Crank Length

jagrazor said:

First, how do i measure crank length. Second, if it's from the center to the end, I have 190mm cranks.

Would it be better for me with an inseam of 35.75 inches (90.8cm) to buy shorter cranks, like 170mm?

Also, do you need to buy a certain rear cassette for a certain crank set?

Suggestions on size of crank? I would go double maybe 50/38 would be best?

Isn't there a rule of thumb, 18.5% of leg length?

jagrazor said:

First, how do i measure crank length. Second, if it's from the center to the end, I have 190mm cranks.

Would it be better for me with an inseam of 35.75 inches (90.8cm) to buy shorter cranks, like 170mm?

Also, do you need to buy a certain rear cassette for a certain crank set?

Suggestions on size of crank? I would go double maybe 50/38 would be best?

Center of pedal hole to center of spindle hole. No on the cassette business. You have a long inseam.In most cases a something longer than 170 would be appropriate. who knows what chainrings are best for you and your type riding,and it also depends on the cassette you choose.

boudreaux said:

Center of pedal hole to center of spindle hole. No on the cassette business. You have a long inseam.In most cases a something longer than 170 would be appropriate. who knows what chainrings are best for you and your type riding,and it also depends on the cassette you choose.

i remeasured, im at 175mm. My bike still doesnt feel right *shrug* I guess I will have to keep messing with the other settings.

[font=Times New Roman]To make a long story short, if you do have 175 mm cranks, depending on the manufacturer, you may already have the longest cranks you can get. Shimano stamps the size on the frame side of the crank. (At least that’s where my cranks are stamped.) So I’d be surprised if you have 190 mm cranks. [/font]

[font=Times New Roman]Google “crank length” or “crank arm length” and you will get more than enough to read. And here are a few lings too.[/font]

[font=Times New Roman]machinehead-software.co.ukcyclist crank length calculator.htmlOpen ↗[/font]

[font=Times New Roman]nettally.comcrankset.htmlOpen ↗[/font]

[font=Times New Roman]cranklength.infocranklength.infoOpen ↗[/font]

[font=Times New Roman]sheldonbrown.comcranks.htmlOpen ↗[/font]

[font=Times New Roman]Actually our inseams are almost identical. And when I was ordering my bike last winter, I wanted 180 mm cranks. And I now ride 175 mm cranks, since that’s as big as they come with a Shimano Ultegra triple. I could have ordered 180 mm cranks, but I would have needed to order a Dura Ace double, or Campy. [/font]

[font=Times New Roman]You should have no problems with 175 mm cranks with your inseam. I would not suggest using a 170 mm crank, unless you really like to spin the cranks. My average cadence is about 85, and like I said, I have no problems.[/font]

[font=Times New Roman]Cassettes and cranks are independent of each other. [/font]

[font=Times New Roman]I’m not sure about your last question. But a standard double usually is a 53/39, and some compact doubles are 50/36. [/font]

bikeguy2004 said:

[font=Times New Roman] So I’d be surprised if you have 190 mm cranks. [/font]

[/font][/size]

You can get all kinds of goofy answers when you measure wrong.

bikeguy2004 said:

[font=Times New Roman]To make a long story short, if you do have 175 mm cranks, depending on the manufacturer, you may already have the longest cranks you can get. Shimano stamps the size on the frame side of the crank. (At least that’s where my cranks are stamped.) So I’d be surprised if you have 190 mm cranks. [/font]

[font=Times New Roman]Google “crank length” or “crank arm length” and you will get more than enough to read. And here are a few lings too.[/font]

[font=Times New Roman]machinehead-software.co.ukcyclist crank length calculator.htmlOpen ↗[/font]

[font=Times New Roman]nettally.comcrankset.htmlOpen ↗[/font]

[font=Times New Roman]cranklength.infocranklength.infoOpen ↗[/font]

[font=Times New Roman]sheldonbrown.comcranks.htmlOpen ↗[/font]

[font=Times New Roman]Actually our inseams are almost identical. And when I was ordering my bike last winter, I wanted 180 mm cranks. And I now ride 175 mm cranks, since that’s as big as they come with a Shimano Ultegra triple. I could have ordered 180 mm cranks, but I would have needed to order a Dura Ace double, or Campy. [/font]

[font=Times New Roman]You should have no problems with 175 mm cranks with your inseam. I would not suggest using a 170 mm crank, unless you really like to spin the cranks. My average cadence is about 85, and like I said, I have no problems.[/font]

[font=Times New Roman]Cassettes and cranks are independent of each other. [/font]

[font=Times New Roman]I’m not sure about your last question. But a standard double usually is a 53/39, and some compact doubles are 50/36. [/font]

i suppose its hard when i have a few independent threads. I have some knee problems, and I think shorter cranks would be good for that, at least for the time being. Then i can move to longer cranks when my knees get stronger or are able to take the larger range of motion.

[font=Times New Roman]Unless I missed it, this is the first time you mentioned knee problems.[/font]

[font=Times New Roman]Is you bike adjusted properly? If your saddle is too low your knees are not extended enough and that can cause problems. OR if your cadence is too slow, that can cause knee problems too.[/font]

[font=Times New Roman]I still think the crank length is OK… (but that’s just me)[/font]

[font=Times New Roman]peterwhitecycles.comfitting.htmOpen ↗[/font]

[font=Times New Roman]sheldonbrown.compain.htmlOpen ↗[/font]

bikeguy2004 said:

[font=Times New Roman]Unless I missed it, this is the first time you mentioned knee problems.[/font]

[font=Times New Roman]Is you bike adjusted properly? If your saddle is too low your knees are not extended enough and that can cause problems. OR if your cadence is too slow, that can cause knee problems too.[/font]

[font=Times New Roman]I still think the crank length is OK… (but that’s just me)[/font]

[font=Times New Roman]peterwhitecycles.comfitting.htmOpen ↗[/font]

[font=Times New Roman]sheldonbrown.compain.htmlOpen ↗[/font]

This isnt the first solution I have looked for. It's either this, or something i don't know about. Seat position has been changed to different places cadence is always high. It's the crank length, thats the only thing that could effect it. shorter cranks don't negetively effect anything, except for your highest possible gear, which i can't use anyway because my knees hurt :P

jagrazor said:

This isnt the first solution I have looked for. It's either this, or something i don't know about. Seat position has been changed to different places cadence is always high. It's the crank length, thats the only thing that could effect it. shorter cranks don't negetively effect anything, except for your highest possible gear, which i can't use anyway because my knees hurt :P

"Long Cranks
The longer your cranks are, the farther your knees will have to flex on each stroke. Different riders will have different amounts of flexibility in this regard, but riding with longer cranks than you are used to can definitely cause problems."

"I’m staying with the 18.5% guide for my customers until something better comes along. It hasn't failed yet."

there are two statements that agree with this possibility for the cause, espeically since i have worked out other possibilities.

My inseam is 34.25" (87cm), and I foolishly went straight out and HAMMERED for a month on longer cranks. and injured my right knee which took a year to get over -- although I still did 14,000km in that year.

I went from 170s to 175s. I totally pannicked, and went back to 170s, and I'm too scared to go back to the long cranks.

jagrazor said:

This isnt the first solution I have looked for. It's either this, or something i don't know about. Seat position has been changed to different places cadence is always high. It's the crank length, thats the only thing that could effect it. shorter cranks don't negetively effect anything, except for your highest possible gear, which i can't use anyway because my knees hurt :P

[font=Times New Roman]If you have covered all of the other possible things that can cause you knee pain, then that leaves the last choice, shorter cranks. Have you tried different cleat positions on your shoes?[/font]

[font=Times New Roman]Cleat Adjustment[/font]
[font=Times New Roman]Some knee problems result from incorrect placement of shoe cleats.[/font]

[font=Times New Roman]I always try to work thru the free fixes first and then I’ll start to consider spending money. And even then, I’ll first go back to my LBS and discuss the problem with them. (weekdays are better than weekends, since they will have more time to help) They have helped a LOT more people with bike fit over the years, and they have the advantage that they can also see your riding position and maybe they can spot what’s causing you the knee problem.[/font]

bikeguy2004 said:

[font=Times New Roman]If you have covered all of the other possible things that can cause you knee pain, then that leaves the last choice, shorter cranks. Have you tried different cleat positions on your shoes?[/font]

[font=Times New Roman]Cleat Adjustment[/font]
[font=Times New Roman]Some knee problems result from incorrect placement of shoe cleats.[/font]

[font=Times New Roman]I always try to work thru the free fixes first and then I’ll start to consider spending money. And even then, I’ll first go back to my LBS and discuss the problem with them. (weekdays are better than weekends, since they will have more time to help) They have helped a LOT more people with bike fit over the years, and they have the advantage that they can also see your riding position and maybe they can spot what’s causing you the knee problem.[/font]

yes i go to My LBS, and yes i've had my cleats readjusted

531Aussie said:

My inseam is 34.25" (87cm), and I foolishly went straight out and HAMMERED for a month on longer cranks. and injured my right knee which took a year to get over -- although I still did 14,000km in that year.

I went from 170s to 175s. I totally pannicked, and went back to 170s, and I'm too scared to go back to the long cranks.

yeah, i think the longer cranks can cause problems if you over use them. Maybe its good for a time trial bike, or something you dont use often, but all the time it probably isnt smart, the same way people change there other things with bike position for races and for different kinds of races, Time trials, Triathlons ect...

jagrazor said:

yeah, i think the longer cranks can cause problems if you over use them. Maybe its good for a time trial bike, or something you dont use often, but all the time it probably isnt smart, the same way people change there other things with bike position for races and for different kinds of races, Time trials, Triathlons ect...

Using the longer cranks all the time would be ok, just as long as you are used to them -- I made the mistake of not easing into the new length.
I would also say that my situation was very uncommon.

531Aussie said:

Using the longer cranks all the time would be ok, just as long as you are used to them -- I made the mistake of not easing into the new length.
I would also say that my situation was very uncommon.

I would bet that it isnt that Uncommon, the guy who i bought this bike had 5 knee surgeries... maybe he still hasnt realized the culprit could be his large cranks. He has about the same inseam as me, maybe a little smaller.

I intend to give him a call and see what he thinks if i can ever get a hold of him 🙂