KillerQuads
05-13-2007, 08:05 PM
I bought a bike that had a stock compact crank with the now common place 50/34 chainrings. It also came with a 12-26 10 speed cassette. The 50T big ring makes sense because as the small cogs have shrunk from 14 to 13 to 12 to 11 teeth, we don't really need 53T big rings to have an adequately tall top gear. The 50T ring saves some weight and lets stay on the big ring even against the wind or with moderate uphill grades.
My problem is with the 34T small ring, which for me and my area (rolling hills in central Virginia) is way too low. Shifting either up or down with the FD is too much of a jump. The 34 is a granny gear which I find useless on the flats. It also shifts noisily or worse yet drops the chain completely off the chainrings.
My solution was to replace the 34 with a 38T inner ring for what I call "semi compact" gearing. I stiill have the advantage of the 50T compact ring, but now have a higher range of gears on the small ring. The "jump" when shifting up front is perfect for rolling hills and when stopping and starting at intersections. For example, when I crest a hill on the small ring and start descending, I shift to the big ring and attack the downhill with power. When slowing for a red light on the big ring I shift to the small ring and am ready to start from a dead stop when the light turns green. The 50/38 combo is perfect for this. Shifting performance is much better (even more so with SRAM's new 10 speed chain).
The 50/38 setup would work well for racing and time trialing too. Just swap the 12-26 cassette for an 11-23. For a mountain tour, it is easy to reinstall the 34T without removing the crank.
I have converted a 50/34 110 BCD crank (compact) to 50/38. I have also converted a 53/39 130 BCD crank to 50/38. FSA makes 50/38 chainrings for both sizes of cranks. Both bikes have much better gearing for both commuting and weekend rides.
One problem is that the big rings have ramps, pins, and teeth optimized for shifting with only certain small rings. It took a little trial and error to find the best way to mount the small ring in relation to the big ring for the smoothest FD shifting.
Tips: You don't have to remove the crank to change chainrings. Make sure you don't over torque alloy chain ring bolts, as they are fragile. Lower the FD as needed when downsizing from 53 to 50T rings. Check the FD set screws after changing rings (should need minimal or no adjustment). For me, the new SRAM 10speed cassettes and chains shift better than their Ultegra counterparts. FD height, FD alignment, FD set screws, and FD cable tension are all very important to front shifting performance, and bike shops may not have the time to adjust the FD perfectly.
My problem is with the 34T small ring, which for me and my area (rolling hills in central Virginia) is way too low. Shifting either up or down with the FD is too much of a jump. The 34 is a granny gear which I find useless on the flats. It also shifts noisily or worse yet drops the chain completely off the chainrings.
My solution was to replace the 34 with a 38T inner ring for what I call "semi compact" gearing. I stiill have the advantage of the 50T compact ring, but now have a higher range of gears on the small ring. The "jump" when shifting up front is perfect for rolling hills and when stopping and starting at intersections. For example, when I crest a hill on the small ring and start descending, I shift to the big ring and attack the downhill with power. When slowing for a red light on the big ring I shift to the small ring and am ready to start from a dead stop when the light turns green. The 50/38 combo is perfect for this. Shifting performance is much better (even more so with SRAM's new 10 speed chain).
The 50/38 setup would work well for racing and time trialing too. Just swap the 12-26 cassette for an 11-23. For a mountain tour, it is easy to reinstall the 34T without removing the crank.
I have converted a 50/34 110 BCD crank (compact) to 50/38. I have also converted a 53/39 130 BCD crank to 50/38. FSA makes 50/38 chainrings for both sizes of cranks. Both bikes have much better gearing for both commuting and weekend rides.
One problem is that the big rings have ramps, pins, and teeth optimized for shifting with only certain small rings. It took a little trial and error to find the best way to mount the small ring in relation to the big ring for the smoothest FD shifting.
Tips: You don't have to remove the crank to change chainrings. Make sure you don't over torque alloy chain ring bolts, as they are fragile. Lower the FD as needed when downsizing from 53 to 50T rings. Check the FD set screws after changing rings (should need minimal or no adjustment). For me, the new SRAM 10speed cassettes and chains shift better than their Ultegra counterparts. FD height, FD alignment, FD set screws, and FD cable tension are all very important to front shifting performance, and bike shops may not have the time to adjust the FD perfectly.