Bike fit is pretty personal, depending a lot on where and how you ride not to mention what you ride ( eg. different geometry and characteristics). Of course, you have folks who need help/ guidance and have the financial resources to pay for it- but, at the end of the day, it is the rider who is in the best position to determine what works best for them- I think the most important advice a bike-fitter ought to provide is how a rider can make those positional changes themselves to safely gain the most they want.
I changed one of my cranks from 175 to 165 and got rid of almost all of my knee pain. Technically it was recommended that I use 160mm, but those are not readily available and cheap. I put a Sora crank on one bike for $90 and a 105 compact set on my road bike for $110. I don't really need specialized parts and would not need the absolute high end parts either. Many people over bike their potential IMO, unless they are seriously into racing. Many things are not even the bikes fault, just some proper training, reconditioning, and reasonable expectations. I guess I could not even afford a bike fit anyway.
Demonstrates my corollary: The price of False Precision increases exponentially with the promised enhancement, and the Placebo effect increases in inverse proportion to the ability to measure improvement.
Plus all these bike fitters are comical in their finite diagnosis when they never spend a single second riding with their clients post fitting. You need to spend at least an hour or two riding alongside the client to finalize the fit since most bike fittings involve a "laboratory like environment" (air conditioned room, perfectly horizontal bike orientation, finite bike position during the fitting, etc).
Any studies saying they perform worse? No? Ok, then it's either good or indifferent. From a biomech perspective it only makes sense that you can tweak the gearing based on which muscles are involved and the strength/condition of those muscles. As natural runners we evolved to have stronger quads (slow twitch to put up with our weight and gravity) and hamstrings are quicker (fast twitch because we tuck our feet into our butt to lower the moment of inertia to bring our feet forward faster). That basic summary would normally mean a lot... except we are talking about a system of efficiency and that means taking advantage of muscles differently to maximize efficiency (think faster on a bicycle than runner, duh). All in all, I would give it a try if I had extra $ but generally speaking it isn't worth the hassle. Just focus more on your "scrape the gum off your shoe and kick the soccer ball." Thanks for the video, it made me think today.
My current bike came with 175mm stock cranks. When I first started riding it, I couldn’t understand why my cadence was so low. I used to keep a handwritten (pre-bike computer) journal of my rides. When looking at my stats on an old Cannondale, I noticed my cadence then was about 10-12 rpm higher. When I looked up the stats on the bike, I noticed it came with a 170mm stock crank. So, I decided to make the change from a 175 to 170mm crank. The difference for me was like night and day. I don’t have a power meter so I can’t speak to changes in power, but my avg cadence improved by about 10 rpm and my pedaling felt perceptibly lighter and more nimble. I can see your point, if a bike fitter was unscrupulously upselling a client, however, I made my decision on my own. Love my shorter cranks. :)
Back in the 90s I changed my cranks from 170 to 165mm as I was experiencing some knee discomfort. In this case 5mm made all the difference for nearly the next 20 years. I am rather short of leg & probably should have changed to something less than 160mm. Now using 150mm cranks due mostly to lower back issues & having had to set cleats further back due to foot pain. I put it down to getting old after 48 years & nearly 250,000 miles of cycling. Just wish I had known all this 30 years ago, now pain free cycling for the 1st time in years. A lot of the short cranks for sale these days seem to have a high Q factor, why would short people want a high Q factor like 160mm. I prefer 130mm but have had to settle for 140mm on all my bikes, as going from a 130 to 140mm on a different bike causes hamstring type muscle problems. Some of my bikes are fitted with triples so 130mm is not possible on these.
Richard Harding Yours is a perfect example of the crank length making a difference. A 5 mm change while it may not produce a huge measurable effect in oxygen consumption or efficiency, it can still have an effect on the kinematics of your pedaling - i.e. how much the knee flexes at the top of the pedal stroke. And clearly the initial change from 170 to 165 mm was just enough which is great. But you're right, given the option (and a perfect world) after some testing I'm guessing something even a bit shorter may have been preferable - IF it were even available at the time. Thanks for watching and I will dig a little more into the q-factor problem too...
I use old 1980s Sugino cranks with a square taper spindle of 115mm length. I also use a middle ring tripler adapter chain ring to attach the granny ring. I'm going to try some Secialites TA cranks. Basically anything which is a straight crank. The modern low profile cranks are really crap for me as they position my feet to far a part. As I said before I have had to compromise with a 140mm Q to get my triple crank set ups to work correctly, but I much prefer a 130mm Q. Only this causes problems with inner hamstrings when going out to 140mm. With a 130mm Q you might get into problems like the crank hitting the chain when your in the small cog on a double setup.
Bike Fit Adviser From my understanding if I shorten the cranks by 5mm I would raise the saddle by 5mm to keep the saddle height the same. The difference at the top of the pedal stroke would be 1cm right? Would this be a considerable change to help with knee pain/ flexion issues? I'm considering going from 170's to 165's maybe I should go to 160mm, but that would be a difference of 2cm at the top of the pedal stroke
amen to this video, almost 25 years riding and the amount of BS is insane !!!!!!!!! hard to believe, especially on bike shops slowly dying with online option!!!!
i'm sure 2.5 mm adjustment in crank length would not affect power.. but i know for damn sure the feel difference between those crank lengths... I don't know if i can feel it in 5 minutes of riding.. but I can definitely feel the difference after a week of riding.
Short cranks rule! :) Allowed me to ride more aero, eliminated knee pain, increased ability to spin, high sprinting top speed! I bought 155mm Rotor cranks and I'm not short lol. People worry about changing crank length by 2.5mm hahaha. Just spend the dosh and give yourself some time to adjust. If it doesn't work at least you finally know.
One huge advantage of the shorter crankset is pedal clearance to the roadway. Also not mentioned is a for example is a 5mm shorter crank really is 10mm difference. A big change. Love my 165's 27.5" inseam....
I can feel the 2.5mm differences between my road bikes with 175, 172.5 and 170 cranks. With age, loss of flexibility, etc, the 175 cranks I used to like now feel like pedaling squares. And I feel more twinges in the hips, lower back and knees if the saddle height and position isn't perfect. The 172.5 cranks feel much more comfortable immediately. Same with the 170 cranks on my older Trek 5900 OCLV. But the cheapest way to experiment is with an older bike that uses square taper cranks -- you can usually find crank arms for as little as $20; no need to replace the chainrings, etc. If you like the fit and feel on the older bike, it'll probably be worth buying the more expensive Ultegra or Dura Ace in BB30 or other standard in your newer bike.
I tell. U this man , l been riding the last 50 years between 5 and 20 thousand km per year . Use every crank lengths , and now I move from 180 mm to 195 mm . Which is great as they give me more torque. I have a slow cadence 60 to 90 rpm. I ride across the country with a load. Hell no boy racer. My conclusion is that the body is a fluid state and is changing over the decades and review you cranks length every decade
If you are purchasing cranks with the intent of alleviating knee pain (which is the case in my situation) the few hundred dollars spent on a crank is cheaper than all the doctor visits, physical therapy or surgery that occurs from an aggravated knee.
It seems like recently I injured my knees using a shorter crank than I am accustomed to, contrary to mainstream thinking. My guess is that unless the seat is moved back to compensate, there is a greater angle of knee to foot with shorter cranks when the crank arm is at the three o'clock position, putting extra strain on the knee. If crank length was adjustable, like the seat post, we could experiment to find the optimal length without additional cost.
I would say that this gentleman is just about the first bike fitter I have heard in this country(USA) to speak the truth. He knows whats going on. Most of these so called bike fitters havent got a clue, let alone ever won a race. I dont know him but with 35 yrs experience in the business i know he also knows a thing or two and is not spewing out the kinda bullshit I constantly hear from my clients. If you are interested ask me and I can rant on an give you some examples.
There might be a change of only a few mm on a linear measurement, but please explain the difference of these mm changes related to the pedal stroke. I went from 172.5 to 165 and found it two very interesting outcomes: #1 I was able to obtain better angles on my set up. #2 I was able to turn my crank arms over faster, raising my Cadence, allowing me to use my gearing, what seemed to be, more efficient. You might be right, mentally I might have felt these things as viable. It's possible.
+PUMA JPUMA you might check out my other video about crank length...I talk about some of the benefits if the shorter cranks (many of which coincide with some of the sensations you noted in your comment)
I have to disagree, I changed my crank set (worn) to a new one, and promptly began to suffer knee pain, It turns out I had gone from 170 to 172.5 that was enough of a change to make me suffer.
*The classic bike shop fit scam in five steps:* 1-You need a better contour, wider, relief saddle for comfort; $120 2-Your handlebars are the wrong width/reach/drop; $100 3-Your stem is the wrong length/angle; $80 4-Your cranks are the wrong size; $400 5-Your shoes/pedals are the wrong size, width, don't have the right float, etc; $120-$300 Truth is some bike shops that do bike fittings have become the new used car lots, and manufacturers have even empowered them with fitting tools...
thechosendude You're not wrong. Unfortunately there are a lot of bad actors out there....many shops got into bike fitting at the behest of a cycling industry or marketing consultant because they saw the potential for it to be a driver of sales of new parts and new bikes. There are a lot of good people out there though that are conscientious and try to be conservative in their approach to new parts during a bike fit. Any time I am broaching the idea of a relatively expensive part, I'll give the client my best 80/20 analysis of that part as far as how much benefit it might bring them and at what cost. I essentially try to relate how married to the change I am. That way they can decide for themselves if there's enough bang for the buck for them
I didn't mean to slag reputable bike fitters if it came off that way, just highlight (having been there from experience) that bike shops and fitters are very different. Two of the 'big three' USA bike brands currently offer some kind of fitting service in their shops; and just about anyone can pass a BG certification course and be sent on their way to sell more components like they were taught. If someone walks into a shop complaining about saddle pains, the odds of upselling are pretty high. Chances are the shop won't even look to see if there are fitment issues with their bike before going into the standard procedure of measuring sit bones, offering stationary bike demos (on a machine or bike that's not theirs), or loaner saddles (to try on a bike that's maybe not properly fitted). Or someone complaining of shoulder pain will get their shoulders measured, and a new bar installed.....back into the same position as the old one nonetheless!
thechosendude I understand....didn't think you were being negative on all fitters. I agree with you that there are a lot of 'used car dealers' out there
I just had a bike fit and the fitter said that I would benefit from moving from 172.5 to 165 length.the reason was to reduce the bend in my knee in the top position of the pedal stroke. I do Crit racing so I wanted my setup more for Crit. He also told me to get +4mm pedals to get my knees to align and move straight up and down. he put in two spacers but that was still not enough.
A Surf I think that could be a reasonable course of action. I'd want to know more about how the +4 pedals work for you....the knee tracking can be a particularly difficult issue to remedy. The knee is the "slave" joint in the context of cycling -- it goes where the foot/ankle and hip tell it to. Sometimes spacing the feet out (or in) will help with alignment but not as often as we'd like so if I'm reading you correctly, he's already put in small pedal spacers which get you to +2mm? On both sides? A lot of whether the +4 is going to do the trick will depend on how symmetrical your movement is - especially how the pelvis sits on the saddle which then translates down to affect how the hips and knees move. Not saying the +4 pedals aren't the right move - they could be. But they're not a cheap solution so in the absence of true validation I'd be cautious
the knee alignment was that last thing we looked at after getting everything else set. Using lasers to check the alignment. The spacers help take some of it out but 2 spacers are all that you can use. I really noticed a difference during my sprint workout this week. My feet felt more under me and I seemed to have a bit more control. cost isn't too bad. 115 USD for Ultegra +4's. Once I have the pedals I will go back and he will check everything again. 100 miles this week and the fit feels good. I had to tilt my saddle down a bit more after a 60 mile ride.
83cm inseam and 170mm cranks on all my bikes. 175 feels like too big. I´ve discovered it by accident when getting a new bike. Always felt better on that bike. Then I´ve got my wife a bike and women bike usually has shorter cranks. Then I realized that I´ve should look at that crank of that good bike and found that it was not the bike. It was the crank. Then I´ve changed all my 5 bike cranks to 170 and now I love them all
Instead of testing how much power you can produce would it be better to try to sustain a certian power for a period of time, before and after a few changes, to see if the changes have made doing such an effort more comfortable?
Bike Fit Adviser I ride 175's on my mountain bike and used to ride 172.5 on my road bike until about a year ago. I decided that in order to maintain consistency and because I needed a new bike that I would switch to 175's on the road. The end result is I also agree there is no noticeable difference.
I understand that all changes on a bike are subjective to comfort and sustainability. And, if I understand your video, you are suggesting that a change of 5mm is, at times, warranted. As a 70yr old competitive cyclist, I found that changing from 172.5 to 165 on my TT bike made a difference. It allowed me to get into a more aero fit via the un-impinging of my hips. But for anyone to suggest, via all the research, that one is more or less powerful is BS. The advantages, wattage, is said to be negligible. However, the ability to turn the crank over with a shorter crank arm, Cadence, is said to increase. Doesn't it depends on what your specific needs are in the discipline you have chosen?
This isn't a fair comment that a 2.5 mm difference is a swindle. A 2.5 mm difference in crank length is significant because the crank rotates 2.5 mm change in radius alters the circumference by 2 x ~3.14 x 2.5 = 15 mm per revolution. Factor that into someone riding at 100 rpm for an hour with 2.5 mm longer cranks, their feet are moving 94.2 m further! I have ridden everything from 180 to 170. All feel very different even with 2.5 mm changes.
I do feel a pretty big difference between the usual lengths, 170/172.5/175. 172.5 being by far the nicest compromise between leverage and ease of pedalling. I use 170s for MTB and commuting, 172.5 for Road.
If you have shorter legs 2.5mm makes all the difference in the world for me It made a big difference I had PR in all my local rides going from 172.5 to 170's!
I'm running a fixie at 172.5 and road bike at 175. Difference is not noticeable. It's more about everything else on a bike, reach, saddle, handlebar drop, etc. that matters far more than the crank length.
Man they is sooooo much BS in the bike industry, even top shows like GCN talk about fore and aft adjustment of the seat based on KOPS. Crank length is a very controversial topic some swear by shorter cranks whilst other talk about height of rider. I think it is not such a big deal. For pure aero position it does appear shorter cranks have advantages by raising the hips and lowering the knee height, but for general riding, not much.
Hei John, greeting from Norway. I really like your videos, you are doing a really good job! However, whenever I hear that crank length does not matter or small difference in length can not be worth of change, I am tempted to tell my story, what happened to me once. Just by a mistake, and completely unaware of it, I rode a bike with two different crank arms, one 5mm shorter that the other. No, I wont tell you how it was. I insist you do such a test yourself. And then tell us, was a negligible difference?
I have gone between 170 and 175 on MTB cranks. I can't say that I can feel any difference. I guess the good news is if you see a set of cranks that you like but they only come in a shorter length, it is not going to make that much of a difference.
Alright I got one for you. I just bought a 2018 Cannondale supersix Evo Dura-Ace disc and it comes with 172.5 crank arms but my inseam including shoes is only 32 in (28 for pants and 30 to bare feet) and since I need to buy a power meter one of the arms being replaced anyways so I might as well spend a hundred twenty bucks and buy the other side and do it right the first time. The bike comes with a semi Compact and a 28 cassette in the back, which is being changed (the cassette that is), so what size crank arms would you recommend 165 or 167.5?
I can say as a short rider 164cm ,69cm inside leg a 175mm cranks is a complete disaster way way to big for me even 170mm is still very uncomfortable and far to big , so I went all the way down to 155mm kids cranks this was way way better and probably would work if high rpm rider , which I am not ,I'm just leisure rider so maybe just slightly to short . So my next move was to try and source 160mm cranks , this is not easy ,it can be done but costs more than the bike , so put it off for few years . Try again few years later got a single speed with 165mm cranks this works , in as much as it gives leverage, but to large to be honest. I have now sourced 160mm for my new bike this should work although 158mm I think would be the sweet spot for me ,if 155mm is just slightly on the short side and 165mm is slightly on the long side (155mm was the best of the 2 ). As a older rider my movement is not what it used to be, so I find small differences are very noticeable. This is my experience over the last 30 +years .
I would say a 5mm diff to be the minimum to make to your fit, but that 5mm can definitely result in a noticeable improvement in comfort, cycling dynamics, power, etc.
Its tempting to believe your comments about 2.5mm difference in crank length not making enough of a difference in performance and comfort but do you have any data to back up your claims?
I'm all for a having discussions on what is "right", what is "measurable", but I don't see the point in saying what is "worth it". Only the individual can say that. Some people may not find it worth it to spend $100 even if you tell them they should shorten their crank arm length by 10mm. Others may say it's worth it to spend $1,000 to go down by 2.5mm. I realize 2.5mm is fairly negligible, but just giving example. Value is in the eye of the beholder. I am comfortable in my current setup, but if I found out some "perfect setup" via a bunch of measurable testing and hip angles, I would spend a lot to change it, because it would be something good for many, many years and thousands of miles.
2.5mm in 172.5mm is 1.5%. Negligible I'd say? However, in terms of knee angles and muscle recruitment, the joint mechanics might amplify this difference, or not? Woudn't this small difference help, not in the bike, but in the marathon afterwards? I mean, even a 2.5mm would deliver the runner in better shape for the run?
Enda Bigarella your thinking about it incorrectly. Yes the crank arm length changed by 1.5 percent but the maximum angle of knee bend would be much less. A quick calculation for myself (I'm about 6' 3") shows that if I changed my crank arm length by 2.5 mm it would only change my total knee angle by .4 percent. Yes less than a half of a percent. Negligible. You can calculate the angle change by measuring from your hip to you knee as length 1, your knee to your ankle as length two and the angle you originally form at your knee. Then you can calculate the length at that angle between your ankle and your hip using the other three knowns of the triangle. Then simply add 2.5mm to that distances and use the three sides of the triangle to calculate the new angle. Divide the new angle by the old angle to find the negligible change. I have a diagram showing this but it won't let me upload the photo.
fernando g. aguirre Up just a bit. When you are a small person you need small bike when you are a tall person you need tall bike. Try some 175 crank and then go on 170 crank it’s only 5mm but if you are about 5.7 short legs then it will be biggest 5mm you will of herd of and cranks are not that expensive ultegra £169 from most online shops
*I AM PUZZLED!* If I look up Shimano Ultegra Hollowtech II cranks I see that the crank arm lengths vary from 165 to 175 mm *only a 6% change* (bike.shimano.com/content/sac-bike/en/home/components11/road/ultegra1/fc-6800.html) My bike (Trek Emonda SL6) with said crank is made in sizes varying from 47 to 64 cm a *30% change* You can see the scaling problem I am concerned about already. (www.trekbikes.com/us/en_US/bikes/road-bikes/performance-road/%C3%A9monda/%C3%A9monda-sl-6/p/1441900-2017/) Standard deviation in height/Mean height (women only, easier to find) = 7.2cm/155.8cm so for 2 sigmas (95% of people) -> 14.4cm/155.8cm= *9.2% change* (journals.plos.org/plosone/article?id=10.1371/journal.pone.0018962) If you combined men and women that percentage would be higher probably ~15%. I also know that walking stride is proportional to height.... *so how can it be that crank lengths vary by so little?* It tells me that the variation in knee bend (top/bottom of pedal stroke) for shorter people is going to be larger given equipment size options and smaller for tall people. Does not "seem" optimal!
if 5mm is insignificant, why do they even bother making different lengths when the standard spread is only 5mm anyway? I would like to try some longer cranks, but I don't see many choices. 180 seems about the best I can do, and even that adds a pretty hefty premium.
Bike fit is pretty personal, depending a lot on where and how you ride not to mention what you ride ( eg. different geometry and characteristics). Of course, you have folks who need help/ guidance and have the financial resources to pay for it- but, at the end of the day, it is the rider who is in the best position to determine what works best for them- I think the most important advice a bike-fitter ought to provide is how a rider can make those positional changes themselves to safely gain the most they want.
I changed one of my cranks from 175 to 165 and got rid of almost all of my knee pain. Technically it was recommended that I use 160mm, but those are not readily available and cheap. I put a Sora crank on one bike for $90 and a 105 compact set on my road bike for $110. I don't really need specialized parts and would not need the absolute high end parts either. Many people over bike their potential IMO, unless they are seriously into racing. Many things are not even the bikes fault, just some proper training, reconditioning, and reasonable expectations. I guess I could not even afford a bike fit anyway.
Demonstrates my corollary: The price of False Precision increases exponentially with the promised enhancement, and the Placebo effect increases in inverse proportion to the ability to measure improvement.
Plus all these bike fitters are comical in their finite diagnosis when they never spend a single second riding with their clients post fitting. You need to spend at least an hour or two riding alongside the client to finalize the fit since most bike fittings involve a "laboratory like environment" (air conditioned room, perfectly horizontal bike orientation, finite bike position during the fitting, etc).
This is soooo true!! ❤
Any studies saying they perform worse? No? Ok, then it's either good or indifferent. From a biomech perspective it only makes sense that you can tweak the gearing based on which muscles are involved and the strength/condition of those muscles. As natural runners we evolved to have stronger quads (slow twitch to put up with our weight and gravity) and hamstrings are quicker (fast twitch because we tuck our feet into our butt to lower the moment of inertia to bring our feet forward faster).
That basic summary would normally mean a lot... except we are talking about a system of efficiency and that means taking advantage of muscles differently to maximize efficiency (think faster on a bicycle than runner, duh).
All in all, I would give it a try if I had extra $ but generally speaking it isn't worth the hassle. Just focus more on your "scrape the gum off your shoe and kick the soccer ball."
Thanks for the video, it made me think today.
+Jon Prevost thank you for watching!
My current bike came with 175mm stock cranks. When I first started riding it, I couldn’t understand why my cadence was so low. I used to keep a handwritten (pre-bike computer) journal of my rides. When looking at my stats on an old Cannondale, I noticed my cadence then was about 10-12 rpm higher. When I looked up the stats on the bike, I noticed it came with a 170mm stock crank. So, I decided to make the change from a 175 to 170mm crank. The difference for me was like night and day. I don’t have a power meter so I can’t speak to changes in power, but my avg cadence improved by about 10 rpm and my pedaling felt perceptibly lighter and more nimble. I can see your point, if a bike fitter was unscrupulously upselling a client, however, I made my decision on my own. Love my shorter cranks. :)
Back in the 90s I changed my cranks from 170 to 165mm as I was experiencing some knee discomfort. In this case 5mm made all the difference for nearly the next 20 years. I am rather short of leg & probably should have changed to something less than 160mm. Now using 150mm cranks due mostly to lower back issues & having had to set cleats further back due to foot pain. I put it down to getting old after 48 years & nearly 250,000 miles of cycling. Just wish I had known all this 30 years ago, now pain free cycling for the 1st time in years. A lot of the short cranks for sale these days seem to have a high Q factor, why would short people want a high Q factor like 160mm. I prefer 130mm but have had to settle for 140mm on all my bikes, as going from a 130 to 140mm on a different bike causes hamstring type muscle problems. Some of my bikes are fitted with triples so 130mm is not possible on these.
Richard Harding Yours is a perfect example of the crank length making a difference. A 5 mm change while it may not produce a huge measurable effect in oxygen consumption or efficiency, it can still have an effect on the kinematics of your pedaling - i.e. how much the knee flexes at the top of the pedal stroke. And clearly the initial change from 170 to 165 mm was just enough which is great. But you're right, given the option (and a perfect world) after some testing I'm guessing something even a bit shorter may have been preferable - IF it were even available at the time. Thanks for watching and I will dig a little more into the q-factor problem too...
What brand of cranks are you using in size 150 with a Q factor of 140? If they are square taper, what length spindle are you using?
I use old 1980s Sugino cranks with a square taper spindle of 115mm length. I also use a middle ring tripler adapter chain ring to attach the granny ring. I'm going to try some Secialites TA cranks. Basically anything which is a straight crank. The modern low profile cranks are really crap for me as they position my feet to far a part. As I said before I have had to compromise with a 140mm Q to get my triple crank set ups to work correctly, but I much prefer a 130mm Q. Only this causes problems with inner hamstrings when going out to 140mm. With a 130mm Q you might get into problems like the crank hitting the chain when your in the small cog on a double setup.
Bike Fit Adviser From my understanding if I shorten the cranks by 5mm I would raise the saddle by 5mm to keep the saddle height the same. The difference at the top of the pedal stroke would be 1cm right? Would this be a considerable change to help with knee pain/ flexion issues? I'm considering going from 170's to 165's maybe I should go to 160mm, but that would be a difference of 2cm at the top of the pedal stroke
amen to this video, almost 25 years riding and the amount of BS is insane !!!!!!!!! hard to believe, especially on bike shops slowly dying with online option!!!!
Right on!! Bad ass video. I love all your bike fit videos. You speak the truth, and have excellent info. I also like your video on kops.
Thank you for watching!
i'm sure 2.5 mm adjustment in crank length would not affect power.. but i know for damn sure the feel difference between those crank lengths... I don't know if i can feel it in 5 minutes of riding.. but I can definitely feel the difference after a week of riding.
Thank you for posting! I've seen this happen myself before!
Short cranks rule! :)
Allowed me to ride more aero, eliminated knee pain, increased ability to spin, high sprinting top speed!
I bought 155mm Rotor cranks and I'm not short lol. People worry about changing crank length by 2.5mm hahaha. Just spend the dosh and give yourself some time to adjust. If it doesn't work at least you finally know.
One huge advantage of the shorter crankset is pedal clearance to the roadway. Also not mentioned is a for example is a 5mm shorter crank really is 10mm difference. A big change. Love my 165's 27.5" inseam....
I can feel the 2.5mm differences between my road bikes with 175, 172.5 and 170 cranks. With age, loss of flexibility, etc, the 175 cranks I used to like now feel like pedaling squares. And I feel more twinges in the hips, lower back and knees if the saddle height and position isn't perfect. The 172.5 cranks feel much more comfortable immediately. Same with the 170 cranks on my older Trek 5900 OCLV.
But the cheapest way to experiment is with an older bike that uses square taper cranks -- you can usually find crank arms for as little as $20; no need to replace the chainrings, etc.
If you like the fit and feel on the older bike, it'll probably be worth buying the more expensive Ultegra or Dura Ace in BB30 or other standard in your newer bike.
I tell. U this man , l been riding the last 50 years between 5 and 20 thousand km per year . Use every crank lengths , and now I move from 180 mm to 195 mm . Which is great as they give me more torque. I have a slow cadence 60 to 90 rpm. I ride across the country with a load. Hell no boy racer. My conclusion is that the body is a fluid state and is changing over the decades and review you cranks length every decade
If you are purchasing cranks with the intent of alleviating knee pain (which is the case in my situation) the few hundred dollars spent on a crank is cheaper than all the doctor visits, physical therapy or surgery that occurs from an aggravated knee.
It seems like recently I injured my knees using a shorter crank than I am accustomed to, contrary to mainstream thinking. My guess is that unless the seat is moved back to compensate, there is a greater angle of knee to foot with shorter cranks when the crank arm is at the three o'clock position, putting extra strain on the knee. If crank length was adjustable, like the seat post, we could experiment to find the optimal length without additional cost.
I would say that this gentleman is just about the first bike fitter I have heard in this country(USA) to speak the truth. He knows whats going on. Most of these so called bike fitters havent got a clue, let alone ever won a race. I dont know him but with 35 yrs experience in the business i know he also knows a thing or two and is not spewing out the kinda bullshit I constantly hear from my clients. If you are interested ask me and I can rant on an give you some examples.
There might be a change of only a few mm on a linear measurement, but please explain the difference of these mm changes related to the pedal stroke. I went from 172.5 to 165 and found it two very interesting outcomes: #1 I was able to obtain better angles on my set up. #2 I was able to turn my crank arms over faster, raising my Cadence, allowing me to use my gearing, what seemed to be, more efficient. You might be right, mentally I might have felt these things as viable. It's possible.
+PUMA JPUMA you might check out my other video about crank length...I talk about some of the benefits if the shorter cranks (many of which coincide with some of the sensations you noted in your comment)
+PUMA JPUMA th-cam.com/video/gwoNCypfg08/w-d-xo.html
I spent $420.00 for change 172.5 to 165. The performance is same but my back pain is gone.
I have to disagree, I changed my crank set (worn) to a new one, and promptly began to suffer knee pain, It turns out I had gone from 170 to 172.5 that was enough of a change to make me suffer.
170mm vs 175mm cranks make a huge difference for me
*The classic bike shop fit scam in five steps:*
1-You need a better contour, wider, relief saddle for comfort; $120
2-Your handlebars are the wrong width/reach/drop; $100
3-Your stem is the wrong length/angle; $80
4-Your cranks are the wrong size; $400
5-Your shoes/pedals are the wrong size, width, don't have the right float, etc; $120-$300
Truth is some bike shops that do bike fittings have become the new used car lots, and manufacturers have even empowered them with fitting tools...
thechosendude You're not wrong. Unfortunately there are a lot of bad actors out there....many shops got into bike fitting at the behest of a cycling industry or marketing consultant because they saw the potential for it to be a driver of sales of new parts and new bikes.
There are a lot of good people out there though that are conscientious and try to be conservative in their approach to new parts during a bike fit. Any time I am broaching the idea of a relatively expensive part, I'll give the client my best 80/20 analysis of that part as far as how much benefit it might bring them and at what cost. I essentially try to relate how married to the change I am. That way they can decide for themselves if there's enough bang for the buck for them
I didn't mean to slag reputable bike fitters if it came off that way, just highlight (having been there from experience) that bike shops and fitters are very different. Two of the 'big three' USA bike brands currently offer some kind of fitting service in their shops; and just about anyone can pass a BG certification course and be sent on their way to sell more components like they were taught. If someone walks into a shop complaining about saddle pains, the odds of upselling are pretty high. Chances are the shop won't even look to see if there are fitment issues with their bike before going into the standard procedure of measuring sit bones, offering stationary bike demos (on a machine or bike that's not theirs), or loaner saddles (to try on a bike that's maybe not properly fitted). Or someone complaining of shoulder pain will get their shoulders measured, and a new bar installed.....back into the same position as the old one nonetheless!
thechosendude I understand....didn't think you were being negative on all fitters. I agree with you that there are a lot of 'used car dealers' out there
I just had a bike fit and the fitter said that I would benefit from moving from 172.5 to 165 length.the reason was to reduce the bend in my knee in the top position of the pedal stroke. I do Crit racing so I wanted my setup more for Crit. He also told me to get +4mm pedals to get my knees to align and move straight up and down. he put in two spacers but that was still not enough.
A Surf I think that could be a reasonable course of action. I'd want to know more about how the +4 pedals work for you....the knee tracking can be a particularly difficult issue to remedy. The knee is the "slave" joint in the context of cycling -- it goes where the foot/ankle and hip tell it to. Sometimes spacing the feet out (or in) will help with alignment but not as often as we'd like so if I'm reading you correctly, he's already put in small pedal spacers which get you to +2mm? On both sides? A lot of whether the +4 is going to do the trick will depend on how symmetrical your movement is - especially how the pelvis sits on the saddle which then translates down to affect how the hips and knees move.
Not saying the +4 pedals aren't the right move - they could be. But they're not a cheap solution so in the absence of true validation I'd be cautious
the knee alignment was that last thing we looked at after getting everything else set. Using lasers to check the alignment. The spacers help take some of it out but 2 spacers are all that you can use. I really noticed a difference during my sprint workout this week. My feet felt more under me and I seemed to have a bit more control. cost isn't too bad. 115 USD for Ultegra +4's. Once I have the pedals I will go back and he will check everything again. 100 miles this week and the fit feels good. I had to tilt my saddle down a bit more after a 60 mile ride.
83cm inseam and 170mm cranks on all my bikes. 175 feels like too big. I´ve discovered it by accident when getting a new bike. Always felt better on that bike. Then I´ve got my wife a bike and women bike usually has shorter cranks. Then I realized that I´ve should look at that crank of that good bike and found that it was not the bike. It was the crank. Then I´ve changed all my 5 bike cranks to 170 and now I love them all
Instead of testing how much power you can produce would it be better to try to sustain a certian power for a period of time, before and after a few changes, to see if the changes have made doing such an effort more comfortable?
Ive ride 175 on an MTB then 172.5 then 170's on my road bike which I'm happy with 👍 crank length should be optional in an off-the-peg bike.
lee a dorney agreed!
Bike Fit Adviser I ride 175's on my mountain bike and used to ride 172.5 on my road bike until about a year ago. I decided that in order to maintain consistency and because I needed a new bike that I would switch to 175's on the road. The end result is I also agree there is no noticeable difference.
Rid-rided-roded-have roded.
Clem-clime -clum-clumed
I understand that all changes on a bike are subjective to comfort and sustainability. And, if I understand your video, you are suggesting that a change of 5mm is, at times, warranted. As a 70yr old competitive cyclist, I found that changing from 172.5 to 165 on my TT bike made a difference. It allowed me to get into a more aero fit via the un-impinging of my hips. But for anyone to suggest, via all the research, that one is more or less powerful is BS. The advantages, wattage, is said to be negligible. However, the ability to turn the crank over with a shorter crank arm, Cadence, is said to increase. Doesn't it depends on what your specific needs are in the discipline you have chosen?
This isn't a fair comment that a 2.5 mm difference is a swindle. A 2.5 mm difference in crank length is significant because the crank rotates 2.5 mm change in radius alters the circumference by 2 x ~3.14 x 2.5 = 15 mm per revolution. Factor that into someone riding at 100 rpm for an hour with 2.5 mm longer cranks, their feet are moving 94.2 m further! I have ridden everything from 180 to 170. All feel very different even with 2.5 mm changes.
I do feel a pretty big difference between the usual lengths, 170/172.5/175. 172.5 being by far the nicest compromise between leverage and ease of pedalling. I use 170s for MTB and commuting, 172.5 for Road.
If you have shorter legs 2.5mm makes all the difference in the world for me It made a big difference I had PR in all my local rides going from 172.5 to 170's!
I'm running a fixie at 172.5 and road bike at 175. Difference is not noticeable. It's more about everything else on a bike, reach, saddle, handlebar drop, etc. that matters far more than the crank length.
Man they is sooooo much BS in the bike industry, even top shows like GCN talk about fore and aft adjustment of the seat based on KOPS. Crank length is a very controversial topic some swear by shorter cranks whilst other talk about height of rider. I think it is not such a big deal. For pure aero position it does appear shorter cranks have advantages by raising the hips and lowering the knee height, but for general riding, not much.
Hei John, greeting from Norway. I really like your videos, you are doing a really good job!
However, whenever I hear that crank length does not matter or small difference in length can not be worth of change, I am tempted to tell my story, what happened to me once. Just by a mistake, and completely unaware of it, I rode a bike with two different crank arms, one 5mm shorter that the other. No, I wont tell you how it was. I insist you do such a test yourself. And then tell us, was a negligible difference?
I have gone between 170 and 175 on MTB cranks. I can't say that I can feel any difference. I guess the good news is if you see a set of cranks that you like but they only come in a shorter length, it is not going to make that much of a difference.
Alright I got one for you. I just bought a 2018 Cannondale supersix Evo Dura-Ace disc and it comes with 172.5 crank arms but my inseam including shoes is only 32 in (28 for pants and 30 to bare feet) and since I need to buy a power meter one of the arms being replaced anyways so I might as well spend a hundred twenty bucks and buy the other side and do it right the first time. The bike comes with a semi Compact and a 28 cassette in the back, which is being changed (the cassette that is), so what size crank arms would you recommend 165 or 167.5?
I can say as a short rider 164cm ,69cm inside leg a 175mm cranks is a complete disaster way way to big for me even 170mm is still very uncomfortable and far to big , so I went all the way down to 155mm kids cranks this was way way better and probably would work if high rpm rider , which I am not ,I'm just leisure rider so maybe just slightly to short . So my next move was to try and source 160mm cranks , this is not easy ,it can be done but costs more than the bike , so put it off for few years . Try again few years later got a single speed with 165mm cranks this works , in as much as it gives leverage, but to large to be honest. I have now sourced 160mm for my new bike this should work although 158mm I think would be the sweet spot for me ,if 155mm is just slightly on the short side and 165mm is slightly on the long side (155mm was the best of the 2 ). As a older rider my movement is not what it used to be, so I find small differences are very noticeable. This is my experience over the last 30 +years .
I would say a 5mm diff to be the minimum to make to your fit, but that 5mm can definitely result in a noticeable improvement in comfort, cycling dynamics, power, etc.
Its tempting to believe your comments about 2.5mm difference in crank length not making enough of a difference in performance and comfort but do you have any data to back up your claims?
where are you located???
Bill Reynolds I'm in Grand Junction, Colorado
Change the crank length and your gears will change, you may spin out with not enough gears at one end or have too large a gear to climb at the other.
I'm all for a having discussions on what is "right", what is "measurable", but I don't see the point in saying what is "worth it". Only the individual can say that. Some people may not find it worth it to spend $100 even if you tell them they should shorten their crank arm length by 10mm. Others may say it's worth it to spend $1,000 to go down by 2.5mm. I realize 2.5mm is fairly negligible, but just giving example. Value is in the eye of the beholder. I am comfortable in my current setup, but if I found out some "perfect setup" via a bunch of measurable testing and hip angles, I would spend a lot to change it, because it would be something good for many, many years and thousands of miles.
2.5mm in 172.5mm is 1.5%. Negligible I'd say?
However, in terms of knee angles and muscle recruitment, the joint mechanics might amplify this difference, or not?
Woudn't this small difference help, not in the bike, but in the marathon afterwards? I mean, even a 2.5mm would deliver the runner in better shape for the run?
Enda Bigarella your thinking about it incorrectly. Yes the crank arm length changed by 1.5 percent but the maximum angle of knee bend would be much less. A quick calculation for myself (I'm about 6' 3") shows that if I changed my crank arm length by 2.5 mm it would only change my total knee angle by .4 percent. Yes less than a half of a percent. Negligible. You can calculate the angle change by measuring from your hip to you knee as length 1, your knee to your ankle as length two and the angle you originally form at your knee. Then you can calculate the length at that angle between your ankle and your hip using the other three knowns of the triangle. Then simply add 2.5mm to that distances and use the three sides of the triangle to calculate the new angle. Divide the new angle by the old angle to find the negligible change. I have a diagram showing this but it won't let me upload the photo.
Best thing I did going to 170 mm crank from 172.5.. 5.7 height about 15%less rotation mass knees feel a lot better
did you have to change your saddle height ? up or down? i'm on the same quest but I can't find it right yet...Thanks
fernando g. aguirre
Up just a bit. When you are a small person you need small bike when you are a tall person you need tall bike. Try some 175 crank and then go on 170 crank it’s only 5mm but if you are about 5.7 short legs then it will be biggest 5mm you will of herd of and cranks are not that expensive ultegra £169 from most online shops
Ah I should add I am 70 years old, possibly thats why, anyway I learned from that and modified my crank to 155 cm (way better for me)
155 cm crank... 70 years old ... Hey, I know you! You're the BFG!
*I AM PUZZLED!* If I look up Shimano Ultegra Hollowtech II cranks I see that the crank arm lengths vary from 165 to 175 mm *only a 6% change* (bike.shimano.com/content/sac-bike/en/home/components11/road/ultegra1/fc-6800.html)
My bike (Trek Emonda SL6) with said crank is made in sizes varying from 47 to 64 cm a *30% change* You can see the scaling problem I am concerned about already.
(www.trekbikes.com/us/en_US/bikes/road-bikes/performance-road/%C3%A9monda/%C3%A9monda-sl-6/p/1441900-2017/)
Standard deviation in height/Mean height (women only, easier to find) = 7.2cm/155.8cm so for 2 sigmas (95% of people) -> 14.4cm/155.8cm= *9.2% change* (journals.plos.org/plosone/article?id=10.1371/journal.pone.0018962) If you combined men and women that percentage would be higher probably ~15%.
I also know that walking stride is proportional to height.... *so how can it be that crank lengths vary by so little?* It tells me that the variation in knee bend (top/bottom of pedal stroke) for shorter people is going to be larger given equipment size options and smaller for tall people. Does not "seem" optimal!
👍👍👍👍👍
if 5mm is insignificant, why do they even bother making different lengths when the standard spread is only 5mm anyway? I would like to try some longer cranks, but I don't see many choices. 180 seems about the best I can do, and even that adds a pretty hefty premium.
Thank you for this video. I’m going from 170 to 172.5 and hoping the change isn’t too dramatic. Reason for upgrade. Is going with shimano from oval.
this is why ebay exists.
2.5mm is a significant difference. 5mm is huge. Author of this video is a complete quack.
Right on,that’s about the thickness of a nickel 🪙