How To Choose The Correct Crank Length – The Most Important Bike Adjustment You've Never Made?

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1. So i got confused, i'm 183 with 83-84 inseam and i'm using 172.5! Is this the correct on or i must go to the bigger one?!
2. This is very helpful information! I have 175.5mm crank. And I am 5'4", I think this might be too long for me, since I do feel a dead spot here at there, and my knees get pretty close to hitting my chest in aero position. No pain though. What would you recommend?
3. too long cranks not only will make your knees get in the way of vertical riding position, but also at the beginning of the push downward your leg is at an absurd almost 90 angle and you just can't get a proper push from that position. look at nba players of any height jumper and they always bounce from more like 135+ degrees angle. also just like in martial arts if you're about to kick the other guy and you start your kick by chambering to 90 degrees in front of you, were the guy get close to you he will effectively reduce your power at the end resulting in more of a push than an impactful kick that hurts, or he'll even just push you off your feet.
4. My road bike uses 170mm and I have no issue. Gotten into mountain bikes recently and the 175mm crank is giving me knee pains T.T
5. What is the saddle and height adjustment from going 172.5 to 165? obviously you have to adjust saddle height by 7.5mm but what about saddle position?
6. I am 6 feet tall (2.83 meters). When I got my current bike, I got a 175 mm crank. After a year of knee pain, I decided I had to try a shorter crank. I switched to 170 mm in the same model of crank. Believe it or not, that 5 mm made a significant difference. I rarely have a problem with knee pain now, after several years with the shorter crank.
7. Well
   Shit I am 5'6 with 175mm cranks no wonder I have back pains
8. The height calculator gives me 190 mm cranks, and the inseam gives me around 193-194 mm cranks. I assume I'll be alright on 175's or what would you say??
9. Does this still work for CX bikes? what about mountain bikes? They are used slightly differently with the rider moving around the bike more so I wondered if made a difference?
   My boardman CX has 175mm cranks. I am 178cm tall so using 9.5% works out at a 169mm crank. Using my inseam gets me a 163 crank!
10. according to the calculations i should be running a 165mm crank (5'8", 30" inseam) but oddly enough my current and upcoming bike both have 172.5mm cranks and feel fine. i might be able to drop to 170 but i think 165 would be too short, not to mention it wouldn't work with the Tiagra crankset i have now
11. Hi guys. Having been riding my Scott CR1 Pro with 175mm cranks for a couple of years, I wondered why my legs felt extremely fatigued after only doing 20-30 miles. I've been using my mates Ribble through winter with 172.5mm cranks and felt much better. Calcs show I should use 170mm cranks. Help?!
12. why add 65??????
13. Hey thanks guys! After watching this crank length is now as clear to me as the Pea soup fog of London in 1873. It really is a science, and very hard to get 100% right. Great stuff from you guys though ;-)
14. Great video. Recently I replace my full suspension for a hardtail MTB. I have tried any kind of fitting adjustment in order to get rid of the knee and back pain but nothing seams to work. I am 5'7" and my frame is a Niner Air9 size medium. Before I replaced my bike I started using a new SLX crankset which I bought having no idea that cranksets came in different sizes. My current crankset is a 175 mm... Do you think this is the solution I was looking for... to get 165mm crankset?
15. Is it okay that i'm 171cm (5'6") and I use 175mm cranks?
16. Longer crank generate more torque. You can't do this with shorter crank. it is basic physics. So, if you have short crank, you put bike in lower gear to produce same amount of power. But you must have higher cadence. And, with higher cadence is much easier to produce power.
    
    But with higher cadence you legs will lactate more quickly. You can't sustain that power for longer. You will be tired. That can see in GSN video in lab. Higher cadance-more lactate. Lactate-not good.
    
    Do you drive your car 100 km/h (62 m/h) in second gear? I don' thing. You can measure consumption. It is 1/4 higher for third gear/fifth gear. I did it today. If you want to go longer, with some speed, with minimal effort, you need lower cadence/rpm. On bike you need longer crank for that.
    
    To fit longer crank on bike and be comfort for longer time you need some proper bike fit and proper cycling technique. Not shorter crank. I'm 183 cm and I have bike with 172,5 and 175mm crank. It is significantly easier to drive longer on longer crank and higher gear. If I'm sprinter I will probably like shorter. But I'm not. 40 km is just warm-up. Not proper ride.
    
    I'm really want to try 177,5 mm crank, 53/39T and 11/28. But, for now, 175, 52/36, 12/25 is good.
17. hi guys I'm 5'9 what size cranks do you recommend for me ?
18. That was really very good. Finding the perfect crank length is something that I've been wrestling with for a decade. At 6'0", with a much longer leg to torso ratio, I rode 172.5 cranks for years. Then in my last road and mountain bikes, I went up to 175, thinking that would be better for my longer legs. I was wrong. It has hampered me in almost every way. I might even be better served with 170mm for road and mountain, and 165mm for Tri. But as you say, it's quite personal. I am quite glad you sited at the beginning that crank arm length has nothing to do with power output. There are still so many that believe this and the more it gets dispelled, the better. Well done. Great video.
19. Hi - really useful and informative videos. HAve watched numerous which have really helped. At 182 cm I currently have a 175mm crank on a newly built bike and was concerned about going to 172.5 - but this would seem to suggest that would be a change that would be 'ok' or even more suitable.
20. Actually, there is quite a bit of literature written about the subject but you're not gonna find it in blogs about cycling, cycling magazines, or the mainstream media. I read 5 peer-reviewed scientific papers about it just today but they were papers I found from my University library website. They were papers from publications such as the European Journal of Applied Physiology (they're quite long, just read the introduction, abstract, and the discussion sections of the papers; the results section won't mean much to you lol). They test crankarm lengths from 130mm to 220mm. What I conclude for them is that going to a shorter crank arm length does not change much your average power output over the long haul, however, with a short crank arm, you can reach your peak power faster. What that means is, if you participate in events like cross-country mountain bike racing in which getting in the best position from the start is very important before you get to stretches where it would be difficult for anyone to pass you, a shorter crank arm would serve you better since you can reach your peak power significantly faster, you can put yourself in a winning position faster. Another research paper found that the optimal crank length for maximum power is 41% of your tibia length or 21% of your leg length. Another paper found that shorter crank arms are more efficient because you consume less oxygen over time. The amount of oxygen consumed is directly correlated to the amount of energy you spend. This is because with shorter crank arm lengths you are able to get into a lower aero position without your knees hitting your chest. As a result, you can reduce the amount of drag by 30% in some cases. Yet another paper found that the shorter the crank arm, the faster your pedaling rate (cadence) using the same gear. That can lead to your going a little faster. Like I said, there are quite a bit of scientific studies conducted regarding the effect of crank arm length on overall performance, but you're not gonna find them just by googling them. You gotta go to those peer reviewed scientific sources.