Too much body roll. Why? Is there a solution?

[TagMan]

As wonderful as the 135i really is, there is definately a lot of body roll in hard cornering. What's the real culprit? More importantly, what can be done about it?

Any ideas or suggestions?

[M3_Dust]

coilovers and swaybars, I'm sure they will be readily available soon.

[TagMan]

Is that a solution that a franchised BMW dealer can take care of? Would it make the ride harsh?... because otherwise, the ride quality is now surprisingly good.

[plien69]

I think any solution to "tighten up" the suspension would involve a trade off in ride quality.

I remember reading an article about the 135i in Roundel where the author interviewed a development engineer about the understeer reported by journalists during previews of the 135i. The engineer said that they specifically went with a thinner rear swaybar to compensate for the shorter wheelbase in order to improve ride quality, at the expense of rear roll stiffness.

[Sherifftruman]

I imagine that a swaybar would not make the ride too much harsher as it really only comes into play in an actual corner. I know I did not notice any harshness in the MINI when I did my rear sway, then again, the suspension is about as harsh as it can be from the factory, so that may not be the best test.

[Disasterpiece]

Drop it and sway bar will do the trick.

[doubleA]

I think part of the reason your not satisfied is due to the lack of the sport suspension. This really makes a big difference, and according to your sig, you don't have it. It's not really a big deal though, as others have said a drop and a sway bar will do wonders.

[plien69]

All 135i's come with the same suspension, the M-Sport suspension, regardless if whether it has the Sport Package or not.

On the 135i, the Sport package adds only: shadowline trim, sports seats, M Sport steering wheel

[Jewpac]

Originally Posted by doubleA

I think part of the reason your not satisfied is due to the lack of the sport suspension. This really makes a big difference, and according to your sig, you don't have it. It's not really a big deal though, as others have said a drop and a sway bar will do wonders.

All 135i's come with a sport suspension.

[doubleA]

^^ Thanks guys, I guess I need to do more research! I really thought the sport package included a tightened suspension lol.

[Jewpac]

Originally Posted by doubleA

^^ Thanks guys, I guess I need to do more research! I really thought the sport package included a tightened suspension lol.

On most BMW's it does. I was confused about this before ordering my car, due to the difference in price of the sport package on the 128 and the 135, so I checked into it and the 135 has the suspension already.

[SCA1]

Thicker rear sway bar will definitely improve cornering by reducing/eliminating understeer. Non-runflat tires should improve the ride quality significantly. So I'd guess any reduced ride quality from the bar would be outweighed by the new tires.

That is my plan anyway.

[Robert]

I would try a thicker rear sway first.

[atr_hugo]

To fix this, something is going to have to be dithered with in the suspension. So I'm moving this to the suspension section.

[coolguy]

Originally Posted by robert

I would try a thicker rear sway first.

Do you know the bmw rear sway bar part no from the performance catalogue? My dealer doesn't know about it. Are you thinking about the ones from H&R and others? I am not sure about the fav one for 335i though.

[kevintran]

are we talking about the front or rear sway bar. Body lean is NOT always bad as most may think. A thinner front anti-sway bar may help the front stick better even though it may seem like your car handles worse. a bigger rear anti-sway may cause some inlift and cause you to loose grip in the rear. Good handling and feeling like you handle better are two different things. Just something to think about.

[adc]

Originally Posted by kevintran

are we talking about the front or rear sway bar. Body lean is NOT always bad as most may think. A thinner front anti-sway bar may help the front stick better even though it may seem like your car handles worse. a bigger rear anti-sway may cause some inlift and cause you to loose grip in the rear. Good handling and feeling like you handle better are two different things. Just something to think about.

Pretty sure the 135 will hit the bumpstops in very hard cornering (track etc.). My 330i ZHP did when stock, and it had a harder suspension than the 1.

A set of sways took care of that problem without altering the ride quality significantly. It's not like the sways available for non-race cars make the car lift a wheel during cornering... you still have similar suspension travel - just not on the bump stops.

Besides this, the front and rear lean rates must be balanced in order for the car to feel right (neutral). I think a rear sway (or perhaps front + rear combo) will help the 1.

[kevintran]

For sure! Im just trying to diffrentiate between how well a person may feel the car handle vs how well it actually handles. Then again I am coming from a FF Civic community lol

[SCA1]

My Cooper S had slight understeer that was completely eliminated by adding a bit thicker rear sway for about $150. Gave it totally neutral cornering. I'd bet the same approach will work on the 135 once one of the tuning companies works out the right bar specs.

[aesthetect]

Originally Posted by plien69

I think any solution to "tighten up" the suspension would involve a trade off in ride quality.

I remember reading an article about the 135i in Roundel where the author interviewed a development engineer about the understeer reported by journalists during previews of the 135i. The engineer said that they specifically went with a thinner rear swaybar to compensate for the shorter wheelbase in order to improve ride quality, at the expense of rear roll stiffness.

and i bet the exact swaybar they had engineered that provided more rear roll stiffness and more neutral steering at the expense of ride quality is the one listed under performance accessories, once it gets to the dealer. that is definitely where i would start. then, if that's not enough, start beefing up your spring/damper rates..

[ersatzS2]

Interesting article in the current issue of 'Sportscar' (SCCA's magazine) by Randy Pobst, possibly the best/most successful sedan racer in the US. He describes how he likes his cars sprung as softly as possible, and says many racecars he tries are too stiff, (and seem to get stiffer the closer they get to Stuttgardt) When the springs are too stiff, he says, it leaves only the tire sidewall to absorb changes in cornering loads. This overheats and overworks the tire sooner than if the suspension had a more progressive loading. I thought that was kind of a nice iconoclastic insight relative to conventional wisdom...

[Guibo]

This is from edmunds.com's first drive:
"Thanks to an added measure of structural rigidity from the coupe's body shell, the car has more forgiving rates for its springs and dampers than the hatchback, although for marketing purposes it is described as an M-sport arrangement. The result is a more compliant ride, although the stiff sidewalls of the run-flat tires continue to generate an inordinate amount of noise on less-than-smooth road surfaces, notably at the front end."

So it seems the M-sport suspension in the 135i isn't as aggressive as other BMW sport suspensions. At least not for the 1.
This is also reflected in some British tests, and their B-roads are notoriously cambered and bumpy. BMW engineers their cars for RHD markets, but from past tests of 1- and 3-Series with the sport suspension, it seems they don't retune the suspension for a particular market, at least not for the UK. Perhaps they figured a compromise for all markets would be good enough, and this seems to be the case: the 135i rides better there than the hatchbacks. Short wheelbase, low-profile runflats, and a sport-tuned suspension can ruin the ride in a hurry.