Bearing buddys replace the dustcap and they have a grease zerk so you can keep grease in the wheel bearings. There is a spring that keeps tension/compacts the grease into the bearings. Mostly used on boat trailers but you can use them on any trailer. Bearing Buddy And for the ST vs LT, one of the other forums I'm on prefers the LT on a 16" rim for alot of the toy haulers. On my toy hauler I have the Maxxis ST and am very happy with them. They came on the trailer when we bought it. It's been 4 years and holding up great.