Steering meandering & bumping off line

bloodysalmon · 04-07-2014, 06:31 AM

I remember my 1st Z4 had a problem with meandering across the road, especially when the surface was uneven or had tram lines of repair. It got resolved like a few have said, by replacing the run-flat tyres. I am not convinced this is the case with my recent Z4 (2004) purchase. As my wheels are 18" the 2 front tyre are different to the rear ones as we know.
What I'm beginning to think is that there could be a problem with the shock-absorbers, as when you go over a grate or small hole the car shifts left or right almost as though the wheels are bouncing. Ball-joints, wishbones, steering rack worn are all areas I have considered, and still could be, but I wondered if anyone else has had this issue. I really dare not gone down a lane road above 50 mph other wise I am sure I will ditch it as I struggle to keep it in straight line ... blinking dangerous. I have also lowered the tyre pressures to 33 front with 36 back and tempted to lower them even more to see if it makes a difference.
Any guidance ideas with 2 way conversations really welcome.
Chris

XMetal · 04-07-2014, 09:44 AM

33/36 is still quite high for street use. Our ///M, which doesn't use run-flats only calls for 30/30 psi. Also check your alignment...too much "toe out", and you'll be darting around like what you've described. I've even tried 32/32 psi and I don't have your issue of keeping the car in a straight line, even with the stiffer suspension.

bloodysalmon · 04-07-2014, 10:13 AM

Hi Xmetal, I think you may be right, I'm going to drop them down to 32's ... even though the Owners manual states 33/36 for 18" wheels. Just been out now and nearly hit oncoming car as it darted and jumped across the cats-eyes.

Clearancediver · 04-07-2014, 03:15 PM

I would seriously have your front control arms/bushings checked.... And if the car has had many miles since they were replaced or are the original control arms... Replace them with new control arms and CABs. I just did my control arms and bushings and it's not that difficult to do....just remember to have an alignment afterwards.

WAMz4 · 04-07-2014, 04:55 PM

The "shifting" on bumps does sound like a bigger issue than just RFT tires, hopefully a simple wheel alignment.
But you didnt state whether this car has RFT tires or not. Non RFT tires can work miracles with this car. For all of BMW's engineering brilliance, The RFT's were a MAJOR FAIL.

bloodysalmon · 04-09-2014, 03:33 AM

I can confirm that my car does have 18" RFT's which form all accounts isn't good on Z4's by the looks of it.
The CAB's have also been replaced just prior to purchase and the wheel alignment was also done last November costing £100 but the problem is definitely still there. I have dropped the tyre pressures and it has made a small difference reducing the bounce and the meandering ... now going to try 30psi.
I also thought someone may say it could have been the shock-absorbers bouncing as worn but they aren't leaking for sure.

04-07-2014, 06:31 AM	#1
bloodysalmon Registered 0 Rep 4 Posts Drives: BMW Z4 3.0i Auto Join Date: Apr 2014 Location: Ravenshead, Notts iTrader: (0)	Steering meandering & bumping off line I remember my 1st Z4 had a problem with meandering across the road, especially when the surface was uneven or had tram lines of repair. It got resolved like a few have said, by replacing the run-flat tyres. I am not convinced this is the case with my recent Z4 (2004) purchase. As my wheels are 18" the 2 front tyre are different to the rear ones as we know. What I'm beginning to think is that there could be a problem with the shock-absorbers, as when you go over a grate or small hole the car shifts left or right almost as though the wheels are bouncing. Ball-joints, wishbones, steering rack worn are all areas I have considered, and still could be, but I wondered if anyone else has had this issue. I really dare not gone down a lane road above 50 mph other wise I am sure I will ditch it as I struggle to keep it in straight line ... blinking dangerous. I have also lowered the tyre pressures to 33 front with 36 back and tempted to lower them even more to see if it makes a difference. Any guidance ideas with 2 way conversations really welcome. Chris
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04-07-2014, 09:44 AM	#2
XMetal Colonel 1131 Rep 2,866 Posts Drives: Anything Join Date: Apr 2010 Location: SoCal iTrader: (0) Garage List 2008 Z4M Coupe [10.00] 2018 Audi S3 [0.00] 2004 X5 [8.50]	33/36 is still quite high for street use. Our ///M, which doesn't use run-flats only calls for 30/30 psi. Also check your alignment...too much "toe out", and you'll be darting around like what you've described. I've even tried 32/32 psi and I don't have your issue of keeping the car in a straight line, even with the stiffer suspension.
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04-07-2014, 10:13 AM	#3
bloodysalmon Registered 0 Rep 4 Posts Drives: BMW Z4 3.0i Auto Join Date: Apr 2014 Location: Ravenshead, Notts iTrader: (0)	Hi Xmetal, I think you may be right, I'm going to drop them down to 32's ... even though the Owners manual states 33/36 for 18" wheels. Just been out now and nearly hit oncoming car as it darted and jumped across the cats-eyes.
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04-07-2014, 03:15 PM	#4
Clearancediver Lieutenant 90 Rep 406 Posts Drives: 2004 Z4 Join Date: Oct 2012 Location: Victoria, BC Canada iTrader: (0)	I would seriously have your front control arms/bushings checked.... And if the car has had many miles since they were replaced or are the original control arms... Replace them with new control arms and CABs. I just did my control arms and bushings and it's not that difficult to do....just remember to have an alignment afterwards. __________________ Sent from my smart phone...
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04-07-2014, 04:55 PM	#5
WAMz4 First Lieutenant 45 Rep 384 Posts Drives: 2006 Z4 3.0si Roady Join Date: Mar 2009 Location: Denver CO iTrader: (0)	The "shifting" on bumps does sound like a bigger issue than just RFT tires, hopefully a simple wheel alignment. But you didnt state whether this car has RFT tires or not. Non RFT tires can work miracles with this car. For all of BMW's engineering brilliance, The RFT's were a MAJOR FAIL. __________________ The Internet said it. I believe it. That settles it!
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04-09-2014, 03:33 AM	#6
bloodysalmon Registered 0 Rep 4 Posts Drives: BMW Z4 3.0i Auto Join Date: Apr 2014 Location: Ravenshead, Notts iTrader: (0)	I can confirm that my car does have 18" RFT's which form all accounts isn't good on Z4's by the looks of it. The CAB's have also been replaced just prior to purchase and the wheel alignment was also done last November costing £100 but the problem is definitely still there. I have dropped the tyre pressures and it has made a small difference reducing the bounce and the meandering ... now going to try 30psi. I also thought someone may say it could have been the shock-absorbers bouncing as worn but they aren't leaking for sure.
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