Anyone know about wheel offsets?

[Audi_A4]

I went to the tire store to check out rims today for my bmw. I had heard that the 2006 3 series uses a special rim, and that the previous generation 3 serioes (1999-2005)wheels WILL NOT FIT. The guy at the tire place heard the same. He asked if I would not mind pulling my car in and he had some e46 wheels that fit. The offset is only 4mm different. my car has 17's ... I want 16's for the winter. the offset is 38 and new offset will be 34 or vice versa. Will this affect at all my handling, speedometer or anything with my car?

The wheel he tested is a 17" but he said there is no difference with the 16". They were also relived that they wouldnt have to order special wheels for just the e90.

So before I buy them, will they work or is the tire store pulling a fast one on me?

[Dirty Sanchez]

I'm sure that this topic is being discussed to death at any of the major bmw forums. or you could call tirerack. I'm sure they have testfit both the e46 and e90 and can make recommendations.

as far as stepping down in size for the winter... the only real advantage is minor cost savings. getting the correct tire for the conditions is more important, imo. If you're running multiple setups for summer and winter I don't recommend all-season tires... as they are a compromise in all conditions.

your speedo shouldn't be affected as long as you achieve the same rolling diameter of the wheel/tire. so with a 16" wheel you'll likely be putting on a higher profile tire to compensate.

[B3RACER1a]

What Crapus said. Also, as long as the wheel offset is really the only thing that is different, you'll change the width and scrub radius. I dont know what either of those are on that car. Width is fairly obvious, but scrub radius is a really big factor in the amount of feedback you get in the wheel. Agian, I'm not sure what the stock form is.

Where's M3? :)

[RacinM3]

The "vice versa" part is somewhat important. If the offset difference is toward the center of the vehicle, it could potentially cause caliper/wheel interference, if it's toward the outside of the vehicle, it should be fine as 4mm is very, very little. I mean, I have 15mm spacers on my 996 and still the tires don't rub on the fenders.

I know people say messing with different offsets can cause anything from bad handling to increased wheel bearing wear, but at 4mm either way, I seriously doubt if the car "knows" the difference.

Not sure if 16's are good or not. Did your car come with 17's? There might be some caliper clearance issues with 16's if so. As far as your speedo goes, that's a function of outside tire diameter, not offset, so offset won't affect it. Make sure whatever tire you go with has an outside diameter equal to (or very close to) the tires that are coming off the car.

Here's a post on bimmerforums where Jim at TireRack claims the offsets on the E36/E46/E90 3's are close enough not to matter: http://forums.bimmerforums.com/forum/showthread.php?t=369765&highlight=e90+offset

It's only 4mm. Either way, I'd bet they work. Congrats on the E90 (post a pic!) - that body style is growing on me - especially in this form:
http://www.netcarshow.com/bmw/2006-320si_e90_wtcc/1024x768/wallpaper_04.jpg
http://www.netcarshow.com/bmw/2006-320si_e90_wtcc/1024x768/wallpaper_05.jpg
http://www.netcarshow.com/bmw/2006-320si_e90_wtcc/1024x768/wallpaper_08.jpg