Drives: 2007 328i, 1998 328i
Join Date: Jan 2007
Location: San Francisco Bay Area, California
Got my car back last night, and did some more driving today. Here are my first impressions. I hope you'll excuse me if I go into detail.
First I have to separate bumps into two categories. There are bumps that cause an impact, a noise, and there are bumps that do not -- smooth bumps.
First, impact bumps. At low speed, these cause more noise. I'm still able to ripple over many small bumps without an impact, but when impacts occur they are louder and there's more vibration making its way to the body, which sometimes excites a couple noises on the passenger side that I've had for a while -- ever since the front M3 control arms went in, actually.
For the non-impact bumps, it's brilliant. The car moves over bumps gracefully and corrects quickly. At low speed it's a busy ride, but not exaggerated and uncomfortable like before.* I would just say the suspension reacts fast to an uneven road, and occasionally that causes a vertical acceleration that is uncomfortable. No more so than the non-sport E36 that I've been using as a benchmark. In fact I'd say, comparing the non-sport E36 to the M3-sprung, M3-valved E90, that they are very similar in character. But the E90 body moves less and corrects faster. Same or nearly-same comfort level. This is on an uneven road; on a smooth road any car is comfortable.
* My complaint with the stock 07 328i ZSP suspension, aside from the miserable tires, is the constant, exaggerated vertical accelerations. It is not a smooth ride at all.
On the freeway, the E90's sublime. I can't think of anything that could be improved. Reactions are quick, the ride is controlled, movement is minimal, and overall feel is soft. There are no instances of discomfort like there are at low speed. Very smooth.
With the stock ZSP and with the performance suspension, the E90 used to compress into large freeway bumps and then launch out of them, raising me off the seat. No more. Now the car compresses into the bump, and that's it, it's over. The rebound after the compression is damped and you feel nothing.
I paid special attention to pitch on the freeway. Cruising at 80 there's no perceptible pitch, it's completely flat, just perfect, at 65 there's a small amount. I have to glance at the door sill against the ground to notice it. The spreadsheet says the "flat ride" tuning is optimized for 62 mph.
There's significantly more road vibration in the steering wheel. Unfortunately it's not useful, it doesn't count in my book as "feel"; but I don't mind it. I was hoping for some torquing and movement of the steering wheel when going over large undulations, esp. on the highway, but it's largely unchanged from before. There is some feel there, but it's muted.
I made one sweeper turn on my way back, and was impressed by grip and lack of roll. I got an impression of STICK like the tires were glued down. But the main thing is the car didn't jounce over the long bumps during the turn. I wasn't slipping at all, so I wasn't even close to testing limit behavior. I will do more testing of steady state turns soon.
At low speed, around town, operating at 6/10, my assessment of roll and body movement is that it doesn't occur. You really have to yank the car to get it to move. At high speed, there is still a slight delay on turn-in if you make a significant input. Small inputs are flat and immediate, but I'd say that was true before too.
My overall assessment so far is that the freeway ride is perfect, and that I hope the rattles and impacts at low speed can be softened a little bit by changing to goflat tires, and/or by breaking in the seals of the Bilsteins.
Here is the equipment that got installed:
Supersport SUFT015 upper spring plates (lowering perch) with no upper rubber piece
E46 front strut mounts
Bilstein struts and shocks, valved to Bilstein's M3 "HD" tuning.
Front spring from 335d, around 150 - 156 lbs/in
Hyperco 525# racing spring with AST height adjuster and Swift nylon bearings
Rubber spring seat for isolation in the camber link
M3 rear camber links
I'm running this on 16" wheels and original runflat tires. I will change to goflat tires soon. All my other equipment is in my sig.
More testing, photos, and measurements to come!
2007 328i ZSP. M3 suspension
: custom valved Bilstein shocks, Hyperco race springs, M3 lower control arms front and rear, M3 sway bars, and M3 subframe bushings. E46 front guide supports. Euro tail lights.
Last edited by luckyu; 11-18-2011 at 05:25 PM.
Reason: some rewording