Bicycle Mechanics - Shimano 105/Ultegra Compact crankset, bike with 145mm rear spacing
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02-14-10, 11:16 AM
I have a Co-Motion Americano (touring bike with 145mm rear spacing). As I rarely tour anymore, I was planning on changing the drivetrain (currently, it has bar end shifters, older 9 speed derailleurs), since I was given 10 speed 105 shifters, and derailleurs.
My old touring triple crankset used a square taper and a 116mm Phil Wood bb, to account for the wider rear spacing. If I switch over to a Shimano 105 or Ultegra compact crankset, will I have chainline issues? I have only used square taper bb's and cranks before, so I don't know if the newer crank/bb combos have "adjustability." Thanks!
02-14-10, 11:36 AM
they don't have "adjustability" and I would not be inclined to trade them off..I would use them with the existing FD the new shifters and RD..what is your chain line..60mm??
02-14-10, 11:57 AM
I'd have to measure, but I'd imagine that it is ~53-55
02-14-10, 12:30 PM
at 53-55 you will have not problems with the newer external bearing cranks...I would still measure and make sure..I like the durability and strength of external bearing cranks very many will argue this point but I like them...as I sit here though I'm just wondering if it really worth the cost of the change though..
02-14-10, 02:56 PM
Well, I figured that I was due for new chain and cassette for my old drivetrain anyway. I forgot to mention that I also was given a new SRAM 10 speed chain and a new Shimano 10 speed cassette (12-25t, 105?), so it might not be that much more just to switch over the crank and bb. I'll certainly measure just for good measure. Thanks!
02-14-10, 03:01 PM
Just use your existing crankset with the 10 speed components. Compatibility issues are rare. The newer chains are only more narrow on the outside and will fit on the older, lower-speed chainrings without issue.
what's the BB width on your frame?
external BB cranksets for road don't work with ISO oversized 73mm shells.
also external BB road cranksets have the same (or very similar) chainline as their octalink and square taper counter parts from previous generations.
02-14-10, 03:44 PM
I believe the BB width is 68. The drivetrain the I ran on this was a 9 speed setup -- Sugino 46-36-26 crankset, LX rear derailleur, 11-32T cassette, and the 116mm Phil Wood BB I mentioned earlier. I checked the Shimano site and the chain lines they list for their road cranks all seem to be nearly 10mm less than my current setup. I would asume that would be bad, no? In general, would the older style BB's (sqare taper, ISIS, Octalink) give me more flexibility in establishing a proper chain line (take in mind my 145mm rear spacing?
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