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Changing the crank? (Stories of the Noob)

There's an upside and a downside to the Tiagra vs. 105 cable routing.

While the under-the-tape routing of the derailleur cables on the current 105 looks cleaner, has less potential for obstruction of handle bar bags, lights, etc. and an ever so slight advantage on aerodynamics, it involves more or sharper bends in the cable path, which can mean marginally more friction and cable wear. For that reason Shimano specifies PTFE (teflon) coated derailleur cables for the current (5700) 105, but not for Tiagra or the older "5600" 105, which is what the current Tiagra is based on.

The difference in cable routing is also the reason why my Bike Friday folding bike has Tiagra shifters while the rest of the group is 105. Basically it needs the extra flexibility from external routing when folding the handle bar, plus with the folding mechanism the routing is less direct already, so more bends along the bars would not be welcome. I heard that when the 6700 Ultegra replaced its 6600 predecessor and Shimano first moved the shifter cables under the bar tape, Bike Friday stopped offering Ultegra to avoid problems for its customers. Ultegra only became available again when Ultegra Di2 came along, since it uses electronic shifting and the electric cables don't care about how they are laid.

Interesting info, thanks! Now to look for some best prices...
 
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