bloomjbmw

While driving down the road my car (2008 550i M-Sport) seems to be ultra sensitive to road imperfections, surface, etc. Also, I noticed that I felt some vibration in my seat bottom as well as in the passenger seat back (you could see it moving during driving). On occasion the car seems to be smooth as butter but more often then not, its a little rough - vibration wise than I expected. I figured out after having my tires balanced that I had two BMW 172 bent rims (both on the right side). After reading up a lot here I took them to a shop that reconditions wheels and had them straightened and refinished. They look great and are straight.

By doing this, I believe I have eliminated the rhythmic vibration but still the car isn't as smooth as I expect it to be.

I realize that 19" wheels and 35/30 series tires aren't going to isolate as well as smaller wheels/larger sidewalls, but still is this normal? Those of you with 550i M-Sports, do you think what I am describing is the nature of the car / suspension, or should i be looking for something else? Also, I bought the car with General UHP's so I realize that doesn't help things.

Thanks,

Joshua

uheenada

A car shouldn't be vibrating like that regardless of suspension, rims etc. If your fixed rims are fixed right then it will be most likely the tires.
My reputable shop told me that if you drive a car with bent rims then THE TIRES will also going to be damaged(not in a danger way but vibration/chimmy issue type).
It's more than likely that your tires are not true/straight anymore.
Get the roadforce balance and see how many lbs of road force is being applied to the tires. I've done this before and the normal range of road force is
between 0-15lbs. But my tires were about 43lbs of road force after driving about 600miles on a bent rim(prior to bent all of my tires were in 5-8lbs range). So I replaced the tires and it's as smooth as a butter.

Hope this helps.

vlad_b

+1 about the tires. When you drive with bent rims for a while tires are taking that shape. If your rims are fixed now it will take some time for tires to get original shape again.

i tottally agree with uheenada that's probably the issue. car shoulndt be "sensitive" and have vibration

DrLev99

My 550i has a lot of "road-feel" in the steering wheel and seats. I, too, feel vibration at times under the seats at highway speeds. I've had this feel on all 3 of my E60's, so I am going to assume it's a BMW thing. My steering wheel only vibrates when the tires have flat spots from sitting all day, but other than that it's not an issue.

acorradi87

I haven't experienced obnoxious vibrations like you've said. I understand that with the 'retuned sport suspension' (that comes with the 550 M) and 19 inch rims there will be, as DrLev said, lots of road feel. Compared to my friend's 335i Conv my car is actually much better at soaking up road imperfections and feels much smoother like it's a highway cruiser as well as good handler. Sorry I can't give you a potential solution but this is just my .02 cents on the matter.

bloomjbmw

Thanks guys. So it sounds like its basically a combination of tires being goofy from the rims being bent and the car having a ton of road feel. Thanks for all the replies. Unfortunately these Generals have a good bit of life left so I wont be changing them for a while...

The car is great otherwise, I guess I owe you guys some pictures. I'll work on that.

sdg1871

My passenger seat back does vibrate some time if the road is rough. I also just found out that both of my passenger side 172 have slight bends in them (Wheelfixit, here we come again) (hardly a surprise given the 19 inch wheels and the horrendous potholes on NYC roads (especially the FDR)).

You have chosen to buy a high powered V8 sedan with low profile, summer tires and a stiffened, sport-tuned suspension. Given how ridiculously high the handling limits are, it is amazing that our car's suspension is as compliant as it is (my 2006 Infiniti M45 Sport also had no body roll but at the expense of no ride compliance at all). Nonethless, a car with high handling performance and all the gear that it takes to produce it is going to be more sensitive to road imperfections than a soft handling car with taller sidewalls.

acorradi87

My mom drives an 07 Infiniti M35 Sport, and I can attest to that. You can feel the road completely. If you compare them back to back you'll probably realize just how compliant the 550 M is, even though it may not seem like it at times.

bloomjbmw

Don't get me wrong, I'm not complaining about the ride quality from the standpoint of bumps...my issue is with vibrations. I've had an E39 M5 with 18's and 45/40 series tires and even it was softer than this. Also, my other car now is a Miata which is very stiff. True though this 550i with ARS is crazy in the curves!

k44ent

I have experienced seat back vibrations on both my E60's and my current E61. All three cars have done this from new and also after tyre changes, it is road surface dependent. I found the best ride was my E60 M-Sport with 172's and 19" non run flat tyres. My current E61 has conventional tyres on 17" rims and can be very smooth and yet over certain road surfaces the passenger seat back will vibrate between 55mph and 75mph. It's done this from new with the run flats as well.