Why do the gears on my bike shift when I dont want them to?

Question

I just bought a new schwinn mountain bike and I have realized a problem with it. Whenever I shift gears, it takes a few seconds before it actually shifts and then it seems to go back and fourth between the two gears (the one I was on and the one I shifterd to) while I pedal. What should I do?

Answer 1

You should have the gears adjusted. They shouldn't do that.

Answer 2

If I had to guess, the bike just is low quality and you'll have to live with it.  Schwinn makes no good MTBs any more (in fact, some of them say not for off road use).  You learned the hard way about how bad department stores are.  That said, if you got it at a local bike shop, take it back and have them fix what they can.  Also, if you got a Schwinn, you prolly have no intention of doing any real mountain biking, so the fact that it randomly shifts is a non-issue.  Also, you could just ignore all that I said above and just take it back to where you got it.

Answer 3

I'm assuming the chain is dancing between the two gears when you are attempting to shift to a lower (easier) gear.  On most all bikes, shifting to a lower gear requires the shifter to increase tension on the cable to "pull" the chain up onto the larger cog.

If the adjustments weren't done correctly when assembled, or the cable has "stretched" a bit during its initial rides, you can expect this to happen...regardless of the component quality.  To correct this yourself, find the "barrel adjuster" at your rear derailleur.  This adjuster screws into the derailleur and works to increase or decrease the amount of cable tension.  Turning the barrel adjuster counterclockwise (looking toward the derailleur) will allow you to increase the tension to take up that bit of slack which is causing your shifting problem.  Make your adjustments in fractions of a turn (1/8 or 1/4) at a time until you get it the shifting dialed in.

Answer 4

you need to adjust your gears if its the shifting in the back (the one with 7-9 gears) then there is a little k**b you can adjust to change your shifting and the same thing goes for the front or if you dont want to mess with it you can take to a bike shop