Quote:
Originally Posted by Mywifes335
Thanks! So 12mm is safer. 5mm won't have the same fitment issue because it's so thin?
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yeah....
Look at the Misc notes on that same link
-All BMWs use hubcentric wheels. When mounted to the car, the wheel rests on a lip instead of the wheel bolts or studs. The lip is usually 9-10.5mm in depth. The lip contributes to the strength of the wheel and the wheel cannot safely be used without a lip. The wheel bolts are not strong enough to support the weight and loads generated through the wheel.
Any spacer smaller than 10mm will not have a hubcentric lip on it. It's physically impossible since the spacer slides over the existing lip but is not thick enough to take the lip's place (the standard lip still protrudes through the spacer). With a 9mm lip, a 5mm spacer will only leave 4mm of stock lip left for the wheel to rest on. This is important to keep in mind when considering your wheel/spacer setup. A wheel with a beveled edge on the back will not adequately rest on the lip, resulting in a vibration because the wheel is not truly centered on the hub.
For most 5-lug BMW applications, Turner Motorsport offers a hub-extender. This takes the place of your hub's dust cap and adds an extra 10mm of lip for the wheel to rest on. Using the example above, instead of 4mm left over on the lip, you now have 14mm of lip to use. With the hub extenders, you can also change spacers around without fear of losing lip space - it can be used with a 3mm, 5mm, 8mm, or 10mm spacer.
Spacers with their own integrated hubcentric lip are: 10mm*, 12mm, 12.5mm, 15mm, 18mm, 20mm, 25mm, and 30mm.
* -- Note that H&R and Turner Motorsport each make a 10mm hubcentric spacer but due to interferences between the spacer and lip, it's best to leave this to specialized applications. The lip on the car must be shaved down so the 10mm spacer will fit flush on the rotor hat.