Wheel wobble at circa 40mph

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theduck
Joined: Wed 16 Mar, 2011 17:54
Posts: 113

  Z3 roadster 2.0
Location: Cradley Heath

Wheel wobble at circa 40mph

Post by theduck »

Have searched and cant find a definitive answer. At around 40mph I get a little wobble through the steering wheel.

Car is on 17s with, iirc, 225 45 at the front and 255 50 at the rear. Pressures seemed very high when I checked them (over 2.5bar front and back). Have dropped them down to 2.0/2.2 as thats what the handbook says to have them at but that hasnt solved it.

I am having the tacking/geometry checked later, but is there anything else I should be looking at?
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Adam
Joined: Sat 21 Jul, 2007 18:43
Posts: 337

  Z3 roadster 2.8
Location: Newport
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Post by Adam »

Wheel balancing I would put money on. One of the wheels has probably thrown a weight. the tyre depot should balance them for you.
J1SUA
Joined: Tue 01 Feb, 2011 20:19
Posts: 234

  Z3 roadster 1.9i

Post by J1SUA »

+1 on that

See if you can see any 'clean' marks on the inside of the wheel where the weight may have come off

Unless you have sit something really hard i can't imagine your tracking going out to cause such an issue
theduck
Joined: Wed 16 Mar, 2011 17:54
Posts: 113

  Z3 roadster 2.0
Location: Cradley Heath

Post by theduck »

it has hidden weights so not very easy to see, wheels are unfortunately quite heavily curbed by previous owner, which made me thinking tracking issue
Greg Allan
Joined: Wed 02 Feb, 2011 11:12
Posts: 23

  Z3 roadster 2.8
Location: Larbert

Post by Greg Allan »

Check your front brake calipers as well. I'd put money on that.

My passenger side front wheel was red hot after long trips because the caliper piston had seized and couldnt return. This meant that it was constantly applying the brakes on that wheel, ever so slightly. On longer and faster journeys the brake disc/rotor would heat up and warp temporarily and cause steering wobble.

The symptoms where a very violent steering wheel vibration, like driving over cobbles in the middle of an earthquake. It usually came on at about at 50 - 60 mph and it often became hard to control to the point where the missus wouldnt want to be in the car.

The wheel vibrated even though I wasn't applying the brakes and this threw me for months and I ruled out the brakes being involved at all.

I noticed it on carrageways and A roads with lots of roundabouts and junctions where you would apply the brakes, drive a bit and apply the brakes again.

Then I often got wheel squeek as the brake rotor cooled as I cruised at 30mph on the streets going back home.

So next time the steering wheel wobbles try stopping when it is safe and then putting your hand near each wheel and if one roasting hot, jack the car up safely when you get home, try and spin that wheel forward with your hands. If it doesnt budge easily then take the wheel of and inspect the caliper piston. You'll see the crumpled rubber on the piston right away.

You can get refurbed calipers on ebay from £40 to £90 and then pay for someone else to do it or DIY.

If all of your wheels move freely and arent overly hot after a journey then you can probably rule that out.
theduck
Joined: Wed 16 Mar, 2011 17:54
Posts: 113

  Z3 roadster 2.0
Location: Cradley Heath

Post by theduck »

Thank you for the detailed response! I will definatley check this. I had the wheels balanced last night, turned out there was no weights on them at all :shock:

It has improved, however there is still a slight wobble at 40mph, though the lightnes at the front end seems to have gone away :)

Bad news is the garage who did the balaning told the other half that one of the front shocks has gone :(

Good news is, I will probably get coilovers now :D

What a mixed bag of emotions! lol, though these things are to be expected.
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TaffZee
Joined: Thu 20 May, 2010 09:45
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Post by TaffZee »

I found that as your tyres wear on the front this can create a slight wobble at certain speeds. Tyres can wear unevenly although you may not be able to see this. If you have had it balanced/checked the calipers/Discs. Dont thing its tyre wear, the last thing I would look at is rear lower wishbone bushes, replacing these on mine stopped a slight wobble on mine that I had when braking. I had already changed the calipers and disc brakes and it still wobbled under braking, until I replaced the said bushes.
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theduck
Joined: Wed 16 Mar, 2011 17:54
Posts: 113

  Z3 roadster 2.0
Location: Cradley Heath

Post by theduck »

Cheers Taff, I know the bushes were all done within last 2 years, so dont think it will be that.

Could it be the one dead shock causing it? I have a feeling it may be the brake caliper as I remember thinking that the rear nearside wheel was warm last night....
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Robin
Joined: Sun 14 Dec, 2003 18:35
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  M roadster S50
Location: Southampton
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Post by Robin »

Possible cause of your wheel wobble.
I had this happen when one of the front brakes was binding. Felt exactly the same as an out of balance wheel.
The disc became temporarily warped from the binding heat so made the wheel wobble due to uneven drag during each rotation. The brakes on these cars are not a great design & tend to do this.
New caliper was solution though they can sometimes be freed off.
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austerman
Joined: Thu 07 May, 2009 19:45
Posts: 9

  Z3 roadster 2.0
Location: Baldock

Post by austerman »

You may like to check the flexible coupling at the base of the steering shaft, my Z failed the MOT because the rivets/bolts in the coupling had
worn, this was at 58000 miles a new shaft had to be fitted but
it solved my problem.
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