Why are the chains of a bicycle always on the right side?

Answer 1

There not.

Most tandems have the timing gears on the left. This is the chain that runs between the front rider (captain) and the rear rider (stoker). The rear rider has a chain on both sides, One going forward one going backwards.

http://www.tandemseast.com/frames/index.html

Hear is a picture of a special tandem that allows the riders to pedal independently.
http://www.davincitandems.com/images/drive2.jpg

Some motorised bicycles have chains on both sides.

There are the "odd" persons around that have built a bike up with the chain on the left. Just to prove they can. (I did say odd)

Yes most are on the right.

John Kemp Starley produced the first successful "safety bicycle", the "Rover," in 1885. This was sold all over the world. Basically setting the standard.
http://en.wikipedia.org/wiki/History_of_the_bicycle.

He was English and placed the dirty chain on the road side of the bicycle so that it could be pushed without getting grease on one's trousers. (The English drive on the left side of the road)

Answer 2

Not unlike a horse, you are "supposed" to mount your bicycle fom the left side. That way you don't spook it's highly sensitive and alert drive train. Luckily it's easy to train both your horse and your bicycle to be mounted from the right. Seriously, I recall reading somewhere that there is a connection between horses and bikes in regards to how they are "mounted". I've seen a kona single speed with dual drive cranks and freewheels. Why someone would do this is beyond me.

Answer 3

rusty is right it is a horse thing. the bike was invented as a mechanical horse and so the customs and practices surrounding it have stuck around ie saddle not seat. changing drive sides is common in bmx where riders grind on their comfortable side and if it hapens to be the right drive trains can be destroyed quickly. i have done the swap and atleast in the bmx world at this point most arts are inter changeable on the bb and all you need is a left side hub on the rear.

Answer 4

Why do we drive on the right side of the road? it's a standard designed to prevent redundency. If the drive side could be either right or left, component manufacturers would have to build doulbe of everything. they'd have to build derailleurs for both the left and right sides.