Yet Another Cycling Forum

General Category => The Knowledge => Topic started by: Samuel D on 10 October, 2018, 11:56:46 am

Title: Cassette wear – how many chains?
Post by: Samuel D on 10 October, 2018, 11:56:46 am
Click on the photograph to see tooth details more clearly.

(https://imageshack.com/a/img922/5418/794qk4.jpg) (https://imageshack.com/a/img922/5418/794qk4.jpg)

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.
Title: Re: Cassette wear – how many chains?
Post by: Cudzoziemiec 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).
Title: Re: Cassette wear – how many chains?
Post by: Samuel D 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.)

(https://imageshack.com/a/img922/6996/AI3gLL.jpg) (https://imageshack.com/a/img922/6996/AI3gLL.jpg)

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.
Title: Re: Cassette wear – how many chains?
Post by: Paul on 10 October, 2018, 01:25:08 pm
Excellent thread. That second pic really helped me appreciate the effect of wear.

 :thumbsup:

Title: Re: Cassette wear – how many chains?
Post by: Cudzoziemiec 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).
Title: Re: Cassette wear – how many chains?
Post by: zigzag 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.
Title: Re: Cassette wear – how many chains?
Post by: Paul H 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.
Title: Re: Cassette wear – how many chains?
Post by: Samuel D 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.
Title: Re: Cassette wear – how many chains?
Post by: Kim 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.
Title: Re: Cassette wear – how many chains?
Post by: LittleWheelsandBig 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.
Title: Re: Cassette wear – how many chains?
Post by: Ian H 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.
Title: Re: Cassette wear – how many chains?
Post by: LittleWheelsandBig 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.
Title: Re: Cassette wear – how many chains?
Post by: sojournermike 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.
Title: Re: Cassette wear – how many chains?
Post by: Brucey 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
Title: Re: Cassette wear – how many chains?
Post by: Hot Flatus 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.
Title: Re: Cassette wear – how many chains?
Post by: LittleWheelsandBig 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.
Title: Re: Cassette wear – how many chains?
Post by: rogerzilla 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.
Title: Re: Cassette wear – how many chains?
Post by: Hot Flatus 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.
Title: Re: Cassette wear – how many chains?
Post by: LittleWheelsandBig 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.
Title: Re: Cassette wear – how many chains?
Post by: Hot Flatus 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.
Title: Re: Cassette wear – how many chains?
Post by: Hot Flatus 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.
Title: Re: Cassette wear – how many chains?
Post by: LittleWheelsandBig 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.
Title: Re: Cassette wear – how many chains?
Post by: Cudzoziemiec 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.
Title: Re: Cassette wear – how many chains?
Post by: Hot Flatus 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.
Title: Re: Cassette wear – how many chains?
Post by: Samuel D 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 (http://pardo.net/bike/pic/fail-004/000.html) 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 (https://www.amazon.co.uk/Everything-need-about-Bicycle-Chains-ebook/dp/B00O46YUW0/) 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.
Title: Re: Cassette wear – how many chains?
Post by: Samuel D on 11 October, 2018, 11:44:54 am
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.

Would you confirm this is roughly what you mean by those terms?

(https://imageshack.com/a/img921/9850/6XhdRb.jpg) (https://imageshack.com/a/img921/9850/6XhdRb.jpg)

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'.

Right. I’ve observed that hooks aren’t strictly necessary to cause the problem, especially, it seems, with small sprockets. And yet the longer pitch of a worn chain would seem, from basic geometry, to increase the chain’s ride height less on smaller sprockets than on bigger ones, in absolute terms (and more importantly, relative to the fixed tooth height). So it’s still slightly surprising to me that small sprockets so readily cause skipping.
Title: Re: Cassette wear – how many chains?
Post by: Cudzoziemiec on 11 October, 2018, 12:09:01 pm
All the same, Shimano recently purged a bunch of 7-speed cassettes (good road-focused ones).
Road-focussed might be the long-term problem. As 8-speed and pretty soon 9-speed slip down the hierarchy, they will cease appearing on new road bikes and only be found on cheaper hybrids and MTBSOs. The Diverge I mentioned is a sort of "gravel bike" (friend uses it for long on- and off-road randonnee type rides) so falls into the gaps Shimano have created between road and mountain.
Title: Re: Cassette wear – how many chains?
Post by: LittleWheelsandBig on 11 October, 2018, 12:56:29 pm
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.

WAP doesn't pick up bolded text.

I wholeheartedly agree about modern Campag. vs. older. They've systematically removed every single reason to choose it over Shimano, hence the reason that HK's newest machines have completely avoided Campag. I don't see that situation changing back.
Title: Re: Cassette wear – how many chains?
Post by: Ham on 11 October, 2018, 01:00:04 pm
I think I probably achieved top chain wear classification when I was doing my cross London Commute a few years ago. I tried all manner of lubricants and regimes and settled on change chain and cassette every two chains. Possibly a bit excessive but it kept everything running sweetly and 9 speed chains and cassettes could be had cheaply
Title: Re: Cassette wear – how many chains?
Post by: grams on 11 October, 2018, 01:08:13 pm
Road-focussed might be the long-term problem. As 8-speed and pretty soon 9-speed slip down the hierarchy, they will cease appearing on new road bikes and only be found on cheaper hybrids and MTBSOs.

Claris and Sora (8 and 9 speed) both got complete redesigns in 2016 so are good for a few years yet. In fact, Shimano used the same speed count for all of the last round of redesigns - nothing moved down the hierarchy.

And as they all now all use very similar designs they don’t really have any other way to differentiate them, and there’s no road 12 speed coming in from the top to push others down, I can see them sticking with the current setup for a while.
Title: Re: Cassette wear – how many chains?
Post by: Hot Flatus on 11 October, 2018, 01:39:39 pm
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.

WAP doesn't pick up bolded text.

I wholeheartedly agree about modern Campag. vs. older. They've systematically removed every single reason to choose it over Shimano, hence the reason that HK's newest machines have completely avoided Campag. I don't see that situation changing back.

I don't blame them, it's just what they have to do to compete. Outsource production, and come up with poor design solutions to the problem of not infringing Shimano patents.

The problem for them is that Shimano do what they do very very well.

I don't know much about SRAM.
Title: Re: Cassette wear – how many chains?
Post by: Samuel D on 11 October, 2018, 01:49:47 pm
Claris and Sora (8 and 9 speed) both got complete redesigns in 2016 so are good for a few years yet.

The recent batch of ‘Claris’ cassettes isn’t ideal for me though, because they all waste metal on 11T sprockets.

All I need for long-term use of 8-speed is a supply of suitable cassettes. My indexed down-tube shifters last a very long time, don’t get damaged in crashes, and I have four pairs in reserve (got nearly for free in a close-out sale). Loads of rear hubs work (unlike for 7-speed). Loads of derailleurs have the right shift ratio, even if they’re not labelled 8-speed (I currently use a 10-speed RD-7800, for example). Loads of chains work whatever their speed label. Loads of chainrings work, and my Spécialités T.A. ones wear very slowly anyway.

Part of my interest in this experiment was to find out how many cassettes I might need for, say, three decades of cycling. By then, as a friend remarked, I might want something cushier than 26T for a low gear (depends where I live then).

Low running costs are an essential part of the freedom of cycling.
Title: Re: Cassette wear – how many chains?
Post by: CrazyEnglishTriathlete on 11 October, 2018, 01:58:58 pm
In summer, I do.

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

It would be great if cycling magazines started talking about how long things lasted rather than how light they were.  However, I suspect that if they revealed the great fraud of modern cycle components (that things wear out quicker) they'd quickly lose all their advertising revenue.
Title: Re: Cassette wear – how many chains?
Post by: LittleWheelsandBig on 11 October, 2018, 02:41:10 pm
Some magazines used to do long-term tests but the riders didn't do enough mileage to talk sensibly about durability before the model was superseded, starting the whole cycle again. I noticed that any deficiencies of a particular model were only mentioned when the subsequent model was released (which obviously solved those problems).
Title: Re: Cassette wear – how many chains?
Post by: Hot Flatus on 11 October, 2018, 03:14:06 pm
Do many high mileage cyclists read cycling mags?
Most of them are pretty poor. Recycled training articles and reviews written by people who don't really know much. I always giggle when I see journos talking about certain wide and deep carbon wheels definitely feeling faster. Light wheels feel fast to me, but the main advantage of deep carbon wheels is that they make a really cool veeeeeerp sound as you ride along.

Why do mags never mention this key selling point?
Title: Re: Cassette wear – how many chains?
Post by: LittleWheelsandBig on 11 October, 2018, 03:17:04 pm
My annual mileage isn't that high but we subscribe to several cycling mags, though one subscription will lapse in February. I eventually couldn't put up with the depth of bullshit created from trivial riding and advertorial puffpieces. HK thinks that most mags are a waste of space.
Title: Re: Cassette wear – how many chains?
Post by: Cudzoziemiec on 11 October, 2018, 03:29:32 pm
Samuel's had to scrap a cassette because two of the sprockets were worn. The other six were still good – that's 75% good, but the whole cassette is scrap! And of course that's the way it always is – the one or two sprockets we use most get worn and the rest are still good. Suddenly I see the point of those combine-your-own-cassette services from, I think, Miche. It's not so much that you get the ratios you pick, it's that you can replace one sprocket at a time. Yes, I know some people do this by dismantling standard sprockets, but then you end up with a pile of sprockets which are all the ones you don't use.

Something like this: https://thecycleclinic.co.uk/products/miche-11-speed-for-shimano-individual-cassette-sprockets
Title: Re: Cassette wear – how many chains?
Post by: mzjo on 11 October, 2018, 04:08:47 pm
Having only one cassette roadwheel in the fleet (the rest are either scew-on in a mixture of french and english threads or mtb cassette wheels) i think the only 8sp road cassettes that interest me will have ceased to be available long before I have used up my box of Maillard and Sachs ARIS sprockets. Only problem could be a shortage of french freewheel bodies since the old Mavic hubs last forever and a day (as do the sprockets)!

re gravel bikes and Claris I have been looking around (only windowshopping of course  ;) ) and it appears that a number of manufacturers have a Claris equipped model at the entry level. There is quite a price difference compared to the first 9sp models (Sora I think). The Diverge is one such, there are others.
Title: Re: Cassette wear – how many chains?
Post by: Whitedown Man on 11 October, 2018, 04:28:44 pm
Unless I’ve missed it there’s been no mention on this thread of rotating chains to get more out of each chain and cassette. Does that mean I’ve been slavishly adhering to a cycling club urban myth all these years?

(i.e. start with new chain & new cassette / at half-life replace part-worn chain 1 with new chain 2 / at end-of-life discard chain 2 and replace with part-worn chain 1 / run until end-of-life and then replace both chain & cassette.)
Title: Re: Cassette wear – how many chains?
Post by: Ham on 11 October, 2018, 04:41:36 pm
Sounds extraordinarily like a more complicated version of my two chains/1  cassette.
Title: Re: Cassette wear – how many chains?
Post by: Cudzoziemiec on 11 October, 2018, 05:39:12 pm
Unless I’ve missed it there’s been no mention on this thread of rotating chains to get more out of each chain and cassette. Does that mean I’ve been slavishly adhering to a cycling club urban myth all these years?

(i.e. start with new chain & new cassette / at half-life replace part-worn chain 1 with new chain 2 / at end-of-life discard chain 2 and replace with part-worn chain 1 / run until end-of-life and then replace both chain & cassette.)
Needs an accurate way of measuring half-life.
Title: Re: Cassette wear – how many chains?
Post by: zigzag on 11 October, 2018, 05:42:55 pm
there's a good case for a single speed setup if one's bulk of the mileage is on flat(ish) terrain - better efficiency, reliability, easier cleaning, lighter, cheaper to run. big part of commuters i see in london don't bother changing gears anyway.
Title: Re: Cassette wear – how many chains?
Post by: tonyh on 11 October, 2018, 05:47:21 pm
I've used a new cassette (9spd 11 to 34) about every 6 chains.
Title: Re: Cassette wear – how many chains?
Post by: Samuel D on 11 October, 2018, 06:01:03 pm
I've used a new cassette (9spd 11 to 34) about every 6 chains.

That’s a good cassette life. How are you measuring your chain?

On another forum, 531colin (designer of the Spa Cycles frames) reports going through about nine chains (https://forum.cyclinguk.org/viewtopic.php?f=5&t=116834&start=15#p1265839) on his current cassette … and it’s still going. He’s measuring with some sort of wear gauge so probably changes chains a bit earlier than I do.

That thread, by the way, has an intriguing reverse-wear method from Brucey. Probably too much work for me in practice, but a nice thought exercise.
Title: Re: Cassette wear – how many chains?
Post by: Samuel D on 11 October, 2018, 06:06:30 pm
there's a good case for a single speed setup if one's bulk of the mileage is on flat(ish) terrain - better efficiency, reliability, easier cleaning, lighter, cheaper to run. big part of commuters i see in london don't bother changing gears anyway.

I often do hilly rides in the Chevreuse Valley area, but if I ever have two bicycles, one will be a single-speed. In riding with others on single-speeds (actually, most of them are fixed-gear machines), I have noticed that most of them are noisy … intolerably noisy. I wonder what they’re doing to these poor things to get them to sound like that. Still, their riders sound happy!
Title: Re: Cassette wear – how many chains?
Post by: Hot Flatus on 11 October, 2018, 06:12:00 pm
Chain too tight or loose and/or poor chainline.

Title: Re: Cassette wear – how many chains?
Post by: zigzag on 11 October, 2018, 06:21:21 pm
yes, correctly set up and maintained drivetrain should be inaudible.
Title: Re: Cassette wear – how many chains?
Post by: tonyh on 11 October, 2018, 06:22:15 pm
I've used a new cassette (9spd 11 to 34) about every 6 chains.

That’s a good cassette life. How are you measuring your chain?

With one of these https://www.sjscycles.co.uk/tools/park-tool-cc32-chain-wear-indicator/
changing the chain as soon as I notice that it's gone past 0.5%. Which is around 2400 miles +/- 30%.

Thanks for that link!
Title: Re: Cassette wear – how many chains?
Post by: Brucey on 12 October, 2018, 09:05:21 am
there's a good case for a single speed setup if one's bulk of the mileage is on flat(ish) terrain - better efficiency, reliability, easier cleaning, lighter, cheaper to run. big part of commuters i see in london don't bother changing gears anyway.

I often do hilly rides in the Chevreuse Valley area, but if I ever have two bicycles, one will be a single-speed. In riding with others on single-speeds (actually, most of them are fixed-gear machines), I have noticed that most of them are noisy … intolerably noisy. I wonder what they’re doing to these poor things to get them to sound like that. Still, their riders sound happy!

A SS setup is usually very quiet when the parts are new; however once the chain is a little worn there is a conflict between elimination of slack and the need to let the chain 'ride out' on the chainwheel teeth, I.e. to the diameter at which the (longer) chain pitch matches  the pitch of the teeth.

If the slack is removed from a slightly worn chain (leaving (say) a nominal 1/2" free play) then the transmission can become very noisy. It is also likely to be wearing very quickly too, since the loads cannot be shared between teeth in the normal way. Any time such a  transmission is noisy, it is very likely that the chain rollers are  moving around on the teeth whilst under load, which causes everything to wear more quickly than normal.

The only situation where I will tolerate noise for any length of time is when  I have let a chainring become slightly hooked, and it is being forced to mate with a new chain. It rarely takes more than a few hundred miles to go quiet.

IME if everything is allowed to wear together, and enough slack is allowed/tolerated (i.e. without unshipping) a SS/IGH transmission remains quiet and smooth even when the chain is worn to ~1.5%. It ain't a smart idea to run chains out this far if you don't have a steel chainring though; the chainring gets into a pretty bad state otherwise.  Presumably there is some loss of efficiency through running with a worn chain but this (unlike noise) usually isn't noticeable.  When everything is knackered, a  new chain and sprocket (less than ten quid for an IGH....) and you are good for another few thousand miles.

However do note that on a fixed gear setup any chain slack is not usually tolerated; for one thing the chain is very likely (more likely than with a freewheel) to unship and for another the sensation of a slack chain with a fixed gear is pretty nasty. Some riders like the feeling of a slack chain less than the noise, so they choose to have noise.  Note that running a really quiet fixed gear setup is not a cheap business; good fixed sprockets are quite expensive and even if they are evenly worn (i.e not hooked, run smoothly under load still) any wear on the sprocket also generates a small amount of backlash, because the chain rollers are no longer located positively between the teeth. SS freewheel and IGH setups are a lot more tolerant of chain/sprocket condition.

BTW thanks for putting the arrows and labels on your photo; it is exactly as you indicate.  FWIW I can usually spot hooks that are bad enough to cause skipping but ramps are more subtle. It is clear that the difference between a tooth shape that will cause skipping and one that won't can be as little as about 10 microns of metal in the wrong place.

One of my mad ideas is that if you have a couple of ramped sprockets that won't play ball with a new chain, it might be that they can be 'shown who is boss' by being used in a (tensioner-less) SS setup for fifty (slightly noisy) miles or so. You could keep a new chain for this exact purpose, perhaps.

Having run a few different systems over the years (maillard freewheels, sun tour freewheels, shimano UG, shimano HG, etc) the same thing happens with all of them; you run out of the sprockets that you use most/wear fastest before any of the others.

 Some sprockets

a) are favoured and see more use than the others and/or
b) are small-ish so wear more quickly anyway and/or
c) appear in every freewheel/cassette you might build (eg if you use the same system for racing and touring)

so with my sun tour 'New Winner' freewheels (BITD I was a sucker for more cogs; I was running 7s in ~1979, i.e. five years before it was available in Dura-Ace) I basically ran out of 15T and 17T sprockets first.  They say the only certainty is change; for a few years there were three bike shops I could go to which each had a fully loaded Sun Tour sprocket board and I could keep things sweet and have the exact ratios I wanted by just buying a few extra sprockets.

With a shimano 8s cassette system you could perhaps use odd UG sprockets in the most-used positions. These sprockets are reversible so you can get extra life out of them. Gawd knows where you would get them now though. Other options include shimano DX BMX sprockets eg
https://www.bike24.com/p217742.html (https://www.bike24.com/p217742.html)
 and Brompton 6s sprockets/SA S3X sprockets (both found  on this page)
https://www.sjscycles.co.uk/sprockets-hub-gear/?page=2 (https://www.sjscycles.co.uk/sprockets-hub-gear/?page=2)

both of which use a modified freehub spline design and are available in 3/32" format. Again some of these (with a small spline modification) are reversible.

  If you start using odd sprockets in an HG cassette then shifting performance is likely to be degraded; you may or may not tolerate this.

cheers




Title: Re: Cassette wear – how many chains?
Post by: Brucey on 12 October, 2018, 10:31:26 am
I've used a new cassette (9spd 11 to 34) about every 6 chains.

That’s a good cassette life. How are you measuring your chain?

With one of these https://www.sjscycles.co.uk/tools/park-tool-cc32-chain-wear-indicator/
changing the chain as soon as I notice that it's gone past 0.5%. Which is around 2400 miles +/- 30%.

Thanks for that link!

FWIW that chain checker (like most) is slightly pessimistic in some cases because it includes an element of roller wear in the overall measurement. Thus chains which wear the roller bushings quickly (more quickly than they 'stretch') may be condemned before their time. Colin uses a similar tool, and knows that he slings some chains a little before their time. But he argues that slinging a chain that cost him £4 or so a couple of hundred miles before its time is no great hardship, and I think he is right.

cheers
Title: Re: Cassette wear – how many chains?
Post by: mzjo on 12 October, 2018, 09:20:12 pm
Have you tried those Shimano DX sprockets on a multispeed cassette (rather than a ss conversion on a cassette hub? I haven't but I have tried SA IGH ones with a similar tooth profile on double sprocket set-ups and they didn't work as well as the more square Sachs pattern (in the same way that heavily ramped cassette sprockets don't work well on a ss set-up) The experience with SA sprockets (and with SRAM ones on a ss conversion) has made me a bit wary about mixing the tooth patterns. I could try with DX ones (with the choice of 3 rhat I have, bit of a short cassette!)

I always thought that that pointed, deep tooth profile was specific to ss and fixed set-ups and was one of the things that contributed to the efficiency and the silence.
Title: Re: Cassette wear – how many chains?
Post by: Brucey on 12 October, 2018, 10:02:14 pm
I've tried a few different things but not every permutation by any means.  It is instructive to look at a few different sprockets that are meant for use in derailleur systems;

(http://www.sjscycles.com/supersize/22346.jpg)
SRAM sprocket for brompton 6s setup

This looks like a standard IGH sprocket that someone has attacked with a grinder. Like UG sprockets it has some (but not all) teeth with truncated tops. It is directional, but only just, because of a few teeth with an extra cutaway. It kind of gives you hope that you could attack an IGH sprocket with a grinder an make it work in a derailleur system. Since there are only a few teeth which are cutaway, it may work in reverse of the marked direction; I have not tried this.

(https://www.sjscycles.co.uk/images/products/medium/22347.jpg)
current Brompton 6s sprocket

This looks nigh-on identical to many HG type sprockets and uses an HG freehub spline. It is also directional because the teeth are cutaway (not just because of the spline).

One thing that may catch you out is that chains will happily run on sprockets (and chainrings) that are a fairly snug fit   in the chain, but the chain won't easily shift off them unless there is enough clearance for the links to twist slightly.

So for SS use, a nominally 3/32" ( 2.38mm) sprocket can be used (which is usually ~2.2 to 2.3mm in singlespeed form), but this isn't going to work well for a derailleur setup; the teeth (at least) need to be thinner; in the range 1.9 to 2.0mm is normal for an 8s chain to work.

(https://www.bike24.com/i/p/2/4/17742_00_d.jpg)
DX sprocket

So if you want a SS type sprocket (like the DX one) to work with an 8s chain as part of a derailleur system  it will do provided you are prepared to do some work with a grinder as necessary. For example you can make the teeth truncated in some cases, and slimmer too, as necessary. You can also grind them (with two angled facets near the top)  to give the functional equivalent of UG-style 'twist teeth' .

BITD I ran out of the Sun Tour sprockets with the correct tooth chamfers to work in some positions on 7s freewheels, but I did have ones with the same centre fitting. I experimented with grinding the tooth tops to give a 'twist tooth' type profile and this gave much improved shifting, regardless of where they were situated. They also wore faster near the tooth top (above the most loaded part of the tooth), which (similarly to HG sprockets I suppose, but for slightly different reasons) meant that they were less prone to becoming obviously hooked. They were still 'ramped' though, and at the time I didn't understand why the chain skipped....

cheers

Title: Re: Cassette wear – how many chains?
Post by: Brucey on 12 October, 2018, 10:26:05 pm
NB there are also more individual shimano cassette sprockets available than you might expect (but not from Madison....). There are quite a few here

https://www.rosebikes.com/bike-parts/cassettes?min-price=2&max-price=36&sort=price_asc (https://www.rosebikes.com/bike-parts/cassettes?min-price=2&max-price=36&sort=price_asc)

IME one or two 9s cassette sprockets doesn't mess up an 8s cassette, and 10s ones can be shimmed to fit and give the correct spacing. Often the 'timing spline' can be modified to allow the sprocket to be fitted so the ramps align better, even if the sprocket is from the 'wrong group'.

cheers