Author Topic: Cassette wear – how many chains?  (Read 8124 times)

Samuel D

Cassette wear – how many chains?
« on: 10 October, 2018, 11:56:46 am »
Click on the photograph to see tooth details more clearly.



On the right is a new CS-HG50-8 cassette with my favourite 13-, 14-, 15-, 17-, 19-, 21-, 23-, and 26-tooth sprockets. I sure hope Shimano never stops making this model.

On the left is an identical cassette with about 16,000 km behind it. I strictly replaced the chain as soon as 12 inches of chain became 12 and 1/16th as measured with a ruler.

I did this five times and was starting to think that under this regime the cassette might last until the teeth wore to narrow spikes and broke off. But no! The sixth new chain skipped on the 15T and 19T sprockets. The 19T sorted itself out after 100 km but the 15T (a staple of Longchamp) did not, so I thanked this cassette for its service and retired it.

Looking at the sprockets closely, I suppose the 15T, being small, does not need as much wear as the 19T to cause problems, because it looks in better shape at first glance.

Sorry for not giving the cassette a bath before the photo.

Cudzoziemiec

  • Ride adventurously and stop for a brew.
Re: Cassette wear – how many chains?
« Reply #1 on: 10 October, 2018, 12:32:19 pm »
Never mind a bath, it looks cleaner than a 16,000 km cassette has a right to! Interesting that the 17-tooth sprocket didn't skip, not only because it's between the two that did, but because some of its teeth look, to me, more worn (to a sharp point) than the 15 and 19. But with teeth being shaped, it's hard to tell visually (to me at least).
Riding a concrete path through the nebulous and chaotic future.

Samuel D

Re: Cassette wear – how many chains?
« Reply #2 on: 10 October, 2018, 01:05:57 pm »
I often tap along in the 19T, and the 15T is one of my most-used gears at Longchamp (a 3.5 km loop usually ridden in a group). But of course I use the 17T plenty. I suppose we can’t know the 17T wasn’t on the verge of skipping.

To eliminate the confusion caused by Shimano’s shaped teeth, here’s the same tooth of each 19T sprocket side by side with an index card behind. (This is after the 19T started working again, but barely.)



If you showed me that photo I wouldn’t have guessed there was danger of the chain skipping. And I’ve also sometimes seen teeth worn to narrower spikes. All of which suggests there’s a fine line between problematic wear and wear that makes no difference.

Paul

  • L'enfer, c'est les autos.
Re: Cassette wear – how many chains?
« Reply #3 on: 10 October, 2018, 01:25:08 pm »
Excellent thread. That second pic really helped me appreciate the effect of wear.

 :thumbsup:

What's so funny about peace, love and understanding?

Cudzoziemiec

  • Ride adventurously and stop for a brew.
Re: Cassette wear – how many chains?
« Reply #4 on: 10 October, 2018, 01:34:08 pm »
Yes, that second photo really shows how the teeth are worn across their length. But it's not so dramatic a difference that you'd notice it without the new cassette for close comparison. So that poses a question for replacement: do you only replace once the problem becomes noticeable in use (and risk a skipping cassette at an inconvenient time), or do you replace as soon as you think it's about to become a problem (and risk replacing needlessly soon)? I guess to an extent it depends on purpose: if you're about to take part in a crucial race, a long event or a long tour, maybe better replace it now. If it's general day to day riding, commuting and stuff, better to wait till it's actually a known problem rather than waste money on it. Or maybe it's possible to measure the size of the most worn teeth on a worn out cassette with calipers and compare to the in-use cassette from time to time, but I don't reckon my precision skills are up to that (your precision might vary, etc).
Riding a concrete path through the nebulous and chaotic future.

zigzag

  • unfuckwithable
Re: Cassette wear – how many chains?
« Reply #5 on: 10 October, 2018, 02:05:40 pm »
most bike shops i know always replace a cassette together with a new chain to avoid customers coming back and saying the gear is skipping (plus they sell more cassettes). i personally replace the cassette when it starts skipping with a new chain. if it doesn't with the new chain it won't when the chain wears in.

Re: Cassette wear – how many chains?
« Reply #6 on: 10 October, 2018, 02:24:08 pm »
If that's the cassette I think it is they're about £15.  How much are you paying for chains?  I'm not sure what the advantage is to using up five chains in 16,000 km to preserve the life of the cassette, does it make economical sense?   I gave up measuring the chains on my Shimano equipped bike, I pay about the same for chains and cassettes so sacrificing one for the other works out more expensive than running both into the ground, current pair have done 6,000km and still running fine, though it doesn't see much wet weather.  Different story on a Campag bike where the cassette cost 3X a chain.

Samuel D

Re: Cassette wear – how many chains?
« Reply #7 on: 10 October, 2018, 04:03:20 pm »
If that's the cassette I think it is they're about £15.  How much are you paying for chains?  I'm not sure what the advantage is to using up five chains in 16,000 km to preserve the life of the cassette, does it make economical sense?

In response to your last question, I’m not sure. This was the first time I rigorously followed a method (changing each chain at 0.5% elongation) to its conclusion (skipping), so until now I didn’t know how long a cassette would last under these circumstances. They start skipping a lot earlier – sometimes on the first new chain – if you ever let a chain wear much more than that.

On the other hand, I don’t know what happens if you run them “both into the ground”. I have avoided trying that because I’m fussy about both shifting and power losses in the transmission. I’ve read some studies that suggest power losses go up with very worn chains and sprockets. Maybe noise too? (Half the single-speeds and fixed-gears in Paris sound like a bag of spanners.) Eventually there may be a non-trivial risk of the chain snapping, especially if you add corrosion into the mix.

The scheme I used ensures perfect operation of the drivetrain at all times. I’d be less fussy with a commuter or something like that.

The other factor is that, despite my wishes, eventually Shimano will stop making the 13–26T CS-HG50-8. When that happens I will be forced to stock up on them before the eBay scalpers get them all. At that point, preserving my cassette stash will matter more to me than saving every penny, so this is an information-gathering exercise for that day. I plan to cycle for several decades and have no great hope of anyone equalling the appeal of Shimano 8-speed – for my needs, natch – in my lifetime.

To answer your other question, my chains have been pretty cheap. I usually add them to online orders for other stuff when I see a good price. My records say I got some SRAM PC-850 chains for €7.63 each and a Wippermann Connex 800 for €9.98 (still in my box of bits). I got a Connex 808 for €13.01 and it lasted nearly twice as long as the SRAM PC-850. I’d like to try another one to make sure that wasn’t a fluke of the season. I got a SRAM PC-830 for €5.49 but it was made of cheese. The PC-850 is pretty good value when you take into account the pleasant fact that replacing a chain with a new one means one less cleaning routine to perform. But the SRAM chains make more noise than a Connex 808 and their quick-links are harder to use.

Kim

  • Timelord
    • Fediverse
Re: Cassette wear – how many chains?
« Reply #8 on: 10 October, 2018, 04:24:52 pm »
Yes, that second photo really shows how the teeth are worn across their length. But it's not so dramatic a difference that you'd notice it without the new cassette for close comparison. So that poses a question for replacement: do you only replace once the problem becomes noticeable in use (and risk a skipping cassette at an inconvenient time), or do you replace as soon as you think it's about to become a problem (and risk replacing needlessly soon)? I guess to an extent it depends on purpose: if you're about to take part in a crucial race, a long event or a long tour, maybe better replace it now. If it's general day to day riding, commuting and stuff, better to wait till it's actually a known problem rather than waste money on it.

That's my approach:  Tourer gets a new cassette when there's reasonable doubt that it'll last until the next chain replacement.  Utility bike gets a new one (possibly the old one from the tourer) when the skipping has caused Bad Words.

LittleWheelsandBig

  • Whimsy Rider
Re: Cassette wear – how many chains?
« Reply #9 on: 10 October, 2018, 04:42:51 pm »
Rohloff do a go/ no go sprocket wear tool for Shimano cassettes. The one I have seems to work ok.
Wheel meet again, don't know where, don't know when...

Re: Cassette wear – how many chains?
« Reply #10 on: 10 October, 2018, 04:47:55 pm »
I'm lazy enough to wear chain and cassette into the ground.  I've only noticed power-loss at the point where the chain has worn so much that the rollers have broken up (only once, unintentionally, towards the end of a 400).  Generally I fit new when gear-changing becomes less reliable.

LittleWheelsandBig

  • Whimsy Rider
Re: Cassette wear – how many chains?
« Reply #11 on: 10 October, 2018, 04:54:52 pm »
On my own bikes, I usually do the same. HK tends to be more fussy, so I'm somewhat less lackadaisical with regards to maintenance.
Wheel meet again, don't know where, don't know when...

Re: Cassette wear – how many chains?
« Reply #12 on: 10 October, 2018, 05:32:27 pm »
Has anyone evaluated the impact of running a worn chain on chainring life? Rings for HollowTech cranksets are not inexpensive.

Re: Cassette wear – how many chains?
« Reply #13 on: 10 October, 2018, 06:27:07 pm »
chainrings definitely wear faster when the chain is worn. If the chain is 0.5% worn then the rollers want to sit 0.5% further outwards on the sprocket/chainring too, and that is what causes the typical hook shape to the loaded face of the teeth.  On a 50T chainring the rollers want to sit 0.5mm further out when the  chain is 0.5% worn. Thus the rollers want to sit 0.25mm further out on a 25T sprocket and ~0.12mm further out on a 13T sprocket. For several reasons the wear is likely to be more aggressive on smaller sprockets.

   The more worn the chain is, the more likely it is that the load won't be shared well between teeth and the more likely it is that the rollers will move (against the tooth face) under load, which means the wear rate (of everything) gradually increases.

Hooks on teeth are obvious but they don't exist without a 'ramp' developing too. The ramp leads from the well between teeth into the hook.  The skipping of the chain at the rear is due to the chain failing to engage with the sprocket as it leaves the guide pulley. It is fairly obvious that a hook can obstruct the chain engagement. What is less obvious is that the ramps can push loaded rollers further outwards on the tooth profile than normal, and this causes the chain to be tight against the teeth where the pitch is longer than the pitch of a less worn chain. In this case the chain won't engage even though there is no obvious 'hook'.

Anyway worn chainrings (with some hooking) tend to be noisy when used with a new chain but usually settle down after a few hundred miles.


I think that ramps don't form so much (in relation to hooks) if the chain wears relatively slowly at first, and faster later on.  New chains actually come between 0 and 0.2% worn (as measured after about 100 miles). If you run some sprockets with several  chains that are + 0.2% from new and then use a +0.0% length chain I think it is likely that the chain will skip.

cheers

Re: Cassette wear – how many chains?
« Reply #14 on: 10 October, 2018, 06:35:42 pm »
Has anyone evaluated the impact of running a worn chain on chainring life? Rings for HollowTech cranksets are not inexpensive.

Yes. It fucks them in short order.

Just this afternoon I've serviced a neighbours bike for him. A Boardman Carbon with Sram Apex. He's had it 3 years, doing 30 miles on a Sunday sometimes.

Straight away I spotted worn ring, with chain sitting above the teeth. I didn't need to ask him if he had ever changed the chain  ;)

He's lucky. I managed to get him a new 50t SRAM ring, a new cassette, and a decent SRAM chain for £65, from Germany, and I fitted it for free.

LittleWheelsandBig

  • Whimsy Rider
Re: Cassette wear – how many chains?
« Reply #15 on: 10 October, 2018, 11:07:13 pm »
It fucks soft chainrings like SRAM and Shimano. TA and older Campag rings seem impervious to years of abuse.
Wheel meet again, don't know where, don't know when...

rogerzilla

  • When n+1 gets out of hand
Re: Cassette wear – how many chains?
« Reply #16 on: 11 October, 2018, 06:40:32 am »
Usual rule of thumb is 3 chains per cassette, if you change them at 12 1/16".  Chainrings may last three cassettes if they're any good, but modern thin pressed ones aren't, and wear out much faster.

On a fixie/singlespeed/hub gear iyou often run the sprocket and chain into the ground and replace them together; they don't generally slip and they get quieter as they wear into each other.
Hard work sometimes pays off in the end, but laziness ALWAYS pays off NOW.

Re: Cassette wear – how many chains?
« Reply #17 on: 11 October, 2018, 07:02:43 am »
Certainly 11sp high end stuff will wear quicker than your dad's old butchers bike, but one is fun to ride and the other isn't.

Assuming 2000 miles per chain, that's 18,000 miles per chainring which is probably about right.

Does anybody ride high end gear for reasons of economy? Of course not.

LittleWheelsandBig

  • Whimsy Rider
Re: Cassette wear – how many chains?
« Reply #18 on: 11 October, 2018, 08:13:26 am »
I choose stuff so that I don't have to replace it every few weeks. Checking and swapping chains monthly (in summer) is a pain in the arse.
Wheel meet again, don't know where, don't know when...

Re: Cassette wear – how many chains?
« Reply #19 on: 11 October, 2018, 08:16:42 am »
It fucks soft chainrings like SRAM and Shimano. TA and older Campag rings seem impervious to years of abuse.

You omitted Campagnolo from the first sentence. The two shittest rings I've ever used were a Campag Centaur, and a rebadged Stronglight c/set.

By contrast I had a DA 7800 that just wouldn't die.

Re: Cassette wear – how many chains?
« Reply #20 on: 11 October, 2018, 08:18:49 am »
I choose stuff so that I don't have to replace it every few weeks. Checking and swapping chains monthly (in summer) is a pain in the arse.

Wow, you must do about 400 miles a week. If I did that many miles I'd be too tired to swap chains too.

LittleWheelsandBig

  • Whimsy Rider
Re: Cassette wear – how many chains?
« Reply #21 on: 11 October, 2018, 08:27:01 am »
In summer, I do.

I did note 'older Campag'. The modern Campag rings I've used are made of mozzarella.
Wheel meet again, don't know where, don't know when...

Cudzoziemiec

  • Ride adventurously and stop for a brew.
Re: Cassette wear – how many chains?
« Reply #22 on: 11 October, 2018, 09:18:58 am »
The other factor is that, despite my wishes, eventually Shimano will stop making the 13–26T CS-HG50-8. When that happens I will be forced to stock up on them before the eBay scalpers get them all. At that point, preserving my cassette stash will matter more to me than saving every penny, so this is an information-gathering exercise for that day. I plan to cycle for several decades and have no great hope of anyone equalling the appeal of Shimano 8-speed – for my needs, natch – in my lifetime.
I know someone who bought a brand new bike, of decent quality (Specialized Diverge) a year or so ago and it came with 8-speed. I think Shimano are calling this their Claris groupset now. So I reckon 8-speed cassettes and chains will be around for a while yet, though of course they might not be making your favourite ratios.
Riding a concrete path through the nebulous and chaotic future.

Re: Cassette wear – how many chains?
« Reply #23 on: 11 October, 2018, 11:08:23 am »
In summer, I do.

I did note 'older Campag'. The modern Campag rings I've used are made of mozzarella.

Yeah, I noticed it, I bolded it.

I view modern Campag as being inferior to Shimano in terms of owning and maintaining it (as you know). The stuff I drooled over in the 80s but could never afford was akin to Leica in terms of quality.

Samuel D

Re: Cassette wear – how many chains?
« Reply #24 on: 11 October, 2018, 11:29:18 am »
Tourer gets a new cassette when there's reasonable doubt that it'll last until the next chain replacement.

That approach does no real harm, but as zigzag said and Brucey explained, if the new chain doesn’t skip at the outset, it won’t skip later in its life. So as long as you’ve test-ridden a new chain to check it doesn’t skip, you can safely take an old cassette on a long trip.

There is a clear explanation of chain wear and why most chain-wear tools measure the wrong thing, plus good diagrams showing a worn chain riding high on the sprocket teeth at Pardo.Net (an antediluvian site that Google renders nearly invisible in searches despite its excellent content).

I also liked Johan Bornman’s e-book, Everything you need to know about Bicycle Chains. It’s cheap and easy to read.

I know someone who bought a brand new bike, of decent quality (Specialized Diverge) a year or so ago and it came with 8-speed. I think Shimano are calling this their Claris groupset now. So I reckon 8-speed cassettes and chains will be around for a while yet, though of course they might not be making your favourite ratios.

I agree that 8-speed parts are going nowhere soon. My last 13–26T cassette came in Shimano’s updated blue box rather than the old grey, which was reassuring.

All the same, Shimano recently purged a bunch of 7-speed cassettes (good road-focused ones). And the bicycle industry is undergoing unprecedented change, so it’s hard to predict the future based on the past. Many of the long-time standards have been dumped recently, and once that wrecking process has been completed, there won’t be much left to protect from fickle change. At that point the floodgates are opened and it’s impossible to predict how Shimano will react. The increasing rationalisation of business in general often leads to niche products being actively hounded out of town. The long tail is dead for physical products.