As per the name. Space the wheels out.
If they're too big and not hubcentric they can damage the hubs. However when used in conjuction with longer studs etc (as spacing the wheels, you're ultimately losing some of the amount of thread you tighten the nut up on, so longer studs are needed), they are perfectly safe. (On various ZR Rally cars I've built, if you run 15"s coupled with a big brake conversion you usually have to run 5-10mm spacers to clear the calipers).
Also, On the rear wheels, the limit of spacing depends on how strong and long the wheel studs are. As alot of the guys in the Euro/Cleaned scene space their wheels 40mm+ at times to get a wider stance, and just use uprated studs to cope with this.
Spacing wheels also affects wheel camber aswell, thus increasing tire wear.
If they're too big and not hubcentric they can damage the hubs. However when used in conjuction with longer studs etc (as spacing the wheels, you're ultimately losing some of the amount of thread you tighten the nut up on, so longer studs are needed), they are perfectly safe. (On various ZR Rally cars I've built, if you run 15"s coupled with a big brake conversion you usually have to run 5-10mm spacers to clear the calipers).
Also, On the rear wheels, the limit of spacing depends on how strong and long the wheel studs are. As alot of the guys in the Euro/Cleaned scene space their wheels 40mm+ at times to get a wider stance, and just use uprated studs to cope with this.
Spacing wheels also affects wheel camber aswell, thus increasing tire wear.