Replace Cassette or Free Hub?

nightofjoy

Just got a second hand bike. Been out on it a few times and the last time, the chain was slipping on the cassette, like the chain had come off, but it was still on front & back cogs.

Back in the day I used to work with bikes - almost 25 years ago, but all that knowledge has left me now. I've been looking online at new cassettes, but they seem to be just the cluster of cogs. I'd have thought the free spinning meant it was more to do with the mechanism within the ridged hub section.

So basically, which part do I need to replace?

Cheers.

nicklouse

Yes.

It depends on what you have. Cassette or Freewheel?

And you are sure that the cassette is not slipping over the cassette?

Some goo link in my sig.


If the chain is not actually slipping over the teeth and you have a cassette then new freehub ( hub specific) or if you have a freewheel (spin-on) then a new one is needed.

nightofjoy

nicklouse wrote:

Yes.

It depends on what you have. Cassette or Freewheel?

And you are sure that the cassette is not slipping over the cassette?

Some goo link in my sig.


If the chain is not actually slipping over the teeth and you have a cassette then new freehub ( hub specific) or if you have a freewheel (spin-on) then a new one is needed.

Hi. Thanks for the reply. I didn't quite understand all of that.

The rear cluster is a Shimano HG50 9speed. I'm only able to look down at the sprocket after it's slipped, so it's hard to tell, but all I know is that the chain is still where it should be and hasn't come off. The bike was £500 - £600 new I'd say, so it shouldn't have the very cheapest gear on. I just replaced the chain, so I guess it is possible that it's slipping over the teeth....

If I change the rear block first and it doesn't solve it, does that mean I'd need an entire new hub or can I replace the section where the sprocket attaches?

Cheers.

jimothy78

nightofjoy wrote:

The rear cluster is a Shimano HG50 9speed.

Cassette, then, not freewheel.

I'm only able to look down at the sprocket after it's slipped, so it's hard to tell, but all I know is that the chain is still where it should be and hasn't come off.... I just replaced the chain, so I guess it is possible that it's slipping over the teeth....

If the "slips" are occasional, especially just when you put a lot of power down, then the smart money's on the cassette teeth being worn, and the chain slipping over them (especially as you state you've replaced the chain).
Replace it it anyway for a few quid: http://www.chainreactioncycles.com/shim ... rp-prod443 (you also need a cassette lockring tool and a chain whip)

If I change the rear block first and it doesn't solve it, does that mean I'd need an entire new hub or can I replace the section where the sprocket attaches?

Most hubs have replacable freehub bodies (the bit that holds the cassette, and houses the ratchet mechanism that allows it to "freewheel") - you'd need to know the make and model of the hub to source a replacement, but hopefully it won't come to that - try the cassette first.

The Rookie

Is it ghost shifting into a lower gear (indexing issue), is their muck in between the cassette sprockets that could be lifting the chain off the teeth?

lets start with the free stuff!

njee20

lets start with the free stuff!

I'd start with the glaringly obvious - new chain, old cassette. New cassette needed.

nightofjoy

I'll start with a new cassette, see what that does.

Indexing is fine and the sprocket is clean.

The thing that's making me thing that the free hub might have gone, is you can do a few rotations of the pedals very smoothly when it slips, it doesn't just slip half a rotation.

Right. Lets get a cassette ordered then....

The Rookie

Sounds very like ghost shifting.......

Chunkers1980

This is a serious question. What actually is ghost shifting? and what are its causes/reasons for happening.

If everything is newish and indexed and setup right then it just works.

njee20

The Rookie wrote:

Sounds very like ghost shifting.......

Does it? Several revolutions of the pedals suggests freehub body I'd say! Nothing like ghost shifting IMO...

The Rookie

Ghost shifting is where it shifts into a lower gear without being requested at the lever, poor indexing or other things can cause it.

The pedals will often feel like they are spinning as you pedal at roughly the same rate as before but as the gear is lower get no resistance so think there is no drive, but if you pedalled about 20% faster (depending on the gear spread at that point) you would find some.

Still think it can be ghost shifting......

nightofjoy

It's definitely not ghost shifting.

I don't use the back sprocket around Manchester - only two of the front three gears. If I start going further afield and taking on more hills I'll need more of the range of gears I have, so I don't want to reduce the overall number, but The only time the chain has traveled up the sprocket so far has been on the work stand to make sure everything was working properly.

The chain is never off the smallest rear cog, and when it slips, it feels like the chain has slipped off the bottom one and is just free spinning, but when I glance down, the chain is still located on the smallest cog.

jimothy78

nightofjoy wrote:

I don't use the back sprocket around Manchester - only two of the front three gears. ...
The chain is never off the smallest rear cog,.

This is poor use of your gears.
You should use the right hand shifter (rear gears) far more often than the left/front. Broadly speaking, with a typical 3 front, 9 rear setup, you should be aiming to use the smallest front ring for climbing, the middle ring for flat or mixed trails, and the largest one for descents or flat roads. Then you select the appropriate rear sprocket to fine-tune the gearing to a comfortable ratio as the gradient changes. (Technically speaking it's a bit more involved than this, and you should avoid certain combinations (notably biggest ring with biggest sprocket and smallest ring with smallest sprocket), but you get the idea)

nightofjoy

Yes, I know. Nothing to do with my current problem though, and it doesn't get away from the fact that around here where it's almost completely flat, I only need two gears....

nightofjoy

So this:

http://www.ebay.co.uk/itm/Deluxe-Freewh ... 540a18837a

And a wrench will do to replace the cassette?

jimothy78

nightofjoy wrote:

Yes, I know. Nothing to do with my current problem though, and it doesn't get away from the fact that around here where it's almost completely flat, I only need two gears....

Yes, but make it two at the back, not two at the front

nightofjoy wrote:

So this:

http://www.ebay.co.uk/itm/Deluxe-Freewh ... 540a18837a

And a wrench will do to replace the cassette?

Yes.

nightofjoy

jimothy78 wrote:

nightofjoy wrote:

Yes, I know. Nothing to do with my current problem though, and it doesn't get away from the fact that around here where it's almost completely flat, I only need two gears....

Yes, but make it two at the back, not two at the front

nightofjoy wrote:

Nah, I'm happy with the way I'm using it now. I'd have to keep it constantly on the largest front cog, and find a rear cassette cog which feels like I'm on the smallest and the middle on the front. And they won't be cogs next to each other on the back, which means I'll have to remember which one. Unless I set my rear mech to only go as far as the other cog I need, but I can't be arsed doing that. 'Fixie' mode on the back and two gears on the front will do just fine for now.

So this:

http://www.ebay.co.uk/itm/Deluxe-Freewh ... 540a18837a

And a wrench will do to replace the cassette?

Yes.

Cheers. I'll get that ordered....

The Rookie

Changing gear at the front moves the tension side of the chain, really clunky, at the rear is the non tension side, much nicer on chain and cassette.

One gear at the front is approx a 30% change, if you are pedaling at a proper cadance you'd want to change half that amount, sop use the rear where the gears are only 10-15% apart and change more often.