on the path

Symptoms: Chain is jumping off cogs and riding/slipping on the pins outside of the plates on the chain.

A quick look at the cassette shows many teeth on just about all of the cogs are rather deformed. Agree?

jyl

Yes

Jarrett2

Are you asking me whether or not I think you should spend money on your bicycle?

Spend away, good sir.

Hell, drop a new groupset on that bad boy while you're at it.

prathmann

I haven't found appearance to be a reliable indicator of excessive wear on a cassette. Some look bad but continue to work fine with a new chain while others have a better appearance but have the chain skip over the teeth. If yours is skipping with a good chain then it's time to replace it.

on the path

Yup, brand new chain. Just looking for reassurance.

And whoever suggested it might not be worth it, the bike is otherwise in great shape.. not banged up, good tires, everything works. For ~$16, replacing cassette is a no-brainer.

BikingZombie

Derailleurs may just need adjusting.

Trevtassie

If you are in hilly country, bugger that stupid Megagear thing off and grab one of the 13-34 that has more even tooth spacing... Shimano HG50 7-Speed 13-34 Cassette

FBinNY 

A fairly definitive test for worn sprockets is to wrap a new chain 180° and add a bit of tension. Then use a screwdriver blade to lift it away at the 1/2 wrap place. A new chain on a new sprocket will barely lift away. With wear on either part the chain will lift away and pull the needed slack along the sprocket. Since you have a new chain, you know that all the wear is the sprocket, and if you can see about 1/8" of daylight under the chain it's a pretty reliable indicator that the sprocket is toast.

Another indicator is visible in the photo, in the form of heavy wear and rolled edge burrs on the back tips of the teeth. This is an indicator that the prior chain was able to pull forward and ride out near the tips of the teeth. After a certain point the roller bears directly on the corner and forces it's way past, causing that rolled burr. That's be best evidence that the sprocket is toast.

on the path

Actually the span is the same as my current one, and the spacing is somewhat similar. I'd consider the one you mentioned but the ad doesn't mention if it's freewheel or freehub. I need a cassette for a freewheel. It's not that easy to find exactly what I want and need.

FBinNY 

I can understand that a cassette for a freewheel would be hard to find. I assume that was a typo, and you meant a cassette for a freehub, or instead of a freewheel

on the path

I trust your visual assessment of the photo and I'll also do that half wrap thing to check it as well. I'm pretty sure the cassette is toast. Visually, I was going by the distorted spaces between the teeth. For the most part they are not half-round at all.

Trevtassie

Ah, not a cassette, but a cluster then. There is a big difference between the Megarange and everything else though. That Megarange you have there will have something like an 8 tooth jump from a 26 to the 34T. That's a big jump. But in a cluster freewheel you'll be pretty well stuck with the same if you want 34T. Though I think there is a more even 32T Sunrace around.

LesterOfPuppets

Freewheel teeth are misshapen when new. That's really no indication that it's time for a replacement.

Who knows, a new one might fix things but I wouldn't hold my breath. I'd say it's worth the $20 gamble if you like the bike otherwise.

Those are usually on pretty cheap bikes, though.

If you have a good craigslist or good used bike parts shops, then a replacement wheel with 7-speed cassette and freehub might be a better idea.

KLiNCK

Slap on a new cluster and it will shift "like new".
Double check the "Hi" and "Low" limit screw adjustments and get riding!

on the path

Freewheel 7 sp cassettes are available, but I'm looking for a certain kind of spacing and span. I may end up getting something cheaper but not exactly what I want. It's not my main bike, I'm more of a roadie. The MTB does come in handy at certain times, like when I want to do a short spin without kit and shoes, and I've lent it out at times too.

Homebrew01

"Freewheel" and "cassette" don't belong in the same sentence unless discussing the difference beween the 2. Determine which you have before ordering.

Homebrew01

Searching "megagear 7 speed" gives lots of results about freewheels.

on the path

It's actually a 24 - 34 tooth jump. The 34 with the small ring is ridiculous. It' hard to keep the front wheel on the ground with that combo. Truly stump pulling gears. I'd be pretty happy with a 12-28 if I could find one for a reasonable price.

on the path

That produced a 14-28 at a reasonable price. Might end up going for it.

Trevtassie

plenty around Shimano MF-HG37 MTB 7-Speed Freewheel or even one with an 11T DNP Epoch 7 Speed Freewheel > Components > Drivetrain, Brakes and Pedals > Freewheels | Jenson USA but you'd need a special cluster remover to get it off.

on the path

This one looks similar, at a much better price:

Shimano MF TZ21 7 Speed 14 28T Freewheel | eBay

Scooty Puff Jr

I agree, doesn't take a lot of research to know the difference, is it a cassette or a freewheel ?

Though it's obvious from to pic it's a Shimano freewheel, good replacements can be had for under $30.

CliffordK

When looking at the upper teeth on the freewheel (or on a cassette),

The pulling side is on the left of each tooth. The slack side is on the right.

The teeth can have all sorts of odd angles and shapes on the slack side from the factory.

However, on the pulling side, the tooth profile should end up relatively vertical.

In this case, some of the slots look elongated, with a rightward angle to the tops of the teeth. Perhaps also some pounding appearance on the left of the tooth.

It looks heavily worn to me.

LesterOfPuppets

DNP freewheel, actually.

But it has Shimano cog spacing.

pressed001

Since this happens ever since you installed a new chain, it is apparent that the old chain was needing to be replaced for quite some time. The over-elongated chain further wore down and warped the cassette.

I would suggest getting yourself a chain-wear-checker tool. It costs about 5 bucks and will let you know when your chain is at the 1% elongation mark for changing. Then, you will only have to replace your cassette once in every long, long while. However, you will be going through perhaps more chains. I think, in the end you will maybe not save too much money, but you will always have great shifting.