You don't need to be an 'investor' to invest in Singletrack: 6 days left: 95% of target - Find out more
My wife is looking for suggestions for Christmas present options for me and, given I've been riding my road bike a lot this year I was toying with the idea of getting a power meter. Evans are listing the left-side only 4iii one for £350 at the moment, for a 11-speed 105 arm. As my current road bike is 9-speed can I just switch the chainset to an 11-speed 105 one without changing anything else - with my thinking being that it'd work because a 9-speed chain is wider?
I'll probably go 11-speed on the bike (or a replacement) at some point but don't want to do that now as it'll mean replacing the wheels.
I believe the ring spacing will be different. It would run but it wouldn't be pretty.
The chainring spacing between inner and outer will be marginally smaller (<1.0mm) which means that you might experience more chainrub when on inner ring and smaller sprockets - not a good idea anyway, plus there might be a bit more transmission 'noise' due to slightly wider chain on chainrings but if you're not super-fastidious about how your bike runs, I'd doubt you'd notice.
As an alternative any idea if an 11-speed 105 left hand crankarm will fit on 9-speed Tiagra chainset?
As long as it's a HT2 crank you'll be fine.
To answer my own question - I ended up just getting the fitting the 4iiii 105 arm to my Tiagra chainset and that seems fine.
Next question though - does that mean I could also fit that 105 arm to the M960 XTR chainset on my Epic if I fancied trying the power meter on the occasional (dry!) off-road ride?
Try it, if it bolts up ok it'll probably work.
I think chainring spacing doesn't get narrower with narrower chains and more gears, the just widen the base of the chainring to stop the chain falling between them.