Gearing and Cadence

What are gear inches?

Gear inches is a system that assigns numerical measurements to gear ratios to indicate how low or high a gear is. It has no physical significance.

Gear inches relate to the diameter in inches of the main wheel of an old-fashioned penny-farthing with equivalent gearing. To convert from gear inches to gear metres divide by 0.08 (more exactly: 0.0798, or precisely: 0.0254π).

So for example level 1 on the Wattbike is 6.2 metres (at 90 cadence see section 4) or 6.2/0.08 =77.5 inches.

The difference between gear inches and gear metres is the factor ∏ i.e multiply by 3.142 to get the distance travelled in one pedal revolution.

Gear inches originate from the old-fashioned penny-farthing when crankarms were attached directly to the large drive wheel. One turn of the pedals moved the bicycle a distance equal to the circumference of the wheel.

The larger the wheel the farther the bicycle went for each turn of the pedals.

The gear-inch system is a holdover from these early days when wheel diameter determined the bike's gearing.

Riding in a high gear on a modern bike is mechanically equivalent to riding a penny-farthing with a large wheel whereas a low gear on a modern bike is the equivalent of a smaller wheel on a penny-farthing.

Gear inches express gear ratios as the diameter of a directly-driven wheel and is  calculated as follows:

Diameter of drive wheel in inches × number of teeth on the chainring / number of teeth on the sprocket.

The gear inches table is based on a wheel diameter of 27 inches. This means that a 48 teeth chainring/18 teeth sprocket setup is usually considered to be 72 inches.

The full gear inches and conversion to equivalent Wattbike settings are shown in Tables 3 and 4.

Table 3- Imperial Gear Table 

How do gears apply on the Wattbike?

Table 5 below shows approximate simulated Gear Metres at each Air Brake Gear Lever setting at 90 cadence:

Table 5 – Air Brake Gear Lever settings and approximate gear metres and gear inches at 90 cadence

This means that for each complete revolution of the pedals a distance of 6.2 metres would be recorded on the Wattbike at setting 1 and 8.8 metres at Wattbike setting 10 (based on constant 90 cadence r/m). 

So if you look at the Air Brake Gear Metre and approximate chainring/sprocket combinations in Table 6 below, level 1 on the Wattbike is equivalent to a 41/14 or 44/15 or 47/16 or 50/17 or 53/18 or 56/19 chainring – sprocket combination on a bike. Level 10 is equivalent to a 49/12 or 54/13 at 90 cadence.

Table 6 below shows the approximate relationship between the Air Brake Gear lever and the equivalent chainring/sprocket combinations. The full gear metre and conversion to equivalent Wattbike settings at 90 cadence are shown in Tables 1 to 4.

Table 6 - Air Brake Gear Lever/Gear Metres and approximate Chainring/Sprocket combinations at 90 cadence

Using high and low gears

If a high air brake gear produces a greater distance travelled per revolution does this mean that it is better always to use a high air brake gear?

In a word ‘NO’ - The Air Brake Gear Lever setting is not an indication of how fast you can go – Air Brake Gear Level 10 is not fast and Air Brake Gear Level 1 is not slow. It is not a measure of how difficult it is to complete a workout. A setting of level 10 is not more difficult than an equivalent setting of 1

The same amount of power (Watts) applied to each pedal revolution will produce the same result whether it is applied when using a high Air Brake Gear Lever setting or when a lower setting is employed.

In the case of a high Air Brake Gear Lever setting the power will be applied through a slower movement working against a higher load. Conversely in the case of a lower Air Brake Gear Lever setting the power is applied more quickly working against a lighter load.

For the same power output a lower gear will require a higher cadence but less force. Conversely, a higher gear allows a higher power output for a given cadence but requires more force.

The optimum cadence (pedal revolutions per minute r/m) is a balance between leg speed and power applied to the pedals and pedalling efficiency.

For general exercise the ideal setting is one that allows comfortable pedal spinning at a cadence of between 70-90 pedal revolutions per minute (r/m) – more experienced cyclists may be able to maintain a cadence of 90-110 revolutions per minute (r/m) and trained cyclists in excess of 110 revolutions per minute (r/m) – sprinters can reach 140 +. Depending on the circumstances cadence can vary from 50 to 200 rpm.

For most people this will be achieved with an Air Brake Gear Lever setting of 1-3 (Gear Metres 6.2 to 6.8) and occasionally up to level 4-6 (Gear Metres 7.2 to 8.0). For short sprints powerful individuals may need to use levels 6-10 Gear metres 8 to 8.8 metres).

How do you set the Wattbike Air Brake Gear Lever setting for Children?

It is particularly important to set the Air Brake Gear Leverat the correct, safe level for children.

With a little experimentation, the correct Air Brake Gear Lever setting that gives the best workout and results can be found. British Cycling restricts the gearing for any rider aged 18 and under (to 31st December of year in which 18th birthday falls). 

To meet this rule children should be restricted to the maximum Air Brake Gear Lever settings shown in the Table 7 and 8 below:

Table 7 - British Cycling Gear Restrictions for Juniors and Youths

Table 8 - Equivalent Wattbike Air Brake Gear Lever setting