[squidlyboy]

Seems like folks in this forum are constantly asking questions about fitment and offset over and over again. But one thing i've noticed about the F30 forum is that there are not a lot of stickies about this subject even though in other forums, its usually the first thing they sticky. In general, as far as F30's go, i don't see much stickied at ALL This is the one thing that to this day, complete BAFFLES me... especially when there are SO MANY of us.

Here are the links that pretty much turned on the lightbulb for me when i first started researching it.

Part I
The first one from Turner that explained the nuts and bolts about fitment and offset, and how they inter-relate, with an emphasis on BMWs. Lots of examples with pictures to boot!

Part II
The second one (calculator) was essential to tell me if what i wanted to go FROM to what i wanted to go TO was going to work. It tells you everything from speedo differential to how much extra "poke" and "stretch" you'll have

Part III
You know the wheels/tires you WANT. The last thing you need to know is what you are STARTING WITH. Sometimes, knowing what your stock car has is harder to find than you would think. This one is actually stickied, so here you go.

The only other factors that i feel needs to be covered that would affect fitment/offset is is

• ride height / lowering your car (more of an art than science)
• camber and (to a lesser extent) toe
• spacers and how they affect "effective offset"

What other resources have you guys found was helpful to you? Anything better? For me, it was these links that pretty much did the trick.

[613Bimmer]

Awesome post! Hopefully this will clear up a lot of confusion for people trying to check the fitment of a new set of wheels/tires. This should be stickied IMO.

*cough cough* MODS!

[mithoowani]

have bought new 2014 435 cab with 19 BMW rims; does not have M brakes; looking to buy winter tyres, would appreciate any help re the right sixe tyres. Do I buy 18 in or 17 in rims? looking to buy after market replica rims.

[squidlyboy]

This question seems to get asked a lot as well. There's actually a pretty easy way to determine what you need. There's a simple trick you can use. But before we get to that, to get some good background information on spacers, start here - i found this article (again from Turner) to be pretty informative:
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go to the link to read the rest of it - very informative!

Here's the trick that Turner describes to do a quick and simple measurement to determine what size spacers you need. You'll need 3 things:

1. Some electrical or masking tape
2. A quarter
3. a metric ruler

Hang the tape off the side of your fender (red line), then hang the quarter at the end of the tape. Wait for it to stop swinging. Grab the ruler and hold it against the tire and measure the distance (in mm) from the edge of the tire to the tape. THAT is how big your spacer needs to be in order to be FLUSH. If you want to be conservative and not go full flush, back (subtract) off a few mm to be safe.
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If you are riding on stock height, you really can take some liberties as your chances of rubbing are going to be very low. Notice that if the tire were pushed so far out, that it extended/poked out past the fender, there is still very little chance you would rub (unless you hit some huge pothole or go over a speed bump fast). But you really have some leeway there.

However.... if you are lowered ....

If you are lowered, you'll have more of a situation like this. Notice now that if your tire gets pushed out too far, you will hit the bottom of the fender. Here, you will need to be more careful as you don't have as much leeway as the stock ride height situation
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In this case, the tape trick will still work, but you'll probably want to back off a few mm just to insure that when you hit bumps, potholes, and other excursions in the road, that your wheels don't scrape against the bottom of the fender.

The beauty of this trick is that you don't even need to know what your original tire/wheel specs are. Since you are just interested in what size spacers you need to get you to flush, you are only interested in the DIFFERENCE between original tire line and new tire line. This DIFFERENCE is the exact size of the spacers you need.