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Crank Arms 165mm vs 170mm

Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

Crank Arms 165mm vs 170mm

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Old 02-12-18, 02:54 PM
  #26  
jillesoom
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i know this is like a decade ago, but still... best awnser
Originally Posted by phidauex View Post
5mm isn't much, but a 165mm crank has 3cm less travel per revolution than a 170mm, and that is a noticable amount.

Also, a bike with 70mm of BB drop, and reasonably long platform pedals (shoe to shoe outer measurement of around 378mm) will strike at 25.6 degrees with 175mm cranks, 26.8 degrees with 170mm cranks and 28 degrees with 165mm cranks.

velocity = sqrt(9.8 * radius * tan (lean angle)), in meters, seconds and degrees.

That puts your max turn speed around a 12m radius at 16.75, 17.24 and 17.69 mph for 175, 170 and 165 mm cranks, respectively. Sure, 5mm isn't much, but that is a meaningful change in max turn speed, nearly 1mph between 175 and 165, all else being equal. You'd have to lower your Q by 20mm to equal the change achieved by lowering crank length by 5mm. Both methods will have the same effect, but crank length or BB drop gets you more turning speed per mm of change than Q.

*puts away his engineering calculator*

peace,
sam
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Old 02-12-18, 03:38 PM
  #27  
EchoBravo
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I was told there would be no math in this thread.
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Old 02-12-18, 04:40 PM
  #28  
Altimis
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Thanks for necro a decade ago thread up for interesting "math", that good read.

Saved.
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Old 02-13-18, 09:45 AM
  #29  
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I just got a cheap Lasko 165mm crank. Luving it so far!
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Old 02-13-18, 11:03 AM
  #30  
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Originally Posted by EchoBravo View Post
I was told there would be no math in this thread.
This thread is all about the math. It was started on 07-12-05....so 7 x 12 x 5 = 420....(might need to get high for this next part)....then the date it was necro'd was 02-12-18....so (420/2) - 12 - 18 =180.....now subtract how many years old this thread is...180-13 = 167

Adjusted for internet error and we have 167.5 cranks as the answer
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Old 02-13-18, 11:11 AM
  #31  
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Velodromes have banked corners, ( & straights) higher on the right side.. going counterclockwise..
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Old 02-13-18, 02:17 PM
  #32  
seau grateau
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That's why track riders always use a shorter crank arm on the right side.
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Old 02-13-18, 09:00 PM
  #33  
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ROM (range of motion) is an issue, such as for triathletes who want a smoother transition from bike to run; and, for those who've had knee replacement surgery, for example, joining the 120 ROM club (active not just passive ROM) is pretty much the requisite minimum level for getting into 165s, not that going to 145s is not okay if that's what is required to enjoy the sport.
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