the deflated tire and tube pretty well protect your rim unless you foolishly decide to maintain the skid to the point of completely ripping the tire apart or throwing it from the rim (neither of which i've ever been unlucky enough to do)--which might be tough to do. if you stop skidding, ride out of it and tend to the wheel, you shouldn't destroy the rim. maybe i'm just not neanderthal enough about it. good bike components are pretty durable and/or repairable. perhaps i've just been fortunate about that though.