Suspension?

UK forum for general and technical discussion about the Z3 roadster
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TomH84
Joined: Sun 15 Dec, 2013 15:22
Posts: 113

  Z3 roadster 2.2i

Suspension?

Post by TomH84 »

Just washed and waxed the car ready for an afternoon roof down blast and noticed something odd.

The inner tread on my offside rear tyre has worn dramatically (about 5k driven). It's down to 1mm, evenly across the inner tyre edge. Both rears (Falken 714s) replaced in Feb this year. The near side rear is wearing normally and well (hardly worn). Rear shocks are new and stock. I've just measured the ride height on both sides (from centre to wing lip). It's 37.5mm offside and 37.8mm nearside.

What could have gone horribly wrong?

Hopefully fixable and not ridiculously expensive...

Cheers,

Tom
2002 BMW Z3 2.2i 82k
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1971(K) MGB GT - the 'other' car
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Del
Joined: Sat 19 Nov, 2011 18:35
Posts: 2136

  Z3 roadster 1.9

Re: Suspension?

Post by Del »

Has the car ever had a "side-on" shunt on the rear side in question - which can slightly distort the trailing arm? May just be worn trailing arm bushes but one would guess at this causing a more balanced issue on both rear tyres.
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TomH84
Joined: Sun 15 Dec, 2013 15:22
Posts: 113

  Z3 roadster 2.2i

Re: Suspension?

Post by TomH84 »

I've been thinking the same. It's possible that it's had a bump before I got it. It's the uneven wear that's suspicious.

The RTABs might be worn, but I would have thought they wear in parallel and affect the rear tyres more evenly?! I do hear a slight knock/clunk from the 'problem' side at low speed (0-20mph). It's intermittent, but audible when car is in gear or coasting. That might be another indication that something is up at that end of the car. It could also be something unrelated.

Is there anything to look / test for if I jack the car up? I'm not that familiar (yet) with the z3 rear suspension. I've only done the shocks/shock mounts. All my other work to date has been engine-related. I'd like to diagnose the problem before undertaking a big job like replacing the offside RTA.

Cheers!

Tom

P.s just been out in the sun with roof down = :) :)
2002 BMW Z3 2.2i 82k
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1971(K) MGB GT - the 'other' car
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TomH84
Joined: Sun 15 Dec, 2013 15:22
Posts: 113

  Z3 roadster 2.2i

Re: Suspension?

Post by TomH84 »

Just taken a picture. You can see the wear!

ImageUntitled by TomHorsley, on Flickr

Tom
2002 BMW Z3 2.2i 82k
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1971(K) MGB GT - the 'other' car
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TomH84
Joined: Sun 15 Dec, 2013 15:22
Posts: 113

  Z3 roadster 2.2i

Re: Suspension?

Post by TomH84 »

deleted double post :)
2002 BMW Z3 2.2i 82k
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1971(K) MGB GT - the 'other' car
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Brian H
Joined: Tue 16 Dec, 2008 19:55
Posts: 2505

  Z3 roadster 3.0i

Re: Suspension?

Post by Brian H »

Tom

Unfortunately the uneven wear is a trait of our cars, the camber on the rear axle leads to this uneven wear, unfortunately there in no adjustment in the rear to rectify this. If your rear tyres are non directional you can get them flipped to balance out the wear.

Brian
Del
Joined: Sat 19 Nov, 2011 18:35
Posts: 2136

  Z3 roadster 1.9

Re: Suspension?

Post by Del »

I'm certainly not a professional so don't take my word as the definitive opinion. I understand that an audible clunking, at low speeds (from the side in question) can support the slightly bent trailing arm view in that it can cause the driveshaft to be slightly "off angle". A bent trailing arm does not mean the car has had a bad smash, more likely it could just have been a previous owner doing something fairly minor like sliding the back end into a high curb. However, as Brian says the simple/common things are often the cause and swapping the tyres may help you.
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TomH84
Joined: Sun 15 Dec, 2013 15:22
Posts: 113

  Z3 roadster 2.2i

Re: Suspension?

Post by TomH84 »

Thanks guys!

I've got Falken ZE 914s on the car. Are these non/uni-directional? I can only see "OUTSIDE" markings on the rim and no direction arrows.

Swapping the rears would be buy me a few months time. After that, it might be worth replacing the offside RTA. False economy buying a new rear tyre ever 6000 miles.

I'll have a poke about underneath the car next wkend and see if I can see anything else unusual.

Cheers!
2002 BMW Z3 2.2i 82k
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1971(K) MGB GT - the 'other' car
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Del
Joined: Sat 19 Nov, 2011 18:35
Posts: 2136

  Z3 roadster 1.9

Re: Suspension?

Post by Del »

I find that I can reverse my car up on standard ramps OK. I would have a good peep underneath with a lamp and check for any obvious wrinkles in the black paint covering the RTAs and perhaps compare some measurements with the good side e.g. distance across the two forks of the RTA and perhaps measurements front a central point on the diff to similar spots on each RTA - I am afraid that I do not know of any "official" measurements to take.
t-tony
Joined: Sun 21 Feb, 2010 23:17
Posts: 353

  Z3 roadster 2.0
Location: torksey lock

Re: Suspension?

Post by t-tony »

You don't need "definitive" measurements at this stage Del. What you need to be able to do is simply compare a given measurement from, say point A to point B on both sides of the car as you already have in measuring the height from ground the wheel arch. This should then tell you if there is a difference between both sides, and therefore a point to start looking.

HTH, Tony.
"Knowledge and experience are not always the same"
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