you tell him what you want the car to do he'll set it up for you.

https://www.spires-st.com/

Thanks I'll check them out. Are they expensive?

 

[brillomaster]

i think a full alignment was about £120, so about average id say. but give them a ring, there might be other options available.

 

[Rldee007]

Great I'll check them out regarding the lower trailing atm bush and wheel alignment. Thanks

Brillomaster would be able to take my car for a spin and give your opinion on the handling please ? weird request I know.

 

[ph001]

The typical ones that wear and cause handling issues are shown with the green dot against them. I wouldn't have through anti-roll bar bushes and drop links would cause such issues - normally just get knocking when they wear.

 

[Rldee007]

The typical ones that wear and cause handling issues are shown with the green dot against them. I wouldn't have through anti-roll bar bushes and drop links would cause such issues - normally just get knocking when they wear.

Z4 bushes_wear.jpg

Thank you for confirming that.

I was told the rear trailing lower bush was key for vague straightness at speed.

Well I replaced the front ARB and drop links because it was a easy job and the MOT side they were a little tired so I thought what the hell with it ,as I wasn't 100% happy with the handling.