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Crank Arm Length...


DRIVETRAIN
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....after my massage last night we went thro' some books...my inseam measurement dictates a crankarm length of 172 up to 175.

 

I am currently riding a 170 and with the new groupset I am advised to go for 172 minimum. Now when you buy a bike or go for an upgrade are they not supposed to "advise / tell you what crankarm length you supposed to have instead of playing around with saddle heights / reach to the bars etc ?????

 

Also on going for set-up's to "someone who know's what they doing" since these oke's praises are  

 
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Big%20smile

 

Sorry guys something went wrong there...asince these okes praises are sung from on high I believe if they knew what they were doing with their measurements they supposed to tell me that 170 was too short????

 

I got my info from books on the Tour de France Pro's like Mercx / Hinualt etc.....these measurements were taken on your height/inseam....

 

 

"DTThumbs%20Up"
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Go do a search on the hub, there was a posting a while ago on bike fitment, and I recall one particular guy from your area (Gautengeleng) who was recommended by quite a few poeple to help with bike setup.

 

From what I've read & been told, longer cranks will enable you to push a bigger gear, i.e. more power, but shorter cranks will enable you to ride at higher cadences a bit easier.

 

So crankarm lenght can also be influenced by what type of pedalling you prefer, "mashing" a big gear, or spinning at higher cadences alla LA.
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normally they will match the crank arm length t othe size of the bike. I think 54/56 is 170 56/58 is 172.5 58/60 is 175.

I dont think crank arm length is that critical compared to the rest of the setup. I have always had a 170 but went for a 175 on my last bike - not a huge difference.

..of course its easy to adjust your seat height, expensive to adjust your crank length.
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Big%20smile

 

I agree on the expense but since I am upgrading I might as well get the right thing: True they mention bigger gears but personally I prefer high cadence ..... I have a 56 & it came with a 170 which I must add have been comfy with all this time...no real complaints.

 

Perhaps then the best thing will be to stay with the 170 ???? If that's what you saying ..

 

"DTThumbs%20Up"

 
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Hi Drivetrain

 

Like just about everything else in our fine sport, recommended crank length seems to be about fashion as much as function.  It seems to me that over the last ten years or so, the "norm" has been for longer crank arms.

 

The other fashion has been towards spinning higher cadences.  Now I mention this because it is easier to spin faster with shorter crank arms, so these two fashions kind of contradict one another.

 

Now, as for your measurements, inseam is more relevant than height, because it is only leg length that dictates crank length.

 

After all of that, if you are riding 170mm cranks and are happy with that crank size stay with it.  With shorter cranks you are foregoing some leverage but gaining increased ability to spin.  If spinning is of more use to you than strength, leave things as they are.  If you are more of a masher than a spinner, then consider changing to longer cranks.

 

One more thing - although going to shorter cranks is easy on your body, riding longer cranks forces your joints to go through larger changes of angle, so it is possible to stress your body by riding too large cranks.
bikemonster2006-10-10 01:40:48
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If the crank length increases and

the pedaling frequency remains the same, the muscles will contract over a

longer distance as a consequence of a larger circular movement of the legs.

However, this should take place within the same time span, which means that the

contraction speed of the muscles will increase. At a higher contraction speed,

the extent in which power can be exercised in the muscles will decrease

 

TNT12006-10-10 01:40:26

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All I know is there are alot of cranky people on the Hub and I don't think it's got anything to do with how long their arms are. LOL

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The argument against 'too large lengthed cranks' is just that, dont let it scare you away from 'longer cranks that fit'

I was always very happy with the 170s, all the fitting guides said I should get a 175 (and I'm more of a 'grinder' than a spinner). I didn't really notice any difference between the two while spinning, but climbing hills out of the saddle definitely improved with the extra leverage - that I could feel.

 

Speak to whoever set up your bike about the crank length. I would also say maybe get the 172.5 as a compromise between what fits you (175) and what you are used to (170).
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Big%20smile

 

Gumpole / WW..just spoke to Arran on bike set-up's you referred to..turns out that the 172 will not be a bad option as the leverage I'll get will be greater, however it would not adversly affect my riding in high cadence per say....he is 189 in height & he opted for something higher than 175 and he is happy with it...

 

choices choices.....

 

'DT Thumbs%20Up"
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On my racing bike I have 172.5, but on my training bike I have 175. I can't feel a diference, no knee problems to speak of sofar, if you think about it, it is only 2.5mm, that is about this long [ ].

 

Maybe someone can tell me if I should have the same length, or if you can just eliminate the difference by adjusting seat height.
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Why dont you try and get a loan crank set, and go for a ride to get a feel for the longer crank set, do some intervals on a flat section and a nice long hard climb, and see for yourself if you can notice any difference.

 

I recently baught a second hand TT bike, my road bike has 172.5 cranks, and the TT bike has 175, the biggest difference I could notice was that I feel more comfortable pushing a bigger gear on the flats with the 175mm cranks, but I can also feel that it's a bit more difficult to sit and pedal on steaper climbs with the longer cranks. But that's me. At the end of the day, you need to be comfortable with your setup, if your comfortable, you'll be efficient IMHO.
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On my racing bike I have 172.5' date=' but on my training bike I have 175. I can't feel a diference, no knee problems to speak of sofar, if you think about it, it is only 2.5mm, that is about this long [ '].

 

Maybe someone can tell me if I should have the same length, or if you can just eliminate the difference by adjusting seat height.

 

Just remeber that its 2.5mm on either side, so combined bigger diameter is 5mm [   ] Wink
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Big%20smileBig%20smile

 

I think saddle height is so minimal that if at all that. But speaking of which I may have to adjust mine say down 1mm if I feel a change from what I'm currently using to that with the 172.5 I will have on soon....

 

I get the idea here that like everything else that different strokes for different folks...some said 11-23..others said 12-23 cassettes....for various reasons mostly based on "their" experience & riding style....for races with extreme hills 12-25....

 

Be that as it may I am looking forward to riding with the new groupset and now especially with the change to the longer crank..watch this space..

 

"DTThumbs%20Up"  

 

 
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This should interest you guys! I ride a 52 frame and i have 175 cranks!! Ive had 170 & 172.5 and the diffirence is minimal.  I still spin the hell out of my 175 cranks!! Won't easily go back to shorter ones!!

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