Skipping and snapping sounds while pedaling
 

I've been having a problem with my Specialized Hardrock mountain bike. While pedaling, sometimes it "skips". I don't know if the chain is slipping off the gears temporarily or if it's something else. It happens no matter what gear or chainring I use. Plus, if I stop pedaling and then start again, I often hear a loud "snap" that sounds like it's coming from the bottom bracket. I don't know if these 2 problems are related or not.

Any clue as to what the cause/solution to this problem is?

I'm a newbie here but you can check a few things. first of all, if you grab the pedals and try to rock them back and forth towards the frame, do you feel any movement? You would be checking for play in the bearings, there should be zero play at all. Is there worn teeth on the rings or cogs? Look at the rear derailleur, are the teeth pointed (worn)?

My bike was doing this, so I took the pedals off, along with the cap on the end of the pedal. There were no bearings in the pedals at all. I don't know who worked on it at the shop(I bought it used from a trek dealership), but I probably won't be going back.
If you have platform pedals, and feel comfortable taking the cap off you might want to consider checking there.

It is not always easy trying to figure out were a sound is coming from as vibrations travel through metal. The usual suspect here is a worn chain, but that could also mean your drivetrain also needs replacing. If on the other hand you recently replaced the chain, the skipping would confirm a worn drivetrain. You didn't say how old your Hard Rock was. Specialized has been making these since about 1987, which is before cartridge bottom brackets, so if you have a loose or caged ball version and have not been servicing it, it likely needs replacement (you can use a modern cartridge BB). To check, rock the crank arms laterally as bobotech explained. If there is any movement at all it most likely needs to be replaced. Check here to R&R the bottom bracket http://www.parktool.com/blog/repair-help/cartridge-bearing-type-bottom-bracket-service-bbt or here http://www.parktool.com/blog/repair-help/adjustable-type-bottom-bracket-service.Otherwise check the chain. Lay it out with the side pins on either side facing up. Find a measuring device over 12" long and lay it on the chain. The pins are 1/2" apart and you need to measure 12" or 24 pins in a row. If the pin at the 12" mark is within a 1/16" of 12" your chain is okay; if it's over 1/8" your drivetrain is probably toast.

Not enough information to answer definitively. But if the snapping/skipping occurs when pedalling under load, it is more likely to be a rear derailleur/sprocket problem rather than a front derailleur/chain ring crank/BB/pedal problem.

Thank you! I checked everything you mentioned. I tried rocking the pedals back and forth like you said and didn't detect any play at all. As for the gears, they aren't completely pointy, but aren't exactly "flat topped" like my other bike has (my good one). However, the derailleur gears have teeth that are very much pointy. Do you think this would be enough to cause the chain to "skip"?

How many miles/kms on the chain , do you know how to check for chain stretch ?

I don't know about the miles. I've had the bike 6 years, but it probably gets some wear and tear from riding in the winter. I don't usually ride more than about a mile in each direction.

I've heard about chain stretch before, but not recalling how to check for it. Something about how many links are supposed to be in a certain number of inches or something like that. I think I actually checked it once before and it was fine.

Do you think my gear teeth being pointy on the derailleur gears is something that could be causing the problems I described before?

How old is the chain? How old is the cassette? How old is the freehub?

Skipping can be caused by a worn out chain. Usually you would replaced the chain and the cassette at the same time, they wear together.

A slightly different kind of skipping can happen if your freehub is getting old. That can be replaced too.

The bike is 6 years old and everything on it is original. I don't how old is considered "old". I've ridden the bike every Winter, and dried it when I got home, although I know winter can still put extra wear on a bike.

Winters can be quite BRUTAL on a bike, I had a paper route in WIS, and Killed a poor Coast-to-Coast 10-speed running it. 5 miles every day, ALL kinds of NASTY weather, sand and salt. Had a ball bearing sheer in half, locking up by back wheel once. The rest of the balls looked more like pebbles. Sand, salt and slush do a number on them! Do the chain measure test, 1/2 inch per link. If it is 1/8 past in 12", it is GONE. Skipping would be particularly bad under load on the smaller cogs.

The teeth on the derailleur pulleys should be rather flat, kind of like looking at a mountain with the top cut off. If they are pointy, that tells me that there is some signficant wear in place. A stretched chain can cause skipping i imagine. Go here and you can see how to measure chain stretch. http://bicycletutor.com/chain-wear/ The teeth on the derailleur pulleys will wear first due to them being plastic.

I just measured the chain like you said and it was 1/4" past in 12". I guess that means it needs replacement. Would that mean I need to replace the gear cassette too? The teeth on the gears are pointy in some places.

1/4 inch past 12 inches? I would say that you would need to replace your derailleur pulleys, and I would replace the cassette too since the teeth have worn in with the stretched chain. Putting a new chain on a very worn sprocket will lead to skipping as well.

You'll have to replace the cassette. With that much wear in the chain, I can almost guarantee that the teeth are worn.

Thanks! I was thinking of just replacing the chain if necessary, but if the cassette and maybe even the deraileur pulleys all need replacing, then it may no longer be worth the expense. I put out $90 just last year for a new headset, on top of other repairs to the hub shortly before that. I bought this bike used for $200, and it's been 6 years, so I might just keep it as it is now. When I ride it "gently", not putting much pressure on the pedals while riding, I don't have any problems. I've only been using it for my daily 2 mile round trip to the library when there's snow or rain to contend with.

If you're not mountain biking with it, there are a lot of choices that would be better suited to your needs.

What kind of bike is it?

A new cassette should be around 25-35 dollars for the Altus level or so. I don't know how much derailleur pulleys will be but i can't imagine much. They are just held on with 2 little 8 or 9mm step bolts. Easy to replace. I don't know how much the chain costs either but it shouldn't be that much.

Once you replace all those parts, things should be much better. I am unsure of whether you will need to replace the front chain rings or not.

If its a decent bike in otherwise good shape, I would just replace the parts and keep riding.

It's a Specialized Hardrock. That cassette price you mentioned was even more than I thought it would be. Plus, I'm not equipped with the tools needed to replace much, so installation and labor costs would have to be considered, for the cassette and the chain both. Someone at a LBS I asked about it said a chain would be around $15 plus $8 for installing it. That, plus the cassette cost/install on top of what I've already spent on the bike and it's getting kind of pricey. When I got that new headset for $90, I thought I was all set for a long time, but that was only a year ago, so I have to wonder what else will go wrong if I put out even more money for the chain/cassette.

Do you have a bike coop near you? That is a place where you can bring your bike and they can teach you and help you fix the bike cheaper than your local bike shop. You still should buy the new parts but they can point you in the right direction.

If you replace those parts, chances are your bike should last quite a while with proper maintenance..

I just googled it and apparently there is! There's a yahoo group for it. By the description, it sounds kind of weird! I might lurk in the area when they have one of their meets to see who's there and what they do. Thanks for telling me about this!

Fixed
 

I replaced my chain and wheels(freehub) and no more sound. Now, I only have the squeaking from the air pocket in my tubulars. =)

It took three years to fix someone else's bike?

Have you checked your chain for a tight link? Pedal backwards very slowly and if a stiff link you will see it as it comes through the derailleur.

Funny to read this reply; you were a newbie when this thread first appeared but now you've been here for two years with over 2,200 posts...