Crankarm Lengths
- Thread starter Hoya1500
- Start date
2.5mm will make little difference to 'spin' and feel of the circle size, but it will affect on your saddle height.
Assuming you're in the correct postion at the moment, you'll most likely drop your seat by ~2.5mm, which means your knees will be ~5mm higher, relative to your hips, through the top of the pedal stroke
Assuming you're in the correct postion at the moment, you'll most likely drop your seat by ~2.5mm, which means your knees will be ~5mm higher, relative to your hips, through the top of the pedal stroke
It all depends on the legs:
http://cranklength.info/crankCalc.htm
http://www.greenspeed.com.au/NewGSweb/web-content/australia/measure.html
I am currently setting up two bikes for a lady with a 71cm standover. She is getting 152mm on one bike and 165 on the other. She previously rode on 160s, I will change the 165s if there are any problems.
http://cranklength.info/crankCalc.htm
http://www.greenspeed.com.au/NewGSweb/web-content/australia/measure.html
I am currently setting up two bikes for a lady with a 71cm standover. She is getting 152mm on one bike and 165 on the other. She previously rode on 160s, I will change the 165s if there are any problems.
Serach this forums, loads of discussion previously on this topic.
Got 4 bikes; 175 on two, 172.5 on one and my crit racer has 170s. Now I "think" I can tell the difference between the 170s and 175s, but that could be more the type of bike. Between the 175 and 172.5 I feel nothing different. Most standard stock cranks are either 175 or 172.5 and the vast majority of bike shops don't even point this out when selling you a bike (cuz it really doesn't matter).
Got 4 bikes; 175 on two, 172.5 on one and my crit racer has 170s. Now I "think" I can tell the difference between the 170s and 175s, but that could be more the type of bike. Between the 175 and 172.5 I feel nothing different. Most standard stock cranks are either 175 or 172.5 and the vast majority of bike shops don't even point this out when selling you a bike (cuz it really doesn't matter).
capwater said:
No! It matters tremendously over the long run as far as trashing your knees (seperate from any performance issues). Overextension can cause irrepairable damage, maybe not noticeable in the short term, but 20 years down the road there will be many unhappy campers with joint replacements looming. If one is a casual recreational cyclist it may not matter much, but if you're putting in well over 5k miles a year, you'd be well advised to get a proper fit.
98% chance of no problems whatsoever. about the only possibility (assuming it's compatible with your bb) would be that on some bikes toe/tire clearance can be an issue, most often when you are using both clips and long front fenders. to check, sit on your bike , foot on pedal, crankarm forward, and turn your handle bars. if you've got a quarter inch or better between the toe of your shoe and the tire or fender, you should be fine.
I would not consider crank length as a single issue. It is an essential part of a complete bike fit. If you are using a professional consultant, then the length of the crank will be in the specs as will the seatpost angle, stem length, wheel size, top tube length, bar width, lever reach, etc..
If you look at post #5, the bike with the 152mm cranks is perfect for her, using the given formulas. It is an off the peg 13" boys mountain bike with 24" wheels, the only change is the city tyres and rear cassette.
The other bike is a road bike, XS 43cm frame, small components, 650c wheels, 165mm cranks, however, the client will not spend the extra $$ on shorter (155mm) cranks until she is confident with the bike. You just cant buy short crank arms in any bike shop, they have to be drilled and tapped from blanks, so a new crankset and bottom bracket will be needed.
I have given the above as practical examples. Are you too shy to post you inside leg measurement?
If you look at post #5, the bike with the 152mm cranks is perfect for her, using the given formulas. It is an off the peg 13" boys mountain bike with 24" wheels, the only change is the city tyres and rear cassette.
The other bike is a road bike, XS 43cm frame, small components, 650c wheels, 165mm cranks, however, the client will not spend the extra $$ on shorter (155mm) cranks until she is confident with the bike. You just cant buy short crank arms in any bike shop, they have to be drilled and tapped from blanks, so a new crankset and bottom bracket will be needed.
I have given the above as practical examples. Are you too shy to post you inside leg measurement?
"So what i'm gathering is if i move from a 170 to a 172.5, i should make the proper adjustments before riding?"
you are talking about 2.5 mm, less than 1/8 inch. most bike shops would never be able to fit you with that kind of exactitude. wearing padded shorts or unpadded would affect your position abou that much. i've never heard of anyone adjusting their saddle height depending on what they are wearing that day. ride it first, and if you can actually feel any difference, then think about changing your seat height.
you are talking about 2.5 mm, less than 1/8 inch. most bike shops would never be able to fit you with that kind of exactitude. wearing padded shorts or unpadded would affect your position abou that much. i've never heard of anyone adjusting their saddle height depending on what they are wearing that day. ride it first, and if you can actually feel any difference, then think about changing your seat height.
philso said:
Ditto! We're talking about 2.5mm (less than 1.5% difference in length from the 170's). One could argue if Hoya was going from 170's to 175's there would be some need to adjust the saddle position.
Some rather in depth crank arm length sites:
http://www.nettally.com/palmk/crankset.html
http://www.cranklength.info/
Bike fit in general:
http://www.cyclingnews.com/fitness/?id=2005/letters08-29#Steve
http://www.cyclefitcentre.com/index.htm
http://www.cyclemetrics.com/Pages/FitLinks/bike_fit_links.htm
DK
philso said:
Ditto! We're talking about 2.5mm (less than 1.5% difference in length from the 170's). One could argue if Hoya was going from 170's to 175's there would be some need to adjust the saddle position.
Some rather in depth crank arm length sites:
http://www.nettally.com/palmk/crankset.html
http://www.cranklength.info/
Bike fit in general:
http://www.cyclingnews.com/fitness/?id=2005/letters08-29#Steve
http://www.cyclefitcentre.com/index.htm
http://www.cyclemetrics.com/Pages/FitLinks/bike_fit_links.htm
DK
Also not worth worrying about. I have at least 1/2 an inch of overlap on my fixed-wheel road bike and, even though I get occasional touches, it doesn't matter - it has never been the cause of a fall for me. Not even a consideration (in my view).philso said:
Regards,
Eoin
the formulas on those sites are a little too long, at least for anyone over ~5'8". For some reason, shorter people seem to handle a proportionately longer crank than taller guys. I know heaps of 5'6" guys on 170s, but I'm the only guy I know on 180s (I'm 6ft), and there's absolutely no way I could ride anything longer.dkrenik said:
531Aussie said:
How do you know?
Crank lengths have been growing for several decades. 170's used to be the norm. Then 172.5's (with Miguel on 180's). Now 175's are ubiquitous with Jan riding 177.5's.
Granted, any formula won't take individual matters in to account like: flexibility, strength, asymmetries, etc. The point is that most folks over 5'8" or so might be better off with significantly longer crank arms.
DK
Indurain is 6'2", so, i'd be very surprised if the 180s he used were anywhere near the 21.6% of his inseam, which is the "formula" Kirby Palm recommends; and it's my guess that even the 190s he occasionally used for time-trials would be well under this percentage. Ullrich is 6ft, so, I would also (gladly) assume that 177.5mm is well under Palm's 21.6%.
Just to generalize for a moment from my own experience, I'm 6ft, with an 89.5cm inseam, and I've used 165 (track bike) 170, 172.5, 175, and am now using 180s. I couldn't imagine using anything longer 180mm, yet Kriby Palm would have me on 192s!!! As purely a personal point of view, that is INSANE!!
The best known proponents of longer cranks, Lennard Zinn (http://www.zinncycles.com/cranks.aspx), Kirby Palm, and, to a lesser extent Andrew Bradley (http://www.cranklength.info/ -- his sight is much more balanced and impartial) freely admit that there's no hard data to prove that longer cranks are more beneficial. Zinn has been trying for years to prove it, but hasn't, as yet. For Zinn and Palm, it's mostly their personal preference: they're tall dudes who prefer longer cranks, which is obviously understandable, and I reckon they've just generalized from their own experiences.
Kirby Palm's reasonings are rediculous -- his whole theory is based on the fact that a bunch of short guys used 170mm cranks in the 'old days', which happned to be roughly 21.6% of their inseam. SO WHAT??!! Maybe they all should've been on shorter cranks. His dismissal on potential knee injuries is irresponsible, and he barely addresses the issue of the 'saddle height conundrum' at all. And, to top it off, he's NO bike rider --- check him out
http://www.nettally.com/palmk/kirby2.jpg
I dunno where he gets his credibility -- he's just an engineer with a website...big deal.
Lennard Zinn was asked why virtually no pros use super-long cranks, and I don't buy his response.
Velonews emailer: "Dear Lennard, You recently stated that Magnus Backstedt used 177.5mm cranks. As a 6-foot-5-inch tall rider I have been following your many articles over the years on crank length which appear to conclude that longer is better for tall riders. I'm surprised then that Magnus doesn't use at least 180mm cranks if not longer. Can you provide further insight into what the tall pros are currently using for crank length and why. Why don't we see more custom cranks in the range of 190-210mm for the Axel Merckx's and Magnus Backstedt's of the peloton?
Nat"
Yeah, good question
Zinn's reply: "I suspect it has less to do with testing and more to do with what is available from sponsors, what a rider has used in the past, and the inertia of tradition in the cycling industry and of professional racing managers, coaches and riders. The industry is devoted to selling product and making a profit, and offering a lot more crank lengths does not make economic sense, because the cost per crank goes up, and they would still sell very few lengths outside of the traditional 165-180mm range. Also, the old-school ideas of their directors sportif and coaches are hard to buck. Not many riders approach their equipment with personal interest in the way that Greg LeMond and Lance Armstrong have, and tall riders are definitely in the minority in the peloton. Miguel Indurain's career was over before I started going to the Tour, but he was reputed to have used custom 190mm Campy cranks."http://www.velonews.com/tech/report/articles/6841.0.html
Does he think the tall pros are only vaguely aware of long cranks, and that team directors wouldn't let their riders use long cranks if they thought they worked? Pros and their support staff know all about long cranks -- Sosenka (6ft7") used 190s for his recent hour record -- and if someone like Axel Merckx thought that 200mm 'levers' would help him win more races he would use them. You've just gotta look at the weird chainrings that Bobby Julich uses to know that pros will use stuff if they think it gives them an advantage.
http://www.velonews.com/tech/report/articles/6807.0.html And let's not forget that Zinn sells cranks.
Here's an article providing a counter point of view which Palm disses on his site: http://www.bsn.com/Cycling/cranks.html
I like this quote:
"despite an increasing number of long femured (tall) competitors, you will see that 175mm is pretty much the longest crank, other than for time trials, that is used. I would not, as has often been suggested put this to conservatism. On the contrary, the fierce competition and prizes of professional cycling are substantial and bring a willingness to quickly adopt what might appear to provide some form of advantage--- which more often than not is at best psychological. In a realm where high tech voodoo and strange science abound I can't accept the arguments to the contrary..."
Andrew Bradley's site is by far the best of the 3 (http://www.cranklength.info/). His own personal preference is for longish cranks, but you've just gotta read the first page to see that he's only presenting a site with a stack of good information, and not telling us all that we should be on long cranks. His site is great; it even includes limb length and leverage discussion, and muscle contraction preferences -- top stuff.
This guy is somewhere in the middle, and his crank length chart is quite reasonable, but he cites Palm's site as a reference, so I'm not quite sure where he stands.
http://www.myra-simon.com/bike/cranks.html
I do favour slightly longer cranks for anyone who's not a sprinter, but, as I suggested on my other post, 21.6% of inseam is way too long for anyone over about 5'8"/5'10"
I suppose it's possible that one day eveyone will use a crank that's 21.6% of their inseam, but I'd be amazed.
Just to generalize for a moment from my own experience, I'm 6ft, with an 89.5cm inseam, and I've used 165 (track bike) 170, 172.5, 175, and am now using 180s. I couldn't imagine using anything longer 180mm, yet Kriby Palm would have me on 192s!!! As purely a personal point of view, that is INSANE!!
The best known proponents of longer cranks, Lennard Zinn (http://www.zinncycles.com/cranks.aspx), Kirby Palm, and, to a lesser extent Andrew Bradley (http://www.cranklength.info/ -- his sight is much more balanced and impartial) freely admit that there's no hard data to prove that longer cranks are more beneficial. Zinn has been trying for years to prove it, but hasn't, as yet. For Zinn and Palm, it's mostly their personal preference: they're tall dudes who prefer longer cranks, which is obviously understandable, and I reckon they've just generalized from their own experiences.
Kirby Palm's reasonings are rediculous -- his whole theory is based on the fact that a bunch of short guys used 170mm cranks in the 'old days', which happned to be roughly 21.6% of their inseam. SO WHAT??!! Maybe they all should've been on shorter cranks. His dismissal on potential knee injuries is irresponsible, and he barely addresses the issue of the 'saddle height conundrum' at all. And, to top it off, he's NO bike rider --- check him out
http://www.nettally.com/palmk/kirby2.jpg
I dunno where he gets his credibility -- he's just an engineer with a website...big deal.
Lennard Zinn was asked why virtually no pros use super-long cranks, and I don't buy his response.
Velonews emailer: "Dear Lennard, You recently stated that Magnus Backstedt used 177.5mm cranks. As a 6-foot-5-inch tall rider I have been following your many articles over the years on crank length which appear to conclude that longer is better for tall riders. I'm surprised then that Magnus doesn't use at least 180mm cranks if not longer. Can you provide further insight into what the tall pros are currently using for crank length and why. Why don't we see more custom cranks in the range of 190-210mm for the Axel Merckx's and Magnus Backstedt's of the peloton?
Nat"
Yeah, good question
Zinn's reply: "I suspect it has less to do with testing and more to do with what is available from sponsors, what a rider has used in the past, and the inertia of tradition in the cycling industry and of professional racing managers, coaches and riders. The industry is devoted to selling product and making a profit, and offering a lot more crank lengths does not make economic sense, because the cost per crank goes up, and they would still sell very few lengths outside of the traditional 165-180mm range. Also, the old-school ideas of their directors sportif and coaches are hard to buck. Not many riders approach their equipment with personal interest in the way that Greg LeMond and Lance Armstrong have, and tall riders are definitely in the minority in the peloton. Miguel Indurain's career was over before I started going to the Tour, but he was reputed to have used custom 190mm Campy cranks."http://www.velonews.com/tech/report/articles/6841.0.html
Does he think the tall pros are only vaguely aware of long cranks, and that team directors wouldn't let their riders use long cranks if they thought they worked? Pros and their support staff know all about long cranks -- Sosenka (6ft7") used 190s for his recent hour record -- and if someone like Axel Merckx thought that 200mm 'levers' would help him win more races he would use them. You've just gotta look at the weird chainrings that Bobby Julich uses to know that pros will use stuff if they think it gives them an advantage.
http://www.velonews.com/tech/report/articles/6807.0.html And let's not forget that Zinn sells cranks.
Here's an article providing a counter point of view which Palm disses on his site: http://www.bsn.com/Cycling/cranks.html
I like this quote:
"despite an increasing number of long femured (tall) competitors, you will see that 175mm is pretty much the longest crank, other than for time trials, that is used. I would not, as has often been suggested put this to conservatism. On the contrary, the fierce competition and prizes of professional cycling are substantial and bring a willingness to quickly adopt what might appear to provide some form of advantage--- which more often than not is at best psychological. In a realm where high tech voodoo and strange science abound I can't accept the arguments to the contrary..."
Andrew Bradley's site is by far the best of the 3 (http://www.cranklength.info/). His own personal preference is for longish cranks, but you've just gotta read the first page to see that he's only presenting a site with a stack of good information, and not telling us all that we should be on long cranks. His site is great; it even includes limb length and leverage discussion, and muscle contraction preferences -- top stuff.
This guy is somewhere in the middle, and his crank length chart is quite reasonable, but he cites Palm's site as a reference, so I'm not quite sure where he stands.
http://www.myra-simon.com/bike/cranks.html
I do favour slightly longer cranks for anyone who's not a sprinter, but, as I suggested on my other post, 21.6% of inseam is way too long for anyone over about 5'8"/5'10"
I suppose it's possible that one day eveyone will use a crank that's 21.6% of their inseam, but I'd be amazed.
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