worn components - how to know when to change

[User6179]

OK, I'll take that as a no. In our out of competition, physics don't change.

Note, chains should be replaced when they have elongated (through wear in the pins and bushes) by 0.5%. If you leave it to 1%, it would already have destroyed the cassette. No chain can wear by 10% It would just be impossible since by then there will be no teeth left on the sprocket. Chains wear sprockets and the more the chain is out of pitch, the more the sprocket is worn down by it. A chain that's 10% out of pitch would have worn through all available meet on the sprocket teeth*.

Further, a worn chain does not affect shifting and conversely, when you fit a new chain, shifting doesn't improve. The two are not linked in that way.

A competitive environment chances nothing. People often say they ride hard or rough. That has no effect on chain wear or spoke wear for that matter. I only mention the latter because that is also often stated but is also a myth.

* The correct term for one tooth on a sprocket or a gear is a cog but I'm farthing against thunder when trying to stick to the definition on that one.

I ran my ultegra set-up 5000 miles then changed only the chain and got a further 3000 miles out the cassette .
When i changed the chain , the old chain was 3/4 of an inch longer for same number of links , I reckon this could be a record

 

[Yellow Saddle]

I ran my ultegra set-up 5000 miles then changed only the chain and got a further 3000 miles out the cassette .
When i changed the chain , the old chain was 3/4 of an inch longer for same number of links , I reckon this could be a record

Pity we don't know how many links it had, then we could have done the calculation and maybe get you into the record book.

 

[User6179]

Pity we don't know how many links it had, then we could have done the calculation and maybe get you into the record book.

Does 110 links sound about right for 52/39 crank with 12/25 cassette ?

 

[Yellow Saddle]

Does 110 links sound about right for 52/39 crank with 12/25 cassette ?

It sounds right but by being out by just one link, the difference is significant. Also, I presume your 3/4 inch is an estimation.

However, lets try. New, 110 links equals 55 inches of chain.
After use, the chains was 55.75 inches long, which is an elongation of just over 1%.

Sorry, no cigar.

 

[sreten]

Hi I try to do most bike maintenance myself to save money and get to know my bike. Something I've never really understood is how to tell when things need changing.

I was recently told by a mechanic to change chains after 1000 miles. I know there's tools for checking the amount of stretch but are these all compatible or do you have to use an expensive laser one.

The biggest mystery to me is the crankset and fear cassette, I've had a few changed in lbs's before after they said 'look can you see how much that's worn' I agreed but tbh couldn't tell at all. Is this very subjective or is there a foolproof way to make a judgement?

All tips much appreciated!

Hi,

Your best bet is to rotate chains every 1000 miles, usually 3. You usually just replace a chain with 1/16" stretch over 12",
but here you can take all three to 1/8" stretch over 12". At this point, you can carry on but will toast the chainwheels.
Alternatively replace all the chains and the rear cassette.
They say about 3 chains per rear cassette and about 3 rear cassettes per chainwheel. With 2 or 3 of the latter
wear will depend on how often each one is used, I split my 2 fairly evenly, and expect to have to change
the cranks only after getting through about 15 chains and 5 rear cassettes. **
Of course just running one chain into the ground will toast the the cassette and the chainrings,
unless it slips so bad you fix it before the front chainrings become no longer usuable.

There are a lot of foolproof indications of wear, you only have to look. Hooked teeth, stretch over 12" of the chain.
Try pulling the chain off the front ring at the front, how much does it move ?* A guy asked me why his rear gears kept
slipping, it was obvious, utterly toasted rear cassette central gears, with the chain running very high on the teeth.

FWIW I've seen posts with stretch far worse than 3/4" over a chain length, much worse.
I just can't recall the actual number, but it was something like 15%, I kid you not.

rgds, sreten.

* A very easy way to indicate to people their chain is worn.

** The erudite will realise that by rotating chains and cassettes the the chain wheels
can be made to last almost indefinitely, by eaking out the stretch of say 15 chains,
and the wear of 5 cassettes and two chain wheels to well beyond normal wear,
say 1/4" stretch over 12" , but most people simply don't want to do that. If you
do I've no idea at what point you will run into insurmountable problems.

 

[Yellow Saddle]

Hi,



FWIW I've seen posts with stretch far worse than 3/4" over a chain length, much worse.
I just can't recall the actual number, but it was something like 15%, I kid you not.

Running a chain over 0.5% wear accelerates wear in all components including the expensive chainrings. The system or rotating several chains merely delays the inevitable with a slightly increased cost comparing like for like. Further, a chain running at 1% wear is pretty noisy on the chainring as the incoming cog bashes against the out-of-pitch roller and forces into a space of the wrong size.

For a chain to elongate by 15% you will have to have 30% elongation at the individual bushings (only every second link wears*) and that would represent a chain that is so out of pitch that the wear will take up more distance than the width of the individual cogs. It simply is not possible to wear out a chain by 15%

I showed earlier on how just 1% wear represents a 3/4 inch increase in a 110 link chain. You can do the math on 15% wear and you'll see that it is not possible.

 

[MickeyBlueEyes]

Loved reading this thread as on Saturday I changed my cassette, chain and both front chainrings. It's the first time I've changed the front rings, they saw just over 23'500miles. The chain saw around 13'000 miles. I don't know the exact figure but I put the 11-28 cassette on for climbing Hardknott Pass back in 2011, so this has also seen the best part of 22'000 miles.
Changing components is waaaay too over-rated in my book Keep on top of your cleaning, look after your kit and you get way more miles than 'they say change it after...'

 

[Deleted member 1258]

On both my Fixed and my geared bike I change chains every 12 months, on the fixed I change cog and chainring every two years, on the geared bike I change the cassette every three years and I'll change the chainrings when they look worn. I do between 4-5000 miles a year split between two bikes.

 

[sreten]

I change chains every 12 months, on the fixed I change cog and chainring every two years, on the geared bike I change the cassette every three years and I'll change the chainrings when they look worn. I do between 4-5000 miles a year split between two bikes.

Hi,

There in no way a fixed gear should need the rear cog and chainring changing at the same time.
I don't ride one, but changing the rear cog and chain at the same time makes more sense to me.

I'm lost with some of these posts, if you look after your chain, and
replace it before it is too worn, chainrings should last utterly ages.

rgds, sreten.

 

[Deleted member 1258]

Hi,

There in no way a fixed gear should need the rear cog and chainring changing at the same time.
I don't ride one, but changing the rear cog and chain at the same time makes more sense to me.

I'm lost with some of these posts, if you look after your chain, and
replace it before it is too worn, chainrings should last utterly ages.

rgds, sreten.

I can get two chains to a cog, theres no point in changing the cog at the same time as the chain, that way I'm just throwing away a component that still has usable life in it, after two years use the chain ring has done over 6000 miles and is visibly worn.