[RED92LX50]

If you do a search on Yahoo or Google with "Wheel Spacers" you can find some neat stuff - some guy wrote a thesis on the mathematics of shear-stress or whatever, and that using washer-style spacers (of any thickness, but especially over .25") is very dangerous. In short, you are no longer mating the wheel to the rotor and getting that direct contact is important - if you use a washer style spacer, all of the force is transferred to the studs, and under hard brakeing or acceleration can break.

The spacer which bolts to the hub, then you bolt your wheel to the spacer is much better, but they are usually 1.25" thick to accomodate the studs holding the spacer to the hub - without sticking out so far that you can't mount your wheel. But these throw off your suspension geometry - as opposed to getting a wheel with the proper offset/backspacing.