Gear problems with my bike?

i have a K2 mach 2 shimano 105s and occasionaly when going up hill or putting strain on the gear the gears will pop and i'll have a full pedal rotation jerk where i have no pull over the bike. (This does not happen when i am changing gears the bike is already in gear when the problem occurs)

If any bikers can understand what i'm talking about how can i fixx the gears to where this won't happen

It happens in lower gears more often than higher gears

Any info on working on gears would be soo helpful thanks

If the derailleur is set up properly, your cable tension is how it should be, and the piece that the derailleur mounts to on the frame (the derailleur hanger) isn't bent, then I'd say you have worn drivetrain components. A worn or broken shifter is also possible, but not likely. Since you said you get a full pedal rotation when it happens, it could also be a broken or sticking freewheel body, but that's also unlikely. To check the derailleur hanger, you'll need to take it to a shop or buy the $50 tool and learn how to use it.

So...if all that is in order, then the most likely culprit is your chain. Go to a shop and have them measure it, or buy a chain-checker tool for $10. If it's worn out, the spacing between the rollers won't mesh with the spacing between the teeth on the gears, and every so often they'll jump and skip like that. Chains last from 500 to 2000 miles depending on how you take care of them and how you ride....new ones are cheap.

The next offender would be your chainring. They wear out relatively quickly. Keeping track of your chain wear and replacing it before it gets worn too badly will help prolong your gear teeth. Since you said it happens in all gears (usually the low ones, but not always), this could be a worn part, too.

Your rear cogs usually last a long time, so it's not likely that they're worn. Start with the chain, have someone knowledgable look at your chainring(s) to examine them for wear, and replace whatever you need to.

Also (and this should really be your first check), look for any bent or broken gear teeth on each gear....and make sure there isn't any grass, twigs, or lube buildup sitting between your rear cogs, causing the chain to ride high and not mesh with them.

If your bike is pretty new or not ridden much yet, then check out that Sheldon Brown link, or browse the Repair Help section at www.parktool.com . They both have excellent instructions and photos on how to set up and adjust your derailleurs (and everything else on the bike). Good luck! Post back if you need more help. :o)

http://www.sheldonbrown.com/derailer-adj...

Ride Urban nailed it.

Worn moving parts in the drivetrain.

Check all the sprockets, they should not be sharp pointed stars, ditto for chain rings. If they are worn you should also splash the cash on a new chain.

Have you replaced your chain lately?

Remember that a new chain means new cassette and usually new chain ring or two, or three.

If you bang a new chain on but don't replace the rest of the drivetrain, the new chain won't mesh with the old parts.

Another thing is the bottom bracket, if your cranks have any lateral play - BB is also rooted and needs replacing.

Any one of these things or a combination of any will result in the symptoms you have described.

And to be honest, if you have one of these problems you will soon have all. A sure fix is to replace the drivetrain with nice new expensive shiny things with Shimano stamped all over them.

It could be wear and tear. IE your rear sproket woucl be worn, along with chain. Check your chain length. 12 links should = 12". If it is over 12 1/8" then you should probably replace both.

Luck