Loseph

the fact that they come with bolts that bolt the spacers to the wheel hub and then you use your OE bolts to bolt the rims to the spacer. They are a great product no vibration and the install is super easy.

arnick'02-6spd

also weight.

allroadCole

with hubcentric spacers the bolts don't support any weight, they just hold the spacer to the hub and the hub to the wheel... they are only stressed in this >---< direction, the bolts should not support any of the cars weight.
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In addition the spacers bolt to the hub, and then the wheels bolt to the spacer, and with some spacers (like my 20mm H&R) they use all stock bolts, so the bolts are not longer, you just have twice as many...

And as I said earlier, if you are using spacers to keep the <B>stock</B> offset you are not changing the geometery, you are using a spacer with a new wheel with a different offset so you can keep the stock geometery. (Obviously if you use spacers on stock wheels you are changing the geometery, and can risk wearing out wheels bearings or what ever else)

anytime you add another part there is one more thing to go wrong or break, but if I needed spacers to keep the origninal geometery, I <i>personally</i> would not sweat 20-30mm, but thats just mho...

paulroad

the footprint was covering a 8" path..in theory say 4 inches off center each side. Now you have a 9" wheel. With the proper spacers you now have 4.5" off center of each side. And this is figuring that the footprint of the wheel is in the centerline of the hub assembly. The geometrical forces..banking turns..is changing. If its a negative I have no clue..its only a caution to the change itself.

allroadCole

but that is a change related to tire width, not the spacer. (i.e. no change if using 7.5" wheel)