Chains advice

[Yellow Saddle]

Shame you couldn't have responded in this manner in the first place.[/QUOTE]

You have been here long enough to have seen the issue debated ad infinitum. The point remains. If you don't understand something, don't pretend you do and then offer any old half-baked answer as advice as if that is your field of expertise. There is merit in silence as well.
Now, get over it and forget about your grudges.

 

[Cycleops]

You've made my point beautifully.

 

[overmind]

It depends who I address when I say you can't see wear. I can see it, I can describe it but most of the people who tell others here that they should look out for shark-toothing and shark-finning are imagining it. No-one has yet shown me a cassette that wears to sharp points (shark-toothing I assume?) or breaking waves shape (shark finning, I assume).

I cannot show you a cassette (because it has long since been binned) but I can relate the following anecdote.

I have a 21 speed (amazon purchased) cheap racing bike. I use this bike for commuting. I ride about 50 miles per week on it. When I had ridden it for approximately 4 years with zero drivetrain maintenance (apart from oiling) the chain used to jump. It got progressively worse until eventually the chain would just slip over the freewheel.

I bought a new bike (B'Twin Triban 3) but decided to see if I could fix the old one rather than getting rid of it.

My understanding is anything to to .75mm stretched you can sometimes get away with just replacing the chain. 1mm means freewheel & cassette/freewheel need replacing. The chain on my bike was about 3mm stretched !!! The freewheel had distinctive shark fin shapes on all of the teeth which were incredibly sharp (it would have made a nasty weapon).

I ended up buying a new freewheel, chain and got a 2nd-hand chainset off an old 1980 Raleigh racer.

Perhaps this does not indicate anything since most people would never let it get that bad and once it gets to this state you have to replace chainset, chain and cassette/freewheel in an case BUT there were definite shark fin shapes on the cassette and the chainset.

 

[Yellow Saddle]

I cannot show you a cassette (because it has long since been binned) but I can relate the following anecdote.

I have a 21 speed (amazon purchased) cheap racing bike. I use this bike for commuting. I ride about 50 miles per week on it. When I had ridden it for approximately 4 years with zero drivetrain maintenance (apart from oiling) the chain used to jump. It got progressively worse until eventually the chain would just slip over the freewheel.

I bought a new bike (B'Twin Triban 3) but decided to see if I could fix the old one rather than getting rid of it.

My understanding is anything to to .75mm stretched you can sometimes get away with just replacing the chain. 1mm means freewheel & cassette/freewheel need replacing. The chain on my bike was about 3mm stretched !!! The freewheel had distinctive shark fin shapes on all of the teeth which were incredibly sharp (it would have made a nasty weapon).

I ended up buying a new freewheel, chain and got a 2nd-hand chainset off an old 1980 Raleigh racer.

Perhaps this does not indicate anything since most people would never let it get that bad and once it gets to this state you have to replace chainset, chain and cassette/freewheel in an case BUT there were definite shark fin shapes on the cassette and the chainset.

You've got your millimeters and percentages confused.
I also suspect you have your cassettes, freewheels and chainrings mixed up.

 

[Dogtrousers]

My understanding is anything to to .75mm stretched you can sometimes get away with just replacing the chain. 1mm means freewheel & cassette/freewheel need replacing. The chain on my bike was about 3mm stretched !!!

Chain stretch isn't normally expressed in mm. It's normally expressed as a percentage.
There are various rules of thumb, like 3 chains per cassette, or replace both chain and cassette if wear is >1%. They are all just general guides and may well be wrong for all I know.

there were definite shark fin shapes on the cassette and the chainset.

Are you quite sure that the unusual shapes on the sprockets were due to wear, and not manufactured ramps and other kinds of cleverness built in to ease shifting.

 

[overmind]

Chain stretch isn't normally expressed in mm. It's normally expressed as a percentage.
There are various rules of thumb, like 3 chains per cassette, or replace both chain and cassette if wear is >1%. They are all just general guides and may well be wrong for all I know.

Yes, I think you are right. 0.75 is a percentage (not sure why I thought it was mm). I reckon mine was about 3%. When I layed it on the floor next to a new chain it was about 3 cm longer (for the same number of links).

Are you quite sure that the unusual shapes on the sprockets were due to wear, and not manufactured ramps and other kinds of cleverness built in to ease shifting.

It was definitely wear. I compared it to a new one. I also look at bikes in the bike store at work. You can tell who maintains their bike because the rear sprockets are in good condition. The bikes that are not maintained look like sharks teeth (mine looked like the bottom on these 2 pictures).

 

[Yellow Saddle]

Yes, I think you are right. 0.75 is a percentage (not sure why I thought it was mm). I reckon mine was about 3%. When I layed it on the floor next to a new chain it was about 3 cm longer (for the same number of links).



It was definitely wear. I compared it to a new one. I also look at bikes in the bike store at work. You can tell who maintains their bike because the rear sprockets are in good condition. The bikes that are not maintained look like sharks teeth (mine looked like the bottom on these 2 pictures).

View attachment 351857

Like I said, you are confusing cassettes, sprockets, chainrings and percentages. 3% wear on a cassette is very hard to do unless you wear all the sprockets evenly, and that's not feasible.

The photos you show are all from driving sprockets, not driven sprockets. Your cassette certainly did not wear like that.

 

[Yellow Saddle]

Both the photos above are of worn driving sprockets i.e. chainrings.
Both the top and bottom chainring was used with an out-of-pitch chain but the top one is suspect in that the sprocket doesn't look like any chainring I'm familiar with. It may be a very cheap chainring because of the lack of ramps, profiles and features typical of a multi-speed bike with aluminium chainrings. Nevertheless, it vague represents Stage 1 wear.

The likelyhood that a cassette will wear with sharp teeth like the bottom sprocket is nil. Some sort of singlespeed bike with very good chain wrap and no tensioner may eventually wear the sprocket to a shape approximating that. I've seen that type of thing in African villages but living with a bike like that is hard. The chain will skate even with good wrap. You'll only be able to feather the pedals lightly.

 

[Tom B]

It depends who I address when I say you can't see wear. I can see it, I can describe it but most of the people who tell others here that they should look out for shark-toothing and shark-finning are imagining it .......

Cassette wear is very subtle and you have to know what to look for. A driven sprocket wears completely differently from a driving sprocket

I'm glad it is not just me then.. I can rarely tell by looking at a worn-out cassette why it is worn. I just know it is because the chain skips.

Both the photos above are of worn driving sprockets i.e. chainrings.
Both the top and bottom chainring was used with an out-of-pitch chain but the top one is suspect in that the sprocket doesn't look like any chainring I'm familiar with. It may be a very cheap chainring because of the lack of ramps, profiles and features typical of a multi-speed bike with aluminium chainrings. Nevertheless, it vague represents Stage 1 wear.

So this is why changing chains as they wear is key to keeping chainrings/cassttes in good order? I suppose you might say it isnt so much the "stretch" that is the issue but the poor fit that it causes?

Where does the "stretch" come from? is it true stretch or is it from wear in the rollers? As another poster has pointed out over the length of a chain it can be quite significant.

 

[Yellow Saddle]

So this is why changing chains as they wear is key to keeping chainrings/cassttes in good order? I suppose you might say it isnt so much the "stretch" that is the issue but the poor fit that it causes?

Where does the "stretch" come from? is it true stretch or is it from wear in the rollers? As another poster has pointed out over the length of a chain it can be quite significant.

Stretch is a swearword. Say elongate.

You are right, the elongation in itself doesn't weaken the chain. The chain elongates by wear on the rivets. It is not the rollers that run on the rivets but their bushings. The bushings wear correspondingly on the inside. Only every second link elongates.
It is the mismatch in pitch between chain and sprocket that causes the problems and the problems are not the same for a driven and driving sprocket. Further, the problems are completely different for a driven sprocket with insufficient wrap and a spring-loaded tensioner a.k.a. a rear derailer.

Here are three rivets. The one on the left is new. The second one has worn enough for the chain to elongate by 0.5% and the third one is off a chain that has elongated by 1%. Incidentally, if you look at how the peen broke off the nearsides of each rivet you know why a rivet cannot be pushed out and re-used.

It is impossible to photograph the wear on the bushing, so here's an graphic from Shimano, showing bushing flank wear.

Here's some roller and bushing detail

This pin is super worn, probably 2% This is just about impossible to achieve on a cassette bike because all the sprockets don't wear at the same rate and the chain will skate on all but say the top and bottom one. This is off a singlespeed chain. Once the chain is worn like this, then the chainring (driving sprocket) shows wear beyond the shark fin stage and into the shark tooth stage.

Someone should write a book about this stuff.

 

[si_c]

Someone should write a book about this stuff.

Well given how much you like to talk about the subject, why don't you give it a shot?

 

[uclown2002]

Well given how much you like to talk about the subject, why don't you give it a shot?

You might want to look at the link in @Yellow Saddle 's signature....