smontanaro 

Well, Friday I did 121 miles on my Trek with Ultegra cranks which I think have 177.5mm arms. (My old eyes didn't see any markings on the cranks but a tape measure suggested 7in c/c which I translated as 177.5mm.) I didn't have any trouble at all (could have gone further). I did focus a bit on keeping my revs up and not standing up on the modest hills I encountered, thereby not mashing up the hills at low rpm. In fact, I felt fine Saturday morning so I did another 20 miles.My normal daily rides are a 12-mile (one-way) commute typical 4x per week with something longer on one weekend day, 40-60 miles, but that only sporadically. I guess my knees can still handle it.

Mrgncty1 

Always rode a 58cm frame, had a 59 for a short time in my 30s. But now, 73 and 1.5 inches shorter a 56cm frame, or even the 55cm I just bought, seems to fit better.

Carbonfiberboy 

Your knees won't get creaky if you've kept active all your life. By active, I mean like hiking, backpacking, climbing, running, biking, weights, stretching, etc. I've 73, wife is 70, knees are just fine. We both ride cranks in mm = 5.5 X inseam in inches. To get inseam in inches, stand barefoot against a wall, push a clipboard up against your pubic bone, measure to the floor. It's not your pants size.

If you haven't been "active," get after it now. It's never too late.

Lemond1985

Well, let's say you have a hand mixer with a crank that gets turned by hand. Imagine how much work it would be with to operate that hand mixer with a 12" long handle vs. a 6" long handle. If you don't need the extra leverage of a 12" long handle to bust up "extra-tough lumps in your pancake batter", you will have far less total movement using the 6" handle, and burn fewer calories.

So translating that to a bike, longer cranks might allow you to push bigger gears, but your total range of movement will be greater so you will burn more calories with each pedal stroke, at least in theory. Additionally, longer cranks put your knees and hips at sharper angles at the top of each pedal stroke, right at the point in your pedal stroke where you're beginning to apply power, increasing the risk of injury.

I really like my 165's (compared to 175's) because there's less wasted movement during each pedal stroke, and my knees and hips bend less, so they feel less stressed during and after rides. YMMV.

Trsnrtr

I'm 5'7" and found 165s my second winter (83-84) of riding when I built up a fixed gear for winter riding and was given a set of 165 track cranks to use. Since then, every bike that I've owned has had 165s for precisely the reason given above.

peterws

I reckon the best reason for using short cranks is the increased revs achievable, With the right gearing, that could be useful. You'd need to rev faster all the time to achieve the same work rate with the lower gearing. Could be interesting to find out the best comfort level achievable with different cranks.
It also sounds time consuming, but it's the sort o' thing most blokes like doing.

Iride01 

I think a 190 mm crank a little excessive (34.5" x 5). Proportional sizing for cranks is a myth in my honest opinion. I think it came about when someone was trying figure out how to keep all your body parts within the other myth which is KOP's.

There might be something for it if you are going to be a masher. But if you are going to be a spinner, then short is better. I'll stick to my 165mm cranks. I've recently tried 170 mm cranks for three or four months and didn't like them. Might try 160's next year.

Even if a person wants to be a masher, I'd only suggest trying longer cranks if they didn't have the lower gear ratio's on their bike that they needed and changing cranks was cheaper than changing gearing.

BKE

Wow, a 10 yr. old thread resurrected, one that"s a legitimate serious topic, but I'm glad to see that ten years ago there were a few members that had a good sense of humor.
Today, in jest, I'd say the crank length might be relative to the explosion of the craft beer industry.

FrenchFit 

Funny, but -- All of you muscle cells are replaced within a 15 year period, so at most...you are 15 years old.

FiftySix

I sure wish that were true. I'm always caught off guard by the middle aged guy that looks back at me when I step in front of a mirror!

bruce19

Just to echo what others have said...I'm 73 and have 3 road bikes with 170, 172.5 and 175 and I really don't notice a difference.

Leisesturm

There are millions, literally millions, of people who's knees got very creaky despite doing all the activities you mention as being preventative. I'm one of them. There is much more to it than your small sample size evaluation has determined. And, I'm not trying to be argumentative, but it just isn't practical in 2019 to try and follow prescribments for something like crank length. Cranks come in 170mm if you are lucky. I75mm if you are not. 165mm if you were a wearer of animal fur in a previous life. 172.5?? GT_OH. Changing a crank from what the manufacturer of your bike has thus decreed will be expensive if you cannot do it yourself, a hassle if you can, and as a result, it won't be done by millions, literally millions of bike owners. Formulas just create stress for people that fall outside of the parameters and don't have any way of fixing that. Or worse it sends people on a wild chase for the perfect crank length. One that they never actually satisfy though they may try and convince themselves if only to justify all the money and/or time spent at it.

fietsbob

Me No, But I do like the Step thru like nature of my Bike Friday and Brompton



I have bikes with 170, 172.5, 175, & one with 180mm crank arms ..

Saddle to pedal measure, is the same on all .




71, still have the knees (& hip joints) I was Born with..







....

Leisesturm

Why do you think 190mm is excessive? It is probably more the case that 170mm is sub-optimal. Racing bikes were mainly developed in Europe in the last Century and at a time when Central Europeans were shorter than today. With a 10.5" BB height, a crank length of ~170mm becomes about as long as you want to go and have a bicycle that you can pedal through the corners safely. Leonard Zinn has designed bikes that can use 200mm cranks. He sells these bikes to extremely tall riders such as yourself. I'll tell you about a couple I know. I'll call them Wayne and Lisa. They ride a custom Co-Motion tandem because he is 6'3" and she is 4'11". He has 170mm cranks and so does she! Why? Because Co-Motion never mentioned changing them or if they did my friends didn't feel like springing for the extra money.

They've ridden this bike all over the country and have even taken it to Europe a few times in the decades they have been riding twogether. I personally do not think that crank length has anymore relation to a riders height than plumbers wrenches have any relation to the size of a plumbers hands (ahem) or their forearm length. Either plumber is throwing away torque if they choose a 10" wrench when a 16" or 17" will fit in the work area. A cyclist is throwing away speed potential when they choose 165mm cranks. Period. For the vast majority that will have no downside. For anyone competitive it absolutely does. If the rules allow 175mm then I imagine that will be what everyone uses.

In the absence of rules, however, what stops a cyclist from going to 200mm besides bike design? Nothing. Increased bend in the knee? Bring it! I submit that if a cyclist finds themselves considering shorter cranks because of knee pain from cycling that it is a sign that their cranks were too short or their bike overgeared, and the answer should be to actually lengthen the cranks! Doesn't get more counter-intuitive than that, I know, but there you are. Most of us want to keep up with our riding buddies and when the pressure is on we get on the big ring and mash. This behavior is not going to go away anytime soon. Longer cranks than 170mm are badly needed on production bicycles to manage the 50-52 x 11 top gears that just about every production bicycle in America now sports.

Leisesturm

Me too, the real question is: do your knees (and hips) FEEL like those of a newborn baby?

canklecat

Same, sorta. 61 y/o. 170-175 cranks on four bikes. Yeah, they feel different for the first few minutes. Then I adapt and don't really notice.

I'm thinking of trying some 165 cranks on one of the road bikes just for giggles. A friend who's in his 70s and my height (5'11") has shorter cranks on one of his old school mountain bikes, and has noticeably less knee flexion while pedaling. But he's comfortable and seems as efficient as with any of his bikes.

For me, longer cranks are more demanding of saddle height and fore/aft position for happy knees, hips and lower back. My road bike with 170 cranks seems less picky about saddle height and position. It has a bit less leg extension than I normally use, but feels fine as-is so I'm leaving it alone for now. Usually a too-low saddle cooks my thighs quicker on hard rides, but that's with 172.5 and 175 cranks.

CyclingFool95 

I'm 5'8" (now probably 5'7", with 29"-30" inseam. When I started riding in my mid 20s, my bike came with 170s, but I switched to 172.5s, which I've been using ever since. Recently, I ended up with a set of compact cranks with 175s for my second bike, and now a second set of 175s with 36/52 rings for my third bike. I'm not really sure I feel any difference. It's really hard to imagine feeling much difference in 1/10 of an inch.

Carbonfiberboy 

Wow. Did I say something very wrong on the internet? I must have missed something, because I don't think I recommended anything other than getting fit. I don't really care anything about what crank length you use. Frankly, I don't think it matters much at all. It's ridiculous to blame some physical malfunction on like a 1° difference in knee flexion, I don't care how many times it's repeated. Standard bottom of stroke knee flexion recommendation is 35°-40°. I doubt I'm even in that range and I've seen many experienced riders and racers who are also not in that range..

I do care about messaging that goes down which discourages experimentation with active therapies. My 86 y.o. couch potato aunt deadlifts, right? Her ankles and knees used to kill her. Just an example. I just learned a new stretch this year which has made a particularly annoying back pain almost completely go away.. "So much to know, so little time."

That said, diagnosed physical disabilities are a different matter. A cyclist buddy with RA is now on her 3rd pair of ankles. She rode with the last pair, but probably won't with these. Not to mention all the other usual RA issues. But barring stuff like that, there's a physical therapy for most issues, well and my friend has had a lot of physical therapy, which has kept her on her feet and moving..My motto is, "don't get a bike fit, get fit." Once a person's fit enough to ride anything, they can worry about the fine points.

If you have no cartilage left in your knees, that's one thing. Everything else is fixable.

fraba

He did not say harder to turn but harder on the knee (because it is more bent at the beginning of the stroke).

Shorter crank also reduce the hip angle, which can be beneficial to some in terms of biomechanic. My opinion is that this is SOOOO personal. Science is not clear about what is the perfect length for a specific rider.

DrDyno

"WorldTour teams including Team Sky appear to believe that shorter cranks are more efficient.
Marc Abbott considers whether we should all make the change..."


https://www.cyclingweekly.com/news/p...-better-188288

gif4445

I shortened my crank from 175 to 165. More as a function of my height than age. Although if I was younger, maybe the extra hip rock from the longer crank wouldn't have affected my back as much. I'm happy with the switch.

fraba

Thanks for the article DrDyno. I agree that in general, crank may have been specified too long based on a false premise that higher leverage means higher power. I am not arguing against shorter crank (I shortened mine), just saying that 1) there is no magic ratio to determine someone's crank length and 2) I doubt someone can feel the difference between 172.5 and 170. A good bike fit is key, especially at our advancing age .

From this article https://www.trainingpeaks.com/blog/t...-crank-length/
"A shorter crank alone will not increase your power output, but it can be used to reduce restriction through the top of the pedal stroke by opening up an impinged hip angle and/or reducing knee flexion. Going back to our definition, if we reduce restriction than power output can increase."
Also, "It can be frustrating to know that there are many available crank options that would work for an athlete. Trying to decide between a 165 and 170mm crank is a waste of time as there is too small of a difference to matter. An athlete should pick the length that allows them to most comfortably apply force to the pedals without restriction."

There is also a lot of references to research about the subject here https://bikefitadviser.com/crank-length-research/

IMHO, there is no black or white when it comes to fitting a very unique body on a bike. While our crank may have been too long for too long, in terms of power generation, we are in realm of "marginal gains", to stay in Sky's vocabulary

mac_flyer9

I'm 5'4" with 28" inseam. When I started riding in my teens, my bike came with 170s, which I've been using ever since. I have just updated an older frame with 160mm compact cranks (50-34) and will see if I notice a difference this year. As a discussion point, you can't find 160mm cranks in Dura Ace or Ultegra. You have to go to 105 to find them. Or if anyone can find them in that length, let me know

Myosmith

Switching from 175mm to 170mm cranks changes the stroke radius by less than 1/5 of an inch. Going to 165mm cranks would only reduce it a little over 1/3 of an inch. Depending on your femur length that will change the angle of your maximum knee bend by only a degree or two. If you find it more comfortable, great, but I doubt it will have a significant impact on knee longevity.

I still contend that if you had two bikes, identical in every way except that one had 175mm cranks and the other had 170mm cranks, 90+% of riders would not notice the difference if you switched bikes on them.

Iride01 

Radius is only half the picture. You have to address the total diameter. So a 5 mm change in crank length means your stroke is 10 mm more, which is .394" or a little more than 3/8ths inch.

Surprisingly for me, the difference was noticeable when I went from 165 mm to 170 mm cranks. YRMV.

As for those that think shorter cranks mean harder pedaling, then they are forgetting to shift down to a lower ratio gear combo.

Since I'm a road bike type and do get in the drops fairly often, I don't need my knees driven an inch further into my chest by using the 190 mm cranks. I'll keep my 165's and be assured that I can pedal while turning without hitting the pavement.

So to me, it still gets back to whether you want to be a masher or a spinner. No formula needed.