Travel easier
Felt Bicycles produces most types of bicycles. They are an American company and advertise that they manufacture mountain bikes, street bikes, racing bikes, and cyclocross bikes.
To make then easier to be spotted by cars.
Literally millions of makes of bicycle have existed, If you are so interested it would be beneficial for you to research it.
If the bicycles belong to ONE FRIEND, it's "friend's bicycles." If the bicycles belong to TWO OR MORE FRIENDS, it's "friends' bicycles."
Bicycles and many glider prototypes
Bicycles make you more fit.
The best time to buy bicycles is typically during the end of the summer or early fall when stores offer discounts to make room for new models.
My answer is that the Wright brothers used parts from bicycles to make the airplanes as they used to make bicycles in their Ohio shop. I can think of several other answers. The question is a little vague to me.
1.8 bicycles.
There is no specific collective noun for bicycles, in which case a noun suitable for the situation is used, for example a rack of bicycles, a row of bicycles, a standof bicycles, etc.
Bones and feet stench