KillerQuads
05-26-2007, 07:28 AM
I changed the gearing on my 2007 Mongoose Bosberg (SRAM Rival). It has a 130BCD (non-compact) crank that came with 53/39T rings and a 12-26T cassette. My other bike has 50/38T rings (with the same 12-26T cassette), so I converted the Bosberg as well. The rings are from FSA. The other bike (Pinarello Galileo Ultegra) has a 110BCD compact crank that had 50/34T rings, so all I had to do was replace the inner ring with a 38T FSA.
The advantage of the 50/38T is that the big ring is compact to take advantage of the shrinking size of cassette cogs. A 53/12 or 53/11 combo is not very useful for most people. The 50/12 gives a top gear of 113 gear inches, which is plenty high enough. The 50T lowers the whole top range, so I can stay on the big ring over a wider range of inclines and even moderate uphills.
I really don't like 34T inner rings, as the jump in gear ranges is too great and always requires mulitple rear shifts to find the right gear. The 50/38T is perfect for commuting. As I roll up to a stop light on the 50T, I just shift to the 38T and I am ready to blast off from a stand still. It is also good for the rolling hills in my area, since I can shift the FD at the crest or base of a hill and often don't need to shift the rear at all. A 34T is too low for the flats, where as the 38T can still be used on the flats or slight downhills. The 38T also shifts up to the 50T much better. The 38/26 combo yields a low gear of 39 gear inches which is plenty low enough for me. For racing it would be easy to swap out the 12/26 for a 11/23 cassette, which would work really well with the 50/38T rings.
The black 50/38T FSA rings contrast nicely with the alloy Rival crank and complement the carbon frame. I installed new black alloy chain ring bolts too. It took a little trial and error to find the best way to mount the small ring in relation to the big ring for optimal shifting (the big ring was marked 50/39/30). Shifting is best when the "FSA" markings on both rings line up with each other.
One nice feature about the SRAM FD is that it has two mounting bolt holes. This allows a wide up and down range for mounting the FD if you have a braze on FD frame mount. To move the FD low enough, I used the second mounting hole. After adjusting the cable slack, the FD shifts really well with the 50/38T combo.
Note: both 130BCD and 110BCD (compact) cranks can be converted to the 50/38T setup. Just make sure your order the correct BCD size. Also, it is not necessary to remove the crank to install new chain rings. Finally, make sure you don't overtorque alloy chain ring bolts, as they are fragile.
The advantage of the 50/38T is that the big ring is compact to take advantage of the shrinking size of cassette cogs. A 53/12 or 53/11 combo is not very useful for most people. The 50/12 gives a top gear of 113 gear inches, which is plenty high enough. The 50T lowers the whole top range, so I can stay on the big ring over a wider range of inclines and even moderate uphills.
I really don't like 34T inner rings, as the jump in gear ranges is too great and always requires mulitple rear shifts to find the right gear. The 50/38T is perfect for commuting. As I roll up to a stop light on the 50T, I just shift to the 38T and I am ready to blast off from a stand still. It is also good for the rolling hills in my area, since I can shift the FD at the crest or base of a hill and often don't need to shift the rear at all. A 34T is too low for the flats, where as the 38T can still be used on the flats or slight downhills. The 38T also shifts up to the 50T much better. The 38/26 combo yields a low gear of 39 gear inches which is plenty low enough for me. For racing it would be easy to swap out the 12/26 for a 11/23 cassette, which would work really well with the 50/38T rings.
The black 50/38T FSA rings contrast nicely with the alloy Rival crank and complement the carbon frame. I installed new black alloy chain ring bolts too. It took a little trial and error to find the best way to mount the small ring in relation to the big ring for optimal shifting (the big ring was marked 50/39/30). Shifting is best when the "FSA" markings on both rings line up with each other.
One nice feature about the SRAM FD is that it has two mounting bolt holes. This allows a wide up and down range for mounting the FD if you have a braze on FD frame mount. To move the FD low enough, I used the second mounting hole. After adjusting the cable slack, the FD shifts really well with the 50/38T combo.
Note: both 130BCD and 110BCD (compact) cranks can be converted to the 50/38T setup. Just make sure your order the correct BCD size. Also, it is not necessary to remove the crank to install new chain rings. Finally, make sure you don't overtorque alloy chain ring bolts, as they are fragile.