Cassette cogs turn instead of wheel?
 

I had finally got my bike the way I liked it, and then something like this had to happen!

I was cycling along when I suddenly felt a jolt and the chain went round far too easily. I stopped the bike to have a look.

It turns out that the final cog (ie. smallest cog) on my rear cassette was turning instead of the wheel.

I decided to change my bike onto the next cog up to see if I could cycle home on that.

At first everything seemed fine. I lifted the back of my bike up and cranked the pedals. The back wheel spun round like there wasn't a problem.

Then, I got on my bike. The very first time I (barely) pedalled, the second cog started spinning like my other one. So now my smallest and second smallest cogs were spinning instead of my wheel.

I've only had this cassette about a month. How can I fix this problem?

I'm going to take a wild stab in the dark here and speculate that your cassette lockring may have come loose, meaning the smallest sprockets were able to slide down the freehub and turn freely.

How do I check that?

Will I need a cassette removal tool?

Yes.

Yes - you'll need a cassette removal tool to remove and then to tighten up the lockring. :thumb:

They are pretty much dirt-cheap on places like Amazon etc..

While you've got it off, take a few moments to check the condition of the freehub body that the cassette mates with - take especial notice of the state of the splines on there - they can often be 'gouged' by loose cassettes. This is why steel bodies are often better than Alu ones.

The recommended torque for tightening cassette lockrings is around 40NM (354 in lbs) which is a *lot*, but IME tightening it so it's 'tight' and then a click or two more seems to hold the cassette just fine. ;)

If the lockring has come off as theorized, all you'll need to do is take the wheel off and all the cogs should come freely off the hub.

I'm suspicious of this diagnosis. For both cogs 1 and 2 to spin, both they and the lockring would need to move outside of the end of the freehub. There's rarely that much room.

I suspect a busted freehub (that's the part the cassette cogs fit onto), or badly mutilated cog splines. Interested to hear the diagnosis.

I agree: The freehub is what I suspect. The only time I ever had a loose lockring, everything worked fine since there was no room for the cogs to come off the splines. The symptom was a "Clunk!" every time I started pedaling.

My thought too.
I suggest taking it to a bike shop.

Hmm - interesting, but if it's something like busted pawls in the FH, wouldn't it show the same symptoms using *all* the sprockets, and not just the smallest 1 or 2?

I suppose that gouged splines could explain that, though. :thumb:

I took the wheel off, and this did indeed happen. The entire thing fell off. I had cogs hanging off the bolt holding the wheel in place.

I don't think I explained myself that well. I only tried changing the chain onto those two cogs. When both of them spun round, I thought I was damaging the cassette more so stopped. If I did move the chain onto any of the other cogs, they would have spun round as well.

Interestingly, my bottom cog is missing a tooth. I don't know where that went, if it was today or earlier, but i've only had this thing about a month. I haven't pedalled particularly violently or anything.

Also, I run my bike in single speed on a cog with 14 teeth (this is the cog that is missing a tooth). Would I be able to swap my entire 6 speed cassette for this? I'm unsure since they also list a 14 tooth cog but say it's compatible with 7 speed, but i've been running my bike on a 14 tooth cog on a 6 speed.

Finally, is this the tool I need?

It seems like there's going to be a DIY say in my future.

EDIT: Also, when I installed the cassette, I just screwed it on with my hands. I didn't tighten it with anything. Was this right? I did notice that when I put the bike upside down and spun the back wheel, the cassette did wobble slightly. My back wheel also wobbles slightly too, even when screwed in tightly. Are both these things meant to happen?

For Shimano cassette, the spec is 260-434 inch-lbs, (22-36 ft-lbs).

http://www.parktool.com/blog/repair-...s-and-concepts

In my experience, that is more than you would think is necessary, and you likely wouldn't apply that much force if not using a torque-wrench.

OP: It still isn't clear whether you have a freewheel, or a cassette.
Please read this and determine which it is: http://sheldonbrown.com/free-k7.html

Definitely *not*! :twitchy:

This is undoubtedly why it worked loose - look at mine and others previous posts for the recommended torque values (PROTIP: It's a lot more than most people would think!).

If you have a lockring, then no - it's not the correct tool - you need a cassette removal tool. :thumb:

And what exactly is 'wobbling' on your bike? If you hold the wheel by the rim and you can feel it 'clunk' from side-to-side, then it's likely that it's the hub bearings that need adjusting. It it's wobbling side-to-side at the rim, between the brake blocks, but there's no play at the axle, then the wheel might have a slight buckle in it.

It's also quite normal for a cassette/freewheel to appear to 'wobble' side-to-side and/or up/down when it's spinning - this is due to slight variations in manufacturing tolerances. :thumb:

The OP has a lockring, so it must be a cassette, no? :thumb:

Right. I have a 6 speed and I have threads on both the cassette and the freewheel. So I must have a freewheel.

When I bought it, the man at the shop called it a cassette. That's why I referred to it as a cassette all this time.

The final bit that goes on the "cog collection" is the final cog. It doesn't look like there is a lock ring at all. The final cog has some thread on it which, when done up tightly enough, secures everything to the wheel.

Do your sprockets look like this:

http://bikeforums.net/attachment.php...hmentid=309548

or this:

http://bikeforums.net/attachment.php...hmentid=309549

Top one is a freewheel, bottom is a cassette.

It sounds like, from what you've written, that it's a 6-speed cassette, which would make the bike pretty old (early-mid 80's?).

If this is so, then the thing that the cassette screws onto is called a 'freehub' and on these models, the smallest sprocket also acts as the lockring. :thumb:

What kind of bike is this, anyway, and how old is it?

Sounds like a freewheel to me.
That last cog should be self tightening. Something has happened to it and allowed at least one other to be free.
If you can't get it to thread back together and tighten properly, you probably need a new freewheel.

6sp freewheels are available. The old one will be tough to get off. You'll need the tool you posted, a good wrench, and maybe a piece of pipe over the wrench to get enough leverage. Instructions here. The new one should just thread on the (greased) hub threads.

^Actually, continuity's right. The UG cassettes had the threaded small cog too.
The clincher is the existence/nonexistence of an interface for that above removal tool.
With a threaded small cog and the interface = freewheel.
With a threaded small cog and no interface = cassette

Because Fumbles mentioned the tool, I'm suspecting he has the former.

I think I understand what you're talking about Continuity.

I bought the cassette separately from my LBS. I think he said at the time that they had been sitting around for a while. I've attached some pictures to show you what I have:

http://bikeforums.net/attachment.php...hmentid=309553

http://bikeforums.net/attachment.php...hmentid=309554

http://bikeforums.net/attachment.php...hmentid=309555

That's definitely right.

My final cog is missing a tooth, so i'll need something new anyway. Like I posted before, I only ever ride my bike in top gear. My current small cog has 14 teeth (13 if you include the missing one) so I was thinking of getting something like this instead. Would this fit my wheel?

I'll order that tool now.

EDIT:What's this "interface" that you're talking about? I'll check if I have one

I have ridges inside my wheel that a tool would fit on. Is that what you mean?

EDIT EDIT: But I haven't got a lockring though have I? My final cog acts as my lockring. Do I still need this tool?

It's a freewheel. You need a removal tool and the info from post #16 from this thread.
If it looks like ridges inside the freewheel body and the above tool should fit, it's a Shimano one.

No - you don't need a cassette lockring tool.

Can you post a picture of just the naked hub without the freewheel on it, and maybe tell us what kind of bike this is?

So i'll need this removal tool instead of the other one right?

Will the 12 tooth cog fit my wheel?

If the answers to the above questions are both yes, i'll order them both now.

I guess you can't post a pic of how the hub looks without the sprockets on it, because you can't remove it because you need the tool! D'oh! ;)

I can't see where the splines are that the freewheel removal tool would fit into on that sprocket cluster, though.

Can you maybe find an image somewhere on the 'net of how the hub looks 'naked'?

Does your hub look like the one on the left in this image?

http://sheldonbrown.com/images/freewheel-vs-k7.jpg

It's threaded, so left.

I remember screwing the freewheel hub on. This is what I meant in post 10 when I said "I just screwed it on with my hands". I put the threaded freewheel sprocket on the threaded hub and screwed it on as far as it would go.

Well, that's OK because the action of pedalling will tighten it up in use. :thumb:

That conversion kit won't work for you, as it's for converting hubs that use cassettes on freehub bodies.

If you want a 'fixie', you should be able to thread on a single track cog in the size that you want.

http://bikeforums.net/attachment.php...hmentid=309562


If you want a single speed with a freewheel, then something like this would suit you:

http://bikeforums.net/attachment.php...hmentid=309563

You haven't told us what kind of bike this is for or how old it is, yet! ;)