shipinabottle

I'm a teen and know basically nothing about bike mechanics and repair, so I wanted to throw this question out.
My problem is... Just recently, the pedals on my new (used) bike have started shifting forward (as if I were changing a gear) when I don't touch the gear control at all. I don't actually end up in a new gear, but it's pretty annoying. Right now it's only when I'm in my top (or hardest gear), but I don't know- it might spread. I was using my dad's bike before this and the problem was even worse.
Is there some simple solution to this?
Or do I just ruin every bike I seem to ride?

p.s. when responding, remember i might not know the exact name of any parts you might refer to...

barba

The cable tension to the rear derailleur have likely stretched a bit and the chain is skipping a bit because the RD is out of alignment. This web page will have directions on how to adjust the derailleur: https://www.parktool.com/repair/readhowto.asp?id=64

Also check out this one: https://sheldonbrown.com/autoshift.html

The other possibility is that the frame is flexing a little under heavy loads (this used to happen on old steel bikes that had a little flex in them and have the cable routed under the bottom bracket).

shipinabottle

So is this something I can figure out myself?

barba

Yes. Follow the directions carefully and you can do it. It will likely be a very cheap adjustment at a shop, however. If you do take it in, ask them to show you how to do the adjustment.

72grandprix

another funky thing that i discovered is that the teeth on the highest gear in the rear sprocket began to hook as it wore down. I had this problem constantly when I snapped my chain and needed a new one. The chain and the teeth wore at the same rate so the new chain was simply not used to the hooking.

godspiral

sounds like your chain is slipping over the cogs.-- if the gears are not changing. Back cogs and chain could be too worn out, and need replacement.