Crank arm length??????

[wheelsONfire]

I believe i will try a 175 instead of 172.5mm. The +5% increase in torque appeals to me.
I hope downsides doesn't show up.

[madcow]

Unless there are some unusual circumstances I'd personally never recommend a rider go to a longer length. I'd say if you want to experiment with crank arm length you should try a length shorter than your current not longer.

[Stefano]

Question-- I know sustained power doesn't change statistically speaking, but are there any data points for pro sprinters and their crank length choices? I ask because I'm a cat 2 level bunch sprinter and went from 170s to 175's and had my best ever season, but it was definitely more attributable to the fact that I trained like crazy. Since peak force at the wheel is decreased with 170's, does that make your jump worse? Is that balanced out by less hip movement and a more fluid pedal stroke at the 130-150rpm top range? Basically asking, should I go back to 170's on my new bike or buy 175's??

[User Name]

^ This is only my anecdote, but I truly feel that longer cranks provide a little more leverage when riding off the saddle, when there are no (or a LOT less) position restrictions of being seated (hip and knee angles).

Magnus Backstedt and Tom Boonen are the only sprinters (part-time sprinters? ) I can think of who apparently used 177.5s, but they are big guys (both 6"4), so that length isn't exactly a stretch for them.

I've said this before somewhere, but I accidentally put myself in a "blind test" one day. I used to do a short daily commute (18km, one way) with running shoes and street clothes, on a couple of crappy bikes with 170s. One sunny day, I grabbed my old race bike and rode off. I was flying over the regular short hills (off the saddle), and couldn't figure out why. I was using a gear or 2 higher for each short hill, and I felt like Superman.

I even got off to check that the cogs were the same as my other bikes, and they were. It wasn't until a few kms later that I realised that the bike had 175s on it. I figure I didn't immediately notice the longer cranks because of the way running shoes somewhat arbitrarily "flop" into the pedals, position wise, even though I had toe-clips and straps.

After that, I became obsessed with crank length for a couple of years.

[User Name]

Here's another anecdote: triple Olympic gold medalist rower, and 5-time World Champion (still with rowing ), 39-year-old Drew Ginn, has totally smashed our group ride on his own a few times, and there are some ok riders there. When the wind is less-than-totally-favourable for wheel-sucking, he can drop almost everyone in the 40-odd-man group, on the mostly flat road.

He could be THE strongest guy I've encountered in my 25 years of smashing people on flat roads, but I'm getting older, so I could be losing it. He came 6th in the 2010 national TT, and the slightly hilly course apparently did't suit him (the inclines were countered by big declines, so I'm not 100% sure about this).

Anyway, he's listed on various websites as being 196cm (6ft5) and uses 175s. I asked him if he'd tried longer cranks, and he said that 180s hurt his knees a bit, and I think he then hinted that it didn't seem to make much difference (it was hard to hear him in the wind ).

Sure, he's an elite athlete with a VO2 in the high 70s, but still.

Anyway, the point: the relatively short cranks (175mm for a 6ft5) guy obviously aren't slowing him down.

[kulivontot]

Lennard Zinn had some articles on Velonews about crank length.
He claimed some anecdotal testing saying that he got significant improvements out of progressively longer cranks. But he's also 6'6" and has a company that specializes in selling extra large frames and cranks to really tall people.

[wheelsONfire]

I changed cranks to 175mm from 172.5mm. Yes, i do feel a difference for sure. I think i can see how those riding very low and long bikes like shorter cranks.
I have a 118mm saddle to bar drop when saddle is at 775mm. I guess if i had used a lower bike i could like shorter cranks due to extreme fit.
My inseam is 88.5cm or a bit more and i am 181.5cm.
It's snow here so i can't really take the bike out. But on trainer it feels very good.
I guess this is subjective and also bound to how you mount your cleats, far back or more forward.
Talking to fitters and bikers i have not managed to get anything but rows of different opinions.
One fitter which has great reputation for fitting told me he uses 175 and 172.5 on his road bikes.
Well, even though i find this weird i now am in same sitaution.
So i guess testing, trial and error is the key if one can afford and extra set of cranks.

[11.4]

Wheels, I find all those different opinions come because some fitters and riders adhere to longstanding traditions (which may not have any rationale), some are into every fad or what pros are riding, and some look hard at their own physical shape and position.

When I'm fitting a rider, I may recommend long cranks or short. To a slight degree it depends on what events the rider is participating in and their general flavor of bike (e.g., road tri versus track sprint frame). But generally speaking, these are the things to consider:

1. If you have chronic knee or hip pain and you are otherwise fitted correctly, it may not be the right crank arm length for you (and probably too long).
2. If you feel your quads pushing up into your abdomen and you are otherwise fitted correctly, it may not be the right crank arm length for you (and probably too long).
3. If you aren't actuating the muscles effectively throughout your legs and hips (not using your glutes, for example, a common problem), you may need to do some PT and potentially change your crank arm length.
4. If you feel a lack of power or sprint power, it probably isn't the crank arms -- you have other more basic issues to deal with.
5. If you are fundamentally limited in cadence or in torque, you may benefit from the slight leverage of longer cranks. But remember, we're talking about 2.5 mm -- a tenth of an inch -- increments. If you do the math, you aren't changing the power equation all that much. You want to be doing a 5 mm or larger change -- so the result is in your legs and not in your head.

There are many ways to look at crank arm length and styles come and go. Track cycling has become very analytical and has fostered interest in shorter cranks, longer reach, and narrower bars. But remember that on the track there's no "finish in your own time." It's all about speed and winning. I race to win so I want to take advantage of these issues. If you ride just for pleasure or to do grand fondos or whatever, track power and speed approaches aren't necessarily the right approach. Similarly, tri cycling has adopted some very idiosyncratic positioning and riding habits, and much of what triathletes do isn't readily transferable to regular road position. It helps to be honest to your own real riding situation and needs, and then address your physiological limitations (bad knees, too much gut, stiff lower back, etc.) which have more to do with crank arm length than inseam, overall height, or anything else.

[wheelsONfire]

11.4 Thanks for your reply!
I have done so little time on the new cranks so i should perhaps just zipp it.
Looking around just says use same or shorter cranks. Some years back all basically told me to swap for 175mm cranks.
They say i could not get the best torque from the shorter i used.
I bought a new crank due to the BB of my new frame and at first i ordered 172.5. I then changed to 175 and I just hope i do not regret it.
Actually been through a lot of saddles to. The best road bike saddle i have used so far, is actually deemed a TT saddle.
It's Bontrager Hilo XXX. I think of all saddles, shapes and ideals, this has a wider nose and shape for sitbones are feeling much better than any of my other saddles.
In drops it's very much better than anything i've used. The cranks also seem to work well in drops.
I was mostly nervous to feel leg is to close to stomach when in pos 12 with longer cranks.
Yes, you are right, i would never dare to change more than 2.5mm.
Luckily it feels good so far.

[bm0p700f]

I have 170mm to 177.5mm cranks on various bikes they all feel like cranks to me, although I mostly use 175mm cranks to keep everythign the same. I do think if the crank length works for you stick with it. If you have a specific problem then changing crank length may resolve it. I do fit different crank lengths to custom builds depending on the inseam of the rider but in reality it probably makes little difference, except for a few very specific cases.

A paper once suggested optimal crank length is around 150mm.

[blasdelf]

I have a 94cm inseam, and 180mm cranks on most of my bikes

Yes it closes your hip angle in the same position, but you also need less saddle setback and that more than makes up for it (especially when you were running out of setback before)

I have 190mm cranks on one of my road bikes with 80mm BB drop and 30mm tires, I corner very aggressively but pedal strike is not a problem. I do hit the tips of the crankarms on roots and curbs sometimes.

I bought my hardtail 29er from someone who had it built around 200mm cranks with a very high BB, it's extreme but I get used to it very quickly.

[Zoro]

What is the concensus on crank arm length. I live in a hilly region... climb quite a bit. My thought with the longer length there is better leverage. I am 6' tall and have been using 175's and would like to try a 180. Is there a downside to my way of thinking or trying the 180's. Thank you.

I'm 6'2". I used to commute (race fast) 270miles a week. I would alternate between my track bike with 165mm and 180mm on my road bike. The feel was hugely different. But the speed (bikes weighed about the same) was about the same. I couldn't figure it out. The longer always felt better. As I moved to the road bike (track bike was stolen) 100% my spin started slowing.
Anyway I settled on 175.
But...I think there was benefit to training on shorter.

[djwalker]

The difference between 170mm and 180mm is 6%. Only 3% between 175 and 180. So, that is the difference in cadence and torque that you would see. If you were putting out a certain power on 170mm cranks at 90 rpm and switched to 180mm cranks your cadence would drop to 85 rpm to maintain the same power. This is hardly gear mashing. I honestly don't think it makes much difference in the small range of sizes available.

[bungis]

Huge difference for me going from 167.5mm to 172.5mm. That 10 mm difference in pedal stroke diameter is a 10 mm difference in pedal stroke diameter and is enough to cause me knee pain.

It's a linear difference that affects your body not a yes/no change.

[wheelsONfire]

I have a question which concerns cranks lenght and fitting.
As is, i have been using 172.5mm cranks and for awhile i thought of getting 175mm cranks.
I did let go of that idea and kept to 172.5mm version.
Due to different reasons i bought 175mm cranks and admittedly, i have only been riding them a few times.
But questions and findings came up.

It seems some riders like to position cleats further back and some further forward. It also seems some riders prefer saddle height a bit lower and some a bit higher.
Some like more setback and some like to be more forward.

Personally, i like to sit a bit higher as it reliefs my rear back.
Whenever i am on a lower position, i soon get pain in the lower back.
I now find that since i use slightly longer cranks, like to sit a bit higher, saddle more forward and cleats a bit more further back it feels great.

To me it is actually giving me a better fit that comes more natural. Sure, i can fit myself with the shorter cranks, but it still is a notable difference with longer and for me, a positive one.
I can't really say i urge to even try a shorter crank. I can pedal just as easily and hold same cadence without any downsides.
What i do notice, is that my fit feels more certain, a narrower sweetspot, but also more obvious in a positive way.

I have actually never encountered any info that suggest that a preference of saddle height or cleat position should be in favour of a slightly longer crank.
For me personally, this is just a win win situation.
I can't really understand why i seem to be more in favour, when most seems to be opposite?

I could just as easily say, if i liked to be seated at the lower end and sit further back in saddle, i don't believe i have had this experience.
So could a longer crank actually work better pending on the riders own preference in final fit?