Anybody's car moving(bouncing) back and forth when coming to a stop?

PurpleSector · 04-21-2018, 10:58 AM

This might be suspension related, as I lowered by car using Eibach Prokit springs about 1200 miles ago on stock shocks. But upon some research, I noticed that many BMWs with relatively aggressive OEM brakes and softer OEM shocks are having this issue as well. So I thought I would ask in General section to see if this is a common problem?

To fully describe what it is:
1. You come to a slow stop. Gradually decreasing speed.
2. Once you feel completely stopped (brake pedal all the way down, wheels not spinning), the car bounces back and forth in slow motion and finally settles after about 3 times (i.e. bounces to front - rear - front - and halt).
*Interesting thing is, when stop&go mode is turned on (i usually turn it off), this symptom goes away completely as the car just.. turns off. Same when using the auto-hold function.

This problem has gotten progressively worse past few hundred miles.
I really do not think this is a engine/tranny related issue, but rather, suspension component issue. It just feels like either 1) brake is grabbing too hard so that the whole chassis is jolting back and forth, or 2) shocks are not in full control, not coping well with the spring rates.

For case 1), this doesn't make sense as BMW won't be that stupid.
For case 2), possibly due to the lower spring, but I mean I have Eibach Prokit, which is the mildest set of springs available! Could it be possible that OEM G30 shocks are so soft that they can't take the Eibach's spring rate?

I had lowering springs pretty much in all my past cars, and never had this issue..

Any help / advice would be appreciated.

dznutz · 04-22-2018, 08:53 AM

simple case of your shocks cant keep up with the spring rate

HighlandPete · 04-22-2018, 09:05 AM

Quote:

Originally Posted by dznutz

simple case of your shocks cant keep up with the spring rate

That is also my thinking. OP hasn't stated whether the OEM suspension is standard or M-sport (704). If standard suspension, would be easy to overwhelm the damping.

JOHNBMWM5 · 04-22-2018, 09:05 AM

Quote:

Originally Posted by dznutz

simple case of your shocks cant keep up with the spring rate

Agreed, never had this on any "M" car or this 540i.

r33_RGSport · 04-22-2018, 10:28 AM

Sound like something is loose.
You may want to check the installation over again or bring it back to the shop.

Dephead2004 · 04-24-2018, 03:59 PM

Is it the over sensitive stop start cutting in as you come too a stop and then releasing as perhaps you like me lift off ever so slightly on stopping

is_niice · 04-25-2018, 05:53 PM

This could be a million things. My guess is either brake line is pinched or obviously suspension issue. Both of which are probably a result of a bad installation. Check and make sure everythings seated properly and ask what they did with the bump stops.

Also, pics of car on Eibach?

is_niice · 04-25-2018, 06:01 PM

Quote:

Originally Posted by JOHNBMWM5

Agreed, never had this on any "M" car or this 540i.

I've had lowered cars of all types, both better and worse than a G30.

I haven't had the spring rate issue happen on any of them prior, hopefully it doesn't happen as i'm installing eibach on my g30 next weekend.

04-21-2018, 10:58 AM	#1
PurpleSector 2018 530i 25 Rep 67 Posts Drives: G30 Join Date: Oct 2017 Location: APAC iTrader: (0)	Anybody's car moving(bouncing) back and forth when coming to a stop? This might be suspension related, as I lowered by car using Eibach Prokit springs about 1200 miles ago on stock shocks. But upon some research, I noticed that many BMWs with relatively aggressive OEM brakes and softer OEM shocks are having this issue as well. So I thought I would ask in General section to see if this is a common problem? To fully describe what it is: 1. You come to a slow stop. Gradually decreasing speed. 2. Once you feel completely stopped (brake pedal all the way down, wheels not spinning), the car bounces back and forth in slow motion and finally settles after about 3 times (i.e. bounces to front - rear - front - and halt). *Interesting thing is, when stop&go mode is turned on (i usually turn it off), this symptom goes away completely as the car just.. turns off. Same when using the auto-hold function. This problem has gotten progressively worse past few hundred miles. I really do not think this is a engine/tranny related issue, but rather, suspension component issue. It just feels like either 1) brake is grabbing too hard so that the whole chassis is jolting back and forth, or 2) shocks are not in full control, not coping well with the spring rates. For case 1), this doesn't make sense as BMW won't be that stupid. For case 2), possibly due to the lower spring, but I mean I have Eibach Prokit, which is the mildest set of springs available! Could it be possible that OEM G30 shocks are so soft that they can't take the Eibach's spring rate? I had lowering springs pretty much in all my past cars, and never had this issue.. Any help / advice would be appreciated.
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04-22-2018, 08:53 AM	#2
dznutz Enlisted Member 2 Rep 44 Posts Drives: M550i Join Date: May 2011 Location: C iTrader: (0)	simple case of your shocks cant keep up with the spring rate
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04-22-2018, 10:28 AM	#5
r33_RGSport General 13100 Rep 18,779 Posts Drives: G09 XM, G05 X5 40, 991.2 T Join Date: Oct 2009 Location: So. Cal iTrader: (6)	Sound like something is loose. You may want to check the installation over again or bring it back to the shop. __________________ Email:sales@rgsport.com \| IG:RGSport_USA \| Web:RGSportShop.com PM for Everyday DEALS!! MSS • iSweep • RaceChip • Sterckenn • AutoTecknic • Akrapovic • Vossen Wheels • Eventuri Active Autowerke • KW • H&R • Ohlins • Remus • and more...
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04-24-2018, 03:59 PM	#6
Dephead2004 Lieutenant 181 Rep 549 Posts Drives: G30 520i Join Date: Feb 2018 Location: UK iTrader: (0)	Is it the over sensitive stop start cutting in as you come too a stop and then releasing as perhaps you like me lift off ever so slightly on stopping
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04-25-2018, 05:53 PM	#7
is_niice Private First Class 57 Rep 164 Posts Drives: Everything Join Date: Feb 2008 Location: Los Angeles, CA iTrader: (2)	This could be a million things. My guess is either brake line is pinched or obviously suspension issue. Both of which are probably a result of a bad installation. Check and make sure everythings seated properly and ask what they did with the bump stops. Also, pics of car on Eibach?
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