Im sort of going all in . the 30 t is on bike .i want to try the 30/66 combo.@bentiverstaurheim wouldn't it just be easier to fit a 29T front sprocket, the difference in ratios between the 28/66 and 29/68 is minimal, 2.357 vs 2.345, and you could probably get one for less than the cost of machining the rear pully ?