Short vs. Long MTB Cranks | Physical Therapist Perspective

[@5DEV]

Wow man. This video is great. Well done. We can confirm we had no part in this video. Super cool the algorithm led us your way this morning. 🔥🔥

[@DrJMTB]

👊🏼👊🏼

[@Ugoeh2]

I ride your 145s. I'm 6'2" and tried 5 sizes from 153 to 130, mostly cut down sram cranks by Bikesmith Design. I got several friends on shorter cranks, one buddy on his Bosch ebike with 155s from you. All of them are faster riders now.

[@jimwing.2178]

I'm 6'2" tall with 34" inseam. I switched from 175mm cranks to 165mm in hopes of reducing knee pain. That was successful and I found that my rides were not as exhausting as they were with the 175s, as you mentioned. I agree with most of what you said except for two exceptions: 1) When torque and power matter the most, I am off my saddle, just like you were in riding portion of the video, and the opposite of your indoor demonstration. When standing on the pedals, I can move around so that I can get my bodyweight going through the ends of the cranks with hips and knees not nearly as flexed as your indoor demonstration shows. That gives the longer cranks a torque advantage. With the shorter cranks, I've adjusted my attack strategy for the steep uphills. It's not necessarily more difficult; it's just different. 2) Having the feet closer together in the fore/aft direction does not provide more stability. For me it is definitely a less stable posture. And if using flat pedals, the rider must press the fore foot forward/heel down and the rear foot aftward/heel up to stay connected to the bike when off the ground or rolling through rough terrain. With shorter cranks, the feet are closer together and the angle makes it more difficult to maintain proper contact. I will keep the 165s on my bike. The benefits outweigh the disadvantages for me, even though I have to ride more carefully on the janky trails that I love and not boost so hard on the jumps.

[@Southerncyclist]

Thats odd. Im 6'3 with a 36.5 inseam. My road bike has 180mm cranks. Love it. Borrowing a MTB with 170mm cranks. Road yesterday I got some knee pain today on the top of the knees .

[@jimwing.2178]

@@Southerncyclist If you are pedaling while sitting on the saddle, you have to raise the saddle to compensate for shorter cranks. Dropper posts are usually set up so that the top of their range is about the same height as a road bike's saddle height. Running cranks that are 10 cm shorter will force you hips and knees into greater extension. If that bothers you (it bothered me), you have to raise your saddle so the to of its range is 10 cm higher.

[@Southerncyclist]

@@jimwing.2178 ya man I raised the seat like 1.5 inches from where the owner had it lol.

[@dcmtbadventures4910]

As a fellow PT and mountain biker with short cranks, I gotta say I love this video. Nicely done!

[@DrJMTB]

Thanks for the kind words 👊🏼

[@petertobey603]

Well done. Over the last two years I have gone from 175 to 165 cranks. I also switched to an oval chain ring, 32 teeth. Great combo where i do most of my riding in Vermont. Soon to be 73.

[@DrJMTB]

Awesome, keep shredding!

[@ChristianPareATLAS]

😋

[@msm624]

This is a load of shit.... You say feet closer together is more stable? Stop giving advise please.

[@FOX1RR]

You have presented solid evidence from many categories of what the crank arm does and can do, both positive and negatively, by being shorter and longer. You've sold me! Now, I want to find my perfect shorter length crank rather than accepting the previous status quo. New journey!!😃

[@tonyrobinson1623]

I switched from 175 to 160 and I feel it's night and day better. Besides the advantages mentioned in the video I have noticed that riding while standing is vastly improved. it's so much smoother and more in control. the transition from siting to standing is much smother. The main reason I'm so pleased with short cranks is that my knees are damaged and painful, but the pain all but disappeared after I switched.

[@DaraParsavand]

What is your inseam? I’m 31.75” and thinking of making the same jump (175 -> 160, or perhaps all the way to 155 like Dr J).

[@glenfinch]

The squat/press analogy is a good one for conveying the effect of the longer lever on your leg joints and muscles

[@marktechsci]

Said by no one who understands squats ever.

[@ronnisullivan9794]

Omg. Finally. Been riding for 30 years. 5’4. Been preaching this stuff to deaf ears. Thank you for hearing me. Glad i found your video

[@stug45]

I find off road you want to go as long as you can for those grinding portions, without it being too short you can't spin. I'm 5'10" with 31" inseam, 170 works well for MTB but 165 does too, especially an e bike since you just need to move your legs to get the motor going. For a fixed position like road or time trial you'll want efficiency and aerodynamics, so even shorter works even better. Hip impingement meant swapping over to 165mm from 172.5. pretty much solved the issue overnight. So I moved from 175 to 170 on the MTB and found it raised my saddle up, making the long travel 26" hardtail ride like a horse! Swapped out that to a better bike has transformed my riding (along with 29 wheels!) My comfort level is massively improved with shorter cranks but I do think there is a limit!

[@flyingnorseman]

Im 6=4 or 194 cm. Run 175 on trail bike and 180s on XC rig. Tried 170s and hated them. 51 years old been riding MTB for 31 years.

[@Defco3d]

I'm 195cm. What is your inseam?

[@xXxTeenSplayer]

I'm 6'4", and 175s feel just right (albeit I haven't tried anything less than 170). Except for the pedal clearance! It just makes it that much more difficult to get through big rocky climbs! I'm on a 120 rear, and the clearance just isn't there...

[@highblackdesert]

I ride a Salsa Mukluk fat bike doing trail work in the National Forest. I am regularly carrying tools that cause the bike to weigh 70 lbs on average. I switched from 175 to 165 last year and have never looked back. I’m 6 feet tall. Game changer! Let pedal strikes, better climbing ability, hips and knees feel great. Will be switching my other bikes as funds allow. Thanks for the video!

[@DrJMTB]

Thanks for the real-world feedback! And thanks for your efforts on trail work 👊🏼

[@chow-chihuang4903]

I was expecting reduction in knee pain but the total lack of hip and lower back pain after I switched from 170 to 160 cranks really surprised me. Should’ve done it years ago.

[@NewMexicoOutside]

Fat bike for the win 🤙. They are great bikes and perfect for rolling and smoothing out trail that has been rutted up by “pizza cutters”

[@Slowrider606]

I have been thinking about trying shorter cranks as I am 5’6” with a 30” inseam. This video just solidified that desire. Your background in PT helps explain a lot of what I experience with longer cranks (175mm)

[@danielmcgowan9534]

I'm 5"7'. 155mm cranks on the gravel/all road bike have been very helpful for nerve pinching and hip issues. They may not make me produce more power; but my average speed has increased. I'm thinking of changing the cranks on the fat tire bike as well.

[@omarcervantes9752]

Did you do it? I have same measurements

[@danielmcgowan9534]

@@omarcervantes9752 I have not changed the length of the cranks on my fat tire bike.

[@chrisallen5293]

Great video. This has been this best video explaining the benefits of short cranks I've seen. And being someone that has lower back pain from time to time the more upright position caught my attention. Gonna try some shorter cranks. Thanks again, good stuff

[@DrJMTB]

Thanks for the kind feedback and enjoy the cranks!

[@chrishorbatt3504]

So I can only speak for myself about this, but I ran 165 cranks on my bike and just could not get used to them . I'm 6 ft tall and whatl bothered me the most was I had to raise the seat post and I just felt too high on the bike. And I could definitely feel the shorter pedaling circle and it felt weird to me.

[@carterschichtel9678]

I recently put 155s on my park bike. First impressions are no negative effects, more confidence and I don’t feel like I’m stretching out each stroke. It’s winter so I haven’t gotten to fully test them yet but i already know I’m going to love it. Will likely get another set for the emtb

[@DrJMTB]

Hope you enjoy them! I love mine.

[@mikestivers8302]

motocross has both pegs at the same spot.. no trouble with it. i use 155 on the parks and downhills, too. i have a 30" inseam and prolly could have gotten away with 150's im tellin ya, shorter cranks improve jumping. ;)

[@skiMTB]

ABSOLUTELY THEE BEST EXPLANTION on this debate (so far). I think I can finally decide on a length and feel like I made the right choice.

[@oiyo5124]

Feet placement on pedal might be another thing to consider with these experiments. I tend to stomp and put it way behind the ball of the foot around the middle when it gets tough uphill, then near my toes when its high speed and manageable.

[@MrRay645]

Foot placement for me is more than going from 165’s to 175’s for sure. Just looking and my mtb cleats vs my gravel bike shoes/cleats shows well over 15mm of difference. Mtb stand and mash shooter cranks my cleats are more mid foot, sit and spin longer cranks on the gravel bike cleats are more on the balls….. end result same stance

[@Twisted_Biscuit]

Apologize if I missed it, but something I don't think you mentioned was the fact that if you shorten your cranks, you have to raise your seat by the same amount to maintain correct pedal to seat height. This now goes against what you were saying about rider comfort for shorter cranks because you are now having to lean more since the seat height increased but your bar height stayed the same, adding more work for your lower back and weight on your wrist/handlebars. I'd rather have more leg movement vs throwing my back out.

[@johnkatakowsi9907]

Well done Sir!!!! I recieved my 155mm cranks a few days back getting ready to install them on my MTB. old mtb gets relief!! 30 inch inseam!!!!😀

[@Osom_mtb]

155mm Hope here too , burning legs in long descents are past now . Almost no pedal strikes also Pedaling uphill didn’t change at all (with an enduro 170mm bike ) so never going back to longer cranks .

[@DrJMTB]

Thanks for sharing 👊🏼

[@zjedinite]

Me neither! Going back I mean 🤙🏽🤙🏽🤙🏽

[@laramiegrinde9246]

I didn't realize how important this was until I got a full sus that came with 170 mm cranks. I never got tired knees, had way better balance, felt stronger on long ascents, and just all around loved the feeling. So I switched out my fat bike cranks to 170 mm also, and added a 28 tooth oval and now it climbs like a beast too. I'm female and 5'6" but mostly annoying long legs so for me this really dialed my bikes. Once you change, you aren't going to believe how much of a difference it makes.

[@TheBlutark34]

Went 155 Canfield cranks when they were the only player on the market. Now 155 Hope going on the new enduro, I'm never going back to "standard" crank length.

[@tonkshred]

How tall are ya ? 175s on my enduro killing my hips on long rides , 5’11 here. Was thinking 165 but now?

[@zixxerlev]

Your take on spec'ing small and medium bikes with 170mm and up cranks is exactly what I've been ranting about to my friends, lol. I'm 5'6", and my knees love the 150mm cranks vs the oem 170mm. And I could probably go shorter! I too, have experienced all the positive results you have highlighted. Thank you for updating what I think is an important topic.

[@DrJMTB]

Thank you for your kind feedback and glad you’ve benefited as I have 👊🏼

[@julianhawker7672]

What did you do with the seat Hight after swapping ? read stuff on this that seams to conflict..............

[@zixxerlev]

Seat height comes up a bit, because the bottom of your pedal stroke won't be as low as it was with longer cranks. Follow a tutorial on finding the proper form, then tweak it to your liking. I think I have my seat height set your proper leg extension, but I rarely ride any parts of my local trails at full extension. I like to sit in the bike, feels good to me.

[@ChrisDunn-h1u]

I'm 6'4" ride 155 on Turbo Levo and Santa Cruz Heckler. No issues. I also weigh 205 and with lower bottom brackets pedal strikes are issue. Not with 155s . One of best additions on my bikes.

[@stephendenagy3396]

Great video! I got some sweet Hope purple 155 cranks, replacing 165 on my Turbo Levo. Wow! Smoother, almost “luxurious “ pedaling, knee pain gone, right inner hip pain leaving. This is insane, bike companies couldn’t care less about fit!

[@xXxTeenSplayer]

You selling the 165s lol?

[@devincook3278]

Physics says higher stability will be obtained from a wider base. The whole feet closer together=better cornering, and more stability is a real head scratcher.

[@aaronsoule8484]

The base is the wheels on a bike, not the feet?

[@tedjohansen6535]

We have hands on the handlebars at a longer distance to provide plenty of fore aft leverage, and that does a pretty good job for motorcycles. The hip twist induced by bike crank positioning makes taking big hits unstable. I could see pedal down turns going either way on stability, but suspect longer might actually provide an advantage for turning bcuz lower COG.

[@sandy_knight]

@@tedjohansen6535 The way I look at it shorter cranks means you have more leg travel left to absorb hits (like running less sag) and also gives you a higher view point for reading the trail ahead. AFAIK motocross riders don't run offset pegs, if there was a handling advantage I'm sure they would.

[@XlogicXX]

That is, without a doubt, the freaking best explanation of short and long crank arms. I squatted heavy back in the day, so I fully understand the deep vs. shollow squat analogy. Thanks!

[@oic1968]

I started riding at age 54 with an emtn bike.. this was informative. Thank you.

[@jasonkroll2735]

I had to switch back from155 to 175..too much pressure in a small section of my knees....needed to spread it through all my knee instead of in the apex of the stroke.

[@JesseStarrPhoto]

155 to 175 is a huge change. 175 to 165 is a much more reasonable place to try.

[@jasonkroll2735]

@@JesseStarrPhoto had profile mini ti cranks on my mini hutch....so tried them. Good for ebikes and dh bikes becauseu don't pedal much at all..but trail to road...u need a bigger rear cassette to equal proper sized crakes. And the cadence to match feels like my knees are flying off the hinges . 170 I even notice it ...and not just on climbs..I'm sticking with what works.

[@JesseStarrPhoto]

@@jasonkroll2735 ok. If that works for you, great. Most people we fit with reasonably shorter cranks see a lot of benefits in road, mountain, and gravel.

[@noelbrown6771]

Yeah I like to keep one of my older bikes around with the 175mm cranks to have more range of motion sometimes.

[@lakevacm]

I like your clarity. Keep conveying. And here we thought clear thinking was out the window in a world gone mad.

[@TaivalOutdoors]

Very interesting! Always thought that messing with crank lengths is something I shouldn't consider as barely a weekend rider, but this certainly got me thinking. I'm 6' 3.5" and fatbiking, but still.

[@karlosxzy]

I work in the industry and 100% agree with this. My boss and I have had many long rants to industry reps about how speccing all sizes of these modern long, slack and low bikes with the same 170mm crank arms flies in the face of proportional bike fit. How can it make sense in any capacity to spec a Shimano XT 170mm crank on both a XS bike and also a XL bike of the same make and model? Even here in Australia it is nearly impossible to buy 165mm cranks from Shimano as they generally only keep stock of 170 and 175 versions. I have a pair of 165s on back order for myself on a large size frame, and am trying to find a supplier for 155 or smaller cranks for my partner who's on a small size frame.

[@UpHillWill]

You killed it with this video!! Great job man!!

[@DrJMTB]

👊🏼👊🏼

[@davewallace9048]

Excellent Description of how Shorter crank lengths can benefit everyone. The MTB community is finally learning we’re not riding road bikes. We’re riding mountain bikes. Going to try a set of E wings at 160mm on my brand new transition spur build. Also gonna do a hybrid drive train set up with the rear derailer being transmission Along with the shifter.. The rest is gonna be the older 12 speed eagle cassette xo1 And chain. I also like to run the absolute black 32 tooth Oval chain ring!! Should be a killer set up along with the new pike ultimate at 130mm On the front fork! Bike should be about 26 pounds along with the Enve carbon stem And 25 mm rise carbon bar!

[@danstanley9341]

I’m 6’5” and need to squeeze out every mm I can get out of my crank length so I can get my seat post/butt as low on the bike as possible, which allows me to lower the stack so I don’t need 40mm of spacers under my stem. Must be nice getting to think about efficiency but when you’re tall you have to be super practical 😢

[@FoVision]

What's your inseam though? I'm 6'5 but I have short legs and 165 feels much better than 175

[@roddas26]

So pretty much the same size as this guy 😂

[@AloiziyBombel]

Same story 6.3. I cant even imagine with my feet 300mm shoes ride smal cranks. How??! It works only for M and S sized guys(maybe).

[@fpsgenerator]

​@user-kb4me4yb6x why would your feet size matter? Less shoe-chainstay rub is a plus imo

[@AloiziyBombel]

@@fpsgenerator because just make an experiment. Rotate cranks with small feet and big one. Its ABSOLUTELY different feelings. On big feet you almost didnt make a virtual circle(cant explain) it feels like forward backward movement but not rotation. It feels strange. There is no amplitude at all. It feels like you dont ride bike, but stroking your legs fast

[@WhatisHealth-q7l]

The torque ratio is the same for 130-180mm cranks- get the shortest crank possible for the style of riding. 165mm, 28t front crank with an 11-50t cassette on AL hardtail, is a climbing beast in Western Colorado. 170mm on the road bike and 170 on the ATB bike. 29.25 inch inseam.

[@miket.220]

I have a Trek Verve 1 with 170mm cranks, 38t single in front, 7spd 14-34t cassette. I’m 6ft even. With the 170s, I normally cruise on flat pavement in 5th-6th gear depending on headwind. I switched to 165mm crank and noticed in riding I had to go a gear lower, cruising 4th-5th gear. Switched back to 170mm cranks and got back into 6th gear cruising. If I wanted to go 165mm cranks for shorter spins, I’d definitely have to switch my front ring to a 36t to get to the highest gear.

[@michaelhenricks4856]

I rocked from side to side on the seat and had sore legs from over flexing. Cheap REI bike has incompatible bottom bracket so I had to chop down 175 to make 156mm. Immediately felt better and started making climbs there were impossible before. But then I buy 29" inseams 'cause I can'g find 28". I run 32T on my hardtail. Two years later and I'm still thrilled.

[@edsinofsky]

just got a new e road bike, a creo Small with 170mm stock. First thing I did was order the shortest cranks I could find that fit, a 165. Will continue to look for shorter ones like 155 or 160.

[@laeljon]

Been racing MTBikes since 1987. Watching video of me racing looked terrible, and I felt that way. Ten years ago I had a machinist shorten my cranks to 135mm. I tried adjustable crank arms from 90 mm to 175 mm Decided on 125mm for the road bike and 135mm for the MTB I think maybe 130 mm would be best for me. I love my shorter crank arms. Everyone always bring up the leverage point. They just don't undrsatand. Great video! Thanks Also I'am 5' 1"

[@DrJMTB]

Awesome story. Sounds like you were ahead of the curve on shorter cranks!

[@patrickkatzmair]

Yeah sure 😂

[@zazhou]

What manufacturers do cranks 155mm or less? I am approximately your height too.

[@evguenistarikov9954]

I probably couldn’t tell all the subtle differences between 170 originally on my bike and 165 I installed later except one fact: clearance is much improved and you stop catching rocks and roots on the trails where you used to with longer cranks. And just that makes my ride experience much better! When I was thinking of switching for a shorter cranks this was my biggest concern

[@tibbar1000]

Great video; lots of information in a relatively short video. I had to hit that subscribe button.

[@amhtxc2960]

I am almost 6'3", with long legs. I was always very skeptical of shorter cranks and always used 175 mm ones. But one day I tried 165 mm cranks on my heavy PropainTyee...I swear by them now, what an amazing difference when climbing and on longer rides they make. My legs just get much less tired so I can ride higher and longer. Better gorund, rocks, roots etc clearance too. And I have not noticed any drawback.

[@here4therides]

This is all great information, but you left out the fact that however much the crank is shortened, the seat will have te be raised by the same amount. I went from 170 to 165 and I had to raise my my seat 5mm to have the same knee angle at full extension. I feel way more on top of the bike. Its fine, but I cant imagine going another 5mm higher on my saddle hieght. Also, the higher the seat, the longer the effective toptube length will be. The effective seat tube angle will be slacker as well. Im not saying dont do it, but theres a lot more to it than just saying samller circles = better. Hopefully MTB companies will study the effects of shorter cranks on Geometry and adjust accordingly. Hell if 160mm becomes the new norm, every company can lower thier BB hieght making, thus lowering the center of gravity.

[@GregAspenson]

I thought about the effective seat angle as well. If I were to raise my seat any higher than it is my weight distribution would be way too far back on the bike especially with my chain stays currently at 415mm.

[@ericbennett-wu4zx]

Sounds like a lot of thought went into your explanation. Lol. If it’s better for you, then it is! There is nothing wrong with finding the best solution for your situation. I haven’t switched yet, but I’m gonna definitely switch. Appreciate everyone’s input for sure!

[@JesseStarrPhoto]

Pushing your saddle forward on the rails can help compensate often.

[@kokonanana1]

Shorter cranks, LOWER your saddle so leg extension at BDC is the same!!!

[@John-dd2oi]

This is incorrect. You should always measure saddle height center of BB to top of saddle across all bikes regardless of crank length. The circle you pedal is a virtual center so the angle of knee will naturally become less the shorter the crank. Do not lower the saddle as you are adjusting your body position.

[@WDPsoldier]

I have been thinking of switching to shorter cranks due to short legs. Pedaling out of the saddle always have me feeling like i am digging too far on the down stroke. The biggest negative with shorter cranks is that the length you are reducing at the cranks, you need to add to your dropper length or height in your seat tube. Unless your dropper falls in the sweet spot, you will end up with less space to move out of the saddle on descents.

[@vaquerosupreme3189]

Great deep dive. Matt Appleman who is 6'2" says he uses 145mm cranks. I've changed my cranks to 155mm and never be looking back.

[@Kaspurr84]

I went from 175 to 165. I wanted to do 160s but the cost options were just out of my range. I like a lot of people overlooked crank length forever. IMO there are no downsides to specing a crank for your proper leg length/ height range

[@texasRoofDoctor]

Thank you for posting this. I have heard a lot of buzz about this, but dismissed it partially as more marketing buzz from the industry. I am 6'1" and have always had some knee issues. Clipless pedals help, but fewer strokes may not hurt either. I enjoy pedal strikes about as much as Pfizer commercials, so there is that as well. Keep up the good work.

[@Clint_the_Audio-Photo_Guy]

I'm 6'1" and thinking about 165mm cranks. I don't really have knee pain, but my hip and back could use a rest. Off-road I'm mostly concerned with pedal strikes in rock gardens. I'm converting to a mullet with a fat 2.8 on the back, but my BB is still dropping a bit.

[@MrGoodaches]

I’ve wondered how we got here with these long cranks. Tables show I should use 165 or 170 cranks but M size production bikes come with 175. The S size bikes my wife gets come with 170 cranks - she should have 155. Interesting to note that my 1986 size M Specialized HardRock has its original 170 cranks. I can maintain a higher continuous speed on this 38 year old bike than I can on my modern hardtails. It is clear to me that the insignificant lesser leverage of my old shorter cranks is surpassed by the greater power I can sustain over time due to not losing as much energy in the excess articulation of my legs. I fully concur with all of bio-mechanical points explained by the good doctor. So,,,,somebody in this industry used to know better. How did we all get stuck with excessively long cranks in recent decades? Shorter cranks X millions of bikes per year would be a noticeable $ material savings for the manufacturers. Why have they been over spending to provide us with less optimal crank fits when it could save them money to give us the proper sizes?

[@DrJMTB]

Thanks for the practical feedback! And I agree, the industry needs to take note!

[@bryankrot2986]

Great real world relevant information, not just charts and time on a trainer. I have a 29" inseam and I have always just ridden the 175's that came with the bike. I think that I want to try 155's because of my inseam and the fact that I have strong legs. Now I just have to find out if I can rent the cranks near me. I might just end up making them in the CNC here at work. Great job on the vid and now as a new subscriber i'll look through all of your content.

[@Hardi26]

Yes after I replaced 172.5mm cranks with 165mm cranks on my cyclocross bike. I was able to climb slopes in forest that I did not dare to even try before. And I was not out of breath when reaching to the top of slope anymore. Also I'm able to ride much longer distances also dismounting the bike got so much easier. It might sound unbelievable, fof those who always had correct crank length, but I really struggled to step down from bike while still moving. And yes control over bike is so much better. Especially on difficult s curves when the curve start with long radius and then need to turn more tighter.

[@havenoutdoors584]

This is a great video! I have been wanting to try shorter cranks for a while. I ride an XL frame and that means most bikes I ride are spec'd with 175mm cranks and that means lots of pedal strikes. This video was very eye opening.

[@RealRandomReview]

I recently got into biking and looked at the geometry on quite a bit of bikes. I thought it was crazy that there was only a 5mm difference with cranks between bike made for 5' tall riders and riders over 6'.

[@earlytimz]

Awesome stuff Dr J! You swapped the 170s for 160s on my Rise before it even left your shop. My thinking at the time was purely less pedal strikes but now I'm convinced it was the way to go for a lot of reasons.

[@DrJMTB]

Hope you’re loving the Rise! Thanks for commenting 👊🏼

[@tonyrobinson1623]

Shorter cranks on a Rise let you get more out of the motor. It's tuned to give maximum power in the 90rpm range. That high rpm is easier to maintain with shorter cranks.

[@DrJMTB]

@@tonyrobinson1623 Very solid point. I knew they were tuned for higher RPM, but hadn't even considered that is a benefit of shorter cranks.

[@johnkatakowsi9907]

Oh Man finally got my 155mm mtb on my Vitus installed Man what a change they are a great change,specially now that I,m getting older!!!! man can i spin so much smoother!!!! 30 inch inseam glad i didn't go with the 160mm!!! thanks again😃!!!

[@HawkSwimming]

I am 5'7" and 70 yrs old. climbing was kicking my butt - especially steep uphill switchbacks where i had trouble pedaling through the turn. dropped from 32 chain ring to a 30 tooth oval which helped some. then, replaced 170mm crank arms with 155 mm from Canfield bikes. Much, much better. No downsides whatsoever. now my skill level has to catch up.

[@oua660]

I’m 5’8” and have shorter legs with a 30” inseam. I strained my patellar tendons last year when my dropper post sunk into my frame. It’s been a long year but I’m looking into this theory HARD! We tune EVERYTHING else on the bike.

[@pkvillager]

I started running 150mm cranks at 5'11" 2 years ago for tuning bike fit that included chopping 25mm out of my seat tube to keep a 170mm dropper and reducing pedal strikes. I was already running 32T oval chainring. Bike fit perfect, pedal strikes all but disappeared and I found I liked spinning smaller circles. Then I see YT blow up with crank length videos over the last year LOL

[@markusilomaki8922]

In climbing the shorter crank reduces the deadspot time and in that way allows for better continuous power delivery. You might want to test if you get the same effect with 160mm cranks and an oval chainring.

[@JamesJozef]

Just a a very niche perspective on this topic from an engineer and athlete: I ride trials at a decently high level. I compete in elite. I’ve experimented with 165, 170, and 175 cranks on the trials bike. There is a noticeable difference in feel between the 165s and 170s on any drivetrain-heavy movements. I do not have the same “snap” in the drivetrain that I do with 170s. Makes sense, it’s a shorter lever, less torque, therefore less acceleration. Now this is a lot of fuss about a single pedal stroke, and it’s a use case that’s far divorced from general MTB use. However, if you appreciate extremely tech climbs where you are planning pedal strokes rather than spinning, I can honestly say the long cranks have some value. If you aren’t into that, 170s definitely have a peakier torque output for most people. With modern 1x12 and the ability to just sit down and spin, there’s not much argument for long cranks. The math behind this all essentially says that power is constant (assuming force generation from the legs is constant) across all crank lengths, but power is a function of torque and rotational speed. Less torque will require a faster cadence for the same power. So sure, you can adjust gearing to obtain the same torque at the wheel, but it all kind of comes out in the wash since power input is constant for all lengths. You’re only giving up peak torque with shorter cranks, but you’re gaining a less peaky delivery of that torque. That’s to say this is basically all personal preference, but there is a lower limit on crank length where torque input will be insufficient for the gearing available.

[@arlandmacasieb2113]

Great video mate! One formula from another mtb channel suggested the length of your inseam in mm x 0.2 will give you a good starting point for crank length. You can always go shorter. So for me, I have an 810mm (32in) inseam and my crank length according to formula is 162mm. I have 170s on my fat bike now but it was the shortest cannondale made. I have 160mm on my tri bike but one of my best Ironman races I did on 145mm cranks.

[@machine7767]

I have read something close to this. They recommended 0.21 or 0.216

[@myair86]

Nice, where do I get 195mm cranks? 😂

[@SecondHalfofLife]

Great video. I'm a tall rider at 6'3" and went from my stock 170s to 165s recently for reduced pedal strikes but like you felt a slight improvement in efficiency and not noticeable in terms of stance. I may end up going even shorter at some point just to try. My hips and knees definitely noticed the change in a good way too. Interesting about stance as someone who rides both dirt bikes and mountain bikes. Obviously mountain bikes have a split stance with one foot forward and dirt bikes you have a side by side fixed stance. I honestly find for steep technical terrain I prefer the side by side of the dirt bike. I think it's something you can adapt to pretty easily FWIW.

[@MrBikegaucho]

Great video….. I’m 6’2 and ride 155s on my bullit and love it! Also at 54 years old I wish I had gone with shorter cranks long ago

[@ABFPV584]

I run 170 on my SS, have for a long time and I love them. My bike has loads of BB clearance so it’s a non issue. I agree with the sentiment in the video, my main concern is the relationship between crank length and saddle height. Too short and saddle goes up meaning more weight on the hands. That being said, my girls bike has 170 and she’s 5 inches shorter, so her saddle height is so low she can’t run a saddle bag. I’ll be swapping her to 160-165. Saddle a bit higher without sacrificing comfort and increasing clearance for a bag.

[@AOL0321]

So funny how you posted this video now. I just bought a new Specialized Epic EVO Pro in a medium and just noticed that they spec’d this model with 175mm cranks? The other EVO Pro Lrd. Has 170 mm cranks, so not sure what they were thinking. I have a 30” inseam and usually do better with 170mm cranks and have not ridden 175’s on a Mtn bike since the late 80’s/90’s. I pick it up tomorrow. Hope it will not get too many pedal strikes!

[@stevem4838]

They put on the cranks they had at the factory the day they built your bike

[@AOL0321]

@@stevem4838 ....or that's part of the sale price. If I can't sell them, I can get another set of 170's for $300. I'm still just over a $2K discount on that bike.

[@twigahappy]

great video, i've been adjusting my 3 boys bikes and trying different crank sizes from aliexpress, the default 175cm are just way too big. I ride 175s, i'm 5foot11 with 32" leg, i think 170 would be the next trial for me, 165 may help with my sore knee when riding

[@Surfratglass]

Great points. I prefer them for the reduced pedal strike and chances of catching a pedal at high speed. In addition helps me ride in a higher cadence that is not only better for my E bike motor, but seems to help with momentum on the non-Ebike.

[@karlnorgaard9447]

I, too, am long in the leg, short in the torso. Also, I'm a roadie, but I'm interested in the topic. Like many of us, I'm likely on frames a bit small for me, compensating with stem, post and crank. One of my roadbikes is larger, and in my opinion, looks too big for me. However, when I ride it, I can't ignore that it feels great. We road guys like to slam our bars low so everyone (no one cares) knows you mean business. This positions the legs for efficiency. But if yer thighs are cramping your abdomen and touching your ribs on the upstroke, you fatigue. You can really breathe on the slightly bigger frame. Then you can run a shorter crank (less weight, less energy loss from perpendicular flex to BB). A shorter crank is safer, where even 5mm shorter arms allow several degrees of additional lean before pedal strike. My right foot has never been the same since I crushed it between a tree stump and my pedal. I was on a short section of single track, riding platforms. On the downstroke, my right foot caught a little stump about 6 inches high. My pedal planted on the stump with my foot under it. My momentum ensured the cranks completed their rotation, launching the bike upwards. I was kinda torn off the bike, my big toe knuckle bearing all my weight under the pedal, also stretched my ankle really awkwardly. These were 175s, had I been on a shorter crank, I mighta missed it. Had I been riding clipless, might have been worse? Don't know. But, on this topic, I concur, riding a crank that's appropriately short is better. Riding fast on single speed road bikes requires long periods of higher RPM spinning. Knees flying all over the place from too long a crank arm also presents an efficiency loss, aerodynamically, mechanically and ergonomically. All this said, and only being my opinion, I also agree the differences are not so great as to keep you off a bike. Most of these discussions arrive at similar conclusions, we are usually arguing over single digit wattage gains, mere seconds on race day, and après ride bragging rites.

[@jeffwestbrook5747]

back in the olden days I bought a pair of cook bros cranks. Raced XC for an entire season, crushing everyone in the climbing sections and podiuming a bunch. It wasn't till they got flexy and I pulled em that I realized they were 185s. Went back to 175s and I was just a mere mortal again.

[@valeriesorrells]

so helpful. I torqued my knee at the beginning of the season and currently looking for shorter cranks. So hard to find a reasonably priced product is hard.

[@lucywucyyy]

switching from 175 / 170s to 152s cured the awful knee pain cycling has always caused me

[@Theclarksonmtb]

I changed my whyte e180 165mm cranks for Hope 155mm, forced to change due to bending a crank arm on a huge pedal strike, but since the change I rarely pedal strike but had to raise the dropper by 10mm to compensate, quite a big change of feel of the bike but they work well.

[@DrJMTB]

Thanks for sharing. It would seem radical to anyone who hasn't struck a pedal on an eMTB, but my opinion is that no e-bike ridden in the woods needs longer than 155mm. May do a dedicated video on this. Hope make some nice looking ones, too.

[@paulseyfert1482]

For those of us not used to US units, since there is no text on the video with the conversion: 5 foot 9 inches of 1.75m. and 31 inches is 79cm.

[@P0rtScann3r]

6'1", 33" inseam and switched to 165s on my MTB and will never ride longer cranks again. Interested in trying 160 & 155. Easier to climb, way easier to start going fast, plus more control in technical situations.

[@a8f235]

Another aspect that I feel makes this even more viable is wheel size. The first thing I noticed after years away from cycling, was with 29er wheels and how important it is to be consciously aware of keeping the pedals in motion while riding uphill. The split second you stop pedaling, it both stops more rapidly as well as it takes more effort to get going again than with smaller wheels. Of course I've also gotten used to using 29er wheels now, but the physics will still be there. I got a bike with a too low bottom bracket for the terrain and riding I use it for, so I am going to swop out the standard 175mm cranks for 165mm cranks this years. For me it's primarily to avoid crankarm and pedal strikes, but I am interested to see the differences in feel during motion.

[@DrJMTB]

As I mentioned, I believe most people will be quite safe in trying 165mm. Happy riding!

[@cben86]

I’m 6’0” and I swapped 170mm cranks with a 32t chainring to 152mm cranks and 30t chainring on my enduro bike. Experienced all the positives you outlined in the video.

[@jayanderson6016]

Great, but inseam length is more important than overall height in determining crank length.

[@cben86]

@@jayanderson6016 My post was intended to highlight that you can go even smaller on crank size than stated in this video and is purely subjective. My inseam is 33".

[@seawalkarrg]

Aww man! That climbing test has got me thinking hard now about 155mm cranks now. We have a lot of short steep climbs like this too where I ride. just got a set of x01 165mm for my Spur (size small) and noticed a big difference going down from 170mm. The only thing I don’t like is sensation of a higher BB/ less “in” the bike. I wonder if it’s worth going even shorter. Hey 5dev, take my money!

[@bscott4010]

This is the best video I've seen on this topic. Thank you.

[@jduran30]

Decided to go with the 165mm which is what I originally wanted when assembling my bike but my local Bikeshop advice against it, cause “I’m a big guy” at 5’10”ish, been experiencing knee pain on the knee positioned behind while going downhill noticed that after placing my feet a little forward in the pedal my pain will ease up by bringing my feet closer together, but that would give me less maneuverability while jumping so decided to order myself a set of 165’s hopefully that solves it, after experiencing that I got a good feeling about this 🤞🏽 great video, a lot of important information you can’t find basically anywhere, I agree that not one size fits all.

[@bradbell4055]

Great video my Farley 7 and Roscoe both have 1x12s lots of power shorter would sure be to my advantage I had negative thoughts about short but it all makes sense I had both legs broke about a inch below my knees thanks for the info.

[@MichaelRobibaro]

I'm on 155 goldix crankset. Pretty much gotten due to cheap price and built in bashguard My issue was I didn't pay attention to Q factor.. which is something like 145+148?mm I get pain in my good knee due to it. I'll be upgrading to 150mm Heir cranks which have full-size Q factor. I may consider 145mm I'm also on a 28T(typically run 32t) I may either swap to a 30T or a 28T oval!

[@NewMexicoOutside]

Very interesting and informative video. I may just have to give these shorter cranks a try and see how it feels.

[@Ian-qf5ny]

Very interesting, i was just thinking about this! Ive never been picky but ive always favoured slightly shorter cranks given the option. Too short does actually feel a bit off to me though due to the short stance. Maybe because i have a background in skateboarding and snowboarding im used to a wider stance.

[@FuriousFilipino]

One thing that’s not really spoken about is that the shorter your cranks (even for shorter riders) the more difficult it is to run enough saddle setback behind the bottom bracket. With the current trend of steep seatpost angles on mountain bikes, you have mutually exclusive things happening. I’m 170cm tall (5’-7”), 77.3cm inseam (30.4”)-with longer relative femurs to tibia, I have difficulty running enough setback with certain saddles on dropper posts even with an XC oriented bike (Trek Procaliber), 170mm cranks is the shortest I go with to avoid my knee going over the pedal spindle. With 165mm on my road and gravel bike, I can just about get my knee about center to 5mm behind the pedal spindle. Any position forward of that on road or mountain makes my knee hurt at threshold pace.

[@ChrisDunn-h1u]

I'm 6'4" 62 yr old been riding mtb and mx for many years. Run 155s on both my bikes and no issues with feet being closer together other then when upright have keep knee bend to keep mass lower. No different then i do riding my kx 450 with feet together so normal to me.

[@AaronVerlengia]

Thanks Doc, recently downsized from 175 to 170 Crankarms and I'm spinning much better, also went to an OVAL CHAINRING.

[@cegalleta]

I'm not sure about less than 165mm cranks (I'm tall, 192cm, use max size on pretty much anything), but I was told repeatedly that I wouldn't notice switching from 175mm to 170mm cranks and they were clearly wrong lol. It's subtle, I don't think I'm more capable with either, but the shorter cranks reduced knee stress and my hips and allow me to ride for longer.

[@amitkumar-wj8gn]

I am 5'3"m going to 145 mm cranks. Even moving from 170 to 165mm cranks has been amazing. I believe shorter cranks would be lovely on road bikes too.

[@DrJMTB]

I’ve been running 160mm on my Stigmata gravel/road rig with no issues 🤙🏼

[@mtbikerbob]

In November 2023 I switched from the stock 170 cranks on my Medium sized bike to 150 cranks. I am 5'6" with a 29"inseam. My first impression is you will feel like a monkey in a circus show. Stay with it though and as this video points out it has advantages. I can pedal out of the saddle and maintain a more even power delivery and my pedals don't strike objects hardly at all. I haven't noticed any change in joint discomfort. You will have to alter your seat post height with this change.

[@SteveWachholz]

I agree about the saddle height part of this. No videos or articles address this. I always thought that you are trying for a certain knee bend angle within a range of course. I went from 170's to 155's and it made sense to raise my saddle 15 mm. I immediately felt I was pedaling in a higher cadence but also that I wanted to ride more in the smaller cogs than before. This goes against the dropping down teeth in your chain ring philosophy. I haven't done enough rides to truly give feedback but once I heard that Ben Cathro is on 165's then it was stupid for me to continue on 170's being 5'6"

[@UnlikelyReply]

Certainly an interesting topic for debate. I get both sides. I do feel like I'm almost slugging my pedals around a wider circle and waiting for the other leg to engage sometimes. I'm tempted to try a 160mm. I also think running flat pedals like I do will be more beneficial with slightly shorter lengths.

[@mibadboy]

I'd love to hear your opinion on 165 with round chainring vs 155 and oval chainring.

[@TrentSiggard]

This was fantastic, I need to give shorter cranks a try (also a benefit for us with bigger bellies)

[@DrJMTB]

👊🏼

[@adamphelps3859]

Excellent video bro! You need more subscribers with content this good! 👊🏼

[@DrJMTB]

👊🏼👊🏼

[@kidzgehlhoff3965]

Great perspective, but as a 6'4" man i thinl that 175mm is the same for me as you 155mm cranks as far as climbing goes. My daughter 5'5" will benefit from this! I like the thought of the closer stance.

[@Tkolbo_]

This video is well done, thought out, and well explained. I’m also a physical therapist and discuss this a lot with patients! The most important thing you mentioned was definitely the muscle length tension relationship in the pedal stroke and the range of motion/overall volume. I will play devils advocate, thoughts on the shorter crank and its increase on overall volume for an individual who already has an overuse injury such as very irritable achilles tendinopathy? Obviously they can limit their time on the bike while injured, but this is just for discussion so say they don’t? Your thoughts on the increased rpm/overall volume in this case? Thanks dude!

[@danwebber9494]

My single speed has 170 cranks and an oval ring to apply more torque at low rpm. My geared bikes are slowly changing over to 160’s, but with multiple bikes it’s expensive.

[@yolandadell6561]

This is an absolutely excellent video which really helped me understand the dynamics a bit more. As a 5ft 3in (153cm) person, I have struggled to find my comfort zone on the mtb. I recently upgraded from a XS mtb to a small and I am struggling with everything. I was advised to get a 155 crank which would then allow me to insert a dropper post as it would thus allow for more drop. I currently have a 165mm crank on my upgraded bike (new bike). Unfortunately, here in South Africa, all of our manufacturers only go as low as a 165mm crank. How the hell am I supposed to work with that! There is definitely no allowance for us shorties 😒😒

[@MrSponjaBob]

After almost a week of searching for information and/or comparison on what is appropriate for me regarding cranksets, YT recommends this video to me now... (Where was this man when I needed him the most? ^^). I ride 175mm cranks, which I find uncomfortable for several reasons, not just because of the proximity to the ground. I think they are causing pain in the kneecap of my right knee. After so much information without any real science, seeing that there are even formulas to determine your proper crank length... (I am 1.80m tall, approx. 5'11"), I see and confirm thanks to Dr. J that I was right, I could perfectly reduce to 165mm with my inseam of 88cm (close to 2'11") without problems. When one does not feel comfortable and after adjusting the entire bike "as the supposed experts say," the best thing you can do is try new things and not just follow the prescribed guidelines, because as we know, what works for your neighbor doesn't necessarily work for you. Thank you, Dr. J, for this wonderful video, full of transparency and information. (I will have to return the 170mm cranks I bought and go for 160/165mm ones and carry out the necessary tests).

[@michaeleguillen]

I struggled immediately with knee pain going from the previous gen patrol with 175 arms to a spire with 165. I agree entirely with what your say here but I think my brain was/is hardwired with the type of power delivery you need for 175's, struggled for a while to just pedal smooth to avoid overworking/missfire. Otherwise most comf platform to pedal on, insane traction over rough ups with short arms. Great vid!

[@DrJMTB]

Certainly going to take some getting used to for most when changing more than 5mm instantly. Glad you’re getting along great, the Spire is an awesome rig 👊🏼

[@CreativeFishDesignsCharlotte]

just as your giving your answer i had the same thought damn , im building a new bike now lol , thank you , iv dislocated both of my knees in high school 20 yrs ago and ive been trying to figure out the upper patella pain on 4rh or more rides , ill try this .