Bicycle Mechanics - chain slipping

i bought a 2010 gary fisher mamba back in august and within a couple weeks the chain started slipping. when i pedal hard (even sitting down) it slipps a couple teeth. i took it back to the shop and the guy adjusted something that affects how much of the chain is touching the rear gears at any given time. it worked ok for like a day then started again. ive tried adjusting it myself, but if i adjust it too much, it wont go into some gears, but if i losen it it goes back to slipping. what can i do?

i bought a 2010 gary fisher mamba back in august and within a couple weeks the chain started slipping. when i pedal hard (even sitting down) it slipps a couple teeth. i took it back to the shop and the guy adjusted something that affects how much of the chain is touching the rear gears at any given time. it worked ok for like a day then started again. ive tried adjusting it myself, but if i adjust it too much, it wont go into some gears, but if i losen it it goes back to slipping. what can i do?

It could simply be a worn chain or cassette, but that seems doubtful given it's age. Just in case though, start by measuring the chain for wear (stretch). If you don't know how, search "Chain stretch" on the internet, and you'll find out about it and how to measure it.

It could also be a lubrication problem. A poorly lubricated chain is slightly stiffer than a well lubricated one and often doesn't properly engage, especially on the smaller sprockets.

Other than that, there are a number of other causes, but we'd need more info to help you. Does it slip on all cogs, or only certain ones? Is it the same regardless of which chainring you're using? Are you sure it's slipping on the cassette and not the chainring? How old is the bike, not in months but in miles?

youre going to have to dumb things down for me, i dont know mountain biking terminology lol

im pretty sure its slipping in the back (not by the pedals), and im not sure how many or which gears it slips on, but it definitely slips on multiple ones.

My first guesses are rear derailleur cable adjustment and derailleur hanger alignment.
Get your eyeball lined up directly behind the drivetrain.
Is the top derailleur pulley lining up well with the intended cogs? (cable adjustment help) (http://www.parktool.com/repair/readhowto.asp?id=64)
Is the derailleur operating on the same plane as the cogs, or is it canted toward the spokes? (hanger alignment help) (http://www.parktool.com/repair/readhowto.asp?id=39)

youre going to have to dumb things down for me, i dont know mountain biking terminology lol


Since the bike is fairly new and your skills are limited, I suggest you take it back to the shop and let them get it working right. Since it's a continuation of an earlier problem, it should still be fixed for free. While they're working on it, ask that they explain some of the basic adjustments and user care to you.

Rear deraillers are a tricky part to get aligned correctly unless you actually put the bike on a stand and inspect if carefully, especially on a mountain bike where they take a lot of abuse. I had a bear of a time getting mine correctly shifting without causing slipping and it turned out that the rear hanger was bent so all my efforts were all for not because I had to pull the derailleur and replace the hanger so it was all properly aligned. After that though, it was like riding a new bike.

Hope that helps.

thanks all. im too busy now to go to the shop, perhaps over winter break in a few weeks. i just hope i can figure this out, this bike wasnt cheap!