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Discussion Starter · #1 ·
While I'm used to most of the arguments around shorter vs. longer cranks for general riding, does anyone have any thoughts on crank length when training on stationary bikes, particularly when it comes to training to build up base mileage and improve my cadence?

A few possible theories I can come up with for length:
  • Same length
    • Training indoors translates more closely to how things feel on my actual bike
  • Shorter
    • Potential Pros
      • Shorter circles would generally suggest a naturally faster cadence at the same level of effort, and get my legs used to the general feel of spinning faster
    • Potential Cons
      • Moving legs through a narrower range of motion might not be as good for building strength that translates to my regular bike
  • Longer
    • Potential Pros
      • Might make it more difficult to go at a faster cadence, which could translate into it feeling easier to keep up that cadence on my regular bike
      • Moving legs through a wider range of motion might be better for building up muscle strength
    • Potential Cons
      • Could be harder on knees
Currently I have 152mm cranks on my bikes ('18 Trek Stache MTB, converted '92 Trek 830 for pavement / gravel riding, & a BMX) and ~130mm on the cheap semi-recumbent indoor bike that I've been using (an Exerpudic 400XL -- it was cheap on FB and is the best that I've found so far to use along with my desk setup in my office and semi-mindlessly ride while I'm working or playing games).

As a point of reference, I just got a cadence sensor a few days ago and so far am finding that I'm naturally somewhere in the 60-70rpm range if I'm riding at what feels like an "easy" pace, getting up to around 90rpm if I push myself, and sustaining somewhere in the 70-80rpm range if I make an effort to go "a little faster".
 

· jcd's best friend
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I never really took crank length into consideration when it comes to improving cadence. I actually do a lot of HIIT sessions on my Peloton Bike+ and my average cadence is up into the 90s now for 20-30 min riding sessions with anywhere between a 40-60% resistance setting. My cadence used to be in the mid 70s back in June. My cadence gains is related to my Peloton and may not reflect my actual riding cadence on the road with a road/gravel bike. Seeing my Peloton is my only bike, I typically use that for my performance comparisons.

Are you tracking cadence mostly on your converted bike or MTB? I've found cadence tracking to be useless on a MTB unless I'm using the bike as my gravel pounder for exercise.
 

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Discussion Starter · #4 ·
Are you tracking cadence mostly on your converted bike or MTB? I've found cadence tracking to be useless on a MTB unless I'm using the bike as my gravel pounder for exercise.
So far I've only tried the cadence sensor on the indoor trainer since I just got in the sensor on Monday and it's been pretty rainy outside this week. I'm using the HR2PV app on Android to pull in both the HR broadcast from my Mi Band 6 and the BLE cadence sensor -- haven't found a good solution otherwise (Xiaomi's app can't read the cadence sensor and Wahoo Fitness doesn't detect the HR broadcast by the watch).
 

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I don't think crank length will matter because your cadence is pretty low. Short cranks can help you spin really fast, over 130 rpm, when it gets difficult to pedal smoothly - even if you have good technique at 100 rpm it still takes some effort to keep things smooth above 130+ rpm.

You just need to practice.
 

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I don’t change crank length when I put my gravel bike on the trainer, but I am thinking about reducing my crank length to help with knee issues.

I would really like to try 170 and 165, but I need to buy both cranks and experiment.
 

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I'd keep it the same if possible.

Are you sure about the crank lengths? Most bike cranks are 165-175 mm. 152 mm seems really short (and not a standard size that I'm aware of), 130 mm ridiculously short but exercise bikes have all sorts of weird sizes.

Always a personal variable, but most people are more efficient with a faster cadence (more like 80-90 rpm) even if that means an easier (less force on pedals, at least) gear
 

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Discussion Starter · #8 ·
Are you sure about the crank lengths? Most bike cranks are 165-175 mm. 152 mm seems really short (and not a standard size that I'm aware of), 130 mm ridiculously short but exercise bikes have all sorts of weird sizes.
Definitely sure on the lengths.

I've tried various lengths and found that the shorter cranks help a lot with reducing pedal strikes on the trail / at the skatepark & overall leave my knees feeling better after rides. On the mountain bike, the corresponding increase in saddle height also means being able to use a slightly longer dropper post.

I've actually tried all the way down to 140mm as an experiment, but found after a few months that 140mm was OK for seated pedaling but required me to drop down a gear for effort to feel roughly the same and just felt "off" for standing pedaling.

130mm is just what came on the indoor bike. Have tried a few other under desk style bikes and some of them use even ridiculously shorter cranks -- usually it's a space-saving measure so that they can either have the cranks closer to the ground or so that they take up less space if you fold up the bike.

Unicycle cranks look like the cheapest compatible option to go a little longer and those seem to cap out around 150mm.

Always a personal variable, but most people are more efficient with a faster cadence (more like 80-90 rpm) even if that means an easier (less force on pedals, at least) gear
I've read that from quite a few sources, hence why I'm trying to look at what's the most effective way of training to increase what feels "normal" to me.
 

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If you are looking to increase your comfort cadence you need to over shoot.

Do something like this:
10 minutes easy spinning.
3 x { 1-minute @90rpm
1- minute easy.
1-minute @100rpm
1-minute easy
1-minute @110rpm
1-minute easy
}
Do this a couple of times and you will find that your natural cadence is coming up.
 
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