The Mountain Bike Crank Length Discussion

I am currently on some 165mm EEwings. Next bike will for sure go down to 160mm. Ridden quite a few lengths while I was at Canfield, and 160mm just felt like the best balance for me. 5'8" 30" inseam.

Tried a set off Canfield 155s as the new bike was lower than the old and I kept bashing toes and pedals as a result (stock were 170). Combined with an oval ring I couldn't be happier with the set up. Ended up going to the same on the other 2 MTBs in the stable and went shorter on the road bike as well. My cadence increased and evened out which makes short tech climbs easier, but most noticeable was how it felt it hitting jumps. I feel more centered and controlled going into a face by not having to use as much body English to set up for it. I haven't noticed any difference in effort when winching up anything that grabbing a lower gear doesn't mitigate, but sustained climbs are less bobby and that feels ace. Only downside is the required raising of the seatpost, meaning I can prob go to a 210ish drop but I'll wait til the posts die or the newbikepartitis gets too severe before ponying up. I had already been running 50mm & 60mm rise bars so didn't feel the need to raise the front, but that's something some folx would do well to keep in mind if going short. I'm 5'10", 32" inseam so pretty average build-wise.

I don't wanna brag, but I've got a set of cranks that are a whopping 175mm in length, fully equipped with power meter and four-bolt chainring.   

I tried miranda 150mm e-mtb ones and you could pedal whilst bombing a dh track, it was surreal

it also felt like I was riding my 3 year old daughters bike, too small. They also bent like a banana pretty quickly.

I like 165, when I get back on 175's on the hardtail it feels so long. 

So I'd say 165, but I think I could ride 160's comfortably.

170mm on my enduro bike and don't want to go shorter.  My current ebike has 165mm cranks, and the last one had 155s which I hated.  5'8", 30" inseam, don't ride trails where I need to pedal going downhill.

170 on my more XC bike, 165 on my endurobro bike with 155 on order. I'm too lazy to buy new cranks for my XC bike, but they would be 165 if I could. 

Excited to give 155 a try, I did stick some 155mm cranks on the wife's enduro bike and she loves them. Granted she's 8 inches shorter than me. 

I recently change from 170 to 165 on my Revel Rail. After a saddle height adjustment, I don't notice any difference other than less pedal strikes. Similarly I went from 175 to 170 on my Transition Spur with the same results. I'm 5'11" with 34" inseam. Just for kicks, I'd like to try 160. I might get a set for my wife and try them on my bike first. 

Thanks for the shout out, Spomer. Like he said, I’m pretty tall and I have very long legs for my height, so I’m one of those weird ones who loves 175mm cranks on my mountain bike. I find anything shorter feels like circus cranks a little bit, and I lose the ability to modulate small but forceful movements when I’m climbing technical sections. I also like the ability to go from 0-60 HARD when I’m cranking for a jump, catching up to someone faster than me, or racing. I’ve tried 170’s and 165’s and keep coming back to 175’s. I even find the bigger, wider foot stance of longer cranks feels more stable when I’m descending, which is basically the opposite of what many people have shared on this thread and elsewhere. Lastly, I already have a sky-high seat, so having my seat 5-10mm higher when I’m doing technical climbing is not a good feeling, especially when it’s paired with a spinning higher-RPM cadence. It feels like I’m completely disconnected from my feet, and just spinning like a madman and getting bounced all over the place in the seat without any fine motor control. Worth mentioning I'm a low RPM guy all the time, typically 45-65 rpm. I am not Chris Froome. I think higher RPM people probably would like shorter cranks.

Interestingly, I love shorter cranks on my road/gravel bike. I have terrible flexibility (in my back, hip flexors, and hamstrings, and everywhere else, too), so I really benefit from the lower hip angle required with a smaller spinning circle. It allows me to maintain a lower riding position with my upper body without feeling like my top leg is getting pinched in my hip. I tried 165’s on my road bike and those were a little too short, but I love my 170’s. It’s funny, because a lot of people my height are on 175’s and even 180’s. 

There's not going to be an answer as to why lever-length changes work when applied to crank arms on a bicycle.  It'd need to come down to a rider having found use of a certain heartrate threshold or a range of repeatable power-output and then what can be sustained given cranklengths.  Some riders have no concept of physical conditioning outside of bike riding, which is also fine because then it's only a priority on engagement while riding.

A Mountain Bike is the last place to try and bring a rational discussion of cranklegth adaptations.  Bring in physiology and limits on body proportions and it can and does revert back to just being engaged on the bike.  

FWIW - Aero Road - 175mm  Sprint Road - 175mm  Hillclimb Road - 172.5mm Gravel - 172.5mm Commuter 175mm Trail/Enduro - 170mm  

Could go shorter on the mountainbike but it would lose punch out of corners.  

I have a question for the gallery:

I have a bunch of Shimano stuff that I'd like to be able to keep while experimenting with crank arm length.  Are there any third party cranksets with multiple length options that also support Shimano direct mount chainrings, and aren't significantly more expensive?

SLX and XT are both available in 165mm, but I don't think anything shorter than that works on the Shimano direct mount chainring standard.

Hope uses their own standard. Canfield uses the old SRAM 3-bolt style chainring. Ethirteen uses its own standard. Appleman is traditional 4 bolt. 5Dev uses the SRAM 8-bolt standard. SRAM makes 155mm NX and X1 cranks (I think they're intended for kids bikes) but obviously those aren't compatible with Shimano direct mount rings. [Editor's note: NSB also makes 155mm cranks, using cinch standard chainrings, and RF just released 160mm cranks, also on the RF cinch standard. Let me know if I'm forgetting any short crank options]

For anyone wanting to experiment with short cranks, Appleman offers a pretty unique rental service where you can rent a set of fit cranks for $50, and a compatible BB and a 32 tooth chainring if needed. The fit cranks offer 175, 165, 155, 145, 135, 100mm lengths. Pretty wide range of choices, not sure how many people will settle on the 100mm setting. You have to put down the full cost of the crankset as a deposit, but then you get it back when you return the cranks.

Worth mentioning that no matter where you mount your pedals, you'll still have cranks that are 175mm long sticking out when you pedal through rocks, and you probably don't want to be smashing rental crank ends through rocks when you put down a $685 deposit. I think it's intended as more of a kinesthetic bike fitting tool than a super intense downhill bike handling tool, aka you can see if you like spinning 155mm circles on smooth roads and trails, not so much how it feels to dance through jagged rock gardens with shorter cranks.

SRAM 155mm are for the kids builds but are manufacturer-only inventory.

Yes but you can find take-offs online.

I only ride E-bikes at max assist: bent 3 sets of 155mm cranks on my Giant Reign e with its way too low 330mm BB. (Descending, not due to poorly timed pedalling, although it messes up technical climbing also)

Currently on 140mm chineseum €40 cranks. I don't really find much negatives with short cranks, I would probably ride 155mm if my BB were higher. 

I think the cheap and easily bent nature of Miranda cranks is a feature: you are actively protecting your motor by sacrificing ~€60 cranks during impacts.

Downvote button is right under here

I am not saying 155mm cranks + Pendulums are the tittays, but 155mm cranks + Pendulums are the tittays.

5ft9/32in. For me, the biggest difference between 155 and 160mm cranks is the saddle height.

To all the short crank converts I thank you for making my preferred 175mm cranks so reasonably priced.  
I tried shorter cranks on my road bike many years ago. After a few weeks I switched back to 175s. I recently demoed a bike with 165mm cranks and was immediately reminded why I run 175s The loss in power was the first thing I noticed. Increased effort to turn over the cranks on steep climbs was also immediately apparent. The pain in my knees followed. Just like many things in biking crank length is a personal preference. That being said what works for me might not be the best for you. If you haven’t tried short cranks definitely give them a go. You might love them but if you don’t that’s fine to. 

I have a 37in inseam and run 165mm on my trail bike, 155 on my DH/Park bike, and 150mm on my DJ. I tried going back to my 175mm on my trail bike to see if it would climb any better and it was so uncomfortable. I felt like I was wasting energy and was having crank strikes everywhere. Shorter cranks are where it's at for several reasons.

I admit to being shorter-crank curious, but there's no way I'm going to buy a crankset just to try it out.  I've been on 175s for 35 years and I've had no trouble with them, so buying a part just because some people on internet say they liked them is hard to justify...especially when all the research says "meh...doesn't matter unless you're having problems"

Only $45 for their 152mm cranks if you want to give shorter a try. www.srsuntour.us/products/zeron-1-x?

I've been running them on my enduro bike paired to a shimano 12sp with no issues. 

I notice the shorter cranks mostly on the descents when the pedals are level. Having my feet closer together is more comfortable and feel like I can turn my hips more easily. I'm 6'0" with a 32" inseam. 

This video is pretty interesting. The guy has an easier time climbing with shorter cranks. I haven't been able to do a back to back test like this. 

I tried 155 for pedaling but didn't like it BUT for bike park and skate park really liked it. So I have 155 on the dh and dj bike while keeping the pedal bikes at 165. 
I really liked the 155 for descending and feel like I'm more centered and able to recovery a bit better. Going through rough stuff fast and taking off jumps is where I noted the biggest improvements but not drastically. 
Conversely I didn't like how they felt on climbs, especially steeper slow sections where torque is key, just felt like i had to put in extra effort. Not a big difference but enough I don't want shorter than 165 on bikes I'll climb with. 
My 2cents 

Just sucks that there are so few options out there for trying shorter cranks. Maybe someday soon more companies will wise up and offer shorter options. I have always wanted to try 155 and plan to in the next couple years but for now its hard to throw out my 165's since with my bike they don't really clip the ground. 

When did you get the Pendulums? Still waiting for mine but you're the first person I've seen who says they got theirs 

I was in the 1st pre-order batch that shipped on12/31 and arrived via UPS four days ago. I obviously have a lot more riding to do before I can pass any judgment but the initial experience has been great. The most comfortable flats I've ever tried.

Same, if you're tall you should think twice about drinking the koolaid. One size does not fit all.

I'm 6'2" and run 175s on singlespeeds and more pedally bikes, 170 on my main trail bike. Happy with all of them.

Short guy here who has been on 165's since I can't remember, got on Canfields a few years ago, have 160 155 and 150's. I'm sold on the shorter cranks are easier/quicker to get spinning thing.

Big Galoot here, 6'3", 200lbs, I started riding 175s in the '80s; went that and longer (180s) in '90s, down to 170s when freeride bikes became a thing in the '00s, back to 175s as a new enduroist in the teens, and, now focusing mostly on the downs, 165mm on the enduro bike, 160mm on the DH. I don't like hitting my pedals and with lots of local rut and rock bashing, those combos works well. I can't tell any power difference, but I don't pay attention to that.

This is very interesting. I'm moving down to 165mm and adding an oval as well. Hoping it yields similar benefits, especially re: jumping. Have previously been on 175 and 170. 5'11"+, 33" inseam.

I run 165's and 170's, but I broke some cranks and my spare pair were 175's.  They were noticeably better climbing - more torque for punchy bits, and I didn't find them to be hard to spin on fireroad climbs.  But they felt long on the way down.  But that has me skeptical of going to the super short lengths - I feel like I'd miss the torque on the climbs.

Chainring size-- solves the torque difference.

It's not quite the same, as knee and hip angles are different with different crank lengths. 

You can achieve the same final drive ratio with a long and short crank with different size chain rings, but they won't feel the same to use.