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short crank-arm length experience?

Viewing 15 posts - 1 through 15 (of 17 total)
  • #93962
    Participant

    Madcow mentions the possible benefits of short crank-arm length in the latest Crank Review.

    Is anyone out there using short cranks on your TT, road or mountain bikes? If so, have you noticed a difference, qualitatively or quantitatively, in your performance since moving from longer cranks? I’m interested in hearing from those out there that have given this a try.

    Cheers!

    Ringtail

    #93973
    Participant

    I have been using 165mm cranks for the last 2 years and I love them. They don’t feel too different from the 170′s that I always used, whereas every time I have tried 172.5′s it felt like my legs were doing more work. The 165′s allow me to get a bit lower on the front of the bike without my thighs hitting my gut. It is easier to spin a higher cadence too. I won’t ever use any other crank length. I ride a 54 cm frame & am 5′-7″ tall.

    Have you ever wondered if there was more to life, other than being really, really, ridiculously good looking?
    #93978
    Keymaster

    I used short cranks (170mm) on my TT bik. I noticed, SRM data, an improvement in my power. It’s hard to say if this was because of an increase in form though. So I compared 20 min efforts TT vs road bike and TT looked better compared to the road bike I didn’t change my cranks on. So… I went shorter there too. :) I’m 6’2″ on a 58cm frame.

    I run the Facebook Page, Twitter Account and write code the rest of the day.
    #94126
    Participant

    I can’t do it. When I was a kid, I rode 165mm on the track and 172.5mm on the road. Now, I have to ride 172.5mm on the track, too. I tried to ride 170mm and 175mm, but it doesn’t work for me.

    #94413
    Moderator

    I have 170mm on my road bikes. I like it but I can’t say that I have any data that proves it works better for me. To be honest I’m not sure if would notice if someone switched them for 172.5.

    #94414
    Participant

    I used to have 170s on my track bike, and 180s on my road bike, but I found when riding the shorter cranks I would ‘hit’ the TDC and BDC and I was smoother, and had a higher cadence with a standardised crank length.

    That said I think if you often change crank length then you can do so more easily than if yo do so occasionally. The British track team have a ‘clown bike’ that has 100mm cranks that Sir Chris was getting to over 300rpm to work on neuromuscular firing rates.

    #94415
    Participant

    It seems that the consensus among the biomechanists is still out on whether shorter is clearly better or not.

    As for myself, I began riding 150mm cranks on my road bike as an experiment 6 weeks ago and I am now a convert. I can climb, tt & sprint as well as before, with the added benefits of:
    -noticeably stiffer crank arms (read 1″ shorter each than my 172.5).
    -effectively lower front end from raising my saddle (better aerodynamics and noticeably better high-speed cornering).
    -more open hip angle (easier breathing, improved comfort, and better power generation).
    -my power stroke now has enough momentum to carry my opposite leg over the TDC dead-spot without needing to recruit my hamstrings to pull that leg up & over (verified on a computrainer last weekend).

    I figure most people don’t have the luxury to test different length cranks and end up going with whatever was sold to them on their first bike. I feel fortunate to have been able to experiment and have now made an informed decision. It’s been a fun and enlightning journey!

    I’ve enjoyed reading the other riders’ input here on this forum and hope others will continue to chime in with their experiences.

    #95417
    Participant

    Hi,

    I was riding 180mm cranks last year as I’m 6’3 tall.
    I tried 165mm cranks and I feel very good with them.

    To Ringtail:

    Where did you find your 150mm cranks? Rotor 3d?

    I would like to try 150mm cranks too.

    #95418
    Participant

    Hi Rick,

    Good guess, they are Rotor 3d+ cranks. I picked them up used on eBay for a steal. Fairwheel Bikes was able to locate and order a conversion BB to allow the UBB-30 Rotor spindle to work with my threaded BB86 frameset.

    I do, however, need to revise the findings on my last post. Being a predominantly out-of-the-saddle climber, I found that the leverage of my 172.5s enables me to climb much easier than the 150s did. Because of this I am once again running my 172.5s on my road bike and am saving the 150s for my TT bike where I think they will really shine.

    Cheers!

    Ringtail

    #95427
    Participant

    Hi Ringtail,

    I think it is because of your gears.How many tooth do you have on your chainring?

    If you work with shorter crank, you have to change your chainring because the “gain ratio” is different if you don’t change your chainring.

    look at this to understand:http://sheldonbrown.com/gears/

    For exemple a 52 teeth chainring with 175mm crank is quite the same as a 50 teeth with 170mm crank.
    The force to apply on cranks remain the same but the spinning speed would be faster.

    To talk about me, I use 165mm cranks with a 46 teeth chainring and 11-23 rear gears.

    I run as fast and for a longer time than other men of my team and they just don’t understand how it could be possible…

    Let me know if you tried it,

    Regards

    #95441
    Participant

    Hi Rick and everyone…

    I have not yet experimented with shorter crank arm lengths, but after doing lots of reading on the subject, I am intrigued. I just checked out Sheldon’s Gain Ratio chart, another great tool.

    Since I am building up a new bike now, my first custom, I was thinking about trying shorter crank arms, but I will probably stay fairly conservative…since I will only have one crank set for the bike.

    Being 175cm tall (5ft 9in) I usually ride 172.5mm cranks
    I am keeping my groupset intact with the Dura-Ace 9000 cranks, so I am looking at Shimano’s options of either 165mm, 167.5mm, 170mm or my usual 172.5mm

    Where I live in Northern California, I am surrounded by hills and mountains, so I was planning on chainrings 50/34 and cassette 11/28.

    I don’t race or TT, just challenging free rides in the hills. What would you suggest for my crank arm length?

    thanks,

    Chris

    #95444
    Moderator

    I’m not entirely convinced by the idea of the gain ratio, or rather, that you can (or should) toss two issues into one bag and solve them at the same time.

    Crank length is crank length and gearing is gearing.

    By changing the crank length, you change how you produce power, not how much, really.

    If your cadence was to go up significantly, then yeah, you’d need to adjust the gearing. I don’t take it for granted that will happen, though. I’ll have to admit that I’m not sure yet what I mean by “significantly”.

    And if it did, you’d adjust your gearing to your crank length, not the other way around. Biomechanics are more important.

    I’m not sure this really helped you with your question, but I’ll have to think about it some more. Not sure how you could just recommend a certain crank length to someone on the internet. I’d probably not go as extreme as 150.

    "Nothing compares to the simple pleasures of a bike ride," said John F. Kennedy, a man who had the pleasure of Marilyn Monroe.
    #95447
    Participant

    Ypsylon,

    Even without all the particulars weighed and measured, your points are well taken.

    My default plan with this current build is to dip down to 170mm from my usual 172.5mm crank length. I imagine that I won’t be able to sense the difference, especially because I’ll experience the new bike and new crank arm length as one new complete system, instead of doing an A/B test of different crank lengths on the same bike.

    Just as an aside, when I mentioned shorter crank arm length to my frame builder, to see if he may want to consider a slight tweak in geometry, he vigorously cautioned against shortening crank arm length, but I take that as the normal expected reaction until this area gets studied more rigorously.

    I guess when it comes down to it, I’m wondering if there are any shorter crank arm experimenters out there who would advise me against going shorter, considering that I’m not a racer or TT guy, and have lots of climbing on most of my rides…?

    #95450
    Participant

    Hi Ypsylon and everyone,

    I’m not here to make people go shorter or believe in it. I just try to help those who want to go shorter by talking about my own experience.
    First I had 180mm cranks last year. I was a good racer but very slow in accelerations and I was very tired after the half of the race. (heart rate dropped down)
    When I bought my Fixie, cranks length was 170mm so I trained with all this winter and it was very good.
    When I took back my race bike with 180mm cranks it was very different. I fell better on the fixie…
    What change? The cranks lengths.

    So , first I putted back the original cranks (175mm) and I feel better in climbing and sprinting and less fatigue after long training.
    So I understood that I could try shorter and I putted 165mm cranks and it is like a bomb. I think I could use the original 50 teeth chainring but I decided to not change the gain ratio fo the moment, maybe later.
    But in fact, using 46×11 is the quite same gearing than 50×12, so in crit. race it makes no problem.

    Theses cranks are not magic, but I help you to raise the saddle and drop the front end. It results in a more aero position so it is like gaining a little power. You produce the same power but you are more aero.
    The second thing is that your foot does a shorter circle to make 1 rpm. So at 90 rpm for exemple, your feet speed is slower with shorter cranks than with original cranks. It results a less oxygen consumption.

    And last your hip angle is more open with shorter cranks, so you’ll have less fatigue at the end of races.

    All theses was taken from different study on the internet. Believe in it or not.

    BUT!

    There are two very important points to know:

    - shorter cranks may not work for some people because of biomechanics feature of each people.

    - you have to try different cranks lengths to find what is the best for you, ands it could be expensive…

    Has you said, the most improvement is first the change in how you produce power but some TT racer seen a gain of 20-30 watts after training six weeks with shorter cranks.

    I don’t have a power meter for now but it could be interesting to test it and compare.

    Regards

    PS: I’m french so forgive me for my bad english

    #95451
    Moderator

    Hi Ypsylon and everyone,

    I’m not here to make people go shorter or believe in it. I just try to help those who want to go shorter by talking about my own experience.<br>

    I didn’t mean to say that you had some kind of agenda, and I appreciate you sharing your findings. You have lots of valid points.

    The gain ratio and it’s implementation still puzzle me a bit. I might have it wrong in my head, but going to a smaller chainring assumes that you will spin faster and while that might be the case for some or most people, I don’t see why that would be the case for everyone.

    "Nothing compares to the simple pleasures of a bike ride," said John F. Kennedy, a man who had the pleasure of Marilyn Monroe.
Viewing 15 posts - 1 through 15 (of 17 total)

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