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Discussion Starter #1
Starting to believe that for AM/Enduro type trails 170mm cranks are the way to go...

Watched some dude reviewing a 2018 Giant Reign & he was having a dig @Giant for spec'ing 175mm cranks on an Enduro mule i.e. he was getting lots of pedal strikes.

I've experienced similar on two AM type steeds.

Initially on my Nukeproof Scout 290 I was running 175mm cranks & got several random pedal strikes on my first few rides. So, I changed the cranks out for 170mm Zee's.

Pedal strikes gone ^^

After last nights ride (650b Enduro bike w/ 175mm cranks) on good AM type trails. I was again getting random pedal strikes & again I'm thinking of shortening things up by 5mm's.

175mm v 170mm cranks for AM/Enduro... What say you??

Anyone run shorter??

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Starting to believe that for AM/Enduro type trails 170mm cranks are the way to go...

Watched some dude reviewing a 2018 Giant Reign & he was having a dig @Giant for spec'ing 175mm cranks on an Enduro mule i.e. he was getting lots of pedal strikes.

I've experienced similar on two AM type steeds.

Initially on my Nukeproof Scout 290 I was running 175mm cranks & got several random pedal strikes on my first few rides. So, I changed the cranks out for 170mm Zee's.

Pedal strikes gone ^^

After last nights ride (650b Enduro bike w/ 175mm cranks) on good AM type trails. I was again getting random pedal strikes & again I'm thinking of shortening things up by 5mm's.

175mm v 170mm cranks for AM/Enduro... What say you??

Anyone run shorter??

Sent from my kltedv using Tapatalk
You really think 5mm makes a difference with regard to the pedal strikes? 5mm isn't much. Just look at a ruler. Crank arm length is a matter of bike fit, not performance.

I run 165, 170, 175 amongst three bikes currently. Aside from different power it takes to pedal each, no difference in pedal strikes.

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Discussion Starter #3
You really think 5mm makes a difference with regard to the pedal strikes? 5mm isn't much. Just look at a ruler. Crank arm length is a matter of bike fit, not performance.

I run 165, 170, 175 amongst three bikes currently. Aside from different power it takes to pedal each, no difference in pedal strikes.

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Don't think.... Know ^^

We'll wait for some educated people to join the conversation ;-P

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I ride 170 as a matter of course on a bike I build plus go for thin platforms. It's all part of setup with priorities for mountain biking terrain instead of setup for road riding where efficiency is a higher priority.
170 is slightly easier but you can use gearing to vary that.
 

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I went to 170s on one of my bikes for fit purposes more than anything...but less worry about pedal strikes is a nice bonus!
 

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If 1/2 of 1cm is causing you to have rock strikes I think you need to focus on your pedaling technique.
Then you don't know. It's not surprising; most bikes are designed a bit conservative here and you have to go out of your way to have a bike where mandatory pedal strikes are part of the experience for an expert. In some environments even an expert will never see the downsides.


5mm is totally perceptible. Strikes that knock you off line become just annoyances, and grazing strikes don't happen. The roadie world is much more obsessed with power/efficiency than we are, and all the studies i've read have come to the conclusion that so long as your gearing is appropriate then crank arm length doesn't affect power in any meaningful way.

That said, i'm running 175s on both my bikes and have excessive pedal strikes cuz i fkn love my old-ass 175mm gravity lite cranks. I designed the hardtail for 650b, so when i get around to building a 650b wheelset for it that extra 7mm of radius will fix the issue. With my FS i enjoy that low LOW BB height way more than i'd appreciate fewer pedal strikes and i don't care enough to buy new cranks.





I think that crank length is kind of bullshit, to slightly change the subject. In the roadie world there have been several efforts to create algorithms to determine crank length based on legs, and they all seem to come to the conclusion that if you're a completely average male cyclist you can gain a <1% advantage by tweaking crank length between the readily available 165-175, but if you're an average woman or really tall like me then the range of available crank lengths is just totally irrelevant to you. It makes sense from a mass production sense- more than 15mm variation in crank length means differing BB drops are necessary for different frames. Not worth it when marketing, purchasing, and engineering are intertwined.
 

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Im only 5'7, 175's are too long. So are 170's for that matter, but I ride them anyway.

I got our daughter 160's, which I thought would be great for her (they are) and figured they'd be silly short for me... but I rode around on her bike and they feel kind of great. I think a lot of people ride cranks that are too long.

170's are just so much easier and cheaper to find than 165s, otherwise id be on 165's on all my bikes.
 

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I went from 175 to 170 for the same reasons

5mm additional clearance significantly reduces pedale strikes, since most pedal strikes are more like "glancing blows"

especially on bikes with a low bb the difference will be felt immediately
 

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I went from 175 to 170 for the same reasons

5mm additional clearance significantly reduces pedale strikes, since most pedal strikes are more like "glancing blows"

especially on bikes with a low bb the difference will be felt immediately
This would make sense if the height of all rocks sticking out of the trail were the same. They're not.

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5mm can effect pedal strike, for sure...common sense.
If you have a rock that is just hitting the pedal at 175, if you change the crank to 170 you will no longer hit that rock.....

However....in a real life situation does that effect me personally, NO.
I try to keep both my pedals level in rough trail or adjust the height of the side I think might hit something.

You do get more torque with a shorter crank as you will have to rotate less to complete a full rotation, cadence may also increase.
It will help reduce range motion at the knee.

With all being said, I believe the crank length is there to help taller and shorter people feel more comfortable riding a bike
 

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5mm is anything but negligible when talking about DH pedal strikes. To illustrate this let the air out of your shock, then angle your cranks to simulate likely riding positions. You'll see just how low your bb is when deep in the stroke, and how little wiggle room your pedals actually have in those deep travel situations.

DH cranks are short for a reason. You do lose leverage as you shorten your cranks. I would say go as long as you can unless DH pedal strikes are an issue. No sense in giving up leverage unless you really need clearance on the DH. If the strikes are on the climbs, even super short cranks will require strategic pedaling. A fast hub and some ratcheting will get 180 cranks up better than 165's pedaling mindlessly, but there's little you can do to get 180's down cleanly.
 

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I switched to 170's on all my mountain bikes. Just feels better on my upper leg when one leg is down weighting a pedal and during a pedal stroke. A benefit is significantly less pedal glances on rocks, roots, etc. 1/5th of an inch doesn't sound like much till you consider a BB height going from 13.4" to 13.2". Same thing.
 

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I disagree.

Longer levers = more torque.
On a mechanical device or machine, sure. When you factor in human biometrics, then definitely not!

My legs go out of the ideal angle to apply power with 175's. 170's too for that matter, but its getting closer to what works.

I can apply better, smoother power for longer with a shorter crank. The mechanical leverage difference stops mattering if it doesnt work with your body.
 

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On a mechanical device or machine, sure. When you factor in human biometrics, then definitely not!

My legs go out of the ideal angle to apply power with 175's. 170's too for that matter, but its getting closer to what works.

I can apply better, smoother power for longer with a shorter crank. The mechanical leverage difference stops mattering if it doesnt work with your body.
Wonder if there is a relation to leg length. My inseam is 34.25" and I seem to be able to push about 2 teeth higher out back with the longer cranks.

However, our trails are almost never a sit and spin matter - almost all out of the saddle grunts.

Now that I come to think of it, those rare times I'm on my mud bike doing back roads, I had come to realize spinning did seem better on shorter cranks.

So, like most everything, I guess the correct answer is, "it depends..."
 

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I switched from 175 to 170 on all my bikes. Less pedal strikes and easier on my knees wished I had done it years ago. I am 5'9" with a 30" inseam.
 

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According to my research, most people would be better served with shorter cranks. The angle of the knee and the biomechanics involved produce more power with shorter cranks, even taller people like me (6' 3").

Also, shorter cranks (yes, even 5mm) can significantly reduce pedal strikes. Most of my pedal strikes are barely clipping rocks and roots. Add 5mm to those and they become more significant events. The worst crash I have ever had was a pedal strike I never saw coming. If I was on 5mm shorter cranks, that may have been enough to save me.
 
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