Bicycle Mechanics - Chain Skipping?

Hello I have a Marin Bobcat trail which is the 2004 model I believe. I just bought it a couple months ago and after about 2 weeks I busted the chain so I ended up buying a new one. THen after that it seemedlike I have had a LOT of trouble shifting from the second to third gear inthe front . Going from the medium sized to the large size gear. Also when I am going up a steep hill rather it be dirt or pavement and I am mashing down on the pedals in 1 gear in the front and 3 in the rear the chain seems to make a large pop and the pedals feel like they are skipping or something. I often lose traction on the pedals its so severe. It sounds like whenyou donthave the chain onthe next gear all the way when you shift and you pushdown onthe pedals and it makes that noise. Sorry about the space problem on the post my keyboard is jacked up. It is a 8 speedin the back and the front is a 3 speed. took it to shop multiple times but they cannot find anything wrong with it.

Hello I have a Marin Bobcat trail which is the 2004 model I believe. I just bought it a couple months ago and after about 2 weeks I busted the chain so I ended up buying a new one. THen after that it seemedlike I have had a LOT of trouble shifting from the second to third gear inthe front . Going from the medium sized to the large size gear. Also when I am going up a steep hill rather it be dirt or pavement and I am mashing down on the pedals in 1 gear in the front and 3 in the rear the chain seems to make a large pop and the pedals feel like they are skipping or something. I often lose traction on the pedals its so severe. It sounds like whenyou donthave the chain onthe next gear all the way when you shift and you pushdown onthe pedals and it makes that noise. Sorry about the space problem on the post my keyboard is jacked up. It is a 8 speedin the back and the front is a 3 speed. took it to shop multiple times but they cannot find anything wrong with it.

Annoying.
1) Do you have the correct chain. I know it sounds simple but sometimes it is
2) Try another chain if you can
3) Any stiff links in the chain
4) Is Bicycle new or not. If not new could be that the cassette at the back is thrashed and the new chain has just highlighted the problem, what this means is that the old chain and the original cassette were nicely worn in together. Now you change the chain and the new chain does not go with the old cassette.
5) Are your gears properly adjusted

Hope some of the above is of use.

I would've said your rear casette/chain is worn to hell. But i'm guessing your LBS would've picked up on that.

It sounds like you are trying to change chain rings under heavy load, not a good idea. Work on predicting gear changes and shift before the load is heavy.

What Enthalpic said. Changing gears under a heavy load or lot or tourque can make it a bit harder for the derailer. This causes a longer shift, which usually makes the chain skip for a bit. Rear derailer not so bad, but front derailer it is, since all the 'pressure' is on that chain ring. Before going up a hill get into your front gear first, and then you can usually change the rear gears easily while going up the hill.

Bike was new when i bought it. It was only a couple months old now. Cassette appears fine but not sure what to look for. The chain is a pc48 chain I believe. Gears are 3 in front and 8 in back. Dont know exact size of all the gearing.. . I shift before I go up the hill so I am not shifting under pressure. It seems to work fine in the other gears fromwhat Ican tell. Also its nearly impossible to shiftfrom second to third in the front. LBS said it shifted fine on the stand but when I ride it I cannotget it to shift at all from 2 to 3.