tygger

One of my bikes uses a Shimano HG-200-8 cassette. A tooth on the second largest cog is bent and makes the change almost skip. If I can't bend the tooth back in place, could I buy a HG-200 7 speed cassette and just replace the one bad cog? Thanks

dedhed

Most Shimano cassette usually the at least 3 largest cogs and spacers are pinned together as a unit. Older was removable screws,newer rivited.You could disassemble and replace 1 cog if needed.

If you're buying something why wouldn't you just buy the 8 speed cassette needed?

WizardOfBoz

The cassette specified has the construction below. The second largest cog is part of a rivetted assembly and can't be replaced by itself. So no, that won't work. A new cassette of that model costs about 20 bucks.
https://www.amazon.com/Shimano-Tourn.../dp/B00N0M5VKE

dedhed

Without the proper tools and SKILLS.....

But I agree, a new piece is readily available and reasonably priced.

rccardr 

If you already own the correct size replacement cog, then yes, you can remove the riveted or screwed in retainer bolts and replace just the individual cog. The retainer bolts simply make it easier to remove and replace the majority of cogs as a unit and do not need to be replaced.

On the other hand, as others have pointed out, a replacement cassette is fairly inexpensive. If you don’t already own a replacement cog, suggest you buy a new cassette instead.

WizardOfBoz

Completely agree. A competent machinist or metal worker could probably de-rivet both a good and bad cassette cluster, and rivet the good old sprocket to the old cluster. But if you have to buy the new cluster anyway, pre-riveted, why tear it apart and put part of it in a used cluster?....

And shop rates being what that are, that's probably in the 100 dollar minimum charge. Plus, you have to ensure that you've got the right material for your rivet.

Speaking of all this, I just did an interesting fix on my grill. I'd tried smoking with a "smoke tube" in a gas grill (not recommended - get a Big Green Egg or a proper smoker!). About 8 hours of low (200-220F) heat. And grease dripping off the pork shoulder into the drip pan. Well, I removed the pork and wanted to burn off the crud from the grill. Big mistake. Grease fire. My thermometer exceeded 750F. A riveted bracket on the back of the firebox held the flame tubes. One succumbed to the heat and broke off . I got some steel pop rivets from Home Despot. I'm hoping that these work. I would have preferred stainless.

The point in all this is that Shimano probably really sweated the material choice for their cluster rivets. Pretty important to get the strength/fatigue resistance right.

dedhed

There is absolutely no need to re-rivet the assembly. The lock ring holds it all together along with the hub splines. The riveting is strictly for ease of assembly. You just have to make sure your cog orientation (ramps etc) and spacers are correct.

CliffordK

It should be easy enough to drill out the rivets at home. And no need to replace them when you're done, just make sure the cassette is tight.

You should be able to get the tooth straight in a few seconds with a hammer and an anvil (or flat plate steel).

If you manage to break a tooth on a sprocket with > 20 teeth, you probably won't even notice it.

WizardOfBoz

Ah, yeah, that makes sense in one way. The freehub splines take the torque. I'd wonder, though, if when using a riveted assembly whether the torque is spread out over all the cogs and lowers wear on the freehub. Probably not, because a lot of clusters have individual cogs.

Still, if you have a perfectly good (rivetted) cluster, why would you take it apart? I guess if you have two clusters, and they each have different cogs that are damages or worn.

But I now know that riveting isn't necessary.

tygger

Thanks all! Search fail on my part. Exact replacement is cheap enough. I'll try to bend it back some more, but if all else fails, I'll just replace it.