zukahn1 

I Have couple sets of fairly nice unused sealed bearing cheaper Asia alloy pulleys in my parts bin that I got awhile back cheap thinking of putting these on one of my bikes with a STX RD too see if it would help a slightly rough drive train. Has any one done this and does it help? I'm also thinking of maybe just doing the bottom pulley and leaving the top since it has a float any thoughts on this having a modern sealed alloy bottom and nicer OEM float pulley on top?

hokiefyd 

I suspect this is in the wrong subforum for a technical question...but yes, it does work. The old STX derailleurs had the smaller pullies typical of the era (9 or 11 tooth as I recall -- I should know -- I have two of them!). I have installed oversized 13t pullies on one of them and it runs fine. If you go too large, especially at the top, you run the risk of the chain conflicting with a few things (the chain retention tab on the cage, the large sprocket in low gear if you don't have enough B tension, etc.). I rather like larger pullies (they tend to run quieter for me, even cheap ones). I had 13t ones in one of my STX RDs from a modern Tourney derailleur and it was just fine.

I did end up going back to the stock pullies just to get back to the original look.