Moving to shorter crank lengths

[Eleven21]

I might just be that I have more time to surf the net during pandemic lock down but there seems to be a bit of a push encouraging folk to move to a shorter crank length. The cynic in me wonders if this is just another ploy by the industry to boost component sales?

Myself an average height rider but with what I consider a relatively long inseam, have ridden 172.5 since forever. My touring bike has 170 crank and TBH I’d struggle to notice the difference between them. But with that said I do realise to make any perceptible difference I’d have to move to a 165mm crank length and that would be an extremely expensive process. Three crank based power meters along with various campapgnolo kitted bikes (and getting hold of 165mm Campag chainsets isn’t easy).

Have many on here bitten the bullet yet?

[bas]

I have an SRM Origin with the tri lobe crank. Always been 172.5, but tried 170 as it was so easy to change. Definitely feels smoother climbing, no other downside that I've noticed in racing/sprinting, etc. So kept at 170

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[ghostinthemachine]

There are two or three recent threads on shorter cranks. Have a search.
Those I know who've tried it on long term like it.
I've had a brief try and it feels good.

[Nickldn]

I understand shorter cranks may provide genuine benefits for TT bikes, due to the riding position.

Not really sure if the same can be said for normal road bikes.

[AJS914]

I've gone back down to 170 from 175. I went to 175s in the 90s because it was the fashion.

I really like the 170s. It stopped my knees from hitting my stomach. I raised my saddle and was able to leave my stem where it was so I got more aero. The decreased hip angle was also more comfortable.

I needed an extra lower gear on the cassette so I could still spin up climbs. This year I went another step and installed a 32 and then set my fastest time (Strava top 20 too) on the 30 minute benchmark climb in our area. It's all a win win for me.

[maxim809]

I can understand why you'd be cautious because sometimes in this sport, it's hard to pinpoint if something is real or if it's just the industry swinging a pendulum to guarantee product pipeline cashflow for the next 3 years.

But the benefit trade-offs around shorter cranks are real.

One way to help dismiss some of the industry cynicism is that shorter cranks aren't being openly marketed, pushed, or shoved down to us from brands with huge marketing power. It's really coming from the anecdotes of regular riders like us, fitters, and key internet cycling influencers. Maybe the last two mentioned have incentive to push short cranks and skim a quick buck if their business model allows, but when I think about who would really win monetarily... it's like... the crank makers. While not impossible, it'd be a very convoluted marketing scheme if they were behind all this. Those freakin' clever Shimano marketers putting short cranks into the hands of YouTube and Cycling blog influencers to dupe the good people like us!! This is why I have trust issues!! I thought you were one of us, Peak Torque / Cam Nichols / Dylan Johnson!!

Anyway, your specific situation is a toughie. I have 3 bikes built with Campagnolo too. As you know, the 2012 5-arm 11spd crankset came with 165mm options. Then for some reason, the 2015 4-arm only went down to 170mm. Now, with 12spd it's possible to get 165mm's once more. So like yourself, I can understand the hesitation because moving to 165mm in a Campag world can seem like both a huge investment or a step down in order to conduct an experiment because you lose compatibility with pre-existing parts such as the crank-based PM in your case.

Others have tried to go down the Crank-based PM Campy route for a 165mm build, and there isn't a great path right now:
https://forums.thepaceline.net/showthread.php?t=255267

Pedal-based PM is the best way to go if sticking with Campag, which becomes a limiter if you need Speedplays for the Q-factor or float. If Speedplays are required, there are conversion kits with certain pedal-based PM's, so that could be a viable solution if you're willing to take it all the way.

I went a different route and built an experimental Shimano-based 165mm build, specifically to not interfere with my Campy builds. The results on 165mm's have been great for me. I'm now slowly planning out how to convert my main Campy bikes to a 165mm 12spd build.

It's a whole thing but it's worth it.

[FactoryMatt]

makes it harder to stay "on top" of a gear. if you have an inherently narrow 'power band' (self-selected cadence range) you may want to consider carefully. if you run a wide-ratio cassette, this make it even more important to have a bit more mechanical leverage that longer cranks provide. people say to just "shift gears", but it's not always that simple.

obviously there are other considerations, and all thngs being equal, shorter cranks are easier on the joints. it will raise your saddle height a touch though.

[bet1216]

I have short cranks on my TT bike (155mm). It makes a huge difference in opening up the hip angle in the TT position. Much more comfortable and easier to stay there and much easier to ride for long periods of time in the TT position. At the time I got the fit for the TT the fitter suggested I switch cranks the road bike too. I went with the short cranks on the roadie for about a year. I had ridden 172.5 for years. When ridding in the drops it was much more comfortable and easier for me. However, I felt I was missing some punch while climbing. I could hit normal watts at a normal cadence but it seemed off. For me it also seemed to increase my efforts on the flats. I already rode at 95-100 cadence normally. I went back to the 172.5 this year. My fitness this year is not as good as last year but I think the "punch" on climbs is better with the longer cranks. At the end of the day I don't think they are a game changer either way on the road bike, except they can definitively provide some comfort in the drops if your flexibility is not great and/or you likely can slam your stem more and get a more aero position because it will open up the hip angle. Do realize though that by going with shorter cranks you will will have raise your seat by the decrease in crank length.

Modular systems like the Rotor cranks are good for experimenting with crank length and using the same spider power meter and/or chain rings.

[none]

I switch crankarms according to my fitness & flexibility.
In the winter time, when I mostly ride on trainers and spin at higher rpm, I use shorter crankarm length 170mm or 165mm.
In the summer time when I'm at higher fitness & flexibility level, I use 172.5mm.
When cycling outdoors, with more variance in terrain, 172.5mm is still ideal for me, but for flat TT or longer distance, shorter crankarms are better suited.

[joeyb1000]

A long time ago, Leonard Zinn did a study with a small group of riders. They repeated a 10 minute test on crank lenghts from 155mm to 190mm. The riders could choose their own cadence and gears. At least with this group, he found little correlation between crank lenght and average watts.

[Nohands83]

I switched from 172.5 to 165mm on my TT a few years back and it made a significant difference, as others have said it really helps open the hip angle and reduce the effect of the dead spot. I suffer with tight hips and power drops significantly with too much hip impingement - if you don't have these issues you may not benefit as much.

I now run 170mm on my road bikes, whilst it does help, the effect isn't as pronounced as my TT bike.

I think it may also depend on what your natural cadence is, I'm a spinner so shorter is good for me. If you're a 'grinder' maybe not so much.

I'm 184cm for reference.

[Pato]

If you ride mostly flat/rolling terrain, a shorter crank works quite well, it allows you to to remain in an aero position more comfortable.
For hilly terrain I still prefer longer cranks, I feel like I have a bigger cadence range within the same gear.
I'm using 170mm cranks in the hill bike vs 165mm in flat bike and the difference can easily be felt especially while climbing. The cadence usually varies by 3/4rpm and also, to feel the same gear ratio while climbing, I need a +2 teeth cog cassette. Basically 170mm + 11-30 roughly equals a 165mm + 11-32

[Hapsmo911]

I might just be that I have more time to surf the net during pandemic lock down but there seems to be a bit of a push encouraging folk to move to a shorter crank length. The cynic in me wonders if this is just another ploy by the industry to boost component sales?

Myself an average height rider but with what I consider a relatively long inseam, have ridden 172.5 since forever. My touring bike has 170 crank and TBH I’d struggle to notice the difference between them. But with that said I do realise to make any perceptible difference I’d have to move to a 165mm crank length and that would be an extremely expensive process. Three crank based power meters along with various campapgnolo kitted bikes (and getting hold of 165mm Campag chainsets isn’t easy).

Have many on here bitten the bullet yet?

I just switched from 172.5 to 170 then again to 165. The quarq makes it a little easier to swallow at $190.00 usd for arms. No big difference to 170 but the 165 got me personally way better position. No net gain in power just better fit. Got used to them without even noticing really. If youre not going for aero gains or to solve a fitting issue I think its a waste. TrainerRoad has a podcast/youtube video on this and so does Cam Nicholls amongst others.

[FactoryMatt]

If you ride mostly flat/rolling terrain, a shorter crank works quite well, it allows you to to remain in an aero position more comfortable.
For hilly terrain I still prefer longer cranks, I feel like I have a bigger cadence range within the same gear.
I'm using 170mm cranks in the hill bike vs 165mm in flat bike and the difference can easily be felt especially while climbing. The cadence usually varies by 3/4rpm and also, to feel the same gear ratio while climbing, I need a +2 teeth cog cassette. Basically 170mm + 11-30 roughly equals a 165mm + 11-32

this. i posted same above. transient power is so important

[c60rider]

The reason for using longer cranks was historical because of the lack of gears that we take for granted these days. When I raced in the 90s 39x21 was the smallest gear I had. As junior it was 42x21!!! Longer cranks was akin to using a longer spanner to get a bolt undone. It was just easier to get it around. Look at pre-90s cycling videos on youtube and you'll see them grinding the gears round on the climbs and a steady upper body rock to get a rhythm going. They were just limited by technology at that time. Smaller cranks (and spanners) you can spin round faster but I think it has to be a big difference between the size to make a notable difference to be worth changing existing components. So now we have huge ranges of gears it's much easier to keep a cadence level well above 90 on almost any terrain. So smaller cranks make sense in that respect and the research seems to suggest that it has very little effect on power output. However I've got 172.5 on all bikes but can still spin quite easily over 120rpm. Going down to 165 would sound like quite a lot but it's only 7.5mm which is just over 4% difference. So personally I'm not sure it's really significant enough to make much difference to me. If I can spin 120+ rpm with 172.5 how much faster do I need to pedal!!! I'm not sure it's really very relevant at all. Try it and if you like it then go for it.