dirt, water and who knows what else in offroad racing will get any bearing eventually. abec35.com - cheap bearings. metal, rubber shielded, some sizes in stainless so you dont have to worry when washing your car with water, ABEC 3 and 5 (for offroad ABEC 3 is better). been using them for couple years and they work great and you cant beat the price.
i did have ACER set on my truggy, but most off them died after 4-5 races. They were replaced by the cheap bearings and since then i actually did not have to replace a single bearing. the got over 6 races on them.
looks like my universal bearing thread answer 