It depends on what kind of valve stem is on the wheel. If they are fully rubber, it is good to change them when they begin to check. At least on S3, Daytona, S4, TT600, Sprint, etc., the valve stes are steel, so there is no need to replace them. I suppose the rubber seal between the valve stem and the wheel could eventually go bad, but that will take a very, very long time.This may sound stupid, but how often do you need to replace the valve stems?
Not every time you change your tires?
My saying 'steel' valve stem is a typo; I have no idea where my head was at that moment in time, as I was trying to relate that to my thinking of the stems as being metal. I meant that they should be straight aluminum valve stems for the stock rear of an 03 S3.Stock 2003 Speed Triples have a straight steel valve stem on the rear wheel. ... If a dealership doesn't give you a straight steel valve stem, it's not the right one for that year, although it may work nonetheless.