There is really no need to send any part of a bicycle to landfill. Simply diverting your tracks could literally be a life changer for the recipient of your bike part. Whatever kind of bicycle or bicycle parts you have, consider donating them to one of the many community bike organisations before recycling or sending to landfill. Bicycles and their parts are eminently donate-able and there are a number of groups who will take your unwanted cast offs. Some community organisations strip, clean and use your parts to make new bicycles or wheel chairs to be sold or given to people in need. Many bicycles are distributed to refugees, street kids and other people who cannot afford a bike. Some organisations fix and send bicycles to poor countries. Others use your parts in workshops to assist people who are fixing their own bikes. Check the Location and Trading tab for you your closest community organisation and information about their work.
Bicycles are made of a number of quite different substances - some more recyclable than others. The wheel and frame are made from steel, aluminium, titanium alloys and composites - epoxies, resins and glass nylon. The mechanical parts are typically steel.
Steel and metal alloys are eminently recyclable, while composites are not.
Newer, lighter bicycles are made of carbon fibre which unfortunately is an environmental nightmare. Carbon fibre is a composite product, designed to last for a very long time and that is just what it is doing in landfill. Give your bicycle parts to someone who can use them!