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PostPosted: Mon Nov 12, 2007 11:31 am 
Anglian AEC / Prison Ship Captain
Anglian AEC / Prison Ship Captain
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Joined: Thu Mar 15, 2007 1:26 am
Posts: 6045
Location: LOWESTOFT the worlds smallest bore fest
im 5'7 and i find 175mm just right buddy but i like the same on road bikes not the 172.5 that other like :D hell stick wth what you know and you cant go far wrong buddy :wink:


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PostPosted: Mon Nov 12, 2007 1:48 pm 
retrobike rider
retrobike rider

Joined: Sun Sep 23, 2007 11:22 pm
Posts: 7305
Location: Hove
This is a very good question. Unfortunately economics argues in favour of standardising everything and most consumers can’t be bothered with thinking about options, so effectively we all get pushed towards 175 for mountain biking, even though it doesn’t deal with the differences in peoples legs and it’s barely any different from what had been established for road biking. Cadence comfort is paramount for road, but much less so for mtb where you need short sharp bursts of power, so I suspect the difference is too little.

Clearly applications like singlespeed where power is most important need longer cranks, but by the same token I would argue that most women should use 180, and indeed men who find climbing a weakness should give it a try.


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PostPosted: Mon Nov 12, 2007 2:39 pm 
BoTM Winner / retrobike rider
BoTM Winner / retrobike rider
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Joined: Thu Nov 23, 2006 2:12 pm
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my Cooks RSRs on the Yeti are 181's but I don't like them offroad - they seem to catch more on rocks/roots etc than 'normal' 175's.

I used to use 180mm Dura-ace on my TT bike BITD (with a single 55 ring) and loved them!


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PostPosted: Mon Nov 12, 2007 4:21 pm 
East Midlands AEC
East Midlands AEC
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Joined: Thu Oct 05, 2006 7:45 pm
Posts: 15067
Location: Derby, UK
does the extra 5mm make that much difference? I'm no good at maths, but using schoolboy formulae the circle circumference of the pedal stroke is 110cm with 175's and 113cm with 180's that's less than 3% difference. I suppose the extra 5mm will catch rocks that are 5mm higher than others...

what do I know? :roll:


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 Post subject:
PostPosted: Mon Nov 12, 2007 5:30 pm 
Old School Grand Master
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Joined: Thu Jan 25, 2007 9:37 am
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A 3% increase in torque for no extra effort is nothing to be sniffed at :wink:

Primarily i'd imagine the real advantage comes from wear to the knee.


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PostPosted: Mon Nov 12, 2007 6:24 pm 
Gold Trader
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Joined: Sat Jul 29, 2006 11:14 pm
Posts: 3830
Location: Somerset
My knees are fine, but my ankles have very little movement in them and almost no strength (due to tallipies as a child, hence stick legs), so I use 170mm on and off road because 175's make me turn a circle bigger than I naturally want to, therefore gicing me a kind of biopacey feel.

I only found this out by accident as my MTB's were always 175 and road bikes 170 as standard and I found the pedalling action on my road bike much more comfortable. So went 170 across the board.

If you can try a few lengths and see what is best for you, I am glad I did!


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 Post subject:
PostPosted: Mon Nov 12, 2007 7:39 pm 
Old School Grand Master
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Joined: Sat May 20, 2006 2:56 pm
Posts: 4776
Location: No brakes? Way to commit soldier.
One difference that isn't often mentioned is that assuming that you always have the same leg extension when you peddle, longer crank arms lower your saddle height, reducing your centre of gravity and making you more stable... in theory anyway.

Wonder if anyone has ever tested this?


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 Post subject: long cranks
PostPosted: Mon Nov 12, 2007 8:28 pm 
Retro Guru
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Joined: Mon Oct 08, 2007 7:47 pm
Posts: 1743
Location: Fairfax, California
I use 180mm cranks on my MTB, and 175mm on my road bike-I'm just over 6 feet tall. If you have an inseam greater than 33" you should be able to turn 180's easily, and here in my neighborhood where we have nothing but hills I can really feel the difference in the woods-however, on the road where RPM is more important I prefer the shorter 175mm arms. Russell pointed out that you must lower the saddle slightly with the longer crank arms, and it's important to remember to do this, as you can hurt your knees otherwise.


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PostPosted: Mon Nov 12, 2007 8:42 pm 
East Midlands AEC
East Midlands AEC
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Joined: Thu Oct 05, 2006 7:45 pm
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Location: Derby, UK
do shimano do 180's lower than XTR in the range? And I mean old stuff (from the 90's) not new.


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 Post subject:
PostPosted: Mon Nov 12, 2007 8:52 pm 
Old School Grand Master
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Joined: Thu Jan 25, 2007 9:37 am
Posts: 4916
orange71 wrote:
do shimano do 180's lower than XTR in the range? And I mean old stuff (from the 90's) not new.


Doubt it. In '94 LX only came in 170mm. Maybe XT in the late '90's?

EDIT: That's a big porkie pie :lol:

http://www.bikepro.com/products/shimano ... table.html


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