# 175mm or 180mm cranks?



## Earthpig (Jan 23, 2004)

Been using 180mm cranks since I first started singlespeeding in 2001. The thought was that with the slightly longer than normal 175mm crankarm you could get a bit more torque and power to the rear wheel. Fiction? Truth? From a purely mathematical standpoint, I get it, a longer lever arm can result in more power, but I'm wondering if 5mm longer cranks make a noticeable difference in power applied to the rear wheel.


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## Hairnet (Jul 23, 2013)

Do what feels best, that will make you stronger/faster. I like them because the pedaling circle doesn't feel small and I get more knee flexion at the top of the circle, which feels very good. 175 feels fine. 170 and below is kinda cramped.


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## Mr. 68 Hundred (Feb 6, 2011)

I run 28 x 17 (29" wheels) with 175's in New Mexico. Pedal strikes are an issue here but even if they weren't, my math puts the torque gain fairly small. ~2.8%. Which means (assuming my math is right), that my legs would feel the same resistance on my 28 x 17 with 175's as on a 28 x 16.5 with 180's. So, maybe, you could gain a tooth in the back.


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## monogod (Feb 10, 2006)

there are a lot more levers in the drivetrain than merely crank arm length. studies don't indicate an increase in power with longer cranks or a decrease with shorter. choose the one you want.


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## JeffL (Jan 25, 2009)

There's a reason why Sheldon Brown included crank arm length in his Gain Ratio approach to gear calculations.

Gain Ratios--A New Way to Designate Bicycle Gears

If you compare different values in this calculation, Mr. 6800 is correct - 5mm change in crank arm length is equivalent to about 1/2 a tooth in rear cog size. A 10mm increase in length, say from 170 to 180, is equivalent to increasing cog size by exactly 1 tooth.

The point is you should choose crank arm length for bike fit and not torque. Adjust your gearing using gears. There's no mechanical benefit in having a longer crank arm - it just means you're effectively pushing an easier gear. The benefit would be in having the best fit for your height / leg length / whatever feels best to you.


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## JeffL (Jan 25, 2009)

Actually, as I think more about this there is one additional effect of changing crank arm length, besides fit. The longer crank arm should result in a faster top speed in the flats on an SS, all other things being equal. Assuming that your your top speed is limited by spin cadence, then for two bikes set up with the same effective gearing (the same Gain Ratio), the bike with the longer cranks will spin slower at the same ground speed. You ought to be able to climb the same on both bikes, while reaching a higher speed in the flats if you spin at the same cadence.

The difference is as significant as the tooth numbers stated above. These two 29ers have an identical Gain Ratio and should climb the same:
170mm crank, 32:18 gearing
180mm crank, 32:17 gearing

We all know the 17T bike will be significantly faster on the flats.


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## J.B. Weld (Aug 13, 2012)

JeffL said:


> Actually, as I think more about this there is one additional effect of changing crank arm length, besides fit. The longer crank arm should result in a faster top speed in the flats on an SS, all other things being equal. Assuming that your your top speed is limited by spin cadence, then for two bikes set up with the same effective gearing (the same Gain Ratio), the bike with the longer cranks will spin slower at the same ground speed. You ought to be able to climb the same on both bikes, while reaching a higher speed in the flats if you spin at the same cadence.
> 
> The difference is as significant as the tooth numbers stated above. These two 29ers have an identical Gain Ratio and should climb the same:
> 170mm crank, 32:18 gearing
> ...


It's easier to spin a shorter crank at higher cadences though, track racers often use 165mm cranks because of this fact.


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## theMeat (Jan 5, 2010)

J.B. Weld said:


> It's easier to spin a shorter crank at higher cadences though, track racers often use 165mm cranks because of this fact.


Exactly
And a longer crank will offer more leverage, so greater acceleration. That's why most road bikes come with 165, and most mtbs with 175. But choose a length that works for your size and bike's geo, and choose a gear ratio for the rest.


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## bikeny (Feb 26, 2004)

theMeat said:


> Exactly
> And a longer crank will offer more leverage, so greater acceleration. That's why most road bikes come with 165, and most mtbs with 175. But choose a length that works for your size and bike's geo, and choose a gear ratio for the rest.


Sorry to inform you, but most road bikes do not come with 165 cranks. More like 170 to 172.5. But yes, they come with smaller cranks because it's easier to spin a higher cadence with shorter cranks.


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## JeffL (Jan 25, 2009)

J.B. Weld said:


> It's easier to spin a shorter crank at higher cadences though, track racers often use 165mm cranks because of this fact.


That makes sense. I wonder if the ease of spinning a shorter crank completely nullifies the mechanical difference of my example? I can't think of a good way to make that a mathematical comparison... it's just academic, though - I wouldn't choose an MTB crank length just for the best spinning conditions. Since I don't race much I rarely spin hard in the flats - that's my time for resting before the next climb.


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## theMeat (Jan 5, 2010)

bikeny said:


> Sorry to inform you, but most road bikes do not come with 165 cranks. More like 170 to 172.5. But yes, they come with smaller cranks because it's easier to spin a higher cadence with shorter cranks.


Ok, then I stand corrected, can't / won't speak for all or most road bikes but all 3 of mine came with 165, maybe because they're older idk


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## 127.0.0.1 (Nov 19, 2013)

yes


180 easier to grunt up hills

180 makes high cadence a little sloppier

I just keep 175's on my SS the difference is not major for what I ride. if you really are all climbs and little flat then 180 would be great. I am 40/60 climbs flats so I need to spin a ton


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## jl (Feb 23, 2004)

I went with what I could afford--175mm. I use to have 180s, I can't really tell a difference...


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## Earthpig (Jan 23, 2004)

I think I'll try the set of 175's I have sitting around for comparison sake.


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## gonzo (Feb 18, 2004)

*no single component replaces fitness*



Earthpig said:


> Been using 180mm cranks since I first started singlespeeding in 2001. The thought was that with the slightly longer than normal 175mm crankarm you could get a bit more torque and power to the rear wheel. Fiction? Truth? From a purely mathematical standpoint, I get it, a longer lever arm can result in more power, but I'm wondering if 5mm longer cranks make a noticeable difference in power applied to the rear wheel.


I ride both, can't tell the difference, so now I just buy 175 because they are cheaper on e-bay.......

fitness is the #1 factor in my riding, no single component replaces fitness.......


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## conrad (Jan 27, 2004)

All my bikes are now 180 (3 geared, 1SS) but I'm 6'2" with long legs and a short body. They just fit me better, performance wise no real difference to my 175s but I like to climb and most of my rides are on hills with very little flat riding.


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## phsycle (Apr 14, 2011)

I used to ride 175's on my SS's for years. Switched to 170's a couple of years ago. I found that initial feel was definitely different. Then as I got used to it after a couple of rides, I really don't see it as a hinderance. I find I can clear everything that I did with the longer cranks, but with the big benefit of being able to spin on the flats/downhills much faster. I've gone 170's on all of my bikes, with the exception of the cargo bike, which has 175 SLX cranks on it, and the only reason it doesn't have 170's is I just don't want to put any money into it. If anyone wants to trade for 170's, shoot me a PM.


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## alhounos (Apr 19, 2014)

I like my 170s just fine. 

If you can't push the gear just go to a bigger cog, no shame in that.

Can spin faster on flats and less chance of pedal strikes and greater ground clearance. 
Of course, if you've got long legs, whatever's comfortable.


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## squareback (Sep 19, 2011)

I love 175 or even 180 on everything except my one-speed with 170.

sent remotely


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## chomxxo (Oct 15, 2008)

Has nothing to do with singlespeed or feel or anything else but your leg length, and somewhat your foot length. You'll see pro cyclists of 6'4" and above still riding them. I regret there aren't more options. However a low bottom bracket is really useful so I've sized down to 180s. You can learn to spin a more efficient cadence by doing one-legged drills. You want to learn to get your average cadence up into the 90s, regardless of SS or geared riding.


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## tigris99 (Aug 26, 2012)

I don't have experience in the ss side but it applies whether u got 1 or 3 rings. Leg length plays a role but simple physics. Leverage. 5mm is going to make only a little but still a difference. Same effect can be done with a smaller chain ring. Everyone talks about gear ratios/gear inches, but leverage ratios matter too.

To put in cyclic terms. Put your bike on a stand so drive train/rear wheel spins freely. There is no load, gear inches matter none. Turn rear wheel by hand by grabbing tire, spins with no effort. Grab spokes closest to hub, turn wheel, more force required.
Now grab ur crank arm where it meets bb try to turn. Grab ur pedal and notice it goes from noticable effort to simply a little weight of your hand on the pedal spins the rear tire.

Its a almost never discussed point and I never thought about it myself till I converted to 1x. Went from 32 to 30 and can ride in same gear inches (Sheldon calc) with w less fatigue and climb better. all because I can move the back tire the same distance with less effort.

If u ss guys wanna play with this, go smaller chain ring and smaller rear gear to maintain ratio/inches but see how much easier u climb and spin out on decents. However there is a tipping point which im gathering plenty may have stumbled into where leverage loss at rear wheel exceeds leverage gain at crank.

As for cadence, bit overrated. I can't spin 90s to save my life, wear out too fast. Spin at my pace and use muscle power instead and ride father, better and faster with less fatigue. Some people spin, some use power, do what's best for you.
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## J.B. Weld (Aug 13, 2012)

I don't know where it is but I read a study that someone here on mtbr referenced showing that crankarm length had surprisingly little correlation with power output. They were putting guys on crazy short crankarms (140mm) who were still able to crank out mega-watts. I realize that mountain biking, and single-speeding even more so have a lot different requirements than road but I found that information interesting.

I'm 6'3" and never could get along with 180's, shorter feels easier on the joints to me.


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## chomxxo (Oct 15, 2008)

Lack of high cadence is due to lack of pedaling skill. I used to grunt through low cadence racing and my legs are both very long and very strong. However the power meter doesn't lie. Don't do what the pros do because they're pro, do it because they perform for a living and others work to make them perform better. The optimum cadence for all is at least in the 90s due to the maximum rapidity that slow twitch muscles can fire without fatigue. Crank length is relative to leg length because longer legs have a shorter range of motion on 180s, which is more efficient. The science is all there, it just takes longer to research and write out than saying "not rly, YMMV."


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## squareback (Sep 19, 2011)

To the last four posters: 

When you say "SS or not doesn't make any difference while I tell you all about my calculations"

Then you just don't get it.

sent remotely


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## tigris99 (Aug 26, 2012)

Forget I tried to explain that accepted findings dont apply to everyone and that I didn't know humanity finally found that bicycles defy the laws of physics....

Try to help out and get morons that think cause someone that did some test that they read about now know everything.
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## nuffink (Feb 21, 2010)

JeffL said:


> Actually, as I think more about this there is one additional effect of changing crank arm length, besides fit. The longer crank arm should result in a faster top speed in the flats on an SS, all other things being equal. Assuming that your your top speed is limited by spin cadence, then for two bikes set up with the same effective gearing (the same Gain Ratio), the bike with the longer cranks will spin slower at the same ground speed. You ought to be able to climb the same on both bikes, while reaching a higher speed in the flats if you spin at the same cadence.
> 
> The difference is as significant as the tooth numbers stated above. These two 29ers have an identical Gain Ratio and should climb the same:
> 170mm crank, 32:18 gearing
> ...


It's an interesting idea in that (taken to its logical conclusion) you can increase top speed on the flat indefinitely by increasing crank length and reducing rear cog size with no penalty. This seems unlikely.
What limits my top speed is not exactly spinning out, more bouncing out. When my cadence gets to a certain point I start bouncing on the saddle. Concentrating on spinning in circles can allow me a few more revs but at some point the bouncing starts. 
I suggest that with the greater amplitude dictated by the longer cranks this bouncing will start at a lower cadence. Therefore, while I agree with your maths, I suspect my true maximum speed will be about the same with any crank length.


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## chomxxo (Oct 15, 2008)

The fallacy of misunderstanding is that we come to a YMMV truce. The hour record was set on 190s by a 6'7" guy. 6'2" Miguel Indurain once time trailed on 190s but he regularly raced 180s. If your duration is short with few hills (and you are tall), a lower cadence and longer cranks could be advantageous. A lower cadence will allow greater power output at the expense of quicker fatigue. Slightly lower cadence in mountain biking (85 instead of 90 rpm average) has to do with the steeper terrain with more obstacles. But it has nothing to do with personal preference.



nuffink said:


> It's an interesting idea in that (taken to its logical conclusion) you can increase top speed on the flat indefinitely by increasing crank length and reducing rear cog size with no penalty. This seems unlikely.
> What limits my top speed is not exactly spinning out, more bouncing out. When my cadence gets to a certain point I start bouncing on the saddle. Concentrating on spinning in circles can allow me a few more revs but at some point the bouncing starts.
> I suggest that with the greater amplitude dictated by the longer cranks this bouncing will start at a lower cadence. Therefore, while I agree with your maths, I suspect my true maximum speed will be about the same with any crank length.


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## mjduct (Jul 31, 2012)

I'm about 5'6 and I use 172 cranks on all my geared bikes and 175 on SS bikes.


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## nuffink (Feb 21, 2010)

chomxxo said:


> The fallacy of misunderstanding is that we come to a YMMV truce. The hour record was set on 190s by a 6'7" guy. 6'2" Miguel Indurain once time trailed on 190s but he regularly raced 180s. If your duration is short with few hills (and you are tall), a lower cadence and longer cranks could be advantageous. A lower cadence will allow greater power output at the expense of quicker fatigue. Slightly lower cadence in mountain biking (85 instead of 90 rpm average) has to do with the steeper terrain with more obstacles. But it has nothing to do with personal preference.


That's absolutely fascinating, however it has nothing to do with my post. 
May I suggest that when you feel the need for a rant either rant on freestyle or pick a post to rant at that is in some way pertinent to the rant.

Just a friendly suggestion.


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## chomxxo (Oct 15, 2008)

I wasn't ranting but contributing factually. Your post doesn't have as much relevance to the OP as does mine, and you're not being friendly. Cadence is a matter of skill and natural ability, not a POV or personal preference. Here, I'll share it again for review.

"The fallacy of misunderstanding is that we come to a YMMV truce. The hour record was set on 190s by a 6'7" guy. 6'2" Miguel Indurain once time trailed on 190s but he regularly raced 180s. If your duration is short with few hills (and you are tall), a lower cadence and longer cranks could be advantageous. A lower cadence will allow greater power output at the expense of quicker fatigue. Slightly lower cadence in mountain biking (85 instead of 90 rpm average) has to do with the steeper terrain with more obstacles. But it has nothing to do with personal preference."



nuffink said:


> That's absolutely fascinating, however it has nothing to do with my post.
> May I suggest that when you feel the need for a rant either rant on freestyle or pick a post to rant at that is in some way pertinent to the rant.
> 
> Just a friendly suggestion.


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## J.B. Weld (Aug 13, 2012)

squareback said:


> To the last four posters:
> 
> When you say "SS or not doesn't make any difference while I tell you all about my calculations"
> 
> ...


I was one of the last four and specifically mentioned that ss does make a difference.



tigris99 said:


> Forget I tried to explain that accepted findings dont apply to everyone and that I didn't know humanity finally found that bicycles defy the laws of physics....
> 
> Try to help out and get morons that think cause someone that did some test that they read about now know everything.
> Sent from my Nokia Stupid Phone using Tapatalk


Since I'm the only one who cited a study I suppose you're referring to me. I'm not sure how you came to the conclusion that I think I know everything, the paper I read contradicted what seemed logical to me and I found it interesting, nothing more. Like I said in my post.

I also think it's interesting that track racers rely on explosive power and acceleration more so than any other racing disciple and yet they use short crankarms. I'm not necessarily implying anything about single speed riding based on that, just noting.


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## chomxxo (Oct 15, 2008)

There are no definitive studies that show that crank length makes a difference, even Lennard Zinn admits this. However there are race performances that show evidence of benefit. Those familiar with track racing know the reason why they use short cranks: so they won't pedal strike and can keep cadence on the steep angle of the track.



J.B. Weld said:


> I was one of the last four and specifically mentioned that ss does make a difference.
> 
> Since I'm the only one who cited a study I suppose you're referring to me. I'm not sure how you came to the conclusion that I think I know everything, the paper I read contradicted what seemed logical to me and I found it interesting, nothing more. Like I said in my post.
> 
> I also think it's interesting that track racers rely on explosive power and acceleration more so than any other racing disciple and yet they use short crankarms. I'm not necessarily implying anything about single speed riding based on that, just noting.


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## nuffink (Feb 21, 2010)

chomxxo said:


> I wasn't ranting but contributing factually. Your post doesn't have as much relevance to the OP as does mine, and you're not being friendly. Cadence is a matter of skill and natural ability, not a POV or personal preference. Here, I'll share it again for review.
> 
> "The fallacy of misunderstanding is that we come to a YMMV truce. The hour record was set on 190s by a 6'7" guy. 6'2" Miguel Indurain once time trailed on 190s but he regularly raced 180s. If your duration is short with few hills (and you are tall), a lower cadence and longer cranks could be advantageous. A lower cadence will allow greater power output at the expense of quicker fatigue. Slightly lower cadence in mountain biking (85 instead of 90 rpm average) has to do with the steeper terrain with more obstacles. But it has nothing to do with personal preference."


Still fascinating. Still has nothing to do with my post. Maybe if you keep posting it the connection will become clear, like one of those 3d images that you can't see until you can.
Maybe not.


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## yesmkay (Sep 5, 2011)

Yes, 180>175 for torque, IMO. All things equal, two SS bikes, the one with longer cranks would provide more torque, but both would have a the same top speed at a given rpm.

That said, I've also had 180's for over 10yrs on my SS for this reason, but my next purchase though will be 175's for comfort reasons, and I don't expect to loose any significant performance due to marginally lower torque.


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## monogod (Feb 10, 2006)

cadence is determined by how many times the crank spindle rotates per minute and has nothing whatsoever to do with crank length. the longer the crank is the faster the foot has to move in order to complete the rotation comparative to a shorter crank at identical rpm. so in reality, at the same rpm the legs/feet will move FASTER on a longer crank vs. a shorter one.

additionally, the longer the crank is the higher the knee has to rise in order to crest the top of the stroke. this means more movement in both the knee and hip joins. the relevance is easy to understand by thinking of doing leg presses. is it easier to move the weight as the legs are more bent or more straight? subsequently a shorter crank should reduce risk of injury since the angle of joint flexion at both the knee and hips is less combined with a lower rotational speed at a given rpm than a longer crank. 

many years ago i also used 180's on my ss bikes, until i actually started researching it. subsequently i've moved to shorter cranks (170mm) on all my bikes whether road/gravel/mtb/ss. i've noticed no loss in power or climbing ability, but have noticed the hip pain/ache i would sometimes get has disappeared. just for kicks i've taken two bikes (one with 170mm the other with 175mm) geared identically with the same tyres and almost identical geometry to the trails to see if there was a seat of the pants difference in low speed mashing climbs and tough, steep, technical climbs. longer cranks provided no advantage.

in reality the amount of leverage that 5 or even 10mm has on usable torque is minimal at best and would really only come into play on very slow, mashing climbs where absolute torque output was needed and all that mattered. for everywhere else they're a liability IMO. more effort to spin at the same rpm as shorter cranks, more pedal strikes compared to shorter cranks, more abuse on hips/knees vs. shorter cranks.

and finally, there are many other lever arms and fulcrums in the drivetrain aside from crank arm length that simply go ignored but that can deliver the torque gains of longer cranks without the liability. for example, moving to larger chainrings and cogs. if you're running a 32/18 go to 39/22. you'll get the same gear ratio but you'll also get a longer lever arm at both the bottom bracket and rear hub. not to mention that as the chainrings/cogs get larger the rotational friction is reduced, so it's like a double whammy for more power.

perhaps it would also bear mentioning that studies like martin/spirduso (2001) and barrat/korff/elmer/martin (2011) showed no significant power variance in cranks ranging from 145-190mm; while the inbar study (1983) suggested the optimal crank length was 166mm. not a big deal since the variance in a 175mm was something like 1.24% IIRC.

so basically, if you want to run 180's then do it. but if you feel like you're getting an advantage just know it's all in your head and you're trading off general rideability for a miniscule super low rpm power increase. and if you want to run 175's then so be it. just get out there and ride! :thumbsup:

oh, and enjoy bashing the rocks and roots that my 170's clear... :lol:


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## chomxxo (Oct 15, 2008)

All the above points to crank length being relative to leg length and not a personal preference. If you don't have longer than average legs, there is no reason to use 180s as it's a liability. As tall pro racers continue to do so, the advantage of an increased range of motion and leverage helps balance out the weight disadvantage of the larger rider. Taller cyclists may be less prone to having fast twitch muscles and so a slower cadence may be more suitable.


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## jeff (Jan 13, 2004)

It should be noted, again, that the first proponants of the 29" wheel firmly believed in shorter crank lengths to overcome the added mass that came with the new size. Easier to spin up to speed they felt, and still do. I had been on 180's SS for 7 seasons prior to adopting the 29"er. I drank the koolaid and built my 1st one with 170's. It Sucked. Felt like I was dragging a piano. I just couldn't torque the climbs like I use to. Once the 180's went on, the bike woke up for me. I'm still on 180's geared and SS. I have many friends still running 170's and loving it. 

[email protected] the science. Run what feels good.


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## Mr. 68 Hundred (Feb 6, 2011)

jeff said:


> It should be noted, again, that the first proponants of the 29" wheel firmly believed in shorter crank lengths to overcome the added mass that came with the new size. Easier to spin up to speed they felt, and still do.
> 
> [email protected] the science. Run what feels good.


There's Ken Ham science--the people arguing for shorter cranks with all else being equal.

And then there's Lawrence Krauss science.


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## chomxxo (Oct 15, 2008)

Mr. 68 Hundred said:


> There's Ken Ham science--the people arguing for shorter cranks with all else being equal.
> 
> And then there's Lawrence Krauss science.


...Neither of which would know what the hell you're talking about if you asked them their opinion on 180s vs 175s. For the love of god or Richard Dawkins, please don't bring up physics.

Here is a candidate for 180mm cranks. I am around the same size. Odds are, you aren't. If there's anybody that suffers from confirmation bias, it would be singlespeeders 

Pro bike: Johan Vansummeren's Cervélo R5 | Cyclingnews.com


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## Hairnet (Jul 23, 2013)

"197cm (6'5") frame manages to fit on to a stock 58cm " 

what??? Is he all leg?


edit: Looking at photos. Yes, yes he is all leg.


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## Mr. 68 Hundred (Feb 6, 2011)

chomxxo said:


> ...Neither of which would know what the hell you're talking about if you asked them their opinion on 180s vs 175s.


Metaphor


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## DrDon (Sep 25, 2004)

I'm 5'11" with a 35in inseam. I've 180s on my 29ers and 175 on my road and 27.5. I'm strong and I believe can produce a good amount of torque but it's wattage that separates the men and women from the boys and girls. 


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## Sandrenseren (Dec 29, 2011)

Wattage is indeed the name of the game. 

Torque only makes sense if combined with a speed as torque * rpm = watt.

Yes, longer crank arms will allow you to deliver a higher torque, but at the same time your feet will have to travel a longer distance, which will probably mean that you'll deliver that higher torque at a slightly lower rpm - essentially resulting in the same power output as before.

Pick a crank length than works well with your leg size and stick with that. If you want different torque numbers mess around with your gearing instead rather than changing to crank arms that might not suit your legs.


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## monogod (Feb 10, 2006)

jeff said:


> It should be noted, again, that the first proponants of the 29" wheel firmly believed in shorter crank lengths to overcome the added mass that came with the new size. Easier to spin up to speed they felt, and still do. I had been on 180's SS for 7 seasons prior to adopting the 29"er. I drank the koolaid and built my 1st one with 170's. It Sucked. Felt like I was dragging a piano. I just couldn't torque the climbs like I use to. Once the 180's went on, the bike woke up for me. I'm still on 180's geared and SS. I have many friends still running 170's and loving it.
> 
> [email protected] the science. Run what feels good.


really? because i was among the first wave of proponents of the 29" wheel and i firmly believed just the opposite in that more torque was needed to bring the bigger wheels up to speed (as did MANY others). the thinking was the longer lever arm of the increased crank length would overcome the increased resistance of the larger wheel. however, once i got all scientifical about it the error of this train of thought became clear and i simply adjusted my gearing.

demonstrable, repeatable science is just that and has consistently shown no appreciable power benefit from 180's over 170's. actually, none from 145-190. but hey, if it makes you feel like a boss to run long cranks then rock them! :thumbsup:


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## Feldybikes (Feb 17, 2004)

monogod said:


> cadence is determined by how many times the crank spindle rotates per minute and has nothing whatsoever to do with crank length. the longer the crank is the faster the foot has to move in order to complete the rotation comparative to a shorter crank at identical rpm. so in reality, at the same rpm the legs/feet will move FASTER on a longer crank vs. a shorter one.


Ok, I'm with you.



monogod said:


> and finally, there are many other lever arms and fulcrums in the drivetrain aside from crank arm length that simply go ignored but that can deliver the torque gains of longer cranks without the liability.


Curious...



monogod said:


> for example, moving to larger chainrings and cogs. if you're running a 32/18 go to 39/22. you'll get the same gear ratio but you'll also get a longer lever arm at both the bottom bracket and rear hub.


Agree that the ratio is essentially the same because both levers are longer by about the same proportion.



monogod said:


> not to mention that as the chainrings/cogs get larger the rotational friction is reduced


Ok, close-enough. But the next conclusion...



monogod said:


> so it's like a double whammy for more power.




Why would you think having two longer levers is inherently better? Smaller cogs are, to some extent, less efficient than larger ones (though it matters a lot more the smaller you go) because of frictional losses, but there's nothing intrinsically better about two longer levers than two shorter ones.


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## JeffL (Jan 25, 2009)

Feldybikes said:


> Why would you think having two longer levers is inherently better? Smaller cogs are, to some extent, less efficient than larger ones (though it matters a lot more the smaller you go) because of frictional losses, but there's nothing intrinsically better about two longer levers than two shorter ones.


This.

The claim that the larger chainring/cog gives you two longer lever arms and therefore is an advantage is ignoring a basic tenet of physics. The two lever arms are not working together - they are working against each other. For each force there is an equal and opposite force. It's true that the larger cog means a larger moment arm to pull the wheel in a forward direction. But, at the same time there is an equal and opposite force along the chain pulling the front chainring backwards, opposing the forward force and motion. The larger moment arm at the chainring, that the chain's rear-ward force is being applied to, exactly cancels the "advantage" of having a larger cog at the rear.

Friction may change when the chainring/cog sizes are changed, but mechanical advantage does not change, at all, if the gear ratio is held constant.


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## monogod (Feb 10, 2006)

...


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## theMeat (Jan 5, 2010)

JeffL said:


> This.


Exactly
and a longer crank has more torque and slower cadence is a matter of fact & physics, not opinion. Of coarse a person's proportions matter. As well as bike's geo/bb height, terrain, and rider's bunny hopping and other skills.


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## monogod (Feb 10, 2006)

theMeat said:


> Exactly
> and a longer crank has more torque and slower cadence is a matter of fact & physics, not opinion. Of coarse a person's proportions matter. As well as bike's geo/bb height, terrain, and rider's bunny hopping and other skills.


a longer crank doesn't have any cadence (higher or lower) in and of itself as it is an inanimate object. likewise it does not have, in and of itself, more torque as a crank arm accomplishes nothing until acted upon by an outside force. perhaps i missed it, but i don't recall anyone thus far expressing the opinion that a longer crank arm would not result in more leverage. a bike crank is a second class lever and as such the longer the arm the more leverage is applied to the resistance/force. however, a bicycle drivetrain is comprised of much more than simply one class 2 lever so there is more to take into consideration.

cadence (pedal rate) is determined by how many times per minute the crank spindle rotates and is determined independent of crank length. this is why a cadence sensor can be placed anywhere along the crank from the base to end. however, at a given cadence the foot itself (pedal speed) will travel faster on a longer crank than a shorter one. in other words, it's the actual speed of the foot (Xmm/sec) that changes with crank length rather than the cadence itself. this is why a lower cadence on longer cranks feels the same as a faster cadence on a shorter crank.

additionally, as crank length increases the knee must bend more. as a result the foot must pass farther past TDC before power can begin to be most effectively applied. thus, the longer the crank the more ON/OFF (and subsequently less smooth) the cadence becomes. as a result it becomes more difficult to pedal smoothly under load and power/efficiency drops. think of it this way: can more weight be lifted doing a full squat or half squat? half, of course. the longer the crank, the more the stroke mimics a full squat.

by gearing down a tad and moving to shorter cranks (170 vs 180) one can not only climb better (less ON/OFF effect) but also becomes more efficient and capable of producing more sustainable power output for a longer period of time when spinning. for example, the gain ratio of a singlespeed with 29x2.1 tyres, 170 cranks, and 32-19 gearing is 3.5; which is identical to that of 29x2.1/180/32-18. so yes, the pure mechanical advantage of a longer crank can be nullified through gearing when using a shorter crank; and comes with it the benefit of higher sustainable power output.

notwithstanding being in the third standard deviation of height (perhaps mid-second if one is "all legs") longer cranks are only a benefit if the only concern is absolute maximum out-of-the-saddle torque output at very low speed, in which case the longer the better. heck, run 200mm+ cranks if maximum leverage at the fulcrum is the only concern/desire. but in real world singlespeed riding for pilots within 1-1.5 standard deviations of height shorter cranks simply make much more sense for the plethora of reasons cited in the thread.

and no, a person's proportions do not begin to matter unless they are well outside the standard deviation. i don't say so, repeated studies (some of which were previously cited) say so. many studies have also implied that even at 2+ standard deviations there is no significant benefit to longer cranks.

i'm admittedly curious what bunny hopping, other skills, bb height, and terrain have to do with torque output variance between longer vs. shorter cranks. please expound.

as an aside, "coarse" does not mean what you think it means.


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## Hairnet (Jul 23, 2013)

Now that all the arm chain physics has been dished out can we get back to post #1?
"Do what feels best, that will make you stronger/faster."


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## slohr (May 22, 2008)

I would have to add to that for older riders, especially ones with back issues, that crank length can be important. You can develop great load on the SS, and that minimum hip angle at the top of the pedal stroke is important to be aware of. If it is too small, it can lead to increasing fatigue for the hips (once again, for older riders with more scaring and range of motion issues), leading to strain on the lower back. I would have to agree to go with a crank length relative to leg length.


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## theMeat (Jan 5, 2010)

monogod said:


> :rant: ...blah... blah... blah...


Aside from the first few words which explain cadence, thanx man, and the last few that have you wondering about bunny hopping/clearing obstacles as if that shouldn't be brought up on a crank length thread, the rest i did not read because i know it's all verbal masturbation simply because you're not in agreement with members, and this time the laws of physics also. Unless the faster cadence has an e=mc2 effect idk, leave that to you. Don't need a study to tell me what's real and factual and you trying to make people drink your cool aid once again is see throu bs. At least that's been my experience so far.
Which has me wondering just how much bs you throw. Do you even ride?


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## theMeat (Jan 5, 2010)

Hairnet said:


> Now that all the arm chain physics has been dished out can we get back to post #1?
> "Do what feels best, that will make you stronger/faster."


Agreed, and sometimes what feels best is what you get most used to or conditioned for. When I mtb alot with 175mm, and get on my road bike with 165s, I feel like my feet are turbo charged and much smother going around. As compared to being able to mash better with longer cranks. On a mtb ss road convert i experimented with both 165 and 175. While I liked being able to corner harder with the short cranks, as well as faster cadence on the flats, the added length/torque was missed on trail, as well as the added control and balance overall


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## Sandrenseren (Dec 29, 2011)

theMeat said:


> the rest i did not read because i know it's all verbal masturbation simply because you're not in agreement with members, and this time the laws of physics also.


If you didn't read it, how do you know it's not in agreement with the laws of physics?



theMeat said:


> Which has me wondering just how much bs you throw.


..and it's not BS to rant about stuff you didn't bother to read?


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## theMeat (Jan 5, 2010)

Sandrenseren said:


> If you didn't read it, how do you know it's not in agreement with the laws of physics?
> 
> ..and it's not BS to rant about stuff you didn't bother to read?


when you're right you're right


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## monogod (Feb 10, 2006)

theMeat said:


> Aside from the first few words which explain cadence, thanx man, and the last few that have you wondering about bunny hopping/clearing obstacles as if that shouldn't be brought up on a crank length thread, the rest i did not read because i know it's all verbal masturbation simply because you're not in agreement with members, and this time the laws of physics also. Unless the faster cadence has an e=mc2 effect idk, leave that to you. Don't need a study to tell me what's real and factual and you trying to make people drink your cool aid once again is see throu bs. At least that's been my experience so far.
> Which has me wondering just how much bs you throw. Do you even ride?


wow, you have some really deep-seated emotional and cognitive issues that become more apparent with each of your vitriolic anti-mono rants. rants which, btw, have absolutely zero bearing on this topic.

didn't read it yet insist it's all wrong? uh... ok. ut: but since you brought it up, why don't you read it and address specifically what is in disagreement with laws of physics by illustrating precisely how and why. otherwise stfu.

the fact that you dismiss/disregard well respected and frequently cited studies illustrates the depth of your profound ignorance and ineptness at participating in such discussions.

yeah, i ride a bit though i don't get in 10k a year like i used to and only log about 6k annually due to academic/professional commitments. but again, what relevance does that have to this subject matter, captain off-topic?


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## monogod (Feb 10, 2006)

Hairnet said:


> Now that all the arm chain physics has been dished out can we get back to post #1?
> "Do what feels best, that will make you stronger/faster."


becoming stronger/faster WAS the whole point of it.


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## monogod (Feb 10, 2006)

Sandrenseren said:


> If you didn't read it, how do you know it's not in agreement with the laws of physics?
> 
> ..and it's not BS to rant about stuff you didn't bother to read?
> 
> ...


oh yes he is! :lol:


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## Hairnet (Jul 23, 2013)

monogod said:


> becoming stronger/faster WAS the whole point of it.


For sure. I think these crank length threads are almost as bad as helmet threads and gun debates, so I pop in "do what feels best."


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## monogod (Feb 10, 2006)

Hairnet said:


> For sure. I think these crank length threads are almost as bad as helmet threads and gun debates, so I pop in "do what feels best."


hahahaha... indeed.

i'd suggest there's also a marked difference between a thread seeking random opinion on what feels best compared to a discussion on what is the demonstrably preferred option and why.


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## theMeat (Jan 5, 2010)

monogod said:


> why don't you read it and address specifically what is in disagreement


Did read a bit more, and it turns out op Samdren was right again, about you not disagreeing with the laws of physics, you're only trying to appease it while you trick it with some intellect. Can't have your cake and eat it to, Can't start a post with you're not arguing nor has anyone claimed that a longer crank arm would not result in more leverage, and then sum up the post with "if you think it's better it's all in your head". It's one or the other. How does this happen to a person?


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## monogod (Feb 10, 2006)

theMeat said:


> Did read a bit more, and it turns out op Samdren was right again, about you not disagreeing with the laws of physics, you're only trying to appease it while you trick it with some intellect. Can't have your cake and eat it to, Can't start a post with you're not arguing nor has anyone claimed that a longer crank arm would not result in more leverage, and then sum up the post with "if you think it's better it's all in your head". It's one or the other. How does this happen to a person?


not so quick, sparky. you said this post was nothing but, and i quote, "_all verbal masturbation simply because you're not in agreement with members, and this time the laws of physics also_". so either elucidate specifically how each point within that post is not in agreement with the laws of physics or publicly retract your statement.

regarding your "_have your cake_" conundrum:

yes a longer arm results in more leverage. i also used qualifying words like "miniscule", "minimal at best", "no appreciable benefit", and so forth. a number being larger on paper does not necessarily equate to being an appreciable difference. even more so when the lever arm discrepancy decreases.

so it's not someone trying to have it both ways as much as it is a case of you being incapable of comprehending what you're reading combined with your profound inability to grasp and reconcile both concrete and abstract concepts/thought.


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## theMeat (Jan 5, 2010)

monogod said:


> so either elucidate specifically how each point within that post is not in agreement with the laws of physics or publicly retract your statement.


I'm pretty sure you're not the boss of me but no worries, your popularity contest is safe, I allsready did that mr reading comprehension.



theMeat said:


> Did read a bit more, and it turns out op Samdren was right again, about you not disagreeing with the laws of physics, you're only trying to appease it while you trick it with some intellect.


Hey, Also pretty sure it was you, justa few days ago, in your last popularity contest ?, telling members that they should learn how to ride if their equipment has them bashing obstacles? Should i be surprised that this time you're saying the equipment matters?


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## JeffL (Jan 25, 2009)

You two need to get a room...


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## Mr. 68 Hundred (Feb 6, 2011)

My better judgment says keep walking. I seldom listen to it.

List of variables which dictate ideal crank length. I suspect that no two rides/days net the same values for each variable.

1)Body size/shape
2)BB height
3)Terrain
4)Wheelbase
5)Gearing
6)Fixie or not
7)Power output/fitness
8)Length of ride
9)Preferred cadence
10)Handlebar width
11)Bar ends or not
12)Suspension or not
13)Racing or not
14)Which 'feels' best
15)Clipless or flats
16)Tires
17)Weather

I probably missed a few.


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## monogod (Feb 10, 2006)

theMeat said:


> ~off-topic, delusional, vitriolic ranting snipped~


that you've shat upon and derailed yet another thread with your obsessive man-crush is duly noted. however, there's no reason everyone should have to suffer just because you're tortured by mental illness.

so please... pretty please... with sugar on top... would you do us all a favor and confine your contributions to being at least remotely related to the topic at hand in lieu of your signature rage-driven pontifications of psychotic vituperation?

thx.


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## monogod (Feb 10, 2006)

Mr. 68 Hundred said:


> My better judgment says keep walking. I seldom listen to it.
> 
> List of variables which dictate ideal crank length. I suspect that no two rides/days net the same values for each variable.
> 
> ...


so these 17 (perhaps more) variables which seldom, if ever, have consistent values upon which to base calculations are used to determine correct crank length?

interesting concept indeed...


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## Mr. 68 Hundred (Feb 6, 2011)

monogod said:


> so these 17 (perhaps more) variables which seldom, if ever, have consistent values upon which to base calculations are used to determine correct crank length?


Thus making for a very difficult calculation, correct? Rube Goldberg-esq perhaps.

Satire


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## theMeat (Jan 5, 2010)

mr. 68 hundred said:


> thus making for a very difficult calculation, correct? Rube goldberg-esq perhaps.
> 
> satire


lol


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## monogod (Feb 10, 2006)

Mr. 68 Hundred said:


> Thus making for a very difficult calculation, correct? Rube Goldberg-esq perhaps.
> 
> Satire


your humor was appreciated and responded to in kind.

levity


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## Mr. 68 Hundred (Feb 6, 2011)

I would like to volunteer my services to test the various hypotheses discussed above. I of course need funding to carry out this research.

My initial proposal is that I'll need 160, 170 and 180 cranks which I'll ride alternately in the southwest for the remainder of the summer. I need a new bike too. And a stipend with specific additional monies allotted for beer. Who's willing to donate to this important cause? It could change your life.


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## theMeat (Jan 5, 2010)

monogod said:


> :madmax:.... :madman:.... :rant:


 it seems you missed something mr coherence https://encrypted.google.com/search...br.com&rls=org.mozilla:en-US:official&spell=1 but my ot (on topic) question was "snipped", hmmm, So which one ?. Was it last week where you told members they need to learn to ride if they're bashing obstacles. Or this weeks where this time the equipment is key? Just a question. which is relevant and imo crystal not only to this topic, but to all threads you participate in since at first you do come across as smart, and members might actually take you for sincere and kind as well, so don't you think we should be informed of your willingness/motivation to say anything that gets you a foot up on your latest you know everything thread. As well it makes total sense that you would put the words sig, and rage driven ... blablabla in the same sentence. In your honor for a while V V V


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## Guest (Jul 18, 2014)

The easiest thing to do is buy one 180 and see if your fit/power preception changes with one different crank.


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## monogod (Feb 10, 2006)

theMeat said:


> it seems you missed something mr coherence https://encrypted.google.com/search...br.com&rls=org.mozilla:en-US:official&spell=1 but my ot question was "snipped", hmmm, So which one ?. Was it last week where you told members they need to learn to ride if they're bashing obstacles. Or this weeks where this time the equipment is key? Just a question. which is relevant and imo crystal not only to this topic, but to all threads you participate in since at first you do come across as smart, and members might actually take you for sincere and kind as well, so don't you think we should be informed of your willingness/motivation to say anything that gets you a foot up on your latest you know everything thread. As well it makes total sense that you would put the words sig, and rage driven ... blablabla in the same sentence. In your honor for a while V V V


your fixation with me and pathological obsession of chronicling the minutiae of my MTBR activity is starting to be of genuine concern. you are clearly mentally unstable, and if you continue in this vein of incessant e-stalking i will request assistance from the mods.

yet again your rambling post has contributed nothing of substance to the thread and is simply vituperative, psychotic ranting. your flagrant display of mental illness was cute at first but has gotten old. so in the name of freud, you bucket of crazy, please either take your meds and stay on topic or stfu.


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## theMeat (Jan 5, 2010)

monogod said:


> your fixation with me and pathological obsession of chronicling the minutiae of my MTBR activity is starting to be of genuine concern. you are clearly mentally unstable, and if you continue in this vein of incessant e-stalking i will request assistance from the mods.
> 
> yet again your rambling post has contributed nothing of substance to the thread and is simply vituperative, psychotic ranting. your flagrant display of mental illness was cute at first but has gotten old. so in the name of freud, you bucket of crazy, please either take your meds and stay on topic or stfu.


If i ask you a third consecutive time could I please have an answer to my on topic question, without blabber about not being on topic as a response? "pretty please.....with sugar on top"....lol 
It's obvious you try to keep it so anyone with an opposing view thinks twice before chiming in, but threatening me with the mods after what you dish out is low and weak


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## jl (Feb 23, 2004)

Wow, this thread has really established some traction. I just wanted to add another reply to see if anyone else on the interwebz can see the difference.

Here's 180s.









Here's 175s.









For me, the joy feels the same...


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## theMeat (Jan 5, 2010)

^nice, aside from bugs I like the 180s better. Hope your pooch was along for that ride too


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## Guest (Jul 18, 2014)

jl said:


> Wow, this thread has really established some traction. I just wanted to add another reply to see if anyone else on the interwebz can see the difference.
> 
> Here's 180s.
> 
> ...


Clearly, the 175s are causing some localized form of Global Warming (or the inverse, or there is no correlation). Maybe dogs are causing Global Cooling. Wait, what size is the dog? Couldn't the dog keep up with you on 180s? Does the "Crank Color" factor into your Joy somehow?


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## J.B. Weld (Aug 13, 2012)

172.5's are the sweet spot, better rollover than 170's and more flickable than 175's.


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## Feldybikes (Feb 17, 2004)

pfft. If you actually measure 172.5s you'll find they're more like 172.


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## theMeat (Jan 5, 2010)

Feldybikes said:


> pfft. If you actually measure 172.5s you'll find they're more like 172.


This ^

And when you compare 170mm to 180 it's at least twice the difference then comparing 175 to 180. With 165 who knows, could be 3 times


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## Hairnet (Jul 23, 2013)




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## Mr. 68 Hundred (Feb 6, 2011)

monogod said:


> levity


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## monogod (Feb 10, 2006)

fair enough. i think it means humor, frivolity, lightheartedness, jocularity. 

what do you think it means?


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## theMeat (Jan 5, 2010)

monogod said:


> what do you think it means?


Think for some people it means nothing while others are happy to make it up as they go along. You know, as it fits their needs. That could come in handy when you need a word to try and confuse and make people think enough, so you can change the subject without them realizing that you constantly rant about doing just that. could work ya know

Great movie btw, and fun for all ages.

look at that ^, it's working already, lol


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## Mr. 68 Hundred (Feb 6, 2011)

monogod said:


> what do you think it means?


I agree with you, I've just been wanting to use that movie clip for a VERY long time so I kind of had to make my own opportunity. In my defense, Princess Bride clips are always funny.


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## monogod (Feb 10, 2006)

Mr. 68 Hundred said:


> I agree with you, I've just been wanting to use that movie clip for a VERY long time so I kind of had to make my own opportunity. In my defense, Princess Bride clips are always funny.


ah, exemplative rather than repudiative. well played, sir. :thumbsup:

your defense is not only accepted but concurred. in fact, i dropped that very line in post #49 - though in his case if it was dropped at each opportune moment it would become monotonous rapidly. :lol:

btw, forgot to mention that your "17 ways" post actually brought rube to mind and spurred reminiscence of a computer game series called "the incredible machine" that i haven't played for years. my guess is you've played it. if not, download it. as with lemmings, it's a must-have for any r.g. fan.


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