Do all parts fit all bikes?

[car5car]

I have a cheap bike and want to order parts from internet sometimes. How can I find out if they will fit?
I bought pedals once and found out that there are 2 different thread sizes. I ordered gear switches today and don't know if they will fit.

[nfmisso]

Welcome to the forum.

It would greatly assist if you would tell us more about your current bike, and share a picture.

Regarding index shifters, the two most common are Shimano (and compatible) and SRAM. SRAM also offers shifters that work with Shimano. SRAM labels the Shimano compatible shifters as MRX and TRX. Indexed shifters have to be matched to the number of gears you have on the freewheel or cassette. SRAM derailluers have 1:1 cable to derailluer movement, Shimano are 2:1.

For more information:
http://sheldonbrown.com/gearing/index.html
http://www.sram.com/sram/mountain/technologies/187

Browse Amazon to get an idea of what can be mixed and matched, and what cannot:
http://www.sram.com/sram/mountain/technologies/187

Another biggie that cannot be is V-brakes and all other types of caliper brakes required different brake levers, though there are some levers that have two cable termination positions and will work with both.
http://sheldonbrown.com/rim-brakes.html
http://sheldonbrown.com/canti-direct.html

[car5car]

(04-08-2011, 02:59 AM)nfmisso Wrote:  Welcome to the forum.

It would greatly assist if you would tell us more about your current bike, and share a picture.

Regarding index shifters, the two most common are Shimano (and compatible) and SRAM. SRAM also offers shifters that work with Shimano. SRAM labels the Shimano compatible shifters as MRX and TRX. Indexed shifters have to be matched to the number of gears you have on the freewheel or cassette. SRAM derailluers have 1:1 cable to derailluer movement, Shimano are 2:1.

For more information:
http://sheldonbrown.com/gearing/index.html
http://www.sram.com/sram/mountain/technologies/187

Browse Amazon to get an idea of what can be mixed and matched, and what cannot:
http://www.sram.com/sram/mountain/technologies/187

Another biggie that cannot be is V-brakes and all other types of caliper brakes required different brake levers, though there are some levers that have two cable termination positions and will work with both.
http://sheldonbrown.com/rim-brakes.html
http://sheldonbrown.com/canti-direct.html

I have Chinese made bike Roadmaster bought from Walmart for $39 about 4 years ago.
Pedals fell off, they didn't have bearings, it was just plastic rubbing metal.
Now shifter cracked. Yesterday I took apart rear hub, ball fell down, which means bearings didn't have grease. 2 bearings had very small balls about 3 mm. I didn't know how many ball to install to each (bearings had different diameter), so I installed by feel and forgot to install one.