Why are shorter MTB cranks suddenly all the rage?

"I'm thinking about getting longer cranks", said no one in 2023. It's definitely true that shorter cranks are a trend right now, but why? Is it all nonsense, or is there something to it? Today we'll take a deep dive into crank length and how it affects your performance. You'll get a highly biased take on the subject from someone with very short legs.

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[DrewPeabawls]

Seth I wanted to compliment you on something you’ve probably heard before but I don’t see often in the comments. That is your script writing skills. The words flow effortlessly and the information is delivered succinctly but with enough color to give me entertainment. And also there the delivery and how you speak to the camera. I know it probably took lots of effort but you sound so natural and relaxed. Kudos to you!

[ChrisBakerElToro]

I never considered shorter cranks until I talked with a professional about my hip pain. It was suggested I use shorter cranks, so I did and now no more hip issues. No more rock strikes is a bonus as well

[addk]

I'm so glad crank length is FINALLY being addressed! Even 15+ years ago it was frustrating to me seeing size medium & even small bikes being sold with 175mm cranks

[divscifres]

This is an important issue for me. Like you, I'm short. I'm also in the "older" category, and have dicey knees. I've watched several "crank length" videos, and this was one of the best. Thank you!

[TheAdminBar]

Man, your ability to create a video is insane man. The storytelling, the filming, the editing, and — most importantly — conveying the message... Dude. It's really good.

[jayaline]

Dude. I have been banging on about this exact same subject with literally exactly the same arguments as you make in this video since the 1990s !! Nobody listened with the answer always the same "bike companies know what they are doing". Hurrrah !! Somebody agrees with me finally. ... I will show this to all my peeps with the tag line "see, whaddiditellya". Made my day 😊

[guylord]

This was much more informative than any of the other videos or articles I’ve seen.

[JustMikeH]

Love your videos.

I had heard the term "making circles with your feet" and it never made sense to me. I always felt like I was stair-climbing on any bicycle I rode for as long as I can remember.

In the last year I learned about shorter crank lengths for shorter inseams. Several methods I used recommended cranks from 150mm to 165mm. I ended up ordering 165 because they were readily available. Changing my from 175mm to 165mm on one of my bikes may not sound like much but it was mind blowing. In the end it didn't change how many watts I could put out, but it did change /how/. I earnestly believed it was going to be a minor change - I was wrong it was a major change.

I wish I understood how much it was going to change things, because I would have been a little more specific about apples to apples testing the same routes before and after.

Some of the things I did notice with concrete certainty:
* My whole body moved a lot less. As you mentioned in the video.
* Also as you mentioned, I made up for raw power by pedaling faster
* I could pedal a LOT faster before I spun out. (In part because my motion was localized to my legs and not whole body). Before I'd start maxing out around 80rpm and could push to 90 for short sprints, any faster I felt like I was flying off the pedals. Now I am comfortable at around 80, often push to 90, and have reached 110rpm on more than one occasion, but feel like I rarely need to ever pedal that fast.

Some things I wish I tested more formally but show marginal gains with data:
* Longer hill climbs seem easier, and my time appeared to have dropped slightly
* My overall endurance seems to have gone up, but at the time of the swap I did not have any longer trips to back it up.

Sometime in the spring I will have time to do something like a 2x centuries with hills and recovery time in between to make them equal tests. I'll swap my cranks between the two and collect all my data from the test. Won't be pure science as it won't account for differences in weather, variations in my physical state, etc, but I think it will show enough differences to suggest changing to shorter cranks is absolutely worth the experimentation.

At the very least, I have experienced the feeling of making circles with my feet for the first time in 40ish years. It feels awesome.

[daleykun]

I've only got a 29.5" inseam and always found my knees started to hurt when cycling for a long time seated on my road bike. Shifting to my 162.5mm cranks I have now completely eliminated the pain overnight - it's "only" 10mm shorter but you get the benefit at the top and bottom of the pedal stroke so it's actually more like 20mm

[HoudiniHawaii]

I had just purchased a set of 155 cranks for my E-bike before watching your video, my justification is - SAFETY!!! My last crash was near the end of a long ride on an an easy section of trail, I was tired and my uphill pedal was hanging a little low as I was coasting along, I didn't notice a little half rotted 6 inch stump that caught my pedal and sent me over hard! Shorter cranks and it would have been a perfect ride.

[lumpyize]

After like 3-4 month break from this, mostly coz of lot of work and hospital visits, it's nice to come back and watch everything I missed. Seth's channels always get me into chill mood, almost feeling the forests breeze and fresh air. Can't wait for better weather and stitches to heal and go back to training mtb

[Todd]

I love the shorter crank move, especially on a ebike.
Seth is in the groove with videos, has been for some time. He’s a pillar for the community now and I am happy about that…such a good dude. I feel fortunate that he makes the content he makes, it checks all boxes for me.
Merry Christmas 🎄

[adamsmith-gt]

Crank length is a huge issue with bike fit. I first slid down this rabit hole while I was fitting my kids on mountain bikes, surprise yes most kids mtb come with too long cranks. I noticed when I put my 3yr old son's seat down for proper leg extension and when he pedalled his knee would come above his hip. This caused him to shift his hips back and forth while pedalling, resulting in poor balance adn bad spinning. Being a proper MTB dad I sourced shorter cranks and have been putting shorter cranks on all new kids bikes. Most kids bikes use square taper BB axle and there are more selection, although heavier. It's great to see more options of shorter cranks with proper hollow thru axles. Thank-you Seth for making this more aware to the community.

[KestrelYI]

Really appreciate this video! Girlfriend is short (5'0) and has often complained of hip discomfort. She has been on 170mm cranks, as that's what came with her 'small' bike. Suboptimal! Glad more manufacturers are looking into this - hopefully somebody brings a budget option to market.

[MaximRecoil]

When I was 11 years old (1986), the neighbor kid who was a year younger than me got a new Diamond Back Cool Streak BMX, and it had 175mm cranks and 44/16 gearing, and when I tried it out I loved it. It was drastically different than my Western Flyer Invader 2 BMX, which I'd had since I was 9, and had 5½" (~140mm) cranks with 36/16 gearing. Each pedal stroke made the bike move so much farther/faster because of the higher gearing, and it wasn't really harder to pedal due to the increased leverage of the longer crank arms.

As an adult (I'm 6' 2") I use 180mm cranks and 44/16 gearing on a BMX. 180mm cranks are common in BMX racing, or at least they were in the 1980s. Some 1980s BMXs even came stock with 180mm cranks, such as the Mongoose Pro Class and the Red Line PL-20. It was usually the top of the line BMXs that came with 180mm cranks, and the lower models usually came with 175mm.

Out of curiosity I checked to see what a modern BMX racer is using for crank length. Niek Kimmann (who's the same height as I am), gold medalist at the 2020 Olympics, said this:

"Crank length is 177.5mm. I used to ride 180mm as first year Junior, then I went to 175mm as second year junior. I knew Worlds was going to be a small track in Rotterdam, so I wanted to make sure I would get out of the gate as fast as possible, so went a little longer to 177.5’s, and stuck with them since then."

[idhvew]

Yep, I would be 187mm cranks but love my 170'S. I do have a 240mm dropper to help out too! Spinning a 30 tooth chain ring to help get my 280+pound arss to the top of our hills. Great work as always!!!

[lucywucyyy]

im 5'5 and switched to 152mm kids cranks and its been a real revelation
knee pain and lower back pain completely cured!
i feel so much better pedaling standing up and pushing harder gears and higher cadences
the ground clearance and stability are noticeable even for my amature riding level
for uphill performance its definitely the way
if my goal was only climbing hills and i didnt care about flat ground speed at all if be running the shortest cranks and smallest chainrings i can find
for flat ground i think i couldnt go much shorter than this

[dkylehall]

I'm 6'2" and went from 175mm to 165mm. Huge improvement. Significantly decreased pedal strikes and really wasn't a noticeable change in leverage. That combined with an oval chainring really helped my climbing.

[markpuccinelli]

Seth, great video. I just purchased a set for my hardtail as it is my guinea pig. You are the voice of reason, keep up the good work.

[ipsgymgirl]

I'm 5'3" and I've been loving my 160 cranks for almost 2 years. 😊 Wishing I could find a set for my fat bike too. Recently settled with 165mm for the fat bike but fingers crossed shorter cranks keep gaining popularity 🤞