Crank size

[Disprin]

Do you think there is any difference between riding 175 and 172.5 cranks? Any difference in power or speed?

 

[erader]

Do you think there is any difference between riding 175 and 172.5 cranks? Any difference in power or speed?

i'm pedalling squares with 175mm. i prefer 172.5 or 170.

erader

 

[Disprin]

i'm pedalling squares with 175mm. i prefer 172.5 or 170.

erader

I've heard that longer cranks are better for time trialing and climbing. So I was wondering - what exactly is a shorter crank good for?

 

[Anonymous]

There is a big difference when it comes to the health of your knees...I have always ridden 172.5's and tried 175's for a few weeks...threw them right out of whack...so get the correct size...tiny difference made a huge difference on knee stuff...so be exact!

 

[180mmCrank]

Yes.

Better people than me will give you chapter and verse on this but basically it's to do with how long your legs are - not that surprising really.

In fact some folk would say that many tall folk ride with cranks that are way too small. The trouble with wanting to ride longer cranks is thay are not always available and most bikes are designed for mmore conventional crank lengths and you start to run into problems with cranks longer than 180mm.

Here's a guy who knows what he's talking about...

http://zinncycles.com/Zinn/index.php/components/custom-cranks

 

[StyrbjornSterki]

It's easier to pedal smoothly with shorter crank arms but you make more torque with longer crank arms. Track sprinters use short crank arms to help spin their fixed gear to a very high cadence, ~160 RPMs. Pro roadracers and mountain goats in particular favor longer crank arms.

 

[lostintime]

I don't think longer cranks hurt your knees anymore than short ones do. The only way to find out is to try them, no one can tell you what will work best. 2.5mm difference is not much, and not noticeable by many.

I like the Kirby Palm site .... his formula is too long for me, I ride 185mm cranks with a 36" inseam. Peter White suggests 18.5% of your femur length.

http://www.nettally.com/palmk/crankset.html
http://www.nettally.com/palmk/crwives.html

Longer cranks have allowed me to stay seated on climbs longer and use what power I do have , more efficiently. One doesnt' gain any power. On the flats, I feel more "normal" than with 175's or 180's, akin to taking a proper stride when walking.

 

[Anonymous]

well, that is good for most folks here..I am just saying, wrong crank size hurt my knees...to me, and my knees have told me and I have known guys for twenty years saying the same thing....get the right crank size...when you f*** your knees up via such a stupid thing, good luck...but hey, if you want to go faster, by all means listen to these guys...

 

[Anonymous]

actually, I don't mean to talk out my **** via this question and knees...get some advice from the real physio pros here like steve hogg...they have a whole column for this...

 

[brianf7]

I've heard that longer cranks are better for time trialing and climbing. So I was wondering - what exactly is a shorter crank good for?

I use 180 cranks for Time trials when I tried them on my road bike I couldnt get our of the corners fast enough.

I am 6'2" and normal use 175 but I noted the BMX riders all go for 180 so that caused me to try then in crits . I was humping a huge gear around the whole course just to hang in what normal I can handle OK.

They soon returned to the TT bike where they belong big and thump big cranks as hard as I can in TT. but normal road racing stick with what you know works.

I noted a differenc in 175 and 172.5 but not a lot.

 

[titleshot]

I am about 5'10" and I used 172.5mm cranks for about 2-3 years of racing. Did mostly crits and short road races that all end in field sprints. So I decided to change to 170mm cranks and instantly improved my cadence and acceleration. With the smaller cranks I can get my legs around faster and have a quicker jump on sprints/breakaways.

I wish I had changed to smaller cranks sooner, I might have won more sprints haha.

Only down fall is I feel slower on long climbs, because of the loss of torque, but I can make up for it by spinning my legs around at a faster cadence.

 

[Captain Serious]

I'm not shooting the messengers, but that Palm stuff is bunch of hooey that he pulled out of his ar'se to suit his own preferences. I've read his site a zillion times, and it's based on nothing more than his opinion.

21% puts me on 188mm cranks, which is so crazy that I can't even get my head around it; and 21.6% would have me on 193mm, and I'm only 6ft!!!!! Insane!

About 5 or 6 years ago i used 180s for about 12 to 15 months (I even bought 3 pairs of DA 7800s), but gave them up as a bad joke, and now use mostly 172.5s. I could never get "on top of" the pedal at the start of the downstroke with the 180s, plus I was having medial knee pain.

I makes me 'cranky' that Palm says that knee pain from long cranks is a myth or an old wive's tale. Sure, most people go to longer cranks with no problems, but plenty do have issues, including me.

Below is Kirby Palm. If this fat 'expert' came up to you at a bike shop and told you that you should use his crank length formula, because it "works for him", would you listen? Does he look like an expert who's based his formula of years and years of riding many, many mles?

http://www.nettally.com/palmk/resume.html

 

[titleshot]

I have found that this article has good logic and has worked for me, since I have a 31-32 inch inseam and rode on 172.5mm for a few years and saw an improvement when I switched to 170mm.


http://www.cptips.com/crnklth.htm

 

[180mmCrank]

Just to be clear... crank length does not change power. (the last quoted article talks about 'having more power')

Power is determined by you and the effort you make

power = (force x distance)/time

That's the force you apply, the distance the pedal moves and the time it takes to move that distance. Much as shifting gears changes the leverage, changing cranks changes how hard it feels to turn the pedal but not the power.

What it does change as many have said is how far your knees go up and down (length of pedal stroke) and cadence for a given speed.

I am 6'6" and use 180mm cranks. I love them and they have definately helped me climb better - I would never go back. But that's just MHO.

 

[M Sport]

I use 175mm for the road racing season and 172.5mm for crit season. Mainly only for the extra ground clearance in the crits.

To be honest I mainly notice the longer cranks 'seem' to be marginally better on the hills, I don't reckon I notice much difference elsewhere. And for the record my knees had no trouble at all, I was a bit concerned about this after having a bad knee injury in another sport years ago. But all was sweet.

I found a good formula when I first swapped to 175's about 18 months ago, will see if I can dig it up again. It seemed to have a lot more science behind it than all the others I looked at.

I would be interested in other riders anecdotal evidence of one size shorter of longer cranks and the effect in a sprint finish? No change?

 

[Tapeworm]

Studies to date have shown that power production is independent of crank size (latest one being done by Jim Martin). The two most important things to consider from here is comfort and position. So pick what you want, the watts won't vary.

 

[Disprin]

Studies to date have shown that power production is independent of crank size (latest one being done by Jim Martin). The two most important things to consider from here is comfort and position. So pick what you want, the watts won't vary.

But there must be a limit to that conclusion. Because tf you were to take it to extremes and have a 5cm or a 1 meter crank, then it would make a difference to power. So maybe it just means there is no recorded noticable difference between cranks of the regular sizes.

 

[titleshot]

I would be interested in other riders anecdotal evidence of one size shorter of longer cranks and the effect in a sprint finish? No change?

I have noticed a large difference in my sprinting when I switch from 172.5 to 170mm cranks. I could noticably reach a high cadence, sitting and standing on the pedals. I can jump quicker/accelerate faster. I can stand on the pedals and spin easier/faster without feeling like im reaching or stomping, they just get around much faster, its a lot of fun when you dont have a dead spot.

I have also noticed I can hold a faster pace when in the time trial position, because my hip angle is more open.

 

[Tapeworm]

But there must be a limit to that conclusion. Because tf you were to take it to extremes and have a 5cm or a 1 meter crank, then it would make a difference to power. So maybe it just means there is no recorded noticable difference between cranks of the regular sizes.

Almost. The particular study tried cranks from 120mm to 190, IIRC. Ie: outside the range you can purchase off the shelf.

FWIW I know people using up to 200mm. They haven't gone any slower/faster by switching. People talk about how it feels better on climbs or sprinting or whatever, which is great, just don't expect to see a magic jump in power. An argument for going shorter cranks in TTs is that it will allow a lower torso position - more aero - faster.

 

[bc_hills]

There was very good thread a while ago about crank arm length. Worth reading again I think, if you've found this thread interesting so far:

http://forum.cyclingnews.com/showthread.php?t=3882

cheers!

 

[lostintime]

Crank length is one another of those ..... I tried it and it worked for me, so what's the problem? Or ..... I tried it and it didn't work for me ..... there is a problem!

I'll agree that the Palm/Zinn "formula" seems radical to many, but that's only because we are not used to such thinking. Let's face it, cycling, like most sports, has a very narrow window of what is acceptable and what is not. The fear of the unknown keeps new ideas on the outside of acceptance.

The Peter White "formula" of 18.5% of femur length is about what works for most people anyways.

The point I get out of the Palm website is ..... decide for yourself. Just because someone, or everyone tells you this this and this will go wrong if you try it ..... doesn't mean you shouldn't try for yourself. The masses are often wrong., yet we follow the masses like pigs going to slaughter.

We are humans , not machines. The body is capable of adapting to many positions ..... it's usually our mind that gets in the way in the form of resistance.

 

[Hawkwood]

Just some very subjective views. I'm 6' 1" and around 1981 went from 170 to 175mm. I personally preferred the longer cranks, and a couple of years later ordered some new 175 ones, the order was mixed up and I actually received 180mm cranks. I decided to try them out and have remained on 180 ever since. During the 1980s I won a number local time trials and hill climbs on the cranks. I've always tended to spin gears and once won a medium gear 25 mile TT on 180 cranks. For non-UK readers `medium' gear is 72 inches or roughly a 52 x 19 gear, so you need to be able to spin. My impression is that while you don't generate more power with them, you can generate more torque which can come in useful when grinding over a shot climb.

I believe that Indurain used specially made 190 mm cranks for some races.

 

[StyrbjornSterki]

...I believe that Indurain used specially made 190 mm cranks for some races.

Yup. Big Mig -- who is 6'2" -- was a masher. He ordinarily rode 180s and TT'ed on 190s. Campy also made their first 56T chanring at his request (and their first roadrace triple crankset).

LA -- 5' 9 1/2" -- rides 175s. AC -- also 5' 9 1/2" -- rides 172.5s. Track great Marty Nothstein -- all 6'2" and 210 lbs of him -- rode 167.5s. Marty had to compromise because he had to sprint from a standing start to hi-40s to 50 mph on a fixed gear, usually on a 50x14 (96"), > 160 RPMs.

 

[Night Rider]

Studies to date have shown that power production is independent of crank size (latest one being done by Jim Martin). The two most important things to consider from here is comfort and position. So pick what you want, the watts won't vary.

Power won't change with Crank size. But torque does.

 

[ChilliConCarnage]

Why do people keep asking the same questions over and over and over again? Google is your friend!

As for the people who like to suggest a formula to deduce your correct crankarm length - multiple studies have been conducted and come to the simple result: crankarm length has no discernible correlation to any physical dimension that they've studied. That's not what people like to hear, and most likely there is a correlation that they haven't discovered yet. As you can see from the comment above, AC and LA have the same height, but prefer different crank sizes.

Most people I've talked to ride whatever crank length came on their bike. The body is a wonderfully adaptable machine, and can adjust to a range of equipment. After adapting to a particular size, though, one can experience pain when switching to something different, at least until one adapts to the new equipment.

My own personal experience (at 5 9, short legs, longer torso), is that I like my 170mm cranks the best. When I switch too another bike that has 175mm, my knees will end up hurting. Which reminds me, I've got to find some more 170mm cranks so I can swap those out...

So, my best suggestion is to try different sizes out and see what you like best.