[lowrydr310]

I'm speculating here, but just wanted to understand how much tires and alignment affect ride quality.

I owned a 325i standard suspension before, and for the past 3 years have been driving a 330i with sport suspension (equipped with brand new Bilstein B4 struts/shocks & mounting hardware.) The car handles incredibly well, exactly what I expect from a BMW.

A few weeks ago I bought a 2007 E93 335i. The car had the original suspension (150K miles) and rode like crap. It sat low because of disintegrated bump stops which looked nice squatting about 1-1.5" lower than where it should have been, but the ride was awful and it scraped when pulling into my driveway. I immediately installed new Bilstein B4 struts and shocks along with new mounts and bolts, new tie rods, new M3 thrust arms, and M3 wishbones. I know I need an alignment, which I have scheduled along with new tires that I'm waiting on for delivery.

When installing the new tie rods (Lemforder) I measured the number of threads from the old ones and assembled the new ones with the same number of threads exposed plus an additional 3.5 turns out to roughly compensate for the additional toe in caused by the M3 wishbones, just to be driveable to the alignment shop.

I can definitely feel the toe isn't set correctly as the steering is vague and wants to wander but what's really bugging me is this springy/bouncing feeling from the front when going over rough roads, almost like there's no dampening. The tires on the car aren't matching (two emergency replacements due to flats by the previous owner) and one of the fronts isn't even the right size (235-45/18) so that will all be addressed soon, but id like to know if there's anything else that I should be looking at which could cause this bouncy feeling.

Is the E93 just that much more flexible than the E90 that it feels bad by comparison?

[whyzee125]

Interesting observations here. Tires and alignment do affect the ride quality but I wouldn't think they would ever cause an underdamped feeling. Possible you're experiencing chassis flex or that you received some bad struts. By any chance are the strut braces missing under the hood?

[lowrydr310]

Originally Posted by whyzee125

Interesting observations here. Tires and alignment do affect the ride quality but I wouldn't think they would ever cause an underdamped feeling. Possible you're experiencing chassis flex or that you received some bad struts. By any chance are the strut braces missing under the hood?

Nope, strut braces are all in place.. One of the front tires is the wrong size with too thick of a sidewall relative to the other (235/45 vs 225/40) My toe is awful too, so I suspect when going over rough roads the front tires are fighting each other for traction and to keep it straight. That same tire also sounds cupped; I thought maybe a bad wheel bearing but hard to tell until I get the new tires and the alignment. I'm not going to worry until I get that sorted first.

[lowrydr310]

Last week I installed a new set of Michelin Pilot Sport 4S tires and got a proper alignment. The overall feeling of the car is significantly improved, though there's still a bit of that front end bounciness that I described in my original post. It's fine on smooth roads and the suspension is definitely working to dampen bumps/dips, but when I'm on a rough road surface (which there are plenty in L.A.) it just has this flex/bounce that I don't feel with my 330i sedan on the same roads.

It may just be chassis flex that's characteristic of a convertible. Now that I think about it, I remember a very similar feeling when I got a brand new Mustang GT convertible as a rental, and again with a Camaro convertible.

I can't really think of anything else that would cause this. It's possible but extremely unlikely that I have bad brand new struts or mounts even. The only front suspension components I didn't replace yet were the swaybar bushings. I didn't think that would cause this feeling, but it has me wondering now since the 'bounce' feeling seems like the left and right front suspension components are fighting each other on rough road surfaces. The bushings don't look new, but they're not clunking or squeaking.

There isn't a whole lot of info about this on the forum here, except a recent post by forum member hellokitty discussing some E93 suspension upgrades. One thing that stands out was the improvement of adding the M3 strut braces. I may look into doing this.

[hellokitty]

Originally Posted by lowrydr310

Last week I installed a new set of Michelin Pilot Sport 4S tires and got a proper alignment. The overall feeling of the car is significantly improved, though there's still a bit of that front end bounciness that I described in my original post. It's fine on smooth roads and the suspension is definitely working to dampen bumps/dips, but when I'm on a rough road surface (which there are plenty in L.A.) it just has this flex/bounce that I don't feel with my 330i sedan on the same roads.

It may just be chassis flex that's characteristic of a convertible. Now that I think about it, I remember a very similar feeling when I got a brand new Mustang GT convertible as a rental, and again with a Camaro convertible.

I can't really think of anything else that would cause this. It's possible but extremely unlikely that I have bad brand new struts or mounts even. The only front suspension components I didn't replace yet were the swaybar bushings. I didn't think that would cause this feeling, but it has me wondering now since the 'bounce' feeling seems like the left and right front suspension components are fighting each other on rough road surfaces. The bushings don't look new, but they're not clunking or squeaking.

There isn't a whole lot of info about this on the forum here, except a recent post by forum member hellokitty discussing some E93 suspension upgrades. One thing that stands out was the improvement of adding the M3 strut braces. I may look into doing this.

What components are you running? I sold my 335is a couple of years ago, but it sounds like your front dampers are a bit too soft. The only thing the M3 strut braces added was responsiveness to the car, but it doesn’t help with vertical bounce. That’s a spring and damper issue.

[lowrydr310]

Originally Posted by hellokitty

What components are you running? I sold my 335is a couple of years ago, but it sounds like your front dampers are a bit too soft. The only thing the M3 strut braces added was responsiveness to the car, but it doesn’t help with vertical bounce. That’s a spring and damper issue.

I kept the stock springs (sport suspension) and installed B4 struts. I used the appropriate struts for the sport suspension, but one interesting thing is that Bilstein lists the same strut for the E90 sedan and E93. These are the exact same struts on my 330, yet the 335i has the stiffer D8 springs in the front.

I think I may be exaggerating the "bounce" I'm describing. The car is perfectly planted and handles very well, it just has a flex or side to side springiness on rough road surfaces. I can't recall the post (yours maybe?) but someone else said the E93 feels more like a touring car compared to the E90 and that's very accurate. The E90 feels lighter (it is) and handles better. I might just be experiencing open top convertible chassis flex that isn't present in the E90 despite all the reinforcements and bracing.

The guy who does my alignments specializes in track cars and races himself. I described the behavior and prior to and after the alignment he tested my car and said everything felt normal.

[hellokitty]

Originally Posted by lowrydr310

I kept the stock springs (sport suspension) and installed B4 struts. I used the appropriate struts for the sport suspension, but one interesting thing is that Bilstein lists the same strut for the E90 sedan and E93. These are the exact same struts on my 330, yet the 335i has the stiffer D8 springs in the front.

I think I may be exaggerating the "bounce" I'm describing. The car is perfectly planted and handles very well, it just has a flex or side to side springiness on rough road surfaces. I can't recall the post (yours maybe?) but someone else said the E93 feels more like a touring car compared to the E90 and that's very accurate. The E90 feels lighter (it is) and handles better. I might just be experiencing open top convertible chassis flex that isn't present in the E90 despite all the reinforcements and bracing.

The guy who does my alignments specializes in track cars and races himself. I described the behavior and prior to and after the alignment he tested my car and said everything felt normal.

It is most likely normal. You are not running track oriented suspension components, so there will be some float on uneven surfaces as the damper tries to absorb everything to avoid beating you up.

Stock springs and B4 is really OEM+. You'll get more performance out of a B16 setup at the cost of comfort.

[lowrydr310]

I had a suspension specialist look at everything and test drive my car. This is a driver with thousands of hours of track time. He stated that it felt fine and was nothing to worry about. I think the E90 is just that much stiffer. I have an easy way to confirm - drive my friend's E93 335is with stock suspension.

Also, while my E90 330i has M3 tension struts with the solid rubber thrust bushings, it has standard (non-M3) wishbones. My E93 has both the M3 tension struts and the M3 wishbones, which may be transferring slightly more of the bumps and harshness from the road throughout the chassis, specifically through the steering wheel. I can confidently push the car in spirited driving and never does it feel unstable. It's just slightly uncomfortable on rough straight roads, but I didn't buy this for comfort.