Bicycle Mechanics - New Cassette?

From what I've read on this forum board it's kind of hard to describe when a cassette is worn and needs replacing. I don't like going to my LBS for this kind of thing because, well, I find bike stores too expensive and I can replace it myself. Maybe they'd evaluate it for free but then I'd feel guilty for not having them do the work. So, can someone here tell me if this cassette needs replacing?

I don't think it does. Shifting still works great. There are a couple of cogs that are starting to get uneven shaped U's, I don't know how serious it has to be. I don't know how many miles are on this bike, a couple thousand maybe? I've replaced the chain once and the current one seems to be fine based on the chain checker I have.

You need to measure the chain with a steel ruler, this should be done without removing it. A 24 pin interval of new chain will measure exactly 12 inches. By the time any 24 pin interval has stretched to 12 1/16 inches it should be replaced. A chain checker is good to check for roller wear but you still need to measure the chain. Measure from the center of a pin to the center of the 24th pin. Chains do not wear evenly all the way around so measure 2 or 3 different intervals. If an interval has stretched more than 12 1/8 inches you have probably caused excessive wear on the cassette cogs. If the cassette cogs don't skip and if there has not been any excessive wear you are good to go.
Any good cassette should outlast at least 3 chains.

Al

The previous post explained how to check the chain.
The only way I know to check a cassette, (other than having it skip with a new chain), is this:

http://www.rohloff.de/en/products/hg_ig_check/

visually, from that picture, it looks worn a bit.

I replaced my chain and cassette on my mountain bike about a month ago, cassette was 8 years old, chain was about 6. She now shifts like a BRAND NEW bike. It shift good before, but the chain was about 1/4" longer than the new, and the cassette was a little worn. Maybe not enough to replace, but I got 8 years out of it.

But, by the looks of it cassette and chain could be replaced. Maybe your chainrings as well? A good way to tell if cassette or chainrings need replacement is to put a new chain on them, if there is a lot of slop between teeth, time for new parts.

and always replace the chain when putting new cassettes/chainrings on. Start with all parts fresh, that way they wear in WITH eachother, and not TO eachother...

Keep your drivetrain clean, as well. I clean my chain once or twice a year, more if it needs it. When I do that, or when I install new chain, I will clean the idler cogs as well, and re-lube them. Get as much grit out of the teeth as you can...makes for a better shifting experience.

You people are complicating a simple issue. If a new chain skips on the old cassette, it's worn out.

P.S That Rohloff cassette measuring tool is of dubious value, go read the instruction manual. You could make that tool yourself, basically a chainwhip...

+1 on operators comment. I replace my chain on my road bike ever 1800 miles. That way I can get 3 chains to every cassette. If I go to 2300+- miles on a chain I get skipping. This is caused by the chain not messing properly with the cassette. Chains and cassettes wear together.

+1 on operators comment. I replace my chain on my road bike ever 1800 miles. That way I can get 3 chains to every cassette. If I go to 2300+- miles on a chain I get skipping. This is caused by the chain not messing properly with the cassette. Chains and cassettes wear together.
I take the opposite approach. I ride 5000 to 7000 miles on a chain and cassette and then replace both together. However, I use fairly low cost cassettes, 105 or Veloce not Dura Ace or Record, so replacing the chain every 1500 or so miles isn't cost effective.

If your current chain/cassette isn't skipping in the smaller cogs, you are fine.

Simply put, all three components wear together (cassette, chain, and chainring). I wouldn't even consider replacing a cassette without replacing a chain. Replacing them at the same time WILL make your drivetrain feel new again, and extend the life of your chainring. Nothing ruins a chainring faster than a stretched chain. It's more expensive to do it this way, but only in the short term.