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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > All-Wheel-Drive (Xi / xDrive) Talk > Blame run flats or blame the suspension?



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      11-15-2013, 10:52 PM   #1
OceanView18
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Blame run flats or blame the 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, 11:12 PM   #2
thegrinchboy
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I would start off by replacing the run flats and take it from there. A sportier suspension such as the KW V1 coupled with RFT will make the ride even more jittery.

BTW, congratulations om the purchase! 6MT is a great purchase.
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      11-15-2013, 11:17 PM   #3
OceanView18
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run flats

thanks ! right now I have all season 17s on there....any particular rating or brand to get as replacement regular tires that you recommend?

And if I do get a flat with these new non-run flats, what are my options? any room to carry a small tire in the trunk?

I splurged for the BMW tire protection plan they sold me,,,,I wonder if I could get money back on that if I switch and get rid of the run-flats
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      11-16-2013, 12:37 AM   #4
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There are certain tires that the tire protection will cover. Check with your SA. You can get a spare tire kit or patch kit. I have the patch kit . Look in the tire section. Also your car is still covered by BMW roadside assistance. If CPO then it is covered for 6yr or 100k miles.

As for specific tires, check TireRack. They have great reviews. All seasons such as Conti DWS or Michelin AS/3are good options. Good luck!
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      11-16-2013, 11:36 AM   #5
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Quote:
Originally Posted by OceanView18 View Post

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!
1) I think the V1's are just a touch stiffer than a stock suspension on a non xi/xdrive. Overall, they are a huge improvement over stock and one of the best mods I've done to my car.

2) Yes. I agree with a previous post saying that RFTs + V1's probably wouldn't be very comfortable, although I've never personally experienced it. I moved from stock 17 RFTs to 19 non RFT and I thought the ride improved.
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      11-16-2013, 12:48 PM   #6
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There are a whole bunch of things that make the xi suspension experience unpleasant. Top of the list is the RFT's paired with the awful stock suspension. Switching to 17" RFT's in your case may fix a lot of what you don't like.

There is no OEM 3-series spare kit but places like Bavauto sells a kit and there is a recent 5 series OEM kit that is the right size as well. Jack + tools etc. It is critical that the circumference stay the same as the other tires. I have this latter 5 series kit I got off eBAy. Ran with a puncture kit for a while but winters here are so hard I decided to get the spare and deal with the weight penalty via peace of mind. I also keep the puncture kit in there just in case that is the easier thing to do.

It may be after getting rid of the RFT's that the suspension is bearable to you. In any case do the tires first and evaluate for a month or two esp with winter closing in.

One of the problems with the stock Xi sup is in order to get higher ride height within manuf constraints, they used stiffer springs (maybe a lot stiffer). Basically if you take Xi springs out and compare them to non Xi (sport or not), they look exactly the same in terms of length coil diameter etc, everything except wire thickness. So they are stiffer and ride higher.

I think in order to compensate for what would be an unbearable ride if the shocks actually matched these springs in terms of standard % critical damping, they reduced the damping force to soften the ride somewhat. So then you get it wallowing all over and jiggly, add the RFT's later in the design process for PC reasons and you have the OEM situation.

What is the point? The point is the OEM springs are too stiff and the dampers are too soft, the latter in both compression and rebound. Then there are the sway bars. And the front vs rear ride height issues.

Anyway back to the main point, swap out the tires first, spend a month or two reading and driving. Improving Xi susp is elusive, or can be.
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      11-16-2013, 01:07 PM   #7
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First thing I did was swap out the run flats. Then got the Bilstein HD shocks a year later. The shocks helped the most with removing jitteriness.
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      11-16-2013, 01:17 PM   #8
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It's all the run flats. Ditching the run flats will make all the difference in the world. Of course, then you'll really notice that the xi suspension (xi's don't have sport suspension) is shit anyway.
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      11-16-2013, 09:05 PM   #9
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If had this setup for four years now / 30,000 miles and have been extremely happy with my 335xi sport AT:
KW-V1
18" Apex ARC-8 wheels 8.5F/9.5R
18" Pilot Super Sport 135F/165R regular tires

I put winter tires on my stock wheels.

The Apex ARC-8 wheels and PSS tires saves ca. 8 pounds per corner, making the handling absolutely superb.
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      11-16-2013, 11:42 PM   #10
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Imo the jittery feeling you describe is most attributable to the soft bushings in the suspension that are in place to accommodate the stiff run flats.

Biggest bang for the buck is in bushings imo.

Last edited by ashmostro; 11-17-2013 at 10:40 AM.
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      11-17-2013, 07:42 AM   #11
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Yeah forgot about the bushings, esp rear subframe. But those are same on non xi.
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      11-17-2013, 12:31 PM   #12
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Seriously ditch those run craps and you will thank god that you did it.

My car though not an XI ( doesn't matter ) was an European delivered full M sport with 19 inch 225M wheels. I didn't understand why the car was crashing on the rear suspension and felt so jittery over imperfect road surface. To one point I had to baby the car over bumps and imperfect roads it was getting tiring to drive!

I decided to take a jump by importing Bird Garage B 3.5 suspension kit that were custom Bilstein shocks with Eibach springs. That took out the rear suspension crashing away altogether and the car felt more planted on the road on high speeds without feeling as nervous before but I still had to baby the car over road imperfections and dips. It was just jittery hard.

Seeing that the stock RFT potenza re050aII 's did not inspire confidence in dry grip levels I made the move to swap to Toyo T1 S's. ( wanted PSS but the slightly fatter sidewalls worried me about scrubbing on the rears ) as the ride height was again lower than the stock M sport suspension and I was also on 15mm spacers on the rear.

The Toyo's even though on wider 235/35 front 265/30 rears with the 225m wheels were a great fit and had a round side wall thus no clearance issues. And the ride?

Immediately apart from the quieter road noise my Immediate impression was that ' why the hell did I not do this from day 1! ' talk about a whole new ride experience, gone were the jittery bumps and hard hits as I skipped gracefully over dips and uneven roads, along the way back to my home there were major construction along the roads and the road surfaces were slightly damaged and totally uneven and even on that I felt for once, comfortable! driving on the 19's!

I hesitated on this change earlier as the stock potenza rears were already rubber band thin on the 255/30 profile and I thought it was probably due to that but oh no, run flats remain run craps and I should have just ditched them just like I did so on my X5 and 7 series earlier.

Mind you just to give you and idea on how harsh the run flats were , all 4 of my wheels were already slightly out of true causing a slight wobble seen during the tire balancing process!

BMW ought to switch these RFT's out, it's just not doing any justice to the ride quality in these bmw's!
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      11-17-2013, 01:15 PM   #13
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I sold the 18" BridgeSTONE RFTs as a 1st mod after test driving 2 different sport models and a non sport model before buying the sport. Next installed new 17" 393 F30 wheels with factory Conti all season RFTs. 17s are used on long road trips for overall comfort and as a spares. 18" PSS are used for the rest of the time. PSS have added comfort compared to the stones & the best grip of all. They aren't as smooth as the 17" Conti RFTs which slide when pushed.

I have installed new & used Bilstein HDs (3 sets of Koni set too) on several past vehicles ranging from 86 Accord to 06 EVO RS. Factory dampers suck.

I have installed poly bushings on several past vehicles ranging from my son's 86 Corolla to my wife's 08 IS250. Usually it's the forum known weak rubber bushings 1st. Poly bushings compliment any suspension. You will get some added NVHM, but it is usually outweighed the handling benefits and even tire wear.

I have no adjustable height coil over experience and usually don't lower cars more than 1".

I feel my car now needs a set of dampers. The OHLINS look good to me, but Bilstein seems practical. Anyone want to donate to my fund? PM me for my Paypal. Thanks in advance.
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      11-17-2013, 08:30 PM   #14
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I'm running kw v1 with 17" continental dws and the ride is much smoother and more forgiving than stock, especially over sharper obstacles.

One thing I noticed about the stock suspension on my car is that the bumpstops are pretty long and springy. Just from looking, it seems to me that the car nearly rides on the stops in the front and has limited travel in the rear. I think that's why some xi owners experience a "thumpy" ride on stock suspension. Since sharp bumps would make the stops slap into the shock mounts
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      11-18-2013, 09:47 AM   #15
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Speaking of RFT's this is pretty cool tech, wonder if it makes it into passenger cars?

http://www.youtube.com/watch?feature...&v=XptlYoqbIvQ
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      11-24-2013, 08:51 PM   #16
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this is extremely helpful - thank you - I'll probably go with the Continental Extreme Contact DWS, and get a spare - - any advice on where I could sell my run flats? I have 4 17inch Continental Contipro contact SSR 225/45R17 19H tires....would love to ditch them asap
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      11-26-2013, 10:56 PM   #17
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Originally Posted by ajsalida View Post
Speaking of RFT's this is pretty cool tech, wonder if it makes it into passenger cars?

http://www.youtube.com/watch?feature...&v=XptlYoqbIvQ
That is super cool.

Reinventing the wheel?
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      02-03-2014, 05:06 PM   #18
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My car had a new set of RFT Bridgestone's when I took delivery and on perfect roads the ride was perfectly fine but here in downtown Toronto it was absolutely terrible. It came time this fall to buy a set of winters and I elected to go with conventional Michelin Xi'3s and all I can say is it completely changed the car. Of course the winters are softer than performance summers but I could not believe the difference. I am definitely swapping my summers as well, it removed all the jarring rough ride without making the car too soft. Its a night and day difference and would strongly suggest you change your rubber before playing with your suspension setup. Just my 0.02
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      02-12-2014, 05:33 PM   #19
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Do non-RFT and Kwv1! There is nothing better (well probably better but this is verrry nice)
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      02-12-2014, 05:34 PM   #20
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Just my 0.02
Its .03 now... inflation
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