Does Size Matter? | How Crank Length Affects Performance On The Bike?

[@gcntech]

Do you prefer long or short cranks? Let us know in the comments 👇

[@OFFSHOREDOUG]

I have 170s in my wattbike, 175 on my road bike. Can’t tell the difference. Unless you are standing or very strong seated you are better off with smaller. You need weight(standing) or strength to turn larger cranks. Obviously smaller means lighter, higher cadences and more open hip angle. You should have looked at efficiency of pedalling stroke too. Proper pedals would need to be used to do you could measure difference in pedal stroke. Shorter cranks also take your toes away from your front wheel which can be advantage.

[@demetriusUSN]

I’m 78” tall, I bought a Canyon Endurace 2XL and it came with 175mm crank. I did some homework, watching GCN and a couple other videos and decided to go to 170mm cranks because I was having knee issues, well I couldn’t be more happy!!! The shorter crank works for me very well.

[@Hardi26]

165mm cranks are right for me. My bike came with 172.5mm cranks.. even though I bought 52 size which is one size smaller than what was recommended for my 173cm body height. I rode 4 or 5 years with those 172.5. Before cot confidence that the shorter might really be better for me. I changed and felt difference right away. With shorter cranks I did not get so much fatigue on uphill and on longer trips. While acceleration and top speed might have decreased a bit.. Top speed probably decreased because after changing cranks length I should change also handlebar reach, but it and stuff.. but doing proper fit is too much trouble. It's fine for me like it is. Shorter cranks definitely was big improvement. I rather ride longer with little better average speed, and less fatigue than that half minute very fast.. with acceleration.

[@philipcooper8297]

Only insecure men choose long cranks.

[@staticx2552]

165 , especially on track bikes/fixed gear . easier on the knees

[@PeakTorque]

The max sprint test was unfair test. The long crank reduced the system gearing, because you kept the trainer resistance the same. You struggled to turn the short crank over, so in reality you'd shift up a cog.

[@mordillokiwi]

I agree. I believe the test was designed for a specific result. I will say introducing a test that yields quantifiable results appears difficult since there are so many variables at play.

[@simonr7097]

Very true, we can see that the cadences reached on these tries were quite slow, so it's no surprise that the longer cranks were massively advantaged. This test was a bit like starting your car in fifth gear and measuring the power procduced after 5 seconds of struggling to get it moving.

[@federicosbetta1368]

the longer crank will start the movement early but at some point you're going to struggle keeping up with the rotation speed.

[@jemwoo2001]

In the science bit at the start, it was posed that increased power came from increased cadence - What you tested was max torque which will always be higher from a longer crank. If you wanted to compare each crank length then I'd suggest you try comparing power from a 5 minute effort (using the gears)... Thus you'd spin the cranks up to their correct speed to generate max power...

[@mapk4655]

I was just waiting for you to come over here and say that. You actually do proper science.

[@scottcullen4750]

1. Never make a bike fit decision based on weight savings. Fit is far more important. 2. Never make a bike fit decision based on what works for someone else. We are all different.

[@vicodinfreeman5504]

True, I don't think anyone finds slammed 140 stem comfortable.

[@dudeonbike800]

3. Never say "never!" Ha, ha. J/K. Good points!

[@bicyclist2]

Amen.

[@aluminati9918]

Interesting topic. I’m 180 tall and recently changed to shorter 165mm cranks from 175mm. Big difference. After knee surgery some years back I’m trying to get my speed from RPMs rather than grinding. And that’s much easier on the shorter cranks.

[@richietattersall2122]

Shorter cranks you're not stressing your knees as much.

[@OFFSHOREDOUG]

Shorter cranks need less muscular power and less mass to move. Which means less knee issues.

[@edmundscycles1]

Plus the knee angle at the top of the stroke , much more friendly to your knees .

[@derekhobbs1102]

@@edmundscycles1 That's my reason for wanting 165.

[@Kimberly_Sparkles]

I've also been advised to do this to accommodate arthritis!

[@sventice]

A good reason to ride shorter cranks is injury prevention. With the shorter crank, your knee and hips are less impinged at the top of the pedal stroke, and you're somewhat less likely to get an overuse injury. I was experiencing knee pain on hilly terrain, went from 175 to 170mm cranks, and the knees stopped hurting within a week or two.

[@markmoreno7295]

You are quite right. If a rider is prone to patello-femoral syndrome, it is recommended to consider shorter crank lengths. This is more important after a hiatus from biking, or for new riders who are building up strength and endurance. A higher cadence is also preferable rather than grinding. As mentioned shorter cranks are easier to spin. I am not as sure with respect to hip injuries however it makes sense that after something drastic, such as total hip replacement, it would be better to have less hip movement via the shorter crank. A difference does exist between gentle riding, such as when trying to gain ROM, vs when riding for cardic benefit. With gentle riding a longer crank may be acceptable. Besides crank length, Q angle is something which needs to be taken into account.

[@louish.994]

I rode several thousand kilometers over the last few months with a 175 mm crank on the left side and a 170 mm one on the right. I never noticed until I had to change the worn out chain rings 😬

[@dickystreets]

🤦‍♂️😳

[@dudeonbike800]

As a broke college student, I mountain biked on 170's for a long time. Was riding with a friend and frame builder when I mentioned my short cranks. He was on 175's and since we ride with the same seat height, he said, "Here, let's switch bikes so you can try the 175's." I thought, "Why not? Can't hurt. Probably won't even feel the difference, being only 5mm." BOY WAS I WRONG! 5mm felt like a MILE! Wow, what a difference! I was truly blown away at how much longer the 175's felt. So from that day forward, I've been on 175's on mountain and tandem. And ironically, this change coincided with an increase in my pedal speed. Using lower mountain gearing, I found I preferred a higher cadence, despite running longer cranks off road. Anyway, thought I'd share that experience.

[@gersonFls7]

How tall are you though?

[@dudeonbike800]

@@gersonFls7 does that matter? My inseam is a bit longer than the average male at my height. Femur length is probably more important than those dimensions anyway. If I prefer 175's on several bikes and have been riding for 40 years, I'm pretty sure my overall height is irrelevant to the discussion. Everything is except my preference and success with this crank length. Plus, my point was how different 5mm of crank length felt in an on-the-trail comparison, so it's actually not important what actual crank length I ride.

[@dudeonbike800]

Another point to consider: I grew up road riding 170's for over a decade, so I was very used to this crank length. And my first two mountain bikes were spec'ed with 170's, which was before the prevalence of longer cranks on medium and large mountain bikes.

[@jeradgilbert2147]

Alright - well crank arm length was typically recommended by femur length, rather than whole leg length. Pedaling techniques has evolved to the spinning is winning meaning shorter crank arm lengths benefit this style, as the longer crank arm lengths require more effort to keep the pedals at the same cadence (possible to condition your body to this however). Longer crank arms generally benefit when standing up or out of the saddle depending on how long you spend out of the seat may influence the crank arm length for you. Remember many sprinters choose shorter crank arm lengths but the gear ratios are much taller than the ones available to the average cyclist. As a bike fitter I found shorter crank arm lengths help with tri, TT and aggressive aero road positions (remember once seeing a brand new Canyon Speedmax in size XS came to me with 172.5mm??) but in the more sportive positions it would have no real benefit to change. More importantly is a bike fit can determine your saddle X&Y co-ordinates with an advisory if you need to change crank lengths based off saddle set back, seatpost offset etc Just a note on cornering - longer crank arms actually help to control centre of gravity and stability as the bike leans over and outside foot is down

[@jameswitte5676]

If you have knee trouble or are over 50 and live where it’s hilly or mountainous go with shorter cranks. I went from 172.5 to 170 and as soon as I hit my first climb (12%+) I noticed the difference. I was able to spin a little faster instead of using more force to get up the hill. I actually went up my climbs faster with the 170’s.

[@AwwSweet]

Damn, that's probably the most insteresting comment section, I've read recently.

[@leofonte]

I am grinder. I went from 170 to 165. It was very good on flat areas, but on hilly or mountainous it was a disaster. I have to put much more power on the the pedals. I went back to 170.

[@kfdaddy]

I'm quite a bit over 50 and I don't, of necessity, ride for speed but for pleasure. My current crank set is a Tiagra 50/34 with a 172.5 crank length. I've just ordered a new 46/34 crank set with a 170 crank length. Admittedly not a huge difference but this video has convinced me that I made the right choice in going with a shorter crank length. Here's hoping I can get another year or two out of my Trek S5 with this option.

[@larsmunch4536]

Isn't this also related to the question of grinding vs spinning? If you feel more comfortable with grinding, you will probably also feel more comfortable with longer cranks. If you feel more comfortable with spinning, you will probably also feel more comfortable with shorter cranks. Maybe not the most scientific, but it seems kind of logic to me.

[@michaelpatrick6950]

I agree. I'm 68 years old and 6' tall, 200 pounds with linebacker/sprinter thighs. My rpms are limited by the point at where the speed of my thighs coming up cause me to start bouncing in the saddle. Someone with the same overall wt/ht but different mass distribution (skinny legs with a belly) would have a different pedal speed sweet spot. I did go from 175s to 170s last year and that opened my hips just enough. Leg position means the momentum of the downstroke and the upstroke are not equal.

[@4nz-nl]

There's one difficulty here: If you increase the crank length, it'll feel like you're spinning at a lower cadence than when your cranks are short. On my bike with 150mm cranks, I'm very comfortable at 110-115 rpm, more than at 95 rpm on 175 mm (I'm tall with long legs and fast-twitch muscles by the way).

[@garethbaus5471]

Seems like it too me, you are doing roughly the same amount of work at a given speed regardless.

[@johndemmer3496]

I think a better comparison would be average heart rate / wattage / crank length, or just do time trials with different lengths. I would think that everyone has a optimum length for their particular biomechanics and it's probably not as simple as for example, femur length.

[@dudeonbike800]

A teammate trained and raced on 180's for over a decade. At one point he suffered an injury where his quad muscle tendon pulled off a piece of bone from his knee. THEN years later he discovered Lennard Zinn's crank measuring system and realized he didn't have to simply accept the 180mm cranks the industry supplied. He was fitted with 203mm cranks and "rediscovered cycling!" It was like a whole new sport. He resumed track racing and couldn't believe how much better he felt and performed. Looking back on his injury, he realized his short cranks so severely lacked the leverage he needed, this caused, or at least, contributed to his injury. Debatable, but one thing is clear: proper crank length was crucial and so badly missed during his young cycling career. So if you're not the typical body type, crank length could be a significant hindrance to your riding.

[@robertwiley7744]

I thought Conor was going to rip Alex’s handlebars clean off the bike in those sprint efforts!

[@rohindhaliwal182]

The only time you’ll see flat pedals on Dura-Ace

[@filip000]

Yes, crank lengths do matter. Not in a way that you'd immediatelly think: longer crank meaning better leverage (since our cadence is not 10 rpm but 60+), but in a way that it helps you get the right seating position if you have unusually long or short femurs. If you have too long cranks, you will have trouble getting the seating position - either on the upmost or lowermost pedalstroke you will have the knee over or under extended. Same goes with too short cranks.

[@wmyers802]

I (XS bike) spent the 2 years on 165 mm, which was okay going from 172.5 mm I'd been running on a steel Ritchey, with bad knees. But now I'm totally fit again, I switched back to 170 mm that I used to race on in the 90's, and my legs are so much happier. It seems like the bigger rotation makes my muscles "breath" more in each rotation. The 165 mm was feeling cramped and underpowered at my somewhat slow (80 rpm) natural cadence.

[@Taz86]

I haven't actually watched the video yet, but I just switched from 172.5mm crank arms to 165mm to accommodate my recovery from a hip injury and Strava says my top speed on the same stretch of flat greenway is almost 6mph faster than it was 6 months ago. I don't know how much of that is the crank length and how much is physical therapy making me stronger, but there's definitely a measurable difference in speed since making the change.

[@TheNeelonRokk]

I am 1m93, and I have 165 on my bike. My knees thank me for it (less extreme bending). The shorter circle my feet have to travel also seems to enable me to spin a bit quicker.

[@natillano]

Kinda fun to watch Connor and Alex go at it. More to this guys 👍

[@gregknipe8772]

and I thought Alex was tall....

[@alextimbol]

170 is the most common in my country. It's challenging to find anything outside that size. When I found 175 cranks, it was a huge relief: easier to run the pace I liked, and easier to go uphill. I'm 190cm so 175 fits me well, but I want to try 180mm.

[@jackofharts94]

I'm 6'5" and i have always used 175mm cranks, but about a year ago i experimented with some 170mm cranks, and i definitely spin better with the 170mm cranks and it's easier to sit on top of the gear at a higher cadence. I don't do much sprinting so the extra leverage is not needed. I'd like to see a video of comparing crank length up hills, maybe multiple hills, short and sharp ones, and long but gentler gradient.

[@labmatthew]

Toe overlap is another consideration. Toe overlap with the OEM 172.5mm cranks was so bad on my Canyon Endurace gravel setup that I couldn't pedal efficiently on twisty single track. I switched 165mm cranks and the problem resolved and my cadence improved.

[@lifeisgood12341]

Connor looked silly with the tiny cranks. He is such a monster

[@philipcooper8297]

He's a landmark!

[@daa2622]

@@philipcooper8297 What a compliment hahah

[@iaintrotter455]

Alex and Connor were a great match up in this video, Connor hilarious in the sprint

[@teuast]

"Time to turn the key and unlock your potential!"

[@gregknipe8772]

this entire crew has a novel quality, as a clutch of bike race lovers and characters. makes it tough to sit through a show with American screen talent in my own accent. really enjoy these GCN productions. humor, factoids, tech education, race coverage. good stuff.

[@DerekNewtonKeswick]

I’m a short rider and was given bugger-all advice about crank length when I was buying my bikes in the 90s & 00s. I used to get shin splints and be in a fair bit of pain. Using 165mm was revelatory and transformed my enjoyment of riding. I’d love to try 160mm but they’re not easy to come by.

[@yisraels4555]

Same here, changed from 170mm to 165mm and would get 160s if they were available . Even the 10mm difference in pedaling diameter makes a difference with shorter legs.

[@gilleek2]

Rotor make 150mm and 155mm cranks as far as I know. Theres another brand that i cant think of now that make them too

[@DarenC]

I'm 171cm (5'7.5") and all of my bikes have 172.5mm cranks. I've never tried anything, but videos like this and others I've seen (FastFitnessTips for example I think) do make me wonder if I should try shorter cranks. I've always had a hard time convincing myself that a few mm will make any difference though

[@gilleek2]

@@DarenC I have a 165 Tri bike, 170 old trek roadbike and a 172.5 roadbike too. I don't feel the difference between the 172.5 and the 170 but the 165 is different and i'd like to get my hands on a 160 or 155 for the Tri bike. Really opens up the hip angle so you don't feel like your banging your knee against your stomach. I'm 180cm.

[@taufikabidin412]

Hase makes adjustable cranks so you can try numerous cranks length before settling

[@tpwkitomobrien131]

My wife and I have both had joint replacements. Hers was a knee, mine was a hip. Flexibility is an issue, and we both prefer shorter cranks. And as you said, you can always use gearing to compensate.

[@Supermotoxl]

I'm short rider at 5'2 running on 160mm crank length on road and 155mm length crank on MTB. Finally i see huge improvement in performance, speed, endurance, cadence and proper torque on my daily cycling routine. No longer feel fatigue or tired on my legs because my spin radius and leg compression fits my legs movement. All these decades i was stuck on standard 170mm cranks thrown in by marketing. So cranks size does matter. Unfortunately smaller size cranks are limited and at premium price. I have to pay twice the price but it was worth it.

[@markj.a351]

Insanely well timed video for me

[@galaxymohit]

Both bikes came originally with factory assembled 170mm crank arms. Having traveled close to 10k miles (brompton5k+ canyon4.3k) I mustered courage to switch to 160mm (upon listening to gcn Simon and team) on the canyon and voila!, within the first 100 mi I find that the muscles are engaged to a significantly larger degree than prior along with desirable reduction in joint fatigue. That brings comfort and strengthens ability into all day riding(and then some). Decreased pressure on the diaphragm area when stroke hits TDC as well as Smooth turnover helps with cruising over rolling hills; last but not the least experiencing joy on bettering the technique thru mech change. ps: Canyon should make this component sizing change at the factory supply/delivery level upfront (my 2 cents) My setup is inseam: 78cms height: 165cms bike1: canyon endurace 2021 wmn xs group: shimano 105 34-50/11-34, r7025 small hands hydraulic. bike2: m type brompton 2011, 3 sp sturmey archer

[@andredegraaf1643]

Been on 175mm cranks since my first racing bike in 1990. I bought it originally with 170mm cranks but upgraded and the longer cranks felt much better. I would have preferred to go to 180mm cranks (a la Indurain) but that was only offered on Campagnolo Record and I was on a Chorus budget.

[@davidburgess741]

As an older rider, the open hip angle is the way to go. You can easily use a smaller gear to compensate. See the Sheldon Brown site.

[@bikebudha01]

My real world test on crankarm lenght. Note, I have a 38" inseam (long legs). My bike shop had a size cycle fitted with a power meter. I did a 20 minute warm up, then tested 3 crank arm lenghs. 175mm, 177.5mm, and 180mm. The test was a 5 minute 'hold x effort' test. So that the power output was 'hard' (not killer) and consistant through the 5 minutes. For me, what changed was heart rate. the 180mm cranks resulted in 10bpm less for the same effort than the 175mm cranks. That's significant. Thus I ride 180mm. If you are serious about knowing what crank lenght works best for you, I strongly recommend doing a similar test. Where you can swap out crank lenghs and see clear cut results.

[@belmontst]

GCN is like magic. My 3 week old new bike has 165mm 52/36 and the previous had 170mm 50/34. I much rather prefer my current 165mm because I can start cranking a little sooner on my turns, and it’s probably the help with larger rings but power has increased more than expected but not much to brag about.

[@djconnel]

The late Sheldon Brown used to say that the most important thing wasn't gear ratio, but pedal velocity. With this in mind, when comparing a 165 mm crank to a 180 mm crank, the gear choice should be adjusted to keep the same pedal velocity (lower cadence at the larger crank). This matches the amount of power you get for a given amount of force (not torque) on the pedals. Since with the platform pedals, force was limited by body mass (approximately), the longer crank will naturally win at the same gear, but using a smaller gear with the shorter crank, the two would be similar. So it comes down to biomechanics. Do you want to spin your legs more times in a smaller circle, or fewer times in a bigger circle? The bigger circle distributes the load over a wider range of muscles, and additionally results in wasting energy. But there's a sweet spot for range of motion, and you want to match that. I thus think your "increased efficiency" point at the beginning was granted to glibly. It's not that simple. "Back in the day" when riders typically had limited gearing options, long cranks were a "cheat" to get away with a larger gear ratio. But now riders can use lower gear ratios (although the larger chain and cassette needed for the smaller crank will partially offset the weight advantage). So this eliminates one reason to nudge up crank length. Clearly spinning 5 cm cranks at a 270 rpm would be inefficient. Similarly turning 35 cm cranks at 45 rpm will result in excessive joint angles. There is an optimum. Same force, same pedal velocity, so it's a choice between cadence and range of motion.

[@Freightlinerbob]

With a 980mm PBH, I tried a KHS Flite 747 which comes with 200mm cranks and an appropriately raised BB. It’s not about anything other than fit as far as I’m concerned. The first bike I’ve ridden as an adult that is sized correctly. I’m not going back to anything shorter.

[@stiffjalopy4189]

Totally agree. I was skeptical when my bike builder suggested 200mm cranks, but then he let me try his mtb with them and my mind was blown. It was like I’d only ever used half my legs!

[@mazevx2451]

I'd say it depends on your size or the length of your legs, there sure is some kind of proportional factor leg to crank length

[@helmyfaisal4696]

in Indonesia, almost all bikes sold on the market use 170mm. very difficult to find other sizes.

[@TomAbramoff]

Your videos have been spot on lately. I just switched from 180 back to 175 after experimenting with them for a few months. I’m 6’4 with long legs, but realized 180 is just too much

[@annieks.2462]

I've got 150mm custom shortened cranks. After having struggled with a severe knee injury for 6 months, my rehabilation at the fysio was finished but I could still not ride my bike without pain. Eventually went from 172mm to 150mm cranks, first few rides were still painful but after getting used to a higher rpm I have never felt my knee again on the bike. I'm 1.55m so super small and my knee was higher than my hip. I can't imagine ever riding like that again.

[@cccycling5835]

My wife says my crank lengths are just fine. Wait until she sees my new SRAM Eagle crankset 😉

[@kibbee890]

Surprised there isn't more variation available. 1.5 cm isn't really that much of a difference considering you have riders from 5 feet to 6.5 feet.

[@BFinesilver2]

You need to double that figure to get the real variation as you need to increase the saddle height by the same amount of decrease in crank length and vice versa. Rotor Aldhu are available from 150mm up. I ride 155mm at 1m 78cm... WAY WAY better than 172.5mm. No comparison. People need to try with proper gearing (smaller chainrings)

[@nigelmcclean4166]

Glad to see Alex is coming into his own as a presenter!

[@michaelpatrick6950]

I just love it when someone talks about 100 g in a system massing 75000-100,000 g. I had a friend who was a national class rider and he went on and on about 5g, 27g 100g...etc. So being engineers we did a blind test. We took a water bottle and put various masses in it consisting of either water, sand or steel shot. He didn't know what was in a bottle when we set him off on a ride. His ability to discern what the change from run to run was basically a guess. On masses of a few hundred grams, he was guessing even on climbs. Respiratory and sweat losses on a ride have more impact than the mass difference between 170 and 180 mm cranks.

[@martijnheil8825]

I'm no weight weenie, but if you do a lot of these minor weight improvements it all starts to add up to something bigger.

[@edrn1842]

Another point for short cranks: reduced toe overlap, particularly on bikes with shorter front-centers. I think there's a neuromuscular aspect when it comes to changing crank length as well, as someone who naturally pedals a certain crank length would be more used to producing power and sprinting on it due to muscle memory. Hence, it's always a good idea to spend at least 2-3 weeks on the bike after making any positional changes to allow the body to adapt before making judgement. Personally, I think the industry's current offerings for crank length are not sufficient for the cycling population. Imagine a 180cm rider on 172.5mm cranks, the crank length is roughly 9.7% of his height. Assuming leg length increases proportionately to height, a 190cm tall rider would need 184mm cranks and a 160cm tall rider would need 155cm cranks. Neither Shimano, Sram nor Campagnolo offer such a range of crank lengths. Only Rotor carries such a range (Cobb only does the shorter end of the spectrum). I also have the view that bike geometry should be designed around crank length as well. Why should sizes from 48cm to 60cm come with the same bottom bracket drop (some manufacturers vary this up to 5mm) when crank lengths can differ up to 20mm? This would cause shorter riders with short cranks to have a higher center-of-gravity and feel less stable when cornering hard, and a taller rider with long cranks to have the risk of pedal strike if he leans the bike too much. OK, rant over.

[@mirzamarcou5168]

I agree with the industry offering. My XS bike came with a 170mm crank but my height means I should have 150-155mm. I’m tempted to change but it’s a difficult and expensive experiment.

[@edrn1842]

@@mirzamarcou5168 Yeah, swapping cranks are costly. I went from 170mm to 165mm to 155mm and then back to 165mm for the road bike. I kept the 155mm for the TT bike. I went back to 165mm on the road bike because I didn't experience hip impingement issues on it compared to the TT bike, where I had a much lower torso angle. The 155mm felt unnerving while cornering at high speeds due to my higher COG. I don't mind the higher COG on the TT bike because I won't be bombing down technical descents on it. TT bike positions suck for anything other than going fast in a straight line anyway.

[@mirzamarcou5168]

@@edrn1842 That’s interesting, I hadn’t factored in the COG aspect, thank you. Maybe a good bike fitter can advise and give some test ones, fingers crossed.

[@paulmcknight4137]

Well, 170 mm was "standard" in the '70s and '80s, providing the right size crank circle for riders of average height. 172.5 for taller riders, on up to 180 for very tall riders, and maybe as far as it goes to avoid scraping the pavement mounting and dismounting and cornering. I agree saddle height and setback affect ideal cadence, defined by sustainable aerobic power, as much as crank length, as y'all are pointing out. I'm 5'8", ride two 54 cm bikes. One positions the rider on a 74 degree seat tube up over the saddle, putting the crank circle more underneath the rider's hips, making spinning circles natural, and exerting awesome power in sprints. The other bike puts the rider further behind the crank, 73 degrees, tightening the angle between upper body and legs, making mad spinning much more difficult, as y'all also implied. 170 was the sweet spot for road bike cadences before mountain bikes went to 172.5 and builders have been experimenting ever since. 170 mm allows for low center of gravity without pedals scraping the ground. Track bikes no doubt have higher BBs, but 165 mm cranks are pretty much standard, not only to clear the banks of the velodrome, but also to enable fast cadences on fixed gears trackies depend on. Also heard tell Mark Cavendish's secret to winning sprints is to tuck low, move forward, and just stomp on the pedals. I rode a friend's bike once with 73 degree setback and 172.5 cranks and couldn't generate nearly as much power as on 170 the legs could handle very smoothly at 100 rpm. I could power the downstrokes nicely but couldn't spin worth a damn. Women shorter than men also do well with 165 mm cranks, very common for years.

[@TheSlurpeeMan]

I've used both 170 and 172.5 mm cranks on my road bike, and I don't think I could ever identify a difference on the road. However, it did make a significant difference on the trainer (at least with regards to comfort). At 172.5, I felt some knee discomfort after being on the trainer for longer than 30 minutes, and that was gone when I moved to 170. Maybe it was the placebo effect, or maybe the reduction of torque on repetitive, static training did help. If you're curious, I did adjust my saddle height accordingly when I changed my crank length too, so it probably isn't position.

[@yogatriathlete]

When sprinting with shorter cranks, you'll get up to speed faster, even if the absolute power transfer is higher with longer cranks. So longer cranks are not necessarily better for sprinting

[@TreFlip1992]

I changed from 172.5mm to 165mm in May 2020 after averaging 700-1000miles each month of the year until my right knee couldn't take it anymore. Since fitting the 165mm cranks, it's meant Im able to run my saddle that little higher for a more open hip & knee angle, maintain a higher avg RPM with less effort and no knee issues whatsoever. I noticed the difference immediately and I'm sold on the 165's. Next bike I get, that'll be the first thing that goes on, if they're not already on.

[@christerlundgren3805]

Opinions are just that... Riding must be in harmony for rider, if your hips twist and jerk around or jumping off the saddle it will affect knees. And neckprobs due to saddle to forward or back. Videotape yourself from side and from the back on a trainer is really a good way to spot issues. Spend a couple of hours to iron out how to adjust the bike. Shorter cranks is one way to raise rpm/cadence.

[@MG_Gily_Wut]

I'm 1m86 and got a 56 (L) frame. The bike came with 175mm cranks but cus of back issues I couldnt ride anymore more as 30minutes. Now with 165mm cranks I ride without pain and I'm verry happy about that.

[@grantbeerling4396]

The proportions were never studied, and so feel and gearing from penny farthings of the 7" crank remained and then adopted by the safety cycle. It would've been interesting to see a short sprint high spin test with a medium gear (72"), with power and acceleration.Another test is the fatigue test of smaller circles v larger circles over varied terrain for 4 plus hours. Like many old gits I've ridden all the various length on the road and noted pro's and con's. The biggest takeaway is the extra fatigue from long cranks ( 175mm 5'11"rider) compared with 165mm. All my bikes have 165's for the past 10 years and no intention of changing, especially concerning hip flexors (incling fixed bikes winter 72", summer 75" OK for Kent). An article based on a ironman Triathlon research paper into 145mm cranks, asking the question what is optimum? Result 110-130mm from rider feedback...Food for thought. Can longer find the exact paper, but this article pretty much summarizes the results, though only with a few examples... How about riding 145mm on a tt bike and looking at comfort factor, aero and how this would convert into long distance TT's 50+ miles....then just for laughs, a 4 up road bike v Simon (Mr TT) over 50 miles....I'm sure you'll all think/brainstorm something for our watching amusement... pubmed.ncbi.nlm.nih.gov/11417428/

[@mkysiak]

So, I understand that the crank arm length influences the torque and power. Then, so does the size of the chainrings. It would be interesting to see how (to what extent and how exactly) you can balance the effect of shorter/longer crank arms with smaller/larger chainrings.

[@vaughanbbrean71]

I ride 175 left and 170 right because I have one leg slightly longer than the other :-) Its amazing the difference 5mm makes and nobody would know about this so maybe everybody should check to see if they are simlarly afflicted 🙂

[@Paul_Paulson]

When you consider that there are plenty of riders who are 150cm tall and also 2m tall - a range of 25% - a choice of cranks between 165 and 180mm is not so wide, it’s less than ten percent. A choice of cranks between 150mm and 200mm would be more in proportion to people’s actual body sizes. Clearly many smaller riders are stuck on cranks that are too long for them and some taller riders could easily go longer than 180. The advantage of a shorter crank (that still fits you) is that is that you can pedal faster - perfect for holding a steady high speed on the track. The advantage of a longer crank is that you can turn it with more torque when the pedals are turning slowly. Which often happens in off road riding. But it’s not not just because of the crank, but the range of movement you get out of your hips. What is to be avoided for everyone however is having a crank which is so low that even with a normal saddle height the thigh presses into the abdomen of chest at the top of the stroke, which is uncomfortable for more than a few minutes. So for a smaller rider wanting to go aero, shorter cranks would be essential. One day a smaller manufacturer (like Rotor) will come out with a 160 TT crank for the women racers and then the bigger firms will follow.

[@djfung]

Power out put test is flawed because as you stated energy transfer can be compensated by gearing . And we all know longer leverage means easier to start from stand still. So the test shouldn't be in a fixed gear rather the rider should allow to change gear according to his preference.

[@g-trax7939]

3:42 If the rider can always apply the same force at the pedals but the crank length is increased, won’t the resulting step up in torque cancel out the effect of a reduced cadence? Meaning one’s power output will remain unaffected by any change in crank length, instead of becoming reduced? You’d still be capable of achieving the same road speeds, but a rethink of your usual gear selection habits would be needed to account for your new lower max. cadence. Interesting video chaps!

[@fluffy13bondjames92]

Technically yes actually but most people produce their best power at higher RPM

[@stiffjalopy4189]

Except there are biomechanics involved, too. That is, I think people have a specific number of times they can fire their leg muscles in a minute and it doesn’t make THAT much difference how big a circle your feet have to go around. When I went from 175mm to 200mm cranks, it took a few hundred miles to adjust, but then I was within 2-3 rpm of my prior average, and I felt WAY better. But I have quite long legs and no knee problems. Everyone’s different, but unfortunately it’s really hard to tinker with

[@GraemeHoldsworth]

On a whim, when replacing a worn chainset, I chose 175cm instead of 172.5cm crank arms (I'm 6'0"). In use, I've found that on a flat ride at higher speeds the drivetrain occasionally goes slack and 'bangs' as the crank arm catches up with the slack in the system... as though my cadence is too slow. This didn't happen with 172.5cm cranks. 175cm cranks have increased toe overlap too. When the time comes to replace this chainset, wondering if it is worth experimenting with 170cm cranks or just going back to 172.5cm. Whimsical choices can be an expensive mistake.

[@jeradgilbert2147]

I'm 188cm, typically ride a 56cm frame aero position, switched between 172.5 and 175. I am also much smoother with 172.5 and my natural cadence is around 70-80 rpm... I wouldn't want to go down to 170.

[@GraemeHoldsworth]

@@jeradgilbert2147 Thank you. I probably won't go down to 170cm thinking about it, I don't fancy having to live with the consequences of a mistake due to the costs involved. 172.5cm it is. :)

[@derekbiggerstaff]

You guys are so good at devising tests that tell us nothing very useful.

[@tfj100]

Ha ha, each bike I have bought seems to have a different length, so it is useful for me to work out if I should have a standardised length. I also enjoyed reading your surname given the big intro into this piece. ;-)

[@russellbrooks2354]

This is an interesting subject, but I’d say there are much more informative videos out there. I moved to 165 on my road bike and the difference in comfort and my ability to ride in a better position is noticeable (for me!). However, on my gravel bike I stuck with 172.5 which works better (for me!) due to the more upright position and improved torque on punchy off road climbs. Don’t get me wrong, I like GCN and enjoy a lot of what you do. However, With the resources GCN has available, I wish more time was spent producing better quality content or subjects like this.

[@DonutEndurance]

‘Time to do max power sprints!” Proceed to hop on the bike with hoodies.

[@taufikabidin412]

Mike Burrows use 140 mm. For recumbents, shorter cranks reduce heel strike on the wheel, more aerodynamic, and means fairing nose can be smaller and sharper

[@TimpBizkit]

In terms of torque with added crank length, over larger motions, your muscles lose leverage the more the leg is bent, so while you increase the muscle's range of motion with longer cranks, it is not as much as the difference in crank length. An example is climbing stairs. If you climb 1 stair at a time, the total amount each muscle moves is more per stair than if you climb 2 stairs at a time. The muscles need greater force because of this. When the leg is very bent, the muscles need far more force (multiple times your weight), just like a scissor jack for a car needs more force to turn when it is almost closed and gets easier as it rises. I'm not sure whether it is more efficient to turn large cranks slowly or small cranks quickly. At the extremes I think the large crank slowly, as there is less change in momentum on the legs and the inevitable losses despite your legs being guided in a circle.

[@retroonhisbikes]

Knee injury forced me to get a 165mm but data also shows I should have a 165mm anyway for my height.

[@supernoodles908]

How tall are you?

[@jeffreylee5770]

For me, the longer cranks would be better due to many hills in my area. Hill climbing seems to me to work far better with longer cranks when more torque and lower speeds are called for.

[@galenkehler]

The max sprint should have been done seated, or it really means nothing, since your hip position is no longer constrained. Standing is no longer a 5 bar linkage, its a 8 bar linkage.

[@gregrobidoux6820]

“Determinants of maximal cycling power: Crank length, pedaling rate and pedal speed” by James Martin is and older study but worth a look. The changes to fit and potential aerodynamics have far greater impact on the cycling experience than max power output. Bottom line is that cranks should be sized for the needs of the rider and not as a relation to size of the bicycle...

[@paulbowen6763]

I'm 55 and 186cm (6' 1" ish) I built a road bike in 2019 using a cx frame 57cm using shimano tiagra compact 4720 with 175mm cranks so 50 34 front and 11 32 rear which is a nice combination out on the road and in the mountains and by mountains I mean the classic alpine climbs of Isere and haute provence. Last year I built a gravel bike using a similar cx frame 57 cm but this time I fitted a 10 speed shimano GRX 46 30 front and 11 36 rear with 165mm cranks ( this was the only grx crankset I could get hold of due to the global shortage of components! I was dubious.. But...), this combination rides just as well, a little less top end speed on the road obviously, but it comes into its own off road, it performs just like a mountain bike (with less weight and no suspension) spinning up climbs with extreme ease and no torque at the knees, so if that's what you are into then shorter is the way to go for gravel !

[@ygtcbee23]

10:15 Connor as a motivational coach! Love it

[@dparrigo]

#AskGCNTech: I think everyone agrees that one of the best upgrades for your bike are carbon wheels. They are expensive, and while I am saving for this upgrade, which size would be my best choice? I ride primarily on the road, and honestly the majority of my miles are on relatively flat roads where I live in Maryland. I am already riding on heavier aluminum rims, so if the carbon rims are relatively equivalent weight, I am fine. But, what would work best for only being able to afford one set? 40mm, 45mm, 50mm, 60mm? I don’t think I am willing to go larger than 60mm because we do get quite a few windy days along the Chesapeake Bay. Thanks!

[@marksharma-drake1016]

Sprint test (as someone else mentioned) didn't take into account different crank lengths effectively changing the gear ratio, so of no particular use. However, where crank length is worth considering is when you're in granny. Shorter cranks effectively limit your easiest gear.

[@HotelPapa100]

A sprint test stating from zero speed and not going up to very high cadence will always favour the long crank. The ergonomic question is how fast the force you can bring to the pedal reduces with cadence and stroke length. This will be different for different riders. Are your muscles fast, or are they strong. You'd have to measure power output of an individual rider over a significant length of time (and ideally track profile, too).

[@DaemonaDarkchild]

When they compared weights, they did so without considering the difference in power output. If you save 10% in weight but lose 20% in power, should the small crank still get that point?

[@whitting54]

A higher bottom bracket will permit tight turns with longer crank arms. Custom frame builders considered that back-in-the-day.

[@sepg5084]

Shorter cranks favor people who have higher than average cadence and people who are more prone to hip impingement from longer cranks. Longer cranks provide better mechanical advantage and would favor people who are flexible enough to use them comfortably. I'm 5'7" tall and use 175mm cranks, though i am flexible enough to sit "asian squat" style comfortably (am asian). I am awaiting delivery of 170mm crank with chainrings that have 2 less teeth in them, to test how it feels to use them. The shorter crank would provide less mechanical advantage, but that mechanical advantage is brought back by having an easier gear ratio on the chainrings. I'd be mashing less and be spinning more.

[@georgehugh3455]

Based on a number of sources, crank lengths in that middle area (~160-180mm) tend to be a wash (==>personal pref) I have found, however, 172.5mm on my uprights to cause knee pain on my recumbents due to the restricted position (==>165mm)

[@paddyotoole2058]

Ahhhh, recumbents. Dear oh dear. This explains everything 😂

[@mjsylver]

Got myself a bike fit at Mack Cycle and Fitness in South Miami.. I’m 71 inches tall with a 32 inch inseam. I’m funning 165 mm cranks on a 50/34 front end with an 11-28 cassette. Seems to work for this 62 year old body.

[@jimmyhor78]

The flaw in this test was the fixed resistance with the same gear for each crank. Resulting in a much harder overall gearing with the short cranks and obviously both of them can't get it up to their optimal cadence for an accurate max effort test.

[@chadkline4268]

Proper crank arm length varies with leg length, which is the most important factor.

[@Triestini]

I thought the crank-arm length depended on the wheelbase of the bicycle. A long wheelbase means a long crank-arm, a short wheelbase means a short crank-arm (Top-Tube length) Think about the end of your toes clipping the front wheel and your heels hitting the rear chainstays. I think the keyword here is geometry.

[@jaredlash5002]

The worst part about the standard crank lengths found on most non-custom bikes is that it doesn't seem to matter if the frame is size XS or XL, you're going to get a crank that is close to 172.5 mm long. For people who have short legs and need the XS frame, their knees will be bobbing up close to their chest when pedaling with the too long cranks.

[@mehmd1913]

Interesting video. We use a multi lever and multi gear ratio scenario. There are at least 3 pivot points, the hip the knee and ankle. Also, where you place your cleat will also determine the start point of initial lever. Thus a combination of crank length, cleat position, saddle height and reach will ultimately determine power. I use a more mid foot position and have downsized to 172.5 cranks and it has been better. I probably could or should have gone to 170 cranks... in any event my knee pain is better and instead of having to average a 50 19 I now average a 50 17 ratio when riding with much less fatigue.

[@trroland1248]

Those DA 7800 cranks are a thing of sculpted beauty.

[@dadigrubi2010]

please also include next to your discussion regarding the crank length to chainring size effect to power, torque and comfort to knee?

[@krug123]

It would seem that crank length has the greatest effect on hip angle, which was not being tested at all in the max-sprint tests in this video because the presenters were both standing on the pedals. Shortening the cranks opens the hips up more at the top of the pedal stroke, which allows the rider to choose a lower stem at the front leading to gains from reduced drag.

[@marks3620]

I’m rocking 172.5 on my new one previously had 175 for years. Wouldn’t want to go less than 172.5mm just preference and feels right.

[@joaob.almeida5176]

a point to be considered is how much they'd be able to maintain their top power on each crank, i think big cranks could probably benefit sprinters but once roling i think smaller cranks are easier to mantain near top effort.

[@JollyGiant0]

Crank length when cornering doesn't matter as you always corner with the inside one uppermost and no one will shorten their crank length to save weight as it would make it so uncomfortable to ride. So it's really short cranks 1 long cranks 3. Oh Conor's gaffs are brilliant even though he doesn't know he's making them!

[@wayneyoung146]

Just like Ford and Holden. H. used high killer watts shorter cranks faster off the line F. Used lower Killer Watts but longer stroke for longer distances with high mounts of Torque. Using longer strokes.

[@markdundon9922]

Watching this video today and seeing the screen in between them reminds me of just how crazy the world was 2 years ago!

[@chrisquijano1333]

From stand still, the longer crank will always give higher power output but on faster speed, I doubt that the longer crank will do better. You should make a test on speed. *Power=2(Pi)(Torque)(Rotational speed)

[@bicyclist2]

I'd love to find a pair of Shimano Dura Ace 7800 cranks in 180. Unfortunately they're impossible to find in the US. I've only ever seen a pair for sale once on ebay. I ride a 172.5 because its the longest I could find. Thanks.

[@burrussw]

interesting topic, 40 years ago it seems every bike came with 170 mm crank arms, didn't matter if the frame size was 50 cm or 65, strange days, being taller (185 cm) I thought I would have liked longer crank arms, I am more comfortable spinning around 100 RPM so for the heck of it I put a 165 cm crank on one of my mtn bikes, loved it for climbing, fair on the flats, sucked on the downhills, fun to change things up to see how it feels

[@BoxCarBoy12]

Shorter cranks are good for high cadence spinners, and longer cranks are good for low cadence grinders because of the lever arm. I'm definitely the latter since I struggle to average more than 70rpm average, so longer cranks work better for me. On the MTB side, they generally come with longer cranks because you're generally putting in a lot of shorter, sharper efforts from low speeds to get over obstacles.

[@gregoryvassilakos9972]

A better test of power would be over a longer period of time with the rider in the saddle. A primary benefit of shorter cranks is the opening of the hip angle, which is not really a factor with the rider out of the saddle. I switched from 170 mm to 155 mm cranks on my triathlon bike to improve my position. The only disadvantage I noticed from having shorter cranks is that I have to shift down more quickly when going up hills.

[@deanrobbins8102]

Now, do those short crank sprints on a recumbent! Have your knee surgeon on speed dial though...

[@dino.techtv]

I had "above the knee" pain using 175mm crank but when I shift to 170mm the pain is gone. I'm riding on a mountain bike though. a 5mm difference seem very small, but it did fix my knee problems.

[@LazyGrayF0x]

Long, run 180mm on MTB, gravel and road. Would run 190mm on road if anyone would make it, but unfortunate for tall riders, industry forgotten us except shimano who still offer 180mm cranks in dura ace line. I have 37in true Inseam and when I switched from 175mm, My fatigue was down and power up and find it much more comfortable

[@FarFlungHeel]

Look at Zinn bikes.

[@richardluvsford7849]

any chance you could try this again on a tt bike? as once up to speed, pushing rpm and in the aero tuck. You can operate with your legs closer to full extension, and running less dystance per revolution.

[@marcusm8374]

Crank Length affects the gear. Long crank 》 reduces gear; shorter crank 》increment gear. So, at the same 53-11 we have diferent gear relation and diferent speed cause cadence in shorter crank will increase.

[@hankdutch9360]

The Q-factor on the 180 seemed larger than the 165 so this will limit the cornering angle for pedal strike. The frame is the main limit here with the BB height being essential for pedal strike.