Originally Posted by Bernard_Jr

That's why I use the yellow seal ceramic bearings. Easier to just copy and paste:

"RC Car & Truck Ceramic Lightning Yellow Seal Bearing kits are specially designed for off-road or excessively dirty driving environments. These ABEC #1 bearings are maintenance free and lubed for life. The heavy duty rubber seal provides extra protection against the harshest elements; the ceramic ball provides lower friction and increased durability. Ceramic hybrids are lighter, have less rolling resistance and can sustain higher operating temperatures than traditional bearings. All Ceramic Lightning Yellow sealed bearings are packed in grease and will require a short break in period to loosen up."