Wobble over uneven surfaces

chrisgillett · 06-02-2019, 04:04 PM

Hi all,

I have had my f30 for about 2 weeks now. I previously had an e46 330i and a e90 330d. This is the 330d xdrive 'luxury' version. It is notable, now I'm pushing on a bit and am more familiar, that it is very uncertain over some high speed corners, particularly if the road surface is less than perfect. Feels as if there is excess 'squirm' from the back. Also, at slower speeds I get similar feeling from minor pot holes, as if the rear wheels/suspension arms are flexible!! At slow speeds or straight lines it's fine.
I have standard suspension (not adaptive and not m-sport) and at the stock ride hight (comedy arch gaps

). These are non-run flat tyres.

So, I plan on getting the alignment checked.
I think I'll also (firstly) increase rear tyre pressure a bit - currently 38psi, I'll go up to 41psi.

Is this a case of "they all do that sir", or might I be able to fix this without spending bulk money on new suspension?

Less confidence inspiring pushing on than my e90 but that was m-sport. And FAR less than my e46 but that was on full coilovers and custom geo, so no real surprise!

Any help folks?

Watsey · 06-03-2019, 05:49 AM

The front lower control arm bushes are very soft, as a consequence of BMW presumably wishing to isolate the chassis (and occupants) from the crashing ride caused by the runflat tyres.

There are several effects including imprecise steering, suspension wallow over undulations, and squirm. Can be remedied to a large degree by replacing the OEM bushes with poly units.

Of course bushes alone won't resolve the crappy BMW OEM dampers.

The rear bushes are much firmer and I haven't needed to replace those.

DieselSport · 06-03-2019, 10:23 AM

The stock suspenion is just bad, plain and simple. I dont have the M Sport either and couldn't deal with the factory setup so i went with coilovers and am very happy.

The owners manual recommends 32 psi and 38 psi respectively but i personally have mine at 31 psi and 33 psi. I feel manufactures over-inflate the tires in order to get better MPG out of their cars. So i always have mine set lower, which makes for a much more comfortable ride i feel. So i dont think your current tire pressure is the problem.

draggy · 06-03-2019, 12:38 PM

If you're on the stock run flats that could contribute to the sensation you're feeling.

chrisgillett · 06-03-2019, 02:58 PM

Quote:

Originally Posted by Watsey

There are several effects including imprecise steering, suspension wallow over undulations, and squirm.

Yes yes YES! This is it exactly. I guess it could be the front although I thought it was coming from the back, but driving God I am not.
I'll investigate some polybushes but I'm not really planning on modifying this car, it is a motorway wafter and soft is really what I am looking for sadly.

I'm mostly looking for reassurance there isn't anything broken... I think I have that.

sspade · 06-03-2019, 03:03 PM

Bilstein B4 or B6 would solve most of your issues. Also, I would not over inflate the tires. Use the drivers door placard and stay within a few PSI max.

06-02-2019, 04:04 PM	#1
chrisgillett New Member 3 Rep 26 Posts Drives: F30 330d xDrive auto Join Date: Jul 2010 Location: Bristol iTrader: (0)	Wobble over uneven surfaces Hi all, I have had my f30 for about 2 weeks now. I previously had an e46 330i and a e90 330d. This is the 330d xdrive 'luxury' version. It is notable, now I'm pushing on a bit and am more familiar, that it is very uncertain over some high speed corners, particularly if the road surface is less than perfect. Feels as if there is excess 'squirm' from the back. Also, at slower speeds I get similar feeling from minor pot holes, as if the rear wheels/suspension arms are flexible!! At slow speeds or straight lines it's fine. I have standard suspension (not adaptive and not m-sport) and at the stock ride hight (comedy arch gaps ). These are non-run flat tyres. So, I plan on getting the alignment checked. I think I'll also (firstly) increase rear tyre pressure a bit - currently 38psi, I'll go up to 41psi. Is this a case of "they all do that sir", or might I be able to fix this without spending bulk money on new suspension? Less confidence inspiring pushing on than my e90 but that was m-sport. And FAR less than my e46 but that was on full coilovers and custom geo, so no real surprise! Any help folks? __________________
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06-03-2019, 05:49 AM	#2
Watsey Major General 6461 Rep 8,524 Posts Drives: F31 330D sDrive M Sport Join Date: Jun 2015 Location: On sabbatical. iTrader: (1)	The front lower control arm bushes are very soft, as a consequence of BMW presumably wishing to isolate the chassis (and occupants) from the crashing ride caused by the runflat tyres. There are several effects including imprecise steering, suspension wallow over undulations, and squirm. Can be remedied to a large degree by replacing the OEM bushes with poly units. Of course bushes alone won't resolve the crappy BMW OEM dampers. The rear bushes are much firmer and I haven't needed to replace those. __________________ Current : F31 330sD, remapped, Ohlins Road & Track, Millway camber plates, Quaife LSD, Stoptech brakes + Pagid RSL1 pads all round, Weichers front strut brace, Eibach front & rear anti-roll bars, Michelin MP4S.
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06-03-2019, 10:23 AM	#3
DieselSport BMW Convert 108 Rep 201 Posts Drives: 2018 BMW 328d Join Date: Mar 2019 Location: Diamond Bar iTrader: (0)	The stock suspenion is just bad, plain and simple. I dont have the M Sport either and couldn't deal with the factory setup so i went with coilovers and am very happy. The owners manual recommends 32 psi and 38 psi respectively but i personally have mine at 31 psi and 33 psi. I feel manufactures over-inflate the tires in order to get better MPG out of their cars. So i always have mine set lower, which makes for a much more comfortable ride i feel. So i dont think your current tire pressure is the problem.
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06-03-2019, 12:38 PM	#4
draggy sucka for a longroof 29 Rep 70 Posts Drives: F31 Join Date: Jun 2018 Location: NYC iTrader: (3)	If you're on the stock run flats that could contribute to the sensation you're feeling.
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06-03-2019, 03:03 PM	#6
sspade Major General 2477 Rep 5,460 Posts Drives: F30 Join Date: Oct 2017 Location: Stevenson, WA iTrader: (3) Garage List 2016 BMW 320i [7.87] 2014 BMW 328i [6.83]	Bilstein B4 or B6 would solve most of your issues. Also, I would not over inflate the tires. Use the drivers door placard and stay within a few PSI max.
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