[nikpik]

Hey guys,

I just recently bought a 2014 BMW 435i M sport and it's been pretty great so far. Well, except for the ride quality which is pretty terrible. Every small bump feels like a medium one, medium ones feel like big ones, and big ones/potholes sound/feel like I just crashed my car. Obviously, I'm not going out and trying to hit potholes and I've been careful to avoid them but on SD streets, it's almost inevitable given how bad these roads are.

It's got 20 inch wheels on it and I believe they're the M Double Spoke Style 405 wheels. I'm pretty sure that's the main culprit, plus they look way too big for the car. I'm sure they'd look better on a lowered car but mine is at stock height. I personally value ride quality/comfort and performance over looks but it's nice to have the car look better too.

Does anyone have any wheel/tire recommendations? Are 18's better or are 19's the way to go? What would be the ideal size or wheel set for a daily driver with occasional spirited driving on back-roads/autocross?

I saw some BBS wheels (19x9.5 and 19x10.5) in the classifieds section. Would they be too big/wide?

Also, if anyone wants to trade for some 20 inch 405's (very light curb rash on one of the wheels) with basically brand new (less than 300 miles) Falken Azenis FK510, let me know.

[alohasurftoad]

all things equal 18's will have the best ride comfort. 19's are somewhat of the "happy medium" of appearance and ride

if you are staying with stock suspension:

if 18" i'd use 235/45/18 on 8.5" ET30-35 + 265/40/18 on 9.5" ET40-45

if 19", 235/40/19 on 8.5" ET30-35 + 265/35/19 on 9.5" ET40-45 rear

if lowering change tire size combos to

245/40/18 front, 275/35/18 rear or
245/35/19 front, 285/30/19 rear (on 10")

[nikpik]

Thanks for the info. I'm a bit confused though.

Why not have 245/40/18 and 275/40/18 on 18x8.5 and 18x9.5 on stock suspension? Wouldn't the tire size have to get narrower to accommodate lowering as opposed to stock?

[alohasurftoad]

Originally Posted by nikpik

I'm a bit confused though. Why not have 245/40/18 and 275/40/18 on 18x8.5 and 18x9.5 on stock suspension? Wouldn't the tire size have to get narrower to accommodate lowering as opposed to stock?

OEM tire diameter = 26.0"
OEM 20" staggered is 225/35/20(26.2")=255/30/20(26.0")

with a 245/40/18(25.7")+275/40/18(26.7") combination, the front vehicle height will be lower than the rear, causing a forward rake appearance and the front sidewall will be smaller and wheel gap will be larger than the rear.

if you want the diameters, sidewalls and tire gaps to be the same you need to choose the appropriate aspect ratio for a given width.

245/40/18(25.7") and 275/35/18(25.6") have a similar profile
245/45/18(26.7") and 275/40/18(26.7") have identical profile