My bicycle gears keeps jumping when im riding, why is this?

Every 5-10 seconds or so it feels like the pedals are jumping because something is happening to the gears. The gears have not been calibrated for some time and it's not an expensive bike, if this is the reason...how can i fix it?

 

Do a net search, or a youtube search for "derailer adjustment" or "derailleur adjustment", or check out the "repair help" on parktool.com or sheldonbrown.com for derailer adjustment.
Might be as simple as turning the barrel adjuster half a turn or so.

 

The other common cause of this problem would be a mis-match of the chain and cassette, eg, a new chain used on an old worn cassette, or vice versa. If the jumping happens only under high-load pedaling, I'd guess it was due to this condition.

For example, I've found I need to replace chains about every 4-6 K miles based on 0.75% wear limits. The used cassette is fine after the first change, but at the second new chain (about 10K miles on the cassette), I'll get skipping under heavy loads unless I also replace the cassette at the same time.

 

Yea maybe the chain is misplaced

 

^^^ This. I'd say that both the chain and your cassette (or freewheel cluster if it's a REALLY old bike) are shot.

 

As, divinemaredi said, you chain is misplaced. There may be some other cause of this problems but the most common one is misplacing of chains. You may try replacing it.

 

Ah, thanks for the read guys.

This was happening to me too and I got kinda worried, but I feel alright now

Was clueless of what was happening, I thought my whole bike was just gonna collapse right beneath me aha.