Cycling Myth Buster #5 Gear range – how does that really work?

A gear range is a set of figures that allows you to caculate the combined effect of a given cassette cog, chainring and wheelsize. This calculation was based on the Penny Farthing bike  where one measured the length of 1 revolution of the front wheel  (see below) and provide a length called X inches of development. Mind you that the Farthing Penny Bikes were very unstable due to the short wheel base and the rider sometimes sitting at a abnormally high position and the your legs peddling forward that actually reduces leverage…hmm reminds you of the A bikes and A design frames with small wheels.

So often for the misinformed,  when they see us on our Minivelos, comments usually are said like  “are you sure you can keep up?” and “don’t you cycle like a hamster?” , “Small kids bike” then have their expression in disbelief when we overtake them with ease.

So how do we do it? In the laws of physics, it is  true, a smaller wheel means you need to peddle more and faster BUT with folding bikes that we range, a bigger chainring ( not to to point where you need tremendous leg power to drive a 75T chainring) gives you the necessary range. You can still get your speed up and peddle at a comfortable pace BUT you need the right combinations.

Let’s do a few baseline understanding.

Gear size (inches)

<40         Mountain and touring bikes

41-50      Hill Climbing

51-60      Lowest gears for flattish course

61- 70     Lowest gears for flat time trials

71-100    Normal gears

>100        Flat out gears

Some Maths formulae.

Chainring size (no of teeth) xwheel diameter(inches)/cassette cog x tread to tread

e.g. (52×26.4 inches) (aka 700C)/14 = 98 inches

So for a Dahon MuEX where they use the top of the  line SRAM Red cassettes, the max range is 55Tx20 inch/11 = 100 inches so now you understand why the MuEX can attain such high velocities.

Even if you take a standard Vitesse D7 or Boardwalk D7 52X20/13 = 80 inches. Most entry level MTBs are using 44T , (44X26/13=88 inches). So you NOW understand why most D7 series bikes actually overtake these MTBs without seeing the rider huffing and puffing away.

Depending on the terrain, but for Singapore where there are  gradual hills and Beginners/Training is usually the initial goal, a gear range from 45 – 114 inches is what you need. ( 52/39 x 12-23). So when you do the specs, you understand why these Flamingos HSF1 and MuP24s can really give you  that mileage.

OK with the ideal gear range…you still need TWO Ls – strong LUNGS and LEGS or all the gear ranges in the world mean nothing.