Bicycle Mechanics - Do I need to replace my casette?

My chain and cogs are not properly meshing all the time. If I pedal the bike with it upside down, I can see that the chain will occasionally not catch the casette properly, and one link will sit up on top if one of the teeth on a cog, rather than laying flat over it. I know it's not a derailleur problem, since I can replicate it even when the wheel is off the bike jsut by running thte chain over it by hand.

Here's a picture showing what I mean:
http://fox302.com/userdata/notfred/files/Biking/bike006.jpg

Do you think it's the chain, or the casette? They're both SRAM X9 9-speed parts.

Here's a closeup pic of a cog from the casette. Does it look worn out? I measured the chain, and twelve links seem pretty damn close to a foot (within 1/16 inch), so I don't think that's the problem, but I'm not an expert.

http://fox302.com/userdata/notfred/files/Biking/bike004.jpg

It's hard to tell. The cogs look OK. I'd replace the chain first and see how that goes. If there is still a problem then change the cassette also. Sorry not much help.

CHEERS.

Mark

I figured out what it is. It's a bent cog on the casette. Is there any way to fix this, or do I just have to buy a new one?

I would just buy a new 14T assuming all the other cogs are in good condition. Otherwise it might be more economical to replace the entire cassette. Although, am I missing something? Because the first picture looks like the link is hanging up on the 16T yet you identified the 14T as the culprit.

There appears to be burrs present on the cog pictured.
This is a sure indication of wear.
Your LBS will have a tool to check cog wear.
Ask them to check each cog before you replace the whole set.
Depending on your riding/shifting style you may not need to replace all the cogs.

Enjoy

what is the tool to measure cog wear? can you give more info: who makes it, what's it called? how does it work.
thanks.

what is the tool to measure cog wear? can you give more info: who makes it, what's it called? how does it work.
thanks.If there really is one, check www.parktool.com it's a steel cog. You got nothing to loose by trying to straighten a slightly bent tooth with a vise grip.

If there really is one, check www.parktool.com

Yes, there really is one. Oddly enough, other companies make bicycle-specific tools; in this case, the tool is made by Rohloff. It's not the most elegant tool, IMHO, but it functions well enough.

what is the tool to measure cog wear? can you give more info: who makes it, what's it called? how does it work.
thanks.
Rohloff makes it; it's often referred to on the interweb as the Caliber 2, though this is incorrect and makes actually finding information about it somewhat difficult. It's most commonly referred to simply as the Rohloff cog wear indicator. Its use is somewhat analogous to the way a chain whip is applied, and based on the way the tool sits on the cogs, provides a rough estimate of how worn they are (this is definitely an oversimplification for our current purposes).
Here's a pic without much info. If your LBS doesn't have one, they can get you one for around the same price you see here: http://www.cambriabike.com/Shopexd.asp?id=13754

[edit because grammar is not my friend this morning]

Yea, that's the one.

I think they work great when used properly.

Enjoy

will this or any other tool tell you about chainring wear rather than cog/cassette wear?

will this or any other tool tell you about chainring wear rather than cog/cassette wear?

This tool will not as it does not work well on rings greater than 26T.
But having said that, chainrings are much slower to wear because the load is distributed among more teeth.
However if you have not monitored chain wear and have been riding on a chain greater than 1-1/8" over 12 links it is pretty safe to say it is too late for any of the drive components.

Enjoy

[QUOTE=notfred].

"Here's a closeup pic of a cog from the casette. Does it look worn out? I measured the chain, and twelve links seem pretty damn close to a foot (within 1/16 inch), so I don't think that's the problem, but I'm not an expert."

That 14 has seen better days. Notice that some of the gaps between cogs are asymetrical, metal has worn off where the chain rollers pull the backside of the teeth. I can see the same type of wear on another cog above the chain in the first picture.
If your chain is close to 12 1/16th/foot, now is a good time to replace it.
I think your best money would be invested in a new chain and new cassette now, even though both are still usable. Normally a good cassette will outlast chains 3 to 1, but in this case I think you are ready for both.

Al