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[chris0628]

My E90 330i M-Sport has 18s and they are pretty harsh on bad roads which is the case most of the time since my route has changed.

Current Rear 255/35R18, Front 225/40R18

I'm thinking of downgrading to 17" (Staggered) and I'm ok with sacrificing a bit of handling

1. Any issues with the diff if I downgrade maintaining the same staggered ratio?
2. Which size(s) Wheel/Tyres should I go for? – I'm looking at a pair with 8Jx17EH2 and 8.5Jx17EH2

[streetpro]

I have gone from 235/265 R18 (8+9x18et40) summer tires to oem style 236 (8x17 et30) square 225/45R17... it drives just perfect... style 236 is around 9,5kg also semi light wheel...

[streetpro]

And they clear Performance brakes with 340mm discs easily...

[Volasko]

Originally Posted by chris0628

My E90 330i M-Sport has 18s and they are pretty harsh on bad roads which is the case most of the time since my route has changed.

Current Rear 255/35R18, Front 225/40R18

I'm thinking of downgrading to 17" (Staggered) and I'm ok with sacrificing a bit of handling

1. Any issues with the diff if I downgrade maintaining the same staggered ratio?
2. Which size(s) Wheel/Tyres should I go for? – I'm looking at a pair with 8Jx17EH2 and 8.5Jx17EH2

You logic is a little flawed, larger rims don't automatically mean better handling. If you're finding the ride particularly harsh it may be more to do with the run-flats than side wall height outright.

[Cole_E90]

I'd also be interested to know this for my E91, currently has 18s and wishing to drop to 17s.

[Soravia]

Skinny tires give better feedback. But that feedback is killed by your control arm fluid bushings and hollow sub frame bushings.
Ride comfort is between the dampers and tire side wall, including RFT. But once the bump is strong that spring can't soak up, the bump stop comes into play for ride comfort.

[K9Leader]

Originally Posted by Cole_E90

I'd also be interested to know this for my E91, currently has 18s and wishing to drop to 17s.

I've got 18x8 ET32 on my 2010 E91 X-Drive with run-flats and even small potholes are jarring. One rim is a bit bent after a really hard hit but is holding air. This is a daily driver/dog hauler so extreme handling is not the goal - good handling and better ride is my goal.

I'm looking at going with ARC-8s (Black Friday sale!) with non-run-flats (probably Michelin AS3s). I want a square setup so I can rotate front-to-back.

Looking for suggestions for width and offset - I want as close as possible to stock fit, prefer not to use spacers or have to make any adjustments. Options are:

17x8 ET20
17x8.5 ET20
17x 8.5 ET40
17x9" ET30
17x9" ET42
17x9.5" ET35
17x10" ET25

The 18s on it now are 18x8 ET32.

I'm leaning toward the 8 or 8.5 widths but not sure about the offset.

Any wisdom would be appreciated, especially if you have direct experience with such a setup. Thanks!

K9Leader
Newark, Delaware

[streetpro]

After some 2,5k km covered I can state that traction/stability is not an issue even with winter 225/45R17 all around... sure, when you floor it there goes a disco on the dash (DCT flashes up to 3rd-4th) however it is predictable and safe... no wild sliding or shitting yourself during turns or highway speeds braking...