Review on 🚴 Enhance Your Cycling Performance with Silver Origin8 Alloy Blade Chainrings by Stoner Fulton

Shimano Octalink 3x9 cranks (3 front, 9 rear or 27 speed total) with 104 bcd are oddly shaped. While the large and medium gears hang together on the same bolt circle (104mm), the medium gear (this one) has a slightly smaller inside diameter than the large gear. I'm not talking about the bolt circle diameter (BCD) but the actual inside diameter of the middle gear. In other words, the middle gear has more metal between the bolt holes and the crank than the big gear. I'm not sure why Shimano did this. Perhaps they wanted to make sure that the middle and large gears couldn't be accidentally misplaced. Whatever the reason, the 32T, 4-bolt, 104bcd gearbox fits perfectly in the middle position where no other gearbox could. Highly recommended if you need a middle gear on this Shimano crankset!