Mountain Bike Gears Popping?

My bike is brand new, got it in February, but took it out today for probably its third ride. I don't know a lot about bikes, but it has 3 front gears, 8 back gears. When I am pedalling, the bike will sometimes slip, the chain kind of like skipping a link or something. This happens no matter which of the front 3 gears I am in. It also happens badly when going up hills, but I figured that is probably because the gear wasn't low enough. (?)
If it helps, it is an Iron Horse Quantum II...I've looked it up online before, but I guess it is sold exclusively at Sports Authority stores. It has Shimano Acera shifting, which I have heard is decent.
Anyways, if you know the problem, please help me out. Also, if it is something I did or am doing wrong when shifting (I am still kind of learning the whole shifting thing, too) please tell me. Thanks!

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5 Comments »

DH1 said:

http://sheldonbrown.com/gearing/index.ht…
learn something about bike drivetrain, or take it to the pros at the LBS. It could be a bad freehub body, chain stretch, poorly adjusted rear dérailleur limit screws, bent dérailleur hanger, improper tension on dérailleur cable.
Acera is alright for recreational use, but in the family of shimano products, it is the second from the bottom of the barrel. They are considered disposeable and wear out quickly at that price point.

# 19 February 2010 at 3:48 am

Reknaw13 said:

Try going into a gear that skips, throw it upsidedown and look where it skips.
I had a problem with some gears on my old freewheel and I diaginosed that some of the teeth bent outwards and I really don’t know how they got like that but they would climb over the teeth.
I replaced the freewheel and they work sweet and I tuned my derailleur/limit screws and even on a fairly cheap bike I get good shifts.

# 19 February 2010 at 8:05 am

I ? vagina? said:

Mine does the same thing,a buddy told me to adjust the derail er,i don’t know much either,but it would probably cost $8 to 10 to have a professional fix it right.

# 19 February 2010 at 12:09 pm

bicyclis said:

Sounds like a tricky one–if there is a LBS near you, ask them….(Don’t tell em where you got it.)
My guess is a tight link in your chain. Sit there with plastic shopping bag gloves and flex every link in your chain 1X1

# 19 February 2010 at 5:04 pm

Sam H said:

Firstly if your bike is brand new then the shop should sort it out if you speak to them. Anyway the gears should not slip even if you jump up and down on the pedals. Im not sure if it is the front or back gears you are talking about but this applies to both.
1. Look at the bolt that holds the cable to the derraileur, check that the cable does not appear to have slipped. If so go to the top gear and change down (but dont pedal the gears). This should create some cable slack. Undo the bolt and pull the cable through 1 o 2mm and tighten the bolt solidly. (not stupid hard or it will snap). You can repeat this a few times if it is unsucessful.
2. This is more complicated so consolt the shimano website. Basically there are two screws one which when loosened allows the derraileur to go higher and one lower. You can play with these to get the correct place but i do not recomend this unless you know what you are doing
If neither of theese help check for,
bent cogs
bent chain links
if the chain is oiled
kinks in the cable
split cables
hope this is a help!!

# 19 February 2010 at 9:35 pm