The last component I was waiting for, a compact chainset, arrived about a week ago. Fitting it was relatively easy; there are two points at which the axial bit from the drive-side crank resists going through the bottom-bracket: these mate with the inner bearing races once everything is installed. Sadly, the friction in the system seems barely diminished – if I repeat the spin-test I applied to the Sora cranks/BB I get pretty-much the same result. Of course, 105-series compact cranks weigh a lot less than Sora-series double cranks, so if all else was equal you would expect the 105 set to stop slightly earlier as they have less angular momentum to fritter away.
The Shimano chain was quite easy to fit: you trim it to length in the usual way and then finish the loop with the aid of a pre-fitted connecting pin on the other end. This means that it is very important to trim it from the other end. SRAM’s powerlink system is as easy to use, and does mean you don’t need a chain tool if the chain is already the correct length (which it never is).
Threading the chain through the dérailleurs is always fiddly, and this time was no exception; connecting the chain once you have done so is even more fiddly as the rear mech spring is fighting against you joining the two ends. You only have to do it once though, and it really isn’t something to worry about.
I did my initial testing in the turbo trainer to check that all the controls worked and everything felt OK, which it did. Since then I have ridden to work and back 3 times and can confirm that my changes have made the improvements I had hoped for. I think I need to fiddle with the saddle height a bit more now I have the shorter crank-arms, but that’s a task for a longer ride at the weekend rather than the 20 minute blast of a commute: I approach commuting as if it were a 10km time-trial, and that’s going to make your legs ache whatever else you do.