Originally Posted by BlazinB4
first off, teflon will make you car alot more free, since metal creates friction. i run the rubber bearings that they make i all my cars (including my tc3 that i run on carpet), but i take the shields off them. so, to anwer your question, metal shield will probably keep the fibers out alittle more, but the car wont be as free. i say probably because im not 100% sure, ive never tried the metal shielded bearings. but, for $1.00 a bearing it wouldnt hurt to try yourself.
Actually, since the metal sheild does not touch the inner balls or the race, metal shields do not add any friction to the bearing (unless it's a poorly made bearing). Teflon sheilds do slightly rub on the inner balls and this will cause more friction on the bearing (at least until the bearing breaks in). Once broken in this is not a problem. But as the bearing gets older, i have noticed that the teflon sheilds have a tendancy pop out quite easily.
Teflon sheilds will keep out dirt and carpet fibers much, much better than metal sheilds. Metal sheild will also dent and when they do the bearing is shot.
It depends on what you expect out of a bearing as to which one you get. If you want good bearing that performs well and lasts long that would require little maintenance, go with the Teflon sheilds (I had a set that came with my TC3 and loved them...very good bearings!) Plus teflon is ligher than metal. The metal shields will offer less rolling resistance but will require much more maintenance. At some carpet tracks I have been too, you would have to remove all 8 wheel bearings after each run to clean them out (have a good pair of tweasers with you at all times if you run on carpet!!).
If you want the best set of bearings and expect them to last forever get the Acer Ceramics (my personal opinion).