[neusaab]

Well, these are my observations since swapping out for H&R sports springs while retaining the stock dampers on my 07 335xi. As expected, of course, the ride is firmer, as overall travel is significantly diminished. Turn-in is quicker, and body roll less, unsurpisingly. The ride quality, day-to-day, on my local road commute, is acceptable. Rebound damping is generally OK.

Problems include the following: the stock dampers cannot keep up with the necessary rebound damping on large amplitude undulations at highway speed. Bounce, bounce, bounce. Sometimes practically skull-to-headliner.

My biggest issue is with bigger hits at any speed, be they potholes, dropoffs, or stepups on the road. BANG! Sickening, whole chassis slamming from the front. I have stock 18's and runflats. This also happened with my winter setup, 225/45/17 Dunlops. I'm shocked that I haven't yet bent and wheels significantly enough to notice.

Do I have some other unrecognized issue? Might this simply be the front supension blowing through the shortened front travel, overwhelming the compression damping of the front shocks? A friend mentioned something about shaving bump stops; is this necessary and will it help? Will replacement, matched dampers solve my problems, or at least mitigate them?

Thanks for your thoughts. I lowered an e46 in a similar fashion previously without this level of stomacheache.

[mike-y]

sounds like you are bottoming out/hitting the bump stops. these cars have little front travel as it is, and putting on a lowering spring without compensating with compression damping, and a shorter bump stop means you will bottom out a lot easier.

[twinship]

Same problem here... I'm planning to install Koni Yellows soon.

[subieworx]

new shocks wont fix the issue outright. You need to change out the bump stops to shorter ones to make it work and even then it is still not enough overall bump travel.

[Gemstone335]

Same problem as well. I originally had the 17" factory run flats and the occasional whack would be quite unnerving. Then I put on conventional 17" Blizzacks for the winteer and it got a bit better. But I changed over to 18" Conti extreme contact DW tires about 4 weeks ago and it made a huge improvement. No more gitting my teeth over the potholes. No it did not get rid of all the issues but it is entirely acceptable. Of course it did not solve the damping/undulation issue. I've read the Bilstein sport shocks are designed for use with lower springs. I plan to get those once the factory shocks are shot.

[Amused]

I am running the Bilsteins with Eibachs and the ride is great. I know the H&R's are a little stiffer but willing to bet the ride quality will be fine.