Old question:Chain wear

[knonist]

are we supposed to replace the chain at 0.75% or 1% wear?

if we are supposed to replace the chain at 0.75%, why the chain wear indicator have both 0.75% and 1%?

Also, is it REALLY better to rotate between two two three different set of chains to make the cassette last longer? Is therer any fact in this theory?

 

[PpPete]

IIRC
At .75 Replace chain, or if not.....
at 1.00 Replace chain and cassette

Never done enough miles to worry about rotating between multiple chains

 

[Alf]

I agree. I suppose you only 'have to' change your chain when it starts slipping over the cogs and you can't ride any more, but if you leave it that long you will probably have to change your chain rings too. If you change your chain at 0.75% you will probably make your cassette last for three chains at least. Keep your chain well lubed and you won't have to worry so much about it because it will last a lot longer anyway.

Alf

 

[GilesM]

Also, is it REALLY better to rotate between two two three different set of chains to make the cassette last longer? Is therer any fact in this theory?

I do this, I have three chains that I change every couple of months on both my mtbs, it helps get a bit more life out of the cassette and chain rings, especially the middle ring for off road riding.

 

[AlanW]

I have three chains that I change every couple of months on both my mtbs, it helps get a bit more life out of the cassette and chain rings, especially the middle ring for off road riding.

How does it?

Sorry but just I cannot figure this one out, as basically, all you are doing is extending the life of the chain by not using it?? Unless it shrinks coz its not being used of course.

I have one chain, when its gets to .75% wear I replace it, is that so complicated?

Then on the fourth chain replacement I fit a new cassette.

 

[andrew_s]

The point in rotating chains is that you are not wasting a lot of money throwing away chains that would carry on working OK for quite a while.

Let's work it out
A Sram PC951 chain costs £18.33
An HG50 9-speed cassette costs £26.

IME, a chain reaches .75% in about 1500 miles, and will start to give trouble at about 7500 miles when not changed at all. Chain wear is very variable but I reckon this is pretty realistic, for my maintenance regime anyway.

So if you buy a cassette and 3 chains (total cost £81) and rotate the chains regularly, you get something like 22500 miles use.
If you change chains at .75% and buy a new cassette every 4th chain, over the course of 22500 miles you will have bought 15 chains and 3 cassettes, total cost £353

OK, using 3 chains to death will leave you with pretty worn chainrings, but replacing them will cost substantially less than the £272 you've saved.

 

[ACW]

Grit and s##t wear the chain, chain wears the sprockets, as the chain stretches it changes the pitch of the sprocket so the new chain then slips.
If you rotate chains then the sprocket and chain combo wont get out of step by much.

I still have the scars from falling off due to the chain slipping on the chain ring when sprinting up a hill, went over the handelbars and landed on my head!

I now ride a recumbent with a chain 3 times as long, so for the same number of miles the chain will go over the sprockets 3 times as less, as i understand it the chain only wears when you bend it over a sprocket, so it should last 3 times as long?

Downside is it costs 3 times a much to replace.

 

[Alf]

The point in rotating chains is that you are not wasting a lot of money throwing away chains that would carry on working OK for quite a while.

Let's work it out
A Sram PC951 chain costs £18.33
An HG50 9-speed cassette costs £26.

IME, a chain reaches .75% in about 1500 miles, and will start to give trouble at about 7500 miles when not changed at all. Chain wear is very variable but I reckon this is pretty realistic, for my maintenance regime anyway.

So if you buy a cassette and 3 chains (total cost £81) and rotate the chains regularly, you get something like 22500 miles use.
If you change chains at .75% and buy a new cassette every 4th chain, over the course of 22500 miles you will have bought 15 chains and 3 cassettes, total cost £353

OK, using 3 chains to death will leave you with pretty worn chainrings, but replacing them will cost substantially less than the £272 you've saved.

I am not convinced. I think there are some assumptions in there that could stand some further scrutiny, if I may say so. 1) You might get 7500 miles out of a chain, before it slips on the sprockets, especially with good maintenance, but I doubt if that would be the same chain, conditions, maintenance, etc that gave you .75% after only 1500 miles. That would imply you could still be riding with nearly 4% wear assuming the rate of wear is linear.

2) The calculation assumes not only that you can do that with one chain but that you could reach that degree of wear with 3 chains and still have teeth left on the cassette. For that to be possible, I think the only factor that can be wearing the cassette would have to be the wear on the chain. In fact, I suspect that the same muck and grit that wears your chain also has an effect directly on the cassette. That implies that if 7500 is the theoretical maximum with one chain, the cassette itself would be too worn to get that much for three chains.

I can see that if you have worn down a cassette as little as possible by changing the chains (say 3 of them) at .75%, you might as well finish the cassette off by making the last chain go to 1%. You might even manage to get a second old chain (if you can find it) up to 1% as well but after that, I think your transmission is going to get increasingly inefficient and you risk undue wear on your chainrings.

Alf

 

[MacB]

Well I've resisted buying a chain measuring device, I sought advice when I started and got a variety. Fancy chain cleaning methods, changing chains as often as every 600 miles, rotating chains. One bike mechanic said that I could do all that or I could just let it all wear together and replace cassette, chain, and chainring if necessary, at same time. I picked up the Mickle Method of chain cleaning from here. Basically run chain, on bike, through a rag and then oil, I do this once a week.

The setup has done about 2.5k miles and no sign of problems yet, even if I had to replace it all now it would still be cheaper than any of the fancier regimes suggested. But this is basic level kit, £40 tops for cassette and chain, if you spend fortunes on them then extending life may matter more. I also don't change gear much, I'll vary tempo, or get out of saddle, and use gear changes as a last resort. Certainly it all works a darn sight better than anything I remember from my youth

 

[AlanW]

OK then, lets look at it in the real world.

I'll leave a chain on till it reaches .75% wear, normally at around 1200 miles or just over a months worth of riding.

Then I take it off and fit a new one and then repeat this for a third time.

When the third chain reaches 0.75% I now replace it with the first chain, which was originally replaced coz it had reached its tolerance?

So I am gaining what exactly?

10sp drive trains have very close tolerances, they do NOT like a great deal of wear. Great idea, but like most good ideas it comes at a cost, ie having to replace the chains more often.

 

[moolarb]

some strange logic here...

cassettes don't cost much more than chains, certainly at the low to mid-price range - I just bought a SRAM cassette for £40 and a chain would cost about £30, so why are you buying 3 or 4 chains to save money on one cassette?

I'm not sure I would get 7500 miles out of a chain as I do a lot of hill/winter riding but I got over 4000 miles on my last chain with no issues at all. So I had to replace the cassette as well (£40), big deal, still cheaper than buying 3 or 4 chains.

 

[knonist]

I have been commuting for 5 months with my "new" bike.
18 miles a day,22 days per month.
that's around 1980 miles.

Some people suggested that the chain will reach the 0.75% mark with around 1500 miles. And so far, my chain hasnt gone down to 0.75% yet.

I dont use the high gears so much, so I guess that reduced the wear?
or worst, my chain wear indicator is not fit for purpuse...