BICYCLE GEARING RATIOS

 BICYCLE GEARING RATIOS

Sample Calculations Using a Mountain Bicycle

The table below uses a common data of 20 kg weight for the whole bicycle and luggage, and 60 kg weight for the cycler. The crank length is 170 mm, and the wheel diameter is for a 26 in wheel. Its circumference is calculated as 2.075 m. For the speed, the cadence is at 60 revolutions per minute, or 1 revolution per second.

The "De for Zero Acc" is the inclination in degrees, when the rider is standing on the pedal. His weight provides the force to move the bicycle forward. This inclination is when the bicycle does not move forward or backward.

This inclination provides some information on the ability of a gear ratio to allow a rider to climb up a hill.It gives you a more objective evaluation compared to just s subjective descriptiion such as "can climb up a hill". We do not even know how steep the hill is.

The motivation to calculate these figures is to verify the effectiveness of the Shimano Megarange. Customer feedback in amazon.com is impressive with comments like, "my son can climb up the hill on the way home".

 

5.0 out of 5 stars Head for the hills
Reviewed in the United States on December 12, 2014
Verified Purchase

This really worked on the hills. I wan't sure if this is what I needed to replace the old freewheel but after a few hills i was impressed. I could climb without getting out of the saddle.

My View

When I compared the inclination for Megarange with the default Beasso gearing ration, I was not impressed. The difference is only 6 degrees.

When I actually tried it climbing up a small hill with an estimated inclination of 20 degrees, I was not struggling as much. In fact, when it slipped to a higher gear, which is 24 T for the Megarange, I found it so uncomfortable that I dismounted and pushed the bicycle up the hill.

DNP 11-34T

The problem with Megarange is the low number of teeth for the high gear. It only provides as low as 14T. When I checked with my table, the maximum speed of 44 km/h at a cadence of 60 cycles per minute, is already too high.

I still ordered the DNP Drift Maniac 11- 34T 7-speed Freewheel for my Supercycle Oscar bicycle which is fitted with a Hub-wheel motor. The idea is to allow my feet to keep up with the electric motor, or even when going down hills. However, because I cannot install a disc brake to the Oscar, it may not be safe at such a high speed.

DRIFT MANIAC 7 Speeds Freewheel 11-34T 7 Spd

 

https://www.aliexpress.com/item/1005001670160452.html?

KCNC 9-52T

 It may have the largest range but may not be as reliable. Read the following comment.

https://www.mtbr.com/threads/kcnc-9-52-12-speed-cassette.1103746/ 

#16 ·
I also bought a KCNC Master 9-52, and the first3 or 4 rides it went ok, but after that it started to jump in the 10 and 11 gear. I adjusted in order to avoid that problem and then I couldn't change from 3 to 4 and 4 to 5 gears. I tried everything, adjusting B screw height, changing chainring and chain and nothing happened. I decided to go back to Sram 10-50.

 Table of Calculations

  Crank Freewheel Deg for Zero Acc km/ h
Begasso 24 28 27 12
Megarange 24 34 33 10
DNP  11-34T 24 34 33 10
Begasso 42 14 7 44
Megarange 42 14 7 44
DNP  11-34T 42 11 6 55
KCNC 9-52T 24 52 57 7
KCNC 9-52T 42 9 5 68 

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