91色情片

Why are the gears and chain always on the right-hand side of bicycles?

Richard Ellam
Bristol, UK

The short answer is because most people are right-handed.

When the first chain-driven bicycles were designed, around the year 1890, the easiest way to attach the sprocket for the chain on the rear wheel hub was to screw it on. The mating screw threads were made using screw-cutting lathes, and these were (and still are) optimised for right-handed users. This meant it was much easier to cut a right-hand thread than a left-hand thread.

A clockwise movement tightens a right-hand thread and it is obviously desirable that the driving force on a bicycle wheel should tend to tighten, rather than loosen, the sprocket on the wheel.

For this to happen when the bicycle is propelled forwards, it is necessary that the sprocket, and hence the chain, should be mounted on the right-hand side of the frame. There is no particular benefit for a bicycle manufacturer to change this to the left-hand side of the bike, even though modern sprockets tend not to be screwed on. This is because all of the other drive chain components, such as cranks, pedals and d茅railleurs, would need to be compatible with a left-hand drive bicycle.

Early chain-driven bicycles were 鈥渇ixies鈥� that couldn鈥檛 freewheel. To brake, the rider had to apply backwards turning pressure to the pedals, so a locking ring was screwed on to the outside of the sprocket to prevent it unscrewing due to this.

@Doctor_Hutch
via Twitter

Drivetrains swapped sides repeatedly in the 1890s, mainly as a marketing gimmick. I think they settled on the right partly because it was easier to use a right-hand threaded sprocket on the wheel.

Bernard West
Toronto, Canada

So that your sword doesn鈥檛 get stuck in the d茅railleur.

David Jackson
Gosport, Hampshire, UK

I imagine the chain and gears are on the right-hand side of bicycles due to historical precedent going back millennia.

Until fairly recently, some horse riders would have carried a sword. As these people were mostly right-handed the sword habitually hung over their left hip, as it had to be drawn across the body because of its length, meaning it would be far easier to mount from the left.

Early pedal bikes were probably made for people who were reasonably wealthy and so used to riding horses, which tend to be mounted from the left. Putting the chain and sprockets on the right would also mean that long skirts and floppy trousers wouldn鈥檛 rub over the oily bits while mounting. This would quickly have become the standard.

Martin Bide
Westerly, Rhode Island, US

This has to do with right or left-leggedness. Most of us are right-legged, and when mounting a bike, will stand on the left of the bike and swing our right leg over. Having the gears and chain on the right reduces the contact with the oily bits in this process.

The same right leg preference is true for mounting horses. And for both horses and bikes, it helps to have a kerb from which to mount: less height to overcome and the rider avoids stepping into the road to get mounted. The result is that the mounted rider, ready to set off, is facing forward on the left-hand side of the road. So the British habit of driving on the left is entirely logical.

@JimSteerforth
via Twitter

On motorcycles, the chain is (usually) on the left-hand side because, traditionally, the kick starter was on the right-hand side.

Adam Henry
via Facebook

It isn鈥檛 always the case that the chain and gears are on the right-hand side.

Some BMX riders prefer a left-side drivetrain. This is so they can more easily perform glides [slides along a ledge or rail] on their right-side pedal, or crank arm, without causing damage to the sprocket or chain.

To answer this question 鈥� or ask a new one 鈥� email lastword@newscientist.com.

Questions should be scientific enquiries about everyday phenomena, and both questions and answers should be concise. We reserve the right to edit items for clarity and style. Please include a postal address, daytime telephone number and email address.

91色情片 retains total editorial control over the published content and reserves all rights to reuse question and answer material that has been submitted by readers in any medium or in any format.

Terms and conditions apply.

听