Moved from 172.5 to 150mm cranks, best decision ever. I'm 5'9''.

At the begining it felt harder, but it was only because the body need some time to adapt, as that was a significant change in lenght. After a few weeks I was fully adapted and felt lot more comfortable in a more aggressive position in the tri bike.

Since you just registered and we haven't heard from H2oFun for several weeks, don't be surprised if someone asks "Dave, is that you?"

Testing. The subject practically cries out for some testing.

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Books @ Amazon
"If only he had used his genius for niceness, instead of Evil." M. Smart

Yep, happy I switched.

I used to find that I'd get a little impinged around the hip as my foot came over the top, moved down to 165's and it's much better.

Not Dave...and not a new reader, just a new poster.

Thanks for the comments. Agrees with everything I've read. I'll more likely than not make the jump.

I went to 155's on my TT bike last year and was pretty happy (from 165's, it didn't feel like that big of a jump). Trying 145's this year on, no feedback yet (I literally just put them on).

Somewhat more controversially (I think), I put 145's (from 165's) on my road bike earlier this winter. Thus far I like it, I may need to change cassettes to get some mechanical advantage back. I do use the faux aero position a fair amount when racing either on the front or off the front (...or off the back, for that matter).

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All we have to decide is what to do with the time that is given to us. ~Gandalf

Whoosh, you missed the joke. He was playing off my Dave (H2oFun) comment. See this thread.

http://forum.slowtwitch.com/forum/Slowtwitch_Forums_C1/Triathlon_Forum_F1/My_testing_to_try_and_find_best_crank_length_with_my_Velotron_P6428199/?forum_view=forum_view_collapsed&;page=unread#unread

I was also thinking of making the move to shorter cranks, but I am always weary of making any changes while training that could possibly lead to injury. How big of an effect would 10mm of crank length have on my bicycle fit?

I have comfortably gone from 172 to 165 now down to 155 and I'm 5-11 and could probably even go with a shorter crank

I moved from 172.5 to 165 on my TT bike and loved it so much i also switched to 165 on my race road bike. I can now stay in drops for entire 2-3 hours.

On the trainer and commuter I'm still 172.5 and will stay this way.

Went from 170 on my tt bike to 155 and will never go back. I still have 170s on my road bike and feel fine so really it all depends on your fit as I'm much more lower on my tt bike. For reference I'm 5'7".

5'7'' with 29 inch inseam here and tried 145mm cranks. Set a pr on a local hill (15%) first time I rode with them.

I was prompted to try much shorter cranks after noticing how uncomfortable I was at the top of the stroke when in the drops (road bike). My position is not that low compared to most, but the shorter cranks definitely helped correct some inefficiency with short legs.

I was worried about losing the leverage for climbing hills but from what I read and experienced, any mechanical leverage that you lose is made up with "biological" leverage. Just like in high school when you first try the leg press and you can lift 500 pounds but only in the last inch of the stroke. Putting the leg press seat in a full squat position resulted in much less weight being possible.

For someone with relatively short legs, another advantage was being able to raise the seat 25-30mm coming from 170's on one bike and 175's on another. Having a relatively long torso to go with my short legs is was often difficult to go low enough on most frames that gave me enough reach. Raising the seat made the relative drop to the bars greater and gave me more fitting options.

I'm 6'3 / 190cm and I moved from 175mm to 170mm cranks on the TT rig and immediately ran better and more efficient off the bike.

5mm might be iffy in terms of big adjustments, but I'd say start with with 10. If you're 5'9, don't see a reason why you could be on 160 or 165mm at most!

Best of luck

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Carson Christen
Sport Scientist , Coach
Torden Multisport

I have experimented a lot going from 115mm (was more of dealing with broken cranks things) to 175mm and everywhere in between. Fitness is a big part of it but my best riding was done at 162.5mm. My inseam is 33.63 but I am 5 feet 8.75 inches. I really like the 160-165mm range for myself and have them on all my bikes. I don't think Lionel moving to 165 a few years back has hurt him at all.

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I'm 6' with 34" inseam. I started cycling pretty seriously on and off in the early 80's. I was on 170's for ~10yrs. Then, following the trend, I went to 175s and stayed on them for ~25yrs. A year ago, as an experiment, I put 170's on the tri-bike and I definitely like them better. I still have 175s on the road bike and I like it less.

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Books @ Amazon
"If only he had used his genius for niceness, instead of Evil." M. Smart

Can you link to the ones you are referencing? I'm 6' with 34" inseam. Curious where that puts me. Thanks.

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https://connect.garmin.com/modern/profile/domingjm

https://cobbcycling.com/collections/cranks

The main reason I switched to short cranks initially was some knee issues. I came for the knee issues, I stayed for the extra aeroness, although still an aero brick.
.

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Dropping 5mm is not going to net you that much power gain. I've gone from 175 to 170 on my road bike and from 170 to 150 in 5mm increments on my tri bike. I found 150 too short and 160 felt best without hip impingement issues I still had at 165. I haven't gained power but can average more power over an ironman in a more aero position. I'm 6' with long legs.

How/what/why did you find 150 to be too short? I've had 175-170-165 on my tri bike and didn't notice any difference going from 175-165 other than lots & lots of improvement. New bike with 170 arms and I now have issues again.. Just ordered a cobb 155 which should solve "all" my problems and perhaps even open up for a even lower front.

My guess is at 150 maybe my muscle memory didn't respond naturally in regard to my pedal stoke. After a few months on them I raced them in a 70.3 and it was as if I drifted in and out where I was locked in and felt powerful and then I was some how out of sync just can't seem to generate power. It also felt I was working my lower back and glutes harder to stay on the power I know I can average for that distance. Maybe if I had of given it more time and played with my position I may have adapted to it but the feel was just too short. When I went to 160 it just felt the right/natural length for me with no hindrance through my pedal stroke and no hip impingement so I didn't see the point in persisting with anything shorter and I developed my position from there. When I stepped from 170 to 165 it felt how did I ever live without these and again to 160 but from there as I say sometimes they felt good but other times I struggled. Climbs also anything below 160 felt a grind to get over. I work a fly in fly out job for weeks at a time where I have a CX bike and put 165 cranks on them since I am racing on 160 and only use it on flat trails and on the trainer while I am away and hate 165 compared to 170 on my road and CX bike at home where your hip angle isn't as closed off. I am sure everyone is different but I definitely think you can go too short.

It's hard to say because there's so many factors such as limb length, fit, and accuracy. But basic physics and bio-mechanics would state that the longer the lever arm the easier (less amount of watts) to turn the same gear, ergo the same velocity. However the shorter the lever arm the faster it will turn around the axis since it has a shorter distance to move. Further more you have to factor in limb lengths because no matter how favorable the lever if you can't put optimal power into it you're still missing out. But in a vacuum, assuming you can adjust any crank size to fit, it would ultimately depend on your goal. In a sprint finish or during anything explosive a shorter crank arm, with that faster velocity seems like it would be the logical choice (assuming proper fit). Also, assuming proper fit, during a period when you're trying to minimize use of watts, say in an Ironman, or a long climb a longer crank (assuming proper fit) will me the more logical choice.

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I still lapped everyone on the couch!