Chain wear (recumbent specific)

[mrandmrspoves]

I recently measured my chain and it showed it was time for replacement - so I did. The new chain immediately started to slip in some commonly used gears and there was also some mild chain suck.
So I decided I needed a new cassette and crank set (I have been using a cheapo 152mm crankset so it is disposable rather than changing rings)
I then thought that as I had no problem previously and was only changing the chain to prevent wear to the rest of the drive train, it made sense to put the worn chain back and continue running it until it became problematic. At least us bent riders never have to fear gonad damage if the chain breaks when out of the saddle!
My question is: assuming that a well cared for recumbent chain is 2.5 x longer than a standard chain it should last 2.5 x longer - but what is the effect of this on the other drive train components? I assume that part of the wear on the other components is caused by the worn chain....but is that really significant or would you still expect to change the other drive train components every time you replace the chain?

 

[mjr]

I wonder what @Yellow Saddle's take on the theory of this is.

 

[numbnuts]

I'm a great believer in “if it ain't bust why fix it”

 

[Yellow Saddle]

At least us bent riders never have to fear gonad damage if the chain breaks when out of the saddle!

I know your comment is 99% in jest but let the other 1% in you please note that a worn chain has no increased tendency to break. Wear is considered to be less than 1% elongations which means a tiny, tiny little bit in reduction of bushing and rivet thickness (0.5% in each) and the remaining bits are still strong enough to support about 3.5 tons.

My question is: assuming that a well cared for recumbent chain is 2.5 x longer than a standard chain it should last 2.5 x longer - but what is the effect of this on the other drive train components? I assume that part of the wear on the other components is caused by the worn chain....but is that really significant or would you still expect to change the other drive train components every time you replace the chain?

A longer chain will spare other drivetrain components only a very small bit over a much shorter chain. The reason is that chain wear only happens at two points in a link's revolution around the train. It happens when:

1) the chain exits the rear (driven) sprocket and makes that reticulation from angled to straight under tension. For instance, if it is a 10-tooth sprocket, the reticulation angle is 36 degrees. The moment the chain exits the sprocket it returns to 180 degrees and that movement is frictional. As that link travels forward it remains stationary on its own pivots and therefore doesn't wear.
2) The chain enters the front (driving) sprocket. As it enters that sprocket it reticulates again at an angle of 360/sprocket tooth count. This time say 10 degrees on a 36-tooth sprocket.

There are the only two significant wear points for a chain. The chicane where it enters the rear cassette via a zig-zag derailer pulley system is in slack so there is very little wear. Ditto for exiting the front sprocket.

Now, on a longer chain you will get more vehicle travel distance per articulated chain link than on a shorter chain. Therefore a longer chain will wear less.

Let's look at the sprockets. They wear from a few mechanisms.

1) Repeated pressure and release of chain roller against tooth with grit in-between.
2 Cross-chaining. If you cross-chain, the sprocket width is reduced, especially on aluminium sprockets. This reduces the area of the pressure face on the sprocket and causes crushing. It can be seen on worn chainrings as material pushed to the side.
3) Teeth being forced into the worn chain's out-of-pitch spacing. Under tension (when the chain link enters the driving sprocket) the teeth are forced into position and this is done with friction.
4) Worn chain causes only one link to support the load on the sprocket. In both the driving and driven sprockets, an out-of-pitch chain will see to it that less teeth take up the tension in the chain. This increases wear.

So, from a sprocket point of view, a worn chain only affects points two and three.

My guess is that a longer chain will lead to reduced sprocket wear but not in a direct correlation to increased chain length. You may now get four chains per cassette whereas on a short bike you will only get three.
3) Fewer teeth supporting the load. As

 

[Yellow Saddle]

I'm a great believer in “if it ain't bust why fix it”

Well, then stop servicing your car. Wait until the engine busts, then fix it.

Maintenance makes sense. It saves us money, it increases the reliability of the product, it saves lives, it saves hassle, it saves you being stranded somewhere and it spreads the cost of ownership and use over a period rather than present it in lumps.

The adage may be cute but it is rubbish.

 

[mrandmrspoves]

Thanks for your extensive thoughts on this @ Yellow Saddle - that all makes sense to me.

I agree with your comment about chain wear not (directly) correlating with the likelihood of a chain breaking to a point - but I would think that advanced chain wear is also an indicator of poor maintenance and that is likely to indicate a neglectful cyclist who may also crunch gear changes, cross chain and other cardinal sins of cycling all of which may also result in chain damage

 

[arallsopp]

I found my upright patterns used to go like this:

• First time the chain stretches to point of needing a replacement, just replace that.
• When chain number two needs replacing, its probably also time to replace the sprockets.
  
• When chain number three needs replacing, its probably also time to replace the chain rings. Or buy a new bike. Or both.

On a bent with a chain that wears about 2.5x as slowly, that resolves as:

• Don't replace anything until the chain rings are worn and the rear sprocket looks like a parade of sharks.
• Then replace it all. Or buy a new bike. Or both.

That's worked for me. For my 8 speed 'bent, I managed to get about 14000 miles out of the drivetrain before doing anything. Often (shame to say) including things like cleaning, lubing, even really noticing its there, to be honest

 

[ufkacbln]

First time I got the run through the rollers the wrong way round, and that caused issues

Now I use fishing line

Tie it to the end of the chain and it will follow the chain route

Then tie new chain on to the line and pull through

Ensures the line is correct, and makes taking the chain through tubing much easier

 

[Yellow Saddle]

I found my upright patterns used to go like this:

• First time the chain stretches to point of needing a replacement, just replace that.
• When chain number two needs replacing, its probably also time to replace the sprockets.
  
• When chain number three needs replacing, its probably also time to replace the chain rings. Or buy a new bike. Or both.

On a bent with a chain that wears about 2.5x as slowly, that resolves as:

• Don't replace anything until the chain rings are worn and the rear sprocket looks like a parade of sharks.
• Then replace it all. Or buy a new bike. Or both.

That's worked for me. For my 8 speed 'bent, I managed to get about 14000 miles out of the drivetrain before doing anything. Often (shame to say) including things like cleaning, lubing, even really noticing its there, to be honest

I'm sure you didn't mean to present this as an indication of how sprocket teeth wear but I do think it needs some clarification. I assume "parade of sharks" refers to the common shark-fin shape of a worn chainring. In that case you'll never replace a chain because rear (driven) sprockets don't wear into that pattern. Because the chain enters the driven sprockets under slack and exits under tension, the chain isn't forced into the mismatched tooth pitch like it is at the front (driving sprocket). Instead, it rides a little higher away from the root of the teeth and wears a pocket into the contact edge. The tooth tip therefore never sharpens but the root lengthens. At the front it is a different story. Here the parade of sharks is a clear sign that the sprocket needs replacing.

 

[byegad]

It's swings and roundabouts.
Swings.
You change the chain at 0.75% worn and the cassettes and Chainrings will last many chain swaps. Cost of 3 chains to make up the run recurs fairly often.
Roundabouts.
You let it all wear until the chain is so worn that it slips on the less frequently used chainring and/or cassette ring. Then you buy a whole new drive-train and it costs a bomb.

I subscribe to the former, using cheapish SRAM chains and Chainsaw oil as a lubricant, I get 3-4000 miles out of a chain and 3 -4 chains to the cassette. Chainrings, I've never had to replace for wear yet.

 

[Tigerbiten]

I've changed my chain every year just before the start of that year tour. This means I've got around 8,000 miles out of it.
My Rohloff sprocket will last two chains on each side, so every 32k miles I will need to replace it. I'll also replace my chainrings at the same time.
Apart from that, I'll just keep it oiled so it runs free.

 

[byegad]

I can recommend Chainsaw oil. It needs an occasional spray of GT85 or similar after around 6 months to keep is 'wet', but one application will usually last the life of a chain.