[X3andZ4owner]

Im thinking on putting spacers on the X3, 10mm on the frontwheels and 15mm on the rearwheels.

Does spacers damage the bearings?

Anyone who have put spacers on the X3 ? If yes whats your opinion ?


http://www.burgertuning.com/BMW_wheel_spacers.html

[Lotus7]

On a "good-sized" car like the X3, a 10mm or 15mm offset is hardly noticeable visually, but is enough to slightly increase wheel-bearing loading. Probably not enough to reduce the bearing life significantly. There are other issues, however. The offset changes the "Ackerman" geometry so tracking is affected and tire wear is increased, and handling is slightly compromised in low speed, low radius turns. Wheel camber is not affected, but caster is, so technically the car becomes mis-aligned, unless the front wheel alignment is corrected.

The X3, like the 3 and 5 Series uses a multi-link rear suspension that actually includes some positive bump-steer components, designed to improve rear stability on undulating road surfaces. It's part of what makes BMWs handle so well. Audi also is using similar rear suspension geometry. Changing the hub offset by 15mm will definitely change the optimized dynamic wheel motions and the wider wheel spacing won't compensate for the geometry errors.

If you’re racing and really need the track-spacing improvement and are willing to do the appropriate realignments and probably add a lot of negative camber, it’s something to consider. The spacers also are appropriate if you're using aftermarket wheels that don't have enough "built-in" offset.

For street use, for only appearance purposes, it seems to me to be too much of a performance compromise.

For the X3 (F25) BMW recommends sticking to the stock wheel offsets within +/- 2 mm. They have good reasons for that recommendation.

[X3andZ4owner]

Originally Posted by Lotus7

On a "good-sized" car like the X3, a 10mm or 15mm offset is hardly noticeable visually, but is enough to slightly increase wheel-bearing loading. Probably not enough to reduce the bearing life significantly. There are other issues, however. The offset changes the "Ackerman" geometry so tracking is affected and tire wear is increased, and handling is slightly compromised in low speed, low radius turns. Wheel camber is not affected, but caster is, so technically the car becomes mis-aligned, unless the front wheel alignment is corrected.

The X3, like the 3 and 5 Series uses a multi-link rear suspension that actually includes some positive bump-steer components, designed to improve rear stability on undulating road surfaces. It's part of what makes BMWs handle so well. Audi also is using similar rear suspension geometry. Changing the hub offset by 15mm will definitely change the optimized dynamic wheel motions and the wider wheel spacing won't compensate for the geometry errors.

If you’re racing and really need the track-spacing improvement and are willing to do the appropriate realignments and probably add a lot of negative camber, it’s something to consider. The spacers also are appropriate if you're using aftermarket wheels that don't have enough "built-in" offset.

For street use, for only appearance purposes, it seems to me to be too much of a performance compromise.

For the X3 (F25) BMW recommends sticking to the stock wheel offsets within +/- 2 mm. They have good reasons for that recommendation.

Thank you for the very good in dept explanation. Guess I won't put spacers on the car. The intention of putting spacers on was merely cosmetic.

[Lotus7]

Yes, on many "older" cars with less sophisticated suspensions, spacer rings are OK and don't cause any real problems except for the extra vertical torque loading of the outer wheel bearings. On "newer" vehicles with advanced, multi-link suspensions, adding a spacer to change the track width, changes the carefully designed suspension geometry and is counterproductive.

On almost any "modern" car, the only "correct" way to get the "wide stance" look is to go to wider wheels, that maintain the correct track centerline width.

Basic wheel specifications for the X3(F25) chassis are:
Bolt Circle = 5 X 120mm
Offset = 45mm (43 to 47mm acceptable)
Hub centering Bore = 72.5 mm (hub ring dia. = 72.47mm)
Bolts = M14X1.25 Spherical seat, 17 mm heads (Note the X3(E83) uses M14X1.5 bolts)
Minimum bolt engagement = 9.5 turns