Crank size

[Captain Serious]

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.

Yeah, spot on. Formulas are as much voodoo as anything else.

On the "they ride what ever length came with their first bike" thing: this is why really short guys are riding relatively long cranks, like 170s and 172.5s. While I believe that formulas are a bit wishy-washy, I reckon many shorter guys would be better off on 165s, or even shorter. It annoys a bit that most extra-small bikes come with 170s. If the bike industry started again today, I reckon smaller bikes would come with smaller cranks.

I have a dodgy 2-bit theory that short guys tend to be less powerful on flats, not because they're not as strong, but because they're trying to push cranks that are too long. Lie I keep sayin': a lever is much harder to push down with your foot if the sarting point has your knee in your chest..... "it's just as theory"

 

[Disprin]

Here is a crank length calculator for the most common formula...

http://www.machinehead-software.co.uk/bike/cranks/cyclist_crank_length_calculator.html

 

[buckwheat]

I'm riding 175's, one ultra torque Record, one square taper Record. I got the square tapers on sale for about $100 and thought the "175" on next to the "Record" looked cooler than the "172.5" graphic. I'm 5'9.5" also with an 85cm inseam and wear 45 to 46 shoes.

Personally can't tell 2.5 mm difference and it sounds insane to me to think someone can. What if you set up your cleats a mm or more different front to back in relation to the ball of your foot? You gonna notice that?

I ran marathons for years and your knees take a hell of a lot more beating from running than they'll ever get from riding. Then again I don't sprint or race so that saves knees too.

 

[180mmCrank]

Not sure what to say except that many people would be sensitive to the adjustments you suggest and would notice the difference. I guess in some ways you are fortunate that you can get by without noticing - certainly less grief when switching bikes and/or equipment.

 

[buckwheat]

Not sure what to say except that many people would be sensitive to the adjustments you suggest and would notice the difference. I guess in some ways you are fortunate that you can get by without noticing - certainly less grief when switching bikes and/or equipment.

really? You can adjust your cleats to a mm of where you intend and then know that is exactly as it should be? A 2.5 mm crank length difference is extremely tiny to me.

Just sayin, askin, curious or whatever about this.

Yeah, you're right though. I can switch up bikes pretty easily. I adapt pretty much to anything within reason.

 

[marathon marke]

really? You can adjust your cleats to a mm of where you intend and then know that is exactly as it should be? A 2.5 mm crank length difference is extremely tiny to me.

Just sayin, askin, curious or whatever about this.

Yeah, you're right though. I can switch up bikes pretty easily. I adapt pretty much to anything within reason.

I think the more you ride, the more you're able to notice small differences. I've never tried 172.5 cranks, but when I went from 170 to 175, it was an extreme change. As far as cleat adjustment goes, it's easy for me to notice a 2 or 3 mm fore/aft change. The same goes for stack height. Some people don't seem to be bothered by a change in stack height, but again, I can easily notice a couple mm difference.

 

[buckwheat]

I think the more you ride, the more you're able to notice small differences. I've never tried 172.5 cranks, but when I went from 170 to 175, it was an extreme change. As far as cleat adjustment goes, it's easy for me to notice a 2 or 3 mm fore/aft change. The same goes for stack height. Some people don't seem to be bothered by a change in stack height, but again, I can easily notice a couple mm difference.

Bro, I've ridden at least 10k miles a year for the last 10 years.

I can notice some differences, but I've noticed that the more I've ridden the less they affect me.

Like the weight of the bike, or the wheels. I was at a cervelo demo day 2 years ago and I heard a guy, with the same madone 5.2 that Contador just won the Tour with, say the bike wasn't stiff enough at the bb. I showed him the bb of my look 381 and laughed.

I think even half a centimeter 5mm is a fairly small difference. Half of that? 2.5 mm? I think 99% of riders would be hard pressed to notice that.

 

[ustabe]

I think even half a centimeter is a fairly small difference. Half of that? 25 mm? I think 99% of riders would be hard pressed to notice that.

My back notices if I move my saddle forward 25mm. My **** tells me if my saddle is 25 mm too high. And moving your cleats forward or back 25 mm will make a difference, especially since your feet are probably 250-300 mm long. Stack height make a difference? Sure, especially if you pedal with any amount of ankle articulation.

I believe fit is more important than frame stiffness, so I'm with the folks who say follow your instincts or fit gurus. I know my climbing improved with longer cranks just as my sprint declined a bit.

 

[marathon marke]

Well I have to confess that in recent years you've got me beat. This is my first year back on a road bike in over 20 years, and so far I have just under 5,000 miles. 20 years ago I was doing more than twice that every year, but that was...20 years ago.

Having said that, we might be talking about two different things here. I said I "notice" these changes the more I ride. As far as "affect" goes, that opens a whole new can of worms, such as: "How does it affect a rider?". To the point of needing to spend a lot of adaptation time? ...to the point of immediate change in performance? ...to the point of injury?

So are you saying that a rider who puts in more miles will not notice the weight of a bike or wheels as much as someone who rides considerably less?

As far as your story with frame stiffness goes, I don't think frame/bb flex is the point of discussion here. Correct me if I'm wrong, but I thought it was an issue of the fit and component fit.

Bro, I've ridden at least 10k miles a year for the last 10 years.

I can notice some differences, but I've noticed that the more I've ridden the less they affect me.

Like the weight of the bike, or the wheels. I was at a cervelo demo day 2 years ago and I heard a guy, with the same madone 5.2 that Contador just won the Tour with, say the bike wasn't stiff enough at the bb. I showed him the bb of my look 381 and laughed.

I think even half a centimeter is a fairly small difference. Half of that? 25 mm? I think 99% of riders would be hard pressed to notice that.

 

[buckwheat]

Well I have to confess that in recent years you've got me beat. This is my first year back on a road bike in over 20 years, and so far I have just under 5,000 miles. 20 years ago I was doing more than twice that every year, but that was...20 years ago.

Having said that, we might be talking about two different things here. I said I "notice" these changes the more I ride. As far as "affect" goes, that opens a whole new can of worms, such as: "How does it affect a rider?". To the point of needing to spend a lot of adaptation time? ...to the point of immediate change in performance? ...to the point of injury?

So are you saying that a rider who puts in more miles will not notice the weight of a bike or wheels as much as someone who rides considerably less?

As far as your story with frame stiffness goes, I don't think frame/bb flex is the point of discussion here. Correct me if I'm wrong, but I thought it was an issue of the fit and component fit.

What I'm illustrating with the highlighted portion is the somewhat warped perception many enthusiasts have about cycling equipment and its effects on every aspect of riding whether it's fit, injuries, performance, whatever.

For all the discussion about these things, unless one is riding at the top of the sport, I don't think many of these things make a difference worth talking about. This is IMHO of course. Of course there are different sensations, but whether they translate to superior performance or that much difference in comfort, is debatable, again, IMHO. Cyclists seem to be a wishful, superstitious sort.

General fit, the saddle, shoes, tires, and a reasonable machine in good working order matter, IMHO. 2.5 mm on cranks? Not so much, unless it gets in one's head.

IMHO, clincher tires and clipless pedal systems are the biggest and most meaningful advances on the tech side.

The best advice, ride lots,,, don't buy upgrades, ride up grades.....be careful, wear a helmet.....everything else, mostly bs.....ATMO

 

[buckwheat]

My back notices if I move my saddle forward 25mm. My **** tells me if my saddle is 25 mm too high. And moving your cleats forward or back 25 mm will make a difference, especially since your feet are probably 250-300 mm long. Stack height make a difference? Sure, especially if you pedal with any amount of ankle articulation.

I believe fit is more important than frame stiffness, so I'm with the folks who say follow your instincts or fit gurus. I know my climbing improved with longer cranks just as my sprint declined a bit.

oops, sorry, I meant 2.5mm not 25mm which is the step in crank lengths..

It wasn't double blind when you changed sizes, was it?

2.5mm is a tiny difference. If I don't like the positioning of my cleats, I may move them, but more likely I'm trying to center their float. If one has fixed cleats, I'm sure you may feel small differences.

Stack height affecting ankle articulation? I would think saddle height would.

What can I say? I may try to adjust my bike mm's but in reality, I believe a quarter cm is a very small difference.

Obviously most disagree. Here's the bike Contador rode in the tour.

http://www.cyclingnews.com/features/pro-bike-alberto-contadors-astana-specialized-s-works-tarmac-sl3

Here's the Trek he rode.

http://autobus.cyclingnews.com/tech/2008/probikes/?id=alberto_contador_astana_trek_giro08

both 52's I believe.

Could he have ridden and won on a 54? I'll bet he could. Could he have ridden an 11cm stem, with no difference other than the feeling? I don't think he'd feel cramped with a 1 cm shorter cockpit.


LA at supposedly approx the same height is riding a 58, which btw, I don't believe. Hincapie is also riding a 58 at 6'3"

IMHO, in a double blind switch, or single blind (the rider) 2.5 mm crank difference is going to be very difficult to ascertain by the average road bike rider. Others disagree. Not much more to say I guess.

 

[Hmmmmm]

I'm 5'-9" and currently use 172.5 mm cranks. I used 170s for years and decided to go up a size and must say I think I climb better with the longer arms but have to concentrate more in terms of spinning. Could be psychological though because when I was younger I pushed bigger gears and did not work on cadence as much. Now though, I've been working on smaller gears and leg speed so I am always working on maintaining a higher cadence whether the road is flat or not. I think equations can be useful, but with something as personal as the human body and leg muscles in general I think there is no hard formula for what is the proper or correct crank length. One must ride and get a feel for things regarding this subject. Now, there are extremes and too long or too short a crank arm length could be a problem, but then again, who's to say what is too long or too short.

 

[marathon marke]

What I'm illustrating with the highlighted portion is the somewhat warped perception many enthusiasts have about cycling equipment and its effects on every aspect of riding whether it's fit, injuries, performance, whatever.

That's close to what I was saying...some of these things I can notice, but do they actually affect my riding? Well, sometimes they do and sometimes they don't. I can't speak for anyone but myself. As others have mentioned, I had also noticed a need to "refine" my spin when I went from 170 cranks to 175. Would I have noticed anything with only a 2.5mm difference? Possibly not. Do I notice a crank that has a lot of flex over a very stiff one? Yes, that has been the case with me. Will the more flexible crank cause me to perform more poorly? Probably not.

For all the discussion about these things, unless one is riding at the top of the sport, I don't think many of these things make a difference worth talking about. This is IMHO of course. Of course there are different sensations, but whether they translate to superior performance or that much difference in comfort, is debatable, again, IMHO. Cyclists seem to be a wishful, superstitious sort.

I wouldn't argue that last statement, but I would like to add that cyclists also seem to be a variable group that possess different levels of sensitivity to some of the things we're addressing.

 

[on3m@n@rmy]

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

Many posters have given good advice. I'll just say for me (went from 175 to 172.5 10 yr ago) I noticed less leverage with 172.5, but a bit easier to spin and easier on the knees. I actually had gotten slight tendonitis in one knee but cleared up right away switching back to the shorter crank.

 

[lostintime]

I decided to try an experiment for myself. I've been so hard headed about using 185's ... I decided to slap on some old 175's I had. Holy cow ..... I felt like I just entered a fun house ..... it was so easy to spin I felt like human flywheel.

I'm no faster, no slower ..... it's just easier to spin. I can spin faster uphill too, there's a slight trade of in perceived power.... I have no way to measure it. But, I feel better spinning the smaller cranks afterward.

For what it's worth ....

 

[Boeing]

The Zinn article is good in theory IMHO because the choice is not a simple as "spin and cadence" as most suggest. It is a great argument for body geometry and bike fit analysis etc. which is the best starting point

However I personally find it a bit over the top; pun intended

Enter a measurement of a 36" inseam and out pops a 197.5 crank. even if you ordered a set, getting on top of one's gear at that length is one thing. fitting it to clear today's carbon roadie chain-stays is another then again running that on a mountain bike clearance is a major issue..

I can't imaging running that length even if it was event specific. ss mountain bike? short TT?

I am no pro but after all my trial and error over the years I run a 177.5 on all bikes except fixed gear. 180 I just couldnt get on top of the gears on the road. 180 was fine for SS mountain bike out of the saddle but once back in I had the same issue

like someone said however, you will only find longer cranks (177.5 and 180) in the upper end REcord, Dura Ace and Red groupo's. Although the SRAM Force offer a 180 now I am told but no 177.5.