I’m seeing more and more spinners on climbs in the TdF.
Since pros are climbing 50-100% faster than the rest of us, isn’t it logical we should have lower gears than they do to support a similar effort?
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Rotor makes 11–36 and 11–39 cassettes that are significantly lighter than Shimano’s cassettes, 230 g and 235 g, respectively.
The way you describe the situation, even with the current cranks, you would benefit from opting for the larger 11–39 cassette if you need to climb 15–20 % gradients.
Well, it’s an issue with an obvious solution. And the way you describe it, even now you would likely benefit from having easier gearing at your disposal.
When I made the switch form 172.5 to 165, I kept the same 11-34 cassette, but went from a compact 50-34 to a semi-compact 52-36. My cadence feels much more natural, and I’m more comfortable on the climbs even with the “increased” gearing.
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5.6 height, 30in inseam, went from 170mm (seat height 640mm, knee touching my torso when in aero position) to 160mm (good aero position, but feeling more loads in my leg, harder overall on my muscle in general, climb or burst of power) then 165mm (good balance, rode for more than 1 year, but i think i may try to 160mm again, because my knee is touching my torso again after i lower my seat height [having knee pain in one side], at the same time i dont want to because i think 160mm burns my muscle much more quickly which may caused by my previous fitting issue. it feels hard to utilize my whole body to output power.)
For me, I could lower my saddle a tiny bit (it was too high, but lowering it caused knee pain). Now my saddle issues are gone AND no more knee issues. The rest (e.g efficiency, gearing…) I didn’t notice.
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I’m a short guy and have always run 170’s. I put 165’s on my Ritchey and like them, but it doesn’t feel like a huge difference. I think if I were making a bigger jump (175’s to 165’s), it would be a lot more noticeable.
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It’s like saying “I made my gearing harder in two ways and I feel much more natural”. Doesn’t make any sense. I understand that shorter cranks could have helped you spin more easily or improve your position on the bike. But shorter crank doesn’t help force production automagically.
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You don’t gain cadence! It is easier to spin at a higher cadence. But to spin at a higher cadence you either need easier gear or you need to go faster. And uphill that means more watts! So no, you don’t gain cadence, you just lose leverage.
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In the same boat, I made the switch anyway. It’s only really a problem when the bike is loaded with bags for longer audax rides - the solution for that scenario is really to switch to a GRX crankset I think, though I’d lose my spider PM… Perhaps not the best solution for a performance road bike though due to top-end loss with a 48t big ring.
I’m on 11 speed mechanical still, so I can happily just make an 11-40 work on all my bikes if I want (hanger extender). See Peak Torque’s youtube video on doing the Fred Whitton at 90kg+ with his similar setup.
Your weight-weenieism is stupid and counterproductive, you will not get stronger; using muscle to grind up climbs is putting daggers in your quads for later in a long ride, and the extra force isn’t good for your knees either.
They all change gearing to suit the race, every single time, though just in a very different range normally (11-28 cassette to a 11-34, but still with a 56t big ring…). For the 2023 Giro mountain TT, Roglic was on a 1x with a 52 tooth cassette for the final climb (so far easier than 1:1) because it was just that steep.
You are correct, it doesn’t make any sense, but for me, it works. My cadence didn’t necessarily increase, but my foot speed at similar cadences is noticeably lower, so feels much better. Does that allow me to put more watts through the pedals? Maybe.
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The shorter cranks mean a smaller circle which means lower foot speed for the same cadence, or a higher cadence for the same foot speed. If the increased saddle height from the shorter cranks means that your hips don’t close as much, it might mean that the same perceived effort leads to more watts through the pedals.
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I know how shorter cranks can help. I do run 155 mm while I am 190 cm tall 
However, physics is physics. Also, if not having big problems with bikefit currently the shortening of cranks won’t automatically improve your power curve.
If your perceived effort is lower, then you can do more work. Some percive the lower effort with longer cranks, however it seems like most perceive the lower effort with shorter cranks.
As evidenced in literature, except perhaps the biggest of issues related to bike fit, the crank length has minimal influence on watts produced even in quite a large range of crank sizes.
If your one subjective experience is different it might point towards the exception I mention.
At 90 rpm the difference in speed to a 50-tooth chainring is marginal, 50.7 km/h vs. 52.8 km/h (about 50/48 - 1 ≈ 4 %). At 100 rpm, it is 56 km/h vs. 59 km/h.
Foot speed, cadence, whatever it is I like it. Actually just picked up a cheap CAAD8 which has 170mm cranks and set up as close to my Madone fit wise as I could, matched the pedal spindle to top of saddle measurement at 94cm, and yea the 165mm cranks on the Madone just feel better overall
If we’re talking performance road bike though then it won’t have a 50T, it will come stock with at least 52T and these days a lot of racers I know are going with 54T or even higher if it’s for road bike TTs. 48T vs 54T is a 12.5% increase, that’s pretty significant if you’re needing to roll at high pace. E.g. Rolling along in a pack downhill or in a tailwind.
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Just chiming in to share I moved from 175s to 165s and have been on them for a few weeks now. I am 6’2’’ for what is is worth but do have a short inseam for my height (lot of torso)
I originally wanted to try shorter cranks after hearing people hail them as amazing fix for any back/hip/knee issues. I was having lower back issues and desperate to fix to figured I would give it a try.
Findings: they did not solve the back issue! My cadence increased, power seemed stable. I enjoy them more for my flat rides but did miss longer cranks a bit when climbing and sprinting. Overall, I think ~170s are probably the sweet spot for me but I don’t want to spend more money switching again so am debating if I want to continue to use the 165 or go back to 175
For me, I didn’t notice THAT big of a difference. I was able to get a bit more aero and increase cadence but it wasn’t drastic. After about 10min of pedaling I couldn’t tell I was on shorter cranks at all. If I had to sum it up I would say overall its better, but if I had to do it again I wouldn’t spend the money on new cranks and would probably just practice the aero position on my 175s a bit more.
Just my two cents!
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Since when is 4% “marginal”, I strongly beg to differ! 