sternforprez

After completing a flat bar to drop bar conversion I've now decided to change the cranks. The specs on the bike list the BB as a Truvativ Power Spline, 113mm spindle, 68mm shell. Cranks are Truvativ Five D 48/36/26, 4-bolt, 175mm. I haven't decided on a compact double or a road triple but I'm confused on which BB to select.

One compact double I looked at calls for a 122mm spindle. That seems awfully long for a double when my triple currently uses 113mm. Another double calls for a "110 / 113mm" spindle. How do I know which? And a triple I'm looking at calls for a 118mm spindle. I realize different cranksets require different spindle lengths but some of this is unclear and/or odd.

If it matters, rear spacing is 130mm.

Andrew R Stewart 

Power spline is a unique to Truvativ design. I would suggest that you avoid it. Andy.

sternforprez

I intend to, that's why my question. I plan to buy a new crankset, and I'm wondering if I just go ahead and use the recommended spindle length even though it seem way off compared to the current setup.

oldbobcat

Your choice of spindle length will depend on the crank you choose, as well as the width of your bottom bracket shell.

122 mm for a double just seems weird. Generally, I've been fitting 122 mm spindles to inexpensive MTBs and hybrids with 130 or 135 mm hubs, 73 mm BB shells, and Shimano or Suntour triple cranksets. There are a couple oddball Suntour MTB cranks that take conspicuously shorter cranks.

The 110/113 mm spec for the double most likely implies 110 for a 68 mm shell, 113 for a 73.

Shimano's data sheets (online and and included in the crankset packaging) are usually pretty thorough about spindle lengths with different applications. Your application, 68 mm shell with a 130 mm rear axle, is pretty standard for road bikes. You could do an end-run and simply get a new Shimano Hollowtech II (Tiagra or R500, maybe) or FSA Mega-Exo (Gosssamer, etc.) crank with outboard bearings.