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Hang on, if you look at my graph of gear number versus ratio, you can see that all I'm doing is making the average step about the same as 19 to 18.
If that's a jump worth having at lower speed, surely there's a use for it at higher speed, no?
I mean, ideally you'd have a CVT that didn't add drag and weigh a ton, but since this provides what you say is more gears than you need for a mere 50g of extra chainring, what's not to like? The gears are there if you want them, otherwise a no-brainer to skip.
Also, imagine the system knew where not only cranks were in the rotation, but cassette too, and delayed shifts to the perfect moment for a seamless shift.
If every shift was so perfect the chain never jumped, you could maybe even have it shift for you, and just tell it how hard you want to go.
Someone jailbreak Di2!
Kimmo-
Someone jailbreak Di2!
As if the official software doesn't crash enough...
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If that's a jump worth having at lower speed, surely there's a use for it at higher speed, no?
My point being that the 18/19 jump isn't worth having, but 18/20 is worse than 12/13 so we're stuck with it on drives which work well within the load and packaging requirements of a bicycle.
⅜" pitch chain would work, and apparently was used by Team GB on the track last time around, so you could switch the cassette from today's typical close ratio TT set of 11-23 to a 15-30 to get nicer chordal action and smaller ratio jumps at the top end. That would be much better from every aspect than a half-step, if you still think the 11/12 shift is too big.a mere 50g of extra chainring
It's not just 50g of chainring on a TT bike, it's changing from a clean 1× drive to a 2× with all the drag penalty of a FD and second ring
TooTallTim
gbj_tester
But it's not a gain. Just the aero drag from adding a FD is going to lose more than being 3rpm away from your "optimal" cadence, e.g. let's take one of the fast men who wants to be at 90rpm:
58/12 at 90rpm = 34.5mph
inclination changes from -1% to +1%
58/12 at 86rpm = 33mph
down-shift to avoid bogging
58/13 at 93rpm = 33mph
Your half-step offers
56/12 at 89rpm = 33mph
but who is that sensitive to cadence? Pursuit riders maybe🙂