[dch37]

Hi Folks,

long-time reader, first time poster here.. I did try the search, here and in other forums, but the answer still eludes me.

I have a 2010 335i Xdrive Coupe with the m-sport pack.

I need to get new tires, but the factory sizes (225/40/18 and 255/35/18) are not available in my region.

A slightly taller ones are available (225/45/18 and 255/40/18).

At the same time I will be changing my shocks, either Bilstein HDs, or Koni Yellows. I don;t have plans of dropping the car (need to drive to the ski slopes, and the kids around).

I am aware of the following:
1. The larger tires will result in a change in speedo readings, slightly reduced acceleration, softer ride, no fitment problems (rubbing, etc...)
2. the new shocks will be stiffer.

So here goes the question:

Would the "harder" shocks compensate for the "softer" tires? What handling characteristics should I expect from the setup?

Regards,
D

[dch37]

I just found a set with the right specs... but I am still interested in the answer.

[ajsalida]

That is a very interesting question. Many of the issues with Xdrive "suspension" are actually due to the runflat tires, and other compromises made with springs and shocks for AWD ride height. Lots of people get rid of the run flats and find the overall suspension feel to be much more compliant.

So to address your question, if you had gone with taller run flats they would be somewhat softer. Better shocks are not necessarily stiffer, especially the Konis, and what you'd find regardless is better control and therefore better ride overall.

The thing about XI suspension is to get the XI ride height and clearance, BMW went with stiffer springs. So a lot of what feels stiff in the car, beyond the tires, is the springs. As you know the shocks are pretty soft, perhaps to offset the stiffness elsewhere.

This may or may not be news to you but many feel that BMW did not exactly do a great job with the XI suspension, myself included. Also there is no such thing as a "sport" XI suspension. They all have the same one. Sport package is just seats and trim on the XI, no susp changes from non-sport.

[dch37]

I am on non-RFTs now. The new ones will be non-RFTs as well. I can't complain from the ride. IN fact I do get a tad ticked at the body lean during cornering. This was my major concern with getting higher profile tires. I run 225/50/17 as my winter setup and the first few days I feel like I am driving over thick moss...

now that I found the right tires, I have to pick the shocks... the threads so far have been inconclusive... the epic questions of FSD vs Yellow vs Bilstein HD still remains

[ajsalida]

Lot depends on where you want to go after shocks. FSD's seem to be well liked by people who don't want to lower the car or do other suspension mods. I am partial to the Koni yellows. Once you start with ant-roll bars things get complicated and more opinionated.

Good that you are reading, lot of info out there, and XI susp. is something of a bear to get sorted out once you start modding.

[dch37]

Yup.. my wife is already looking at me strange..