gear ratio

Meanings

1. 1nouncountabletechnical

   The relationship between how fast two connected gears turn, shown as the number of teeth on one gear divided by the number on the other.

   Grammar: Countable: use 'a gear ratio' or 'gear ratios' with a number or fraction.

   Patterns

   • a gear ratio of something
   • the gear ratio between something and something
   • change/adjust the gear ratio

   A gear ratio of 3:1 means the smaller gear spins three times for every single turn of the larger one.

   Engineers chose a lower gear ratio to give the truck more pulling power on steep hills.

   If you change the gear ratio, the bike will climb hills more easily but lose top speed.

2. 2nouncountabletechnical

   The number that shows how many times an engine or motor turns for each single turn of the wheels it drives.

   Grammar: Countable; often written with a colon, as in '4.10:1'.

   Patterns

   • a final drive gear ratio
   • a high/low gear ratio

   This car has a tall gear ratio, so the engine runs slowly at highway speed and saves fuel.

   Mechanics sometimes swap the rear axle to get a gear ratio better suited to towing.

   The spec sheet lists the gear ratio as 3.73:1.

Word forms

Common combinations

gear ratio of 3:1

The gear ratio of 3:1 gives the small gear three turns for each turn of the big one.

low gear ratio

A low gear ratio multiplies force, which helps when starting on a slope.

high gear ratio

A high gear ratio lets the wheels turn fast while the engine stays calm.

change the gear ratio

You can change the gear ratio by fitting a different chainring.

calculate the gear ratio

To calculate the gear ratio, divide the number of teeth on the driven gear by the number on the driving gear.

Synonyms and how they differ

gear reduction

Use this when the output turns more slowly than the input; it stresses the slowing effect rather than the plain numerical relationship.

transmission ratio

This is the broader term used for the whole transmission, while 'gear ratio' usually refers to one pair of gears.

Word family

gear noun

One of a set of toothed wheels that fit together to pass motion along.

gearbox noun

The metal case holding several gears and the parts that shift them.

gearing noun

The arrangement of gears in a machine, or the ratio they produce as a whole.

Commonly confused: gear ratio or gear?

Practice

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