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Old 10-04-2012, 02:30 PM   #3
Registered User
Join Date: Apr 2010
Location: Murrieta, CA
Posts: 9,243
My Ride: '94 325iC & '00 323i
19s are on the verge of being too big for the car, much of the problem being weight and some of it being that the tire options are seriously limited and the options available should be expensive. The car takes a 225/45x17, so if you wanted to use a 225 on a 19, then you would get a 225/35x19, the 225/40x19 will be too tall. You might find that there is no such thing as 225/35x19, but you can look on to see if it is an available size.

Moving on...

The factory wheel is a 7.5x17 (width x diameter). There are other options, but this one has an ET of 41. ET is the distance from the surface that fits against the hub to the centerline of the wheel. I get a bit turned around, so feel free to correct me on this next point -- If a 7.5 wheel takes an ET of 41, then an 8.5 wheel should see the ET at about 47 to 50. The idea is that as the wheel gets wider, you need to move the plate in the center of the wheel to maintain the same distance to the centerline. If the wheel is wider and the ET is the same, then all of the new width is pushed outboard, if the plate in the center of the wheel is also pushed outboard, then the wheel is drawn in to maintain clearance with the fenders.

If the ET is low then the tires will be moved outboard where the issue is that they can strike the fenders, if the ET is high then the tires can strike the suspension components. Tires striking anything other than the ground is usually bad, and in some cases striking the ground is even worse than hitting stuff on the car.
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