Being out of the bike industry insider club for several years, I missed the regular technical updates from Shimano and SRAM. The pages that make up these manuals are a bike designer's bible. When I designed the chainstays of the cross frame, I used what I had and thought I had all my bases covers so that a road compact crank would be compatible with the cross frame.
Well, I got it almost right. I physically checked the frame by installing compact cranks with external bearings from both SRAM and Shimano. External bearing cranks have no left/right adjustability with regards to chainline, arm clearance, ring clearance. Bearings go in. Cranks go on. Done. So I installed cranks from both Shimano and SRAM and thought - good, they fit.
Doh! I didn't check the new Shimano 105, Ultegra, and Dura Ace compact cranks. It seems their arm stance is narrower than their Tiagra compact or R600 compact cranks by enough that these cranks are not recommended on the Black Mountain Cycles cross frame.
Check out the chart below and notice the dimension W5. Here are some cranks and their respective W5 dimensions for reference.
SRAM Red, Force, Rival, Apex, S900, S500 compact doubles: 60.0 to 61.0mm (okay)
Shimano Dura Ace FC-7950 - 57.2mm (too narrow)
Shimano Ultegra FC-6750 and 105 FC-5750 - 57.6mm (too narrow)
Shimano Tiagra 4550 - 59.5mm (okay)
Shimano R600 - 61.0 (okay)

Well, I got it almost right. I physically checked the frame by installing compact cranks with external bearings from both SRAM and Shimano. External bearing cranks have no left/right adjustability with regards to chainline, arm clearance, ring clearance. Bearings go in. Cranks go on. Done. So I installed cranks from both Shimano and SRAM and thought - good, they fit.
Doh! I didn't check the new Shimano 105, Ultegra, and Dura Ace compact cranks. It seems their arm stance is narrower than their Tiagra compact or R600 compact cranks by enough that these cranks are not recommended on the Black Mountain Cycles cross frame.
Check out the chart below and notice the dimension W5. Here are some cranks and their respective W5 dimensions for reference.
SRAM Red, Force, Rival, Apex, S900, S500 compact doubles: 60.0 to 61.0mm (okay)
Shimano Dura Ace FC-7950 - 57.2mm (too narrow)
Shimano Ultegra FC-6750 and 105 FC-5750 - 57.6mm (too narrow)
Shimano Tiagra 4550 - 59.5mm (okay)
Shimano R600 - 61.0 (okay)

In summary, Dura Ace, Ultergra, 105 compact cranks - not compatible with my cross frames. Any others are good to go. Sometimes compromises need to be made to fit those fat tires. I'm not sure about the compatibility of the previous generation of Dura Ace, Ultegra, 105 cranks, but will try to squeeze the info out of Shimano.
(What's playing: KWMR Musical Variete and some Albert King)
(What's playing: KWMR Musical Variete and some Albert King)









































