Mountain Bike Reviews Forum banner
1 - 20 of 75 Posts

·
Registered
Joined
·
111 Posts
Discussion Starter · #1 ·
Just got a set of 185 e.Thirteen singlespeed cranks, wanted 175's but they were unavailable. So I went with 185's. All my other bikes (Yeti Big Top SLX, and Spot SS XT) have 175's Will I really notice a difference for good or bad? I am 6'4 with a 34 inch inseam.

These will be going on a new Spot Single Speed.

Any thoughts
 

·
Registered
Joined
·
1,875 Posts
mberesn1 said:
Just got a set of 185 e.Thirteen singlespeed cranks, wanted 175's but they were unavailable. So I went with 185's. All my other bikes (Yeti Big Top SLX, and Spot SS XT) have 175's Will I really notice a difference for good or bad? I am 6'4 with a 34 inch inseam.

These will be going on a new Spot Single Speed.

Any thoughts
dood. with your inseam (similar to mine), you should be on the 180s. especially on your single speed. i have 180s on all my single speeds and 1X6 or 1X9 xc bikes.
 

·
Registered
Joined
·
1,908 Posts
I felt uncomfortable on my rigid 29'er singlespeed with 175mm crankarms. Once I upgraded to XT 180mm (like my other bike) it became a beast and I love it.

There is a LOT of advice out there that says that it doesn't make a difference and you get the same effect if you just lower your gearing. IMO, those of us that are 6'+ shouldn't be on the same crankset as the vertically challenged. If a short person's walking stride is 18", it would be strange if a tall person tried to mimic that stride.

KEEP the 180's and don't look back. You won't regret the "mistake".
 

·
likes to ride bikes
Joined
·
893 Posts
Another thing I'd like to point out is shoe size. I wear size 51s (size 15 shoes). The distance from my ankle to the pedals horizontally is much greater than the average Joe. I felt like a ballerina pedaling 175s.

To the OP, your true inseam may be greater than 34", that may be your pants inseam.
 

·
Registered
Joined
·
111 Posts
Discussion Starter · #9 ·
Great!
Thanks. Seems like the 180's will be sweet.
Maybe a swap out will occur on my other bikes as well.
 

·
Registered
Joined
·
498 Posts
There is a general school of thought that SS should run longer cranks than 3x geared setups to give extra leverage on the pedal stroke. There is also a school of thought that mtb cranks should be longer than road cranks for the same rider.

I used to run 175's on all my bikes but I have switched down to 172.5's on my road bike and am about to install my 180's on my new SS. I have only briefly used them on my Chameleon set up as SS before so I can't really comment on whether they were better.

The road bike cranks definitely feel better though. I also got a complete bike fit done when I fitted the new groupset.

Having said all that I am shorter and have a much shorter inseam than the OP. With those lanky legs I don't think you will regret 180mm cranks.
 

·
Underskilled
Joined
·
4,750 Posts
I am 6'7 the only difference I noticed when borrowing my wife's 160mm cranks (from my 180), is that shimano deore cranks are flexy.

It is only 2cm compared to 6'6 it is nothing.
 

·
Professional Crastinator
Joined
·
6,402 Posts
You will be fine, esp. at your height.

But I have heard (have not done myself) that it is harder to spin a really high cadence with longer cranks compared to shorter cranks. ...at the cost of some leverage, I guess. I guess that's how you'll determine what cog to run.

-F
 

·
Registered
Joined
·
3,626 Posts
from http://www.peterwhitecycles.com/fitting.htm

So how long should the cranks be? Well, that's a good question. I wish I had a good answer but I don't. It should be obvious that a 5' 2" rider would not want to use the same length crank arms as a 6' 7" rider unless they somehow managed to have the same leg length (highly unlikely). Some research has been done to determine the optimum percentage of leg length to crank length. I doubt that there is an optimum percentage that would apply to all people. One writer in a major magazine article quite a few years ago claimed that after considerable testing with many different riders, 18.5% of the distance from the top of the femur to the floor in bare feet should be the crank length. You can find the top of the femur pretty easily. It's 5" to 6" below your hip bone, and moves rearward when you raise your knee. After reading this I promptly changed from the industry standard 170mm cranks for road bikes to 175mm cranks. There was an immediate improvement in power and endurance. I began using this formula when recommending cranks to my customers. So far, I haven't gotten any complaints. But of course that doesn't mean my customers wouldn't be as happy or happier with some other length. And I must admit that I have never tried still longer cranks than 175mm for enough time to tell if I would be even happier with them.
 

·
Registered
Joined
·
1,819 Posts
http://zinncycles.com/Zinn/index.php/components/custom-cranks

I used their method and at 5 10 w/ 32" inseam came up with 170 or 175mm cranks.

There was a big thread on this lately and the conclusion as I saw it was that unless you are way outside the norm you could ride anywhere from 160s to 180 and feel pretty good with them. The math and physics seem to concluded that there is no mechanical advantage to running longer or shorter cranks but there may be something said for the ergonomic benefit. It does make sense to me that if you are really big or small you should build your whole bike accordingly including crank length but for most people the standard 175mm cranks will be fine.

Other things can be considered. BB height. If it's low shorter cranks will help a bit with hitting stuff. I did the math in the past as I think I came up with 5mm crank length = about 1 tooth on the chain ring. So running a 180 over a 175 is the same as going to a 31 from a 32 ring. (180=31)
 

·
Registered
Joined
·
1,908 Posts
modifier said:
http://zinncycles.com/Zinn/index.php/components/custom-cranks

I used their method and at 5 10 w/ 32" inseam came up with 170 or 175mm cranks.

There was a big thread on this lately and the conclusion as I saw it was that unless you are way outside the norm you could ride anywhere from 160s to 180 and feel pretty good with them. The math and physics seem to concluded that there is no mechanical advantage to running longer or shorter cranks but there may be something said for the ergonomic benefit. It does make sense to me that if you are really big or small you should build your whole bike accordingly including crank length but for most people the standard 175mm cranks will be fine.

Other things can be considered. BB height. If it's low shorter cranks will help a bit with hitting stuff. I did the math in the past as I think I came up with 5mm crank length = about 1 tooth on the chain ring. So running a 180 over a 175 is the same as going to a 31 from a 32 ring. (180=31)
A shorter crankarm will be stronger than a longer one and since "The math and physics seem to concluded that there is no mechanical advantage to running longer or shorter cranks", we should all switch to 50mm cranksets. I do believe you are onto something here.
 

·
Registered
Joined
·
1,819 Posts
Lumbee1 said:
A shorter crankarm will be stronger than a longer one and since "The math and physics seem to concluded that there is no mechanical advantage to running longer or shorter cranks", we should all switch to 50mm cranksets. I do believe you are onto something here.
If your avatar is any indication that might work out for you just fine. ;)

I'm obviously talking about a average range of crank length. Like 170s vs 180s. It feels like you're pushing a lower gear with a 180 because of the slight mechanical advantage but you have to push it farther (make a bigger circle) to get the same results so over all you use the same energy.
 

·
J:
Joined
·
5,128 Posts
cool thread

modifier said:
http://zinncycles.com/Zinn/index.php/components/custom-cranks
I did the math in the past as I think I came up with 5mm crank length = about 1 tooth on the chain ring. So running a 180 over a 175 is the same as going to a 31 from a 32 ring. (180=31)
Thanks for this info exactly what I was looking for.

Re; the 185 cranks, wouldn't they give more torque in short bursts? Like tech uphills where your 1/3 ratchet/cranking.
 

·
likes to ride bikes
Joined
·
893 Posts
Yes, if you have the leg length and power. Pedal strikes are the only real downside, especially with 29ers and the trend to lower bottom brackets.

DeerhillJDOG said:
Thanks for this info exactly what I was looking for.

Re; the 185 cranks, wouldn't they give more torque in short bursts? Like tech uphills where your 1/3 ratchet/cranking.
 

·
Registered
Joined
·
1,819 Posts
TunicaTrails said:
Yes, if you have the leg length and power. Pedal strikes are the only real downside, especially with 29ers and the trend to lower bottom brackets.
I could be mistaken but I thought that BB height was about the same on 26ers and 29ers but with 29ers the relationship between the BB and the wheel axle center is lower which is done to keep your center of gravity low and the stand over height down. So if that is true then there is no additional tendency for pedal strikes on a 29er.
 

·
transmitter~receiver
Joined
·
9,333 Posts
modifier said:
http://zinncycles.com/Zinn/index.php/components/custom-cranks

I used their method and at 5 10 w/ 32" inseam came up with 170 or 175mm cranks.

There was a big thread on this lately and the conclusion as I saw it was that unless you are way outside the norm you could ride anywhere from 160s to 180 and feel pretty good with them. The math and physics seem to concluded that there is no mechanical advantage to running longer or shorter cranks but there may be something said for the ergonomic benefit. It does make sense to me that if you are really big or small you should build your whole bike accordingly including crank length but for most people the standard 175mm cranks will be fine.

Other things can be considered. BB height. If it's low shorter cranks will help a bit with hitting stuff. I did the math in the past as I think I came up with 5mm crank length = about 1 tooth on the chain ring. So running a 180 over a 175 is the same as going to a 31 from a 32 ring. (180=31)
pretty well put. :thumbsup:
i think the best science that I've seen has indicated that there is no performance reason to chose one length over the other, and so the best choice is what feels good (ergonomic). basically, out of the range of cranks available, there isn't one you "should" be on based on your body size or performance. the best one is whatever feels right, and there doesn't (yet) seem to be a ruler for that.
 
1 - 20 of 75 Posts
Top