Gear ratios

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flag Dirtlines
Posted: Aug 8, 2014 at 4:19 Quote
When finding the right single speed gear raito i found that there was a sum (crank x wheel size divided by cog) and for a 26" mtb the average is 54. If its over 54 would the cranks be more spinnier or less spinnier?
flag cmc4130
Posted: Aug 9, 2014 at 11:40 Quote
Dirtlines wrote:
When finding the right single speed gear raito i found that there was a sum (crank x wheel size divided by cog) and for a 26" mtb the average is 54. If its over 54 would the cranks be more spinnier or less spinnier?

Yeah, but it's actually 55 that is the norm for BMX. The reason we say 55 is the norm is that for all of the 1980's most of the 1990's, 44 / 16 X 20" wheels was the normal/stock gear ratio. That comes out to 55 gear inches. 44 / 16 X 20 = 55.

FRONT TEETH divided by REAR TEETH multiplied times WHEEL DIAMETER = GEAR INCHES

In the early 2000's to later 2000's, people used 36/13 and 25/9, with 20" wheels, which is 55.38 and 55.5.

Unsecure image, only https images allowed: http://i255.photobucket.com/albums/hh138/upsetbmx/WhatGearRatio.jpg
Obviously, people can still pick any gear ratio they want.... it's just helpful to know what the "norm" is. A higher "gear inches" number is harder to pedal, but you go faster. Singlespeed road bikers and velodrome track riders sometimes have gear inch numbers in the 70's and 80's. http://www.bikeforums.net/track-cycling-velodrome-racing-training-area/222590-gear-ratio.html



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flag ricar
Posted: Aug 9, 2014 at 18:54 Quote
Yes, and they have legs that make tree trunks jealous. There are few that can effectively push such a gear and you will notice how well they stay in each others draft. One large bit of help is following the draft of several riders and you will notice their pedals go up and down together as well. They also do (I think) two laps before falling to the back of the line and letting the next rider lead. Such ratios are not effective on dirt, but really impressive regardless.

http://f*ckyeahcycling.tumblr.com/post/18033245101/the-legs-of-team-britain-cyclist-chris-hoy-are
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