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BMW 3-Series (E90 E92) Forum > BMW E90/E92/E93 3-series General Forums > General E90 Sedan / E91 Wagon / E92 Coupe / E93 Cabrio > Blame run flats or blame suspension?



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      11-15-2013, 09:50 PM   #1
OceanView18
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Talking Blame run flats or blame suspension?

Recently got a 2011 e90 CPO 328xi sedan, 15k miles barely and 6 speed manual and sport package - overall I do really like the car, and finding manuals with sport package and low mileage was a miracle in and of itself. I guess i was surprised though by the slightly jittery nature of the stock suspension on the xi (that unfortunately even with the sport package, doesn't include the sport suspension)

Question is: though the car still handles fairly well, on rutted boston roads the car seems to be extra jittery on potholes, more than other cars I've driven. I'm sure the run flats play some role. Plus, the suspension could be tighter.

I'm really thinking of getting the KW variant 1 coilovers that supposedly will not only improve the handling of the car but also make the suspension a bit more forgiving? (this is hwat I've read in the forums multiple times),

1) how close to the feel of the e90 328i sedan with sport suspension will this car get if I go with the variant 1? I'm not looking for anything very stiff but want to get as close to the stock sport suspension available on the rear wheel drive cars.

2) Does it make sense to dump the run-flats at some point? Can I do so and fit some type of spare into the trunk ? I truly think regular tires and a tighter suspension should make for a much better ride.

Thanks!
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      11-15-2013, 09:56 PM   #2
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Ditch the run flats throw some Michelin PSS all around. Its a day and night difference
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      11-15-2013, 11:09 PM   #3
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I've learned recently that as the run flats wear in the front (and maybe regular tires also in this car I don't know yet) the car will react that much more to variations in the road.

I thought it was excessive when I purchased mine and new tires made all the difference. It now is way less wayward when it has to deal with ruts.
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      11-15-2013, 11:48 PM   #4
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Quote:
Originally Posted by OceanView18 View Post
Recently got a 2011 e90 CPO 328xi sedan, 15k miles barely and 6 speed manual and sport package - overall I do really like the car, and finding manuals with sport package and low mileage was a miracle in and of itself. I guess i was surprised though by the slightly jittery nature of the stock suspension on the xi (that unfortunately even with the sport package, doesn't include the sport suspension)

Question is: though the car still handles fairly well, on rutted boston roads the car seems to be extra jittery on potholes, more than other cars I've driven. I'm sure the run flats play some role. Plus, the suspension could be tighter.

I'm really thinking of getting the KW variant 1 coilovers that supposedly will not only improve the handling of the car but also make the suspension a bit more forgiving? (this is hwat I've read in the forums multiple times),

1) how close to the feel of the e90 328i sedan with sport suspension will this car get if I go with the variant 1? I'm not looking for anything very stiff but want to get as close to the stock sport suspension available on the rear wheel drive cars.

2) Does it make sense to dump the run-flats at some point? Can I do so and fit some type of spare into the trunk ? I truly think regular tires and a tighter suspension should make for a much better ride.

Thanks!

I recently did the switch from 17" square setup with 225/45/17 conti ssr RFT's to 18" staggered non-RFT's on my 335xi... If i had known how much of a dramatic improvement it would have been... I would have done this as my very first mod rather than doing all my FBO mods first. Because i also need this car for daily winter duty... I had to cross off the MPSS (those r summer tires and the rubber gets damaged permanently when the temps go under 40*F is what i hear). I was able to find these new Michelin Pilot Sport A/S 3's (a new performance all season tire)... I have to say that I LOVE THESE TIRES... Run flats, NEVER AGAIN!!!!!

I used to think like u as well... Thinking i would need to upgrade my suspension, but the truth is... Do the swap to non RFTs and the see if u really need to get the KW's. I would put money down that if u get he MPS A/S 3's, all your problems will go away.
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      11-16-2013, 12:16 AM   #5
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Yes, there are donuts that fit the E90 available on eBay and other sites. You could also pack a plug kit and a small compressor. I am planning on changing to "normal" tires on my wife's 328i when she needs new tires. There is a noticeable ride difference between her E90 with rfs and my E83 w/o rfs.
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      11-16-2013, 01:16 AM   #6
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get the suspension upgrade first, tires alone will not make the difference u r looking for

go the xdrive section of this forum for all the answers u are looking for... kw v1 will not make it more compliant tho, but will make cure most of the body roll and vagueness/floatiness which is inherent in the xi suspensions
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      11-16-2013, 07:54 AM   #7
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The suspension on my 2007 335i with sport package was so hard that the car was for all practical purposes undriveable on New York City roads. I was constantly having "Pothole Explosions" and destroyed 6 tires and bent 5 rims. I replaced the RFTs with Continental Extreme Contact DWS and installed a set of Koni FSDs. That transformed the car. The suspension is firm, but not harsh, no more pothole explosions and the car no longer bounces around on rough surfaces. Handling is better than when the car was stock and the ride quality is an order of magnitude better.

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      11-16-2013, 08:13 AM   #8
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ditch the runflats.

I was like you before thinking if my runflats were the cause of a harsh ride over bumps or was it my suspension. As soon as I switched over to non rft's, so much more comfortable over bumps, and lighter too.

I'm a happy camper. Hmm.. I haven't tracked fuel mileage yet cause I've been pretty happy with the ride comfort.
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      11-16-2013, 08:45 AM   #9
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OP what brand of RFT is on your car? I thought that recent gen of RFT (Conti) were far more better than the horrible Bridgestone RFT of circa 2005-2008.

It looks to me that BMW messed up with the choice of shocks for the E9X with added weight (xdrive, cabrio)... and they didn't for the RWD sedan/coupe.

For me I would have lowered the suspension since day one, but if you don't mind the wheel gap, just start with the tires. BTW, if ever you go with 18" get 225/45/18 and not 225/40/18... your ride will take a few steps back.
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      11-16-2013, 09:35 AM   #10
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I too thought the runflats are the cause of the harsh transition over expansion joints, etc. This is true but besides those issues I discovered that the tire manufacturers have the tire weights close to regular tires (within a pound for the Michelins I ran). My theory of unsprung weight was true when the runflats first came out but isn't now.

I ran Conti's which for a runflat is a terrific tire and went to Michelin Pilot Sport A/S since I run Pilots on both my M3's. Ride was better mileage sucked bad. I dropped almost 3 mpg so it rolling resistence isn't good.

I went back to Michelin Primacy's and I am happy with these. Transition is still harsher than a non runflat but much better. Jitter is still there which was not there with the regular Pilots.

Suspension is all what you want to make it but I agree a tire change does make a difference. Also be really careful reading these reviews. Many times the suspension springs and struts are tuned for a smooth road and someone who can stand a stiff noncomplying ride. I ruined my 325 with sport suspension years ago doing this. It made a well handling, well performing ride into a ride that would bounce across expansion joints.
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      11-16-2013, 09:54 AM   #11
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Quote:
Originally Posted by E90_boostjunky
Ditch the run flats throw some Michelin PSS all around. Its a day and night difference
Truth brother, truth!
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      11-16-2013, 10:25 AM   #12
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The "sport" suspension setup in the E9X series sucks. It's way too harsh on normal roads and it oscillates at speed during cornering if there are any minor imperfections on the road. My M3 with the OEM suspension @ 80k miles felt better. For reference, I got my 335 with 21k miles on it.

Koni FSD's and Swift springs are the solution to this problem.
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      11-16-2013, 10:28 AM   #13
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Ditch the run flats for sure.then take it from there. IF you want to upgrade your suspension, we are a PM away
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      11-16-2013, 01:24 PM   #14
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Does adding KW V1's mess up your Xdrive? I.e does it make it less effective? I know that with the KW V1's you can lower the car, and I was just thinking whether or not lowering messes up the x drive system. There is a reason why the X drive cars are higher than other BMW's. Also how "stiff" is the ride with them on? Does it make it unbearable to drive?
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      11-16-2013, 01:47 PM   #15
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Lowering an Xdrive does not "mess" it up in any way. Go too low and you will wreck the handling, just like any car. Xdrive is marketed for snowy climates where you don't want a low car for various reasons.
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      11-16-2013, 02:21 PM   #16
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Quote:
Originally Posted by OceanView18 View Post
Recently got a 2011 e90 CPO 328xi sedan, 15k miles barely and 6 speed manual and sport package - overall I do really like the car, and finding manuals with sport package and low mileage was a miracle in and of itself. I guess i was surprised though by the slightly jittery nature of the stock suspension on the xi (that unfortunately even with the sport package, doesn't include the sport suspension)

Question is: though the car still handles fairly well, on rutted boston roads the car seems to be extra jittery on potholes, more than other cars I've driven. I'm sure the run flats play some role. Plus, the suspension could be tighter.

I'm really thinking of getting the KW variant 1 coilovers that supposedly will not only improve the handling of the car but also make the suspension a bit more forgiving? (this is hwat I've read in the forums multiple times),

1) how close to the feel of the e90 328i sedan with sport suspension will this car get if I go with the variant 1? I'm not looking for anything very stiff but want to get as close to the stock sport suspension available on the rear wheel drive cars.

2) Does it make sense to dump the run-flats at some point? Can I do so and fit some type of spare into the trunk ? I truly think regular tires and a tighter suspension should make for a much better ride.

Thanks!
The first thing is ditch the run flats and get a decent quality tire. PSS is the top of the line tire but 99% of drivers do not have ability to use their capability therefore they are not neccessary. Also, extreme summer tires turn into hockey pucks below 40 deg F and you need to put on winter rubber. Alternatively you can get a good a/s rubber but a/s tires a comprimise as they do not perform well neither in hot nor in cold temps.

I see you are in Boston and would recommend that you get a 17" 225/45 winter tires and get a feel for the ride, if you don't have them alredy. Then in the spring get a squre 245 set of summer rubber that you want, I would not put on 19" wheels in your case. If you are still unhappy with the ride quality mod your suspension but keep in mind that BMW suspensions are very complex and you may need to mod more than initially planned to achieve desired results. For example, you may need to replace subframe bushings.

Also, pay attention to the tire sidewall thickness, the more sidewall the better ride quality, i.e. 17" vs 19". Take time to do research and understand the pros and cons.

GL
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      11-16-2013, 03:06 PM   #17
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Both are to blame. I always change my BMW suspension b/c the Sport suspension plus RFTs equate to a very rough ride on the streets in the Chicago area. This is my 4th BMW with Sport suspension. That being said, I usually change my suspension first, then the RFTs. I am on BMW Performance suspension and the ride is a ton better versus sport suspension. My RFTs are done so I am buying PSS' in the Spring. GL.
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      11-16-2013, 03:43 PM   #18
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My '08 328i has the sport suspension. With the stock runflats (225/45R17 front, 255/40R17 rear), it felt like I was driving on rocks, and they tramlined like crazy... I had to fight every rut in the road. I ditched the runflats for Michelin PSS (225/40R18 front, 255/35R18 rear), and it was like driving a new car. The handling and ride comfort were both massively improved.

PSS are pure summer tires, so I got a set of Hakkapeliita 7 tires for the winter, had them installed on my stock 17" rims, and they simply rock.

Cheers!
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      11-16-2013, 05:19 PM   #19
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Ditching the runflats made a HUGE difference in improving the ride quality of my 335xi
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      11-17-2013, 11:21 AM   #20
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I'm seeing a trend here of:
1) ditch the RFTs
2) if you still aren't happy then upgrade suspension
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      11-17-2013, 11:29 AM   #21
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I ditched the runflats and went up one width on the tires - improved for me.
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      11-17-2013, 01:20 PM   #22
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Quote:
Originally Posted by curiouz_g View Post
The "sport" suspension setup in the E9X series sucks. It's way too harsh on normal roads and it oscillates at speed during cornering if there are any minor imperfections on the road. My M3 with the OEM suspension @ 80k miles felt better. For reference, I got my 335 with 21k miles on it.

Koni FSD's and Swift springs are the solution to this problem.
Disagree. #1, I'd prefer Bilsteins butt-unfelt due to previous successes with other cars. They are more compliant in my experience, to the point that while I haven't felt them in an E90, I'd certainly try them over the Konis.

#2, he has an XI. No swifts for him!
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