Author Topic: Chain length and chain stretch. Should I shorten chain?  (Read 2970 times)

steve216c

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Chain length and chain stretch. Should I shorten chain?
« on: March 22, 2021, 11:56:34 AM »
When I initially fitted my chain, I was not aware that Rohloff's should be run a little slack. I counted the number of links on the old chain I was removing on my 'new 2nd hand bike' and replaced with same number of links on a reversed sprocket. I needed to move my dropouts from furthest position to nearest position- and I have to confess, the chain was pretty darn tight to begin with. I suspect I caused some additional stress to chain and BB as a result- which might have added premature wear to the chain.

I realize I have non-Thorn dropouts, and most of you will adjust your typical Thorn eccentric- but you may have experienced the same issue when you have reached the maximum distance you can place between front and rear cogs- and I suspect your advice to my problem will be equally valid regardless and presumably transferable to any IGH or fixed gear bikes.

In around 8000+km I've adjusted my dropouts as a running repair a couple of times as the chain has stretched. My signal to the task being when the chain attempts to disengage from the sprockets and where no other cause is apparent. Up until now, gradually increasing the distance between the cogs has cured the chain from wanting to jump as it slowly stretches. But now I have reached the furthest point I can move my dropouts. I reckon that if I removed 2 links and slid dropout to shortest position, I can probably continue to ride on this chain a while longer. The chain is optically in good condition and kept pretty clean inside the chainglider. The sprocket still looks usable and not overly worn at this time. Right now, chain is working fine as I only just adjusted the dropouts. But I want to address this in good time before the bike starts warning me I need to take action. At 7000km chain was at 0.75 wear on my tool. Now the tool drops in snuggly suggesting the 0.75 is since exceeded.

If I had fitted my chain +2 links longer initially, it would have been too loose for the shortest dropout position even if having a more healthy Rohloff chain slack to begin with. But then I'd have probably reached the maximum adjustment distance sooner- given the chain would have started closer to the finish line. But with most of my experience repairing bikes coming from derailleurs with springs taking up the slack, I am unsure what is the most appropriate way to deal with chain slack on IGH bikes.

Do any of you guys remove links to extend usable life of chain when there is no more adjustment room in eccentric/dropouts?
Is it effective as a permanent solution that holds for months- or is it just a 'get me home' solution when out on the road?

cheers
Steve







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martinf

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Re: Chain length and chain stretch. Should I shorten chain?
« Reply #1 on: March 22, 2021, 12:49:28 PM »
If the chainring isn't too worn, at this point I'd turn the sprocket over and fit a new chain, with its original factory lube.

Then when the 2nd chain gets to the same state of wear, turn the sprocket over and put the 1st chain back on (after thorough cleaning and relubrication) and carry on until wear starts to cause problems. And finally put the 2nd chain back on to completely wear out the sprocket.

Depending on the chainring, it might be possible to turn that over as well and start over with a new chain and sprocket.

Andre Jute

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Re: Chain length and chain stretch. Should I shorten chain?
« Reply #2 on: March 22, 2021, 03:42:02 PM »
That chain has to go before it damages more expensive parts. I take the view that the chain is the cheapest part of the transmission, and I throw mine off at 0.5 wear, cf traditional cycling advice to throw it off at 0.75. In addition to a worn chain wearing sprocket and chainring faster that it should, it brings on the sprocket flip or replacement faster than it should, something a Rohloff owner doesn't want to do if he still operates the first series sprocket and fixing, which has been known in a significant number of cases to baulk. The cure is to take the sprocket off once a year and put copper grease on the threads, but if you haven't, you've been tightening that joint every time you pedal the bike...


PH

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Re: Chain length and chain stretch. Should I shorten chain?
« Reply #3 on: March 23, 2021, 12:36:21 AM »
I follow the advice in the Thorn literature somewhere, to replace chain and replace or flip the sprocket and chainring at the same time.  I do this when it all starts to look worn, I don't see the point in measuring the chain on a single set up, the sprocket wears at the same rate (Is worn by the chain) and you can see that without the aid of tools. Usually there's enough wear to warrant a change within or around a full throw of an EBB, if not I'll add a link or half link. I'm more likely to do so if it didn't start an the maximum extension and on the older Mercury's mini EBB I'd do this anyway. There's also some chains that "stretch" an extraordinary amount in the first few hundred miles, I don't know why that is, some kind of bedding in maybe, I'm sure it isn't wear, I'd add a link in that circumstance. There's plenty of other factors, not least the expected bike usage, and I'll sometimes change before entirely necessary because I'd doing a service and it's unlikely to last till the next.
I don't buy into the idea of the chain being expendable to protect the rest of the drivetrain - You'd have to consider what you're buying to work out if that's for you. I'm using the KMC e1 chain originally designed for Rohloffs, I stocked up when they were on offer for 18 but I've seen them for up to 30, I'm undecided if they're worth it, but they are very good.  One side of a chainring is 22 and half a sprocket 11, even without the faff, it isn't clear cut.  Neither is the engineering case as clear as it is with a derailleur.  Yes we all know that worn chains wear the teeth on a sprocket, but so what?  If they're wearing at the same rate, which on a single set up is likely, they'll still work well many miles after a derailleur set up has been scrapped.  There's some pictures on here somewhere of a sprocket almost worn away and it was still functioning. On a cassette, the problems arise from uneven wear, the chain and most used sprockets wear together and when you move it over to a lesser used on it rides up the teeth and skips.

steve216c

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Re: Chain length and chain stretch. Should I shorten chain?
« Reply #4 on: March 23, 2021, 09:00:47 AM »
I knew you can flip the rear cog, as I had to do this on purchasing my bike as it was shark-finned from previous owner.

I was not aware that one can reverse the chainring. I have a Truvativ 4 bolt chain ring. Do these flip well?

My actual plan for the drive chain is actually to change old style 17 toothed sprocket to a splined 16 tooth on rear when I reach the point of no more life in the existing chain/sprocket. So I'm not overly concerned of excess wear on the chain/cogs as they'll be swapped out before the end of 2021. I already have the splined socket and 16 tooth on hand, and was considering replacing the Truvativ chain ring which must be the original. But flipping it, assuming one can, is a more attractive proposition to me.
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PH

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Re: Chain length and chain stretch. Should I shorten chain?
« Reply #5 on: March 23, 2021, 11:05:17 AM »
I was not aware that one can reverse the chainring. I have a Truvativ 4 bolt chain ring. Do these flip well?
It depends on the ring, the Thorn rings are intended to be reversible, as is the Surly SS one, even some not originally intended to flip can be, it needs to be a plain ring without shifting ramps/pins and sit equally well in both directions. The profile of the teeth is I think always symmetrical, so if reversing gets them in the right place, then it should be OK.
It's a pity you've already got the sprocket, if not I'd have recommended a bigger one and the corresponding reduction in chainring for the same gearing.  It's obvious that the more teeth it has the longer it'll last, but what's less obvious is that the larger diameter also reduces chain wear, 19T works for me, next time round I might even go 21.

steve216c

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Re: Chain length and chain stretch. Should I shorten chain?
« Reply #6 on: March 23, 2021, 01:01:03 PM »
I was not aware that one can reverse the chainring. I have a Truvativ 4 bolt chain ring. Do these flip well?
It depends on the ring, the Thorn rings are intended to be reversible, as is the Surly SS one, even some not originally intended to flip can be, it needs to be a plain ring without shifting ramps/pins and sit equally well in both directions. The profile of the teeth is I think always symmetrical, so if reversing gets them in the right place, then it should be OK.
It's a pity you've already got the sprocket, if not I'd have recommended a bigger one and the corresponding reduction in chainring for the same gearing.  It's obvious that the more teeth it has the longer it'll last, but what's less obvious is that the larger diameter also reduces chain wear, 19T works for me, next time round I might even go 21.

Actually I was going smaller at back as I find wanting for more speed than 17 teeth gives me. So the alternative would be bigging up on the front. The loss of a tooth on the rear will still allow me to use my Hebie Chainglider which is set for 15-17 teeth. Of course, if I don't like 16, the splined carrier should make it easy enough to revert to 17.

On the same size wheels and similar size frame/weight derailleur bike I can push almost 5km/h more downhill at the same cadence as 14th on my Rohloff allows for. I do have 3 steepish hills on my commute, but I can manage these in 2nd gear without much issue- so I don't think I'll miss 1st on the Rohloff too badly. And if it gets really steep, I have an MTB with megarange 1st that allows you to pedal 19 to the dozen and scale ridiculous inclines very slowly.
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PH

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Re: Chain length and chain stretch. Should I shorten chain?
« Reply #7 on: March 23, 2021, 02:19:16 PM »
Actually I was going smaller at back as I find wanting for more speed than 17 teeth gives me. So the alternative would be bigging up on the front. The loss of a tooth on the rear will still allow me to use my Hebie Chainglider which is set for 15-17 teeth. Of course, if I don't like 16, the splined carrier should make it easy enough to revert to 17.
Ah yes, I wasn't considering the Chainglider.  There may also be a conflict between that and some chainrings intended to be reversible, but others will know better.
I went from 40/16 to 47/19 which is a fraction higher, but not enough for me to notice, both work well for me.  There is an efficiency gain from reducing the radius of the chain, I've seen it in the comparison tables, but again it's too small for me to notice.
« Last Edit: March 23, 2021, 03:50:38 PM by PH »

steve216c

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Re: Chain length and chain stretch. Should I shorten chain?
« Reply #8 on: April 06, 2021, 10:57:10 AM »
 :-[ :-[ :-[
I'd like to return to my question at the beginning of this post- and embarrass myself by sharing with you the mistake I made when asking it.

I had tried to move my dropouts as far as they would go, and thought I had reached the limit. As I removed my wheels at the weekend to replace my winter spikes with regular tyres, I decided to clean in all those hard to get places before remounting them. I found a almost a centimeter of solid earth stopping my drop outs slide back any further - and being the cause of my concerns that I wouldn't be able to take up excess slack in the future.

Easy solution. I removed the drops outs, pushed out the solidified earth, cleaned it up nicely and refitted it all. Now I have bags of adjustment space and don't need to remove any chain links after all.

I did spot another problem when doing so. When I bought my 2nd hand bike, the rear sprocket was already very warn. Reversing it has allowed for almost 9,000km of uneventful but reliable use till now. But I spotted one of the teeth on the reversed sprocket has partially broken off. While the bike is riding fine (much better after fixing the dropouts) I am resigned to the fact that the sprocket will need replacing sooner rather than later. I was hoping I could push chain and sprocket beyond the next oil change @ 10,000km most likely end of May- but now I'm wondering if to change it out then rather than pushing it beyond 10k despite having plenty of adjustment room for the chain suddenly available. Not yet decided on how to proceed.

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PH

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Re: Chain length and chain stretch. Should I shorten chain?
« Reply #9 on: April 06, 2021, 06:05:53 PM »
I think one tooth missing will be fine, as long as the others look OK, if your gearing is even numbers on both, you can even set the chain for the missing tooth to be redundant anyway.  If the chain is too slack and the you're really unlucky and the missing tooth has left a big enough gate for the chain to escape, there might be an issue, but in terms of engagement I'd have no concern.
Well done for finding the missing adjustment, now you have, it'd be a shame not to use it.

HugoC

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Re: Chain length and chain stretch. Should I shorten chain?
« Reply #10 on: May 11, 2021, 04:55:54 PM »
Just FYI when my Thorn Raven Twin tandem timing (front) chain was at full stretch and could not be tensioned any further using the eccentric BB, I removed links to take up the slack and then eventually did the same to the drive chain when it too became too loose. At the time there was no visible wear on the sprocket and chainrings so didn't reverse them. When the slack on the shortened chains couldn't be taken up by adjusting the EBB any further I replaced both chains, reversing the chainrings (even though there was no visible signs of wear). The new chains seem to be wearing much more slowly and I am attributing this to the use of wax as a lubricant, rather than liquid lubes. The waxing process is a bit of a faff as all the original factory lube has to be removed, but is well worth it!

steve216c

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Re: Chain length and chain stretch. Should I shorten chain?
« Reply #11 on: June 03, 2021, 09:54:07 AM »
Just as an update, I made it to 9800km since asking my chain shortening question.  The chain began to play up again last week skipping a little when accelerating. On removing the chain glider I was surprised I'd not had the chain come off. There was so much slack that the chain was visibly sagging on both the top and bottom line.

I'm planning to do the 5000km oil change, fit a splined carrier and new chain ring (although I might try reversing the current chain ring first) in the very near future. But ahead of that, my curiosity got the better of me. Seeing as I have all the brand new replacements (except for chainring) on hand, I thought I'd try shortening the chain by 2 links as per my initial question to the forum- and see how the bike performs.

I'm on sliding drop outs and NOT and eccentric, so I slid from max to min position. I removed 2 links and refitted the chain to the bike. The shortened chain had no obvious slack, but is not overly tight either. I know that it is said that Rohloffs prefer a bit of slack, but having removed 2 links and moved to drop outs to the shortest possible distance to the chainring, there was no option to add any additional slack. Finally, adjusting the gear cable thumb screws as the wheel and cabling were now around 15mm closer creating a bit too much slack for all gears to to work correctly.

I did a 5km test round yesterday after shortening, wanting to test it before the 17km commute this morning. The answer to my question is YES. You may be able to shorten the chain if circumstances needs must and extend the use of the chain and sprocket. The initial tests including hills and acceleration under load on my morning commute showed noticeable improvements over the chain skipping situation I had found myself in the last few days. Other than the ground opening up and Lucifer trying to drag me under for sins of they cycling modification kind, my bicycle performance since the chain shortening has been boringly reliable thus far. No noticeable noises, no noticeable friction and no chain skipping. In all, an improvement over how my daily ride has been in the last 7 or so days since the chain began to play up.

Although you MAY be able to do this, SHOULD YOU? There are good and valid arguments as to why changing a worn chain earlier saves wear and tear on more expensive components such as sprocket and chain ring. I do not dispute these arguments. BUT there may be times where such an exercise MIGHT make sense. e.g. if you are touring and don't have the necessary parts/tools to replace the sprocket/chainring/chain available at the time. Or as a GET ME HOME fix if your chain got damaged, but where shortening as a roadside repair is the only option other than walking with the bike (assuming you have a chain tool with you when it happens).

Obviously, just 30km is not reflective of how such a fix performs over time. So, in the interests of science, I'm throwing caution to the wind, and planning to try to see just how far the experiment will take me and want to see if this can at least take me 500-800km of commuting till the school holidays start at the end of the month and when I'm planning to replace the entire drive chain (if it doesn't break on me first  :o)

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PH

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Re: Chain length and chain stretch. Should I shorten chain?
« Reply #12 on: June 04, 2021, 10:20:39 AM »
Finally, adjusting the gear cable thumb screws as the wheel and cabling were now around 15mm closer creating a bit too much slack for all gears to to work correctly.
I can't see any harm in experimenting, if the chain isn't falling off all is fine.
I don't get the above?  Do you have an enclosed cable run?  If so it shouldn't matter how slack it is, there's no stops between shifter and Ex-box and the only measurement that matters is how much longer the inner is compared to the outer.  Moving the wheel won't change that, I've moved wheels between bikes where it had a comical amount of slack cable and the shifting was unaffected.
Quote
Although you MAY be able to do this, SHOULD YOU? There are good and valid arguments as to why changing a worn chain earlier saves wear and tear on more expensive components such as sprocket and chain ring. I do not dispute these arguments.
Well, I dispute those arguments, or at least suggest there's too many variables for anyone to make a definitive claim.  On a derailleur it's pretty clear cut - don't change the chain in time and after 10 - 15% more mileage you have to  replace more components.  That isn't the case with any single drivetrain, It becomes a matter of nerve, I haven't worn a set out yet, I've replaced because the amount of wear is making me nervous, or I wanted to make some change for other reasons and it seemed an appropriate time to replace.
I've had as little as 3,000 miles from a derailleur chain and almost 15,000 from a Rohloff one, guessing on average that'll be around 3:1, so two extra chains to save one side of a sprocket and chainring.  It wouldn't take much variation either way, in usage or price of components, for the economical case to change.
« Last Edit: June 04, 2021, 10:23:35 AM by PH »

steve216c

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Re: Chain length and chain stretch. Should I shorten chain?
« Reply #13 on: June 04, 2021, 02:27:25 PM »
To PH- I have a Rohloff hub without ex-box so the slack does need to be accounted for and there are thumb screws for that job. The gears cable outers hung slightly outside of the grip shifter on the two out gears, and it did not let me in to 14th till Id adjusted.

As for chain wear, you are right on derailleur chains wearing faster than single speed or IGHubs. My experience was approx 10,000km out of chain ring with 6000km on first chain and sprocket followed by 4000km on second chain/cassette change. At around 10,000km Id switch out and renew all 3 components. The previous owner of my bike estimated around 10,000km total ridden when selling. I reversed sprocket and installed new chain when I bought bike and have added another 10,000km on that set up. At this point, approx 20k total on 1 chainring (not reversed yet), 1 sprocket (reversed once) and 2 chains. Not bad economics in comparison to derailleur if the only cost was a single chain in 20,000km.

But are you saying that a worn chain wont wear out ring or sprocket quicker on a single drive train?
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PH

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Re: Chain length and chain stretch. Should I shorten chain?
« Reply #14 on: June 04, 2021, 09:50:18 PM »
To PH- I have a Rohloff hub without ex-box
:-[ Of course!  I'm so used to dealing with Ex-box I hadn't considered it. 
Quote
But are you saying that a worn chain wont wear out ring or sprocket quicker on a single drive train?
No, wear is wear.  What I'm saying is that on a single drive, it'll function fine with a lot more wear than with a multi sprocket/chainring.
There's no real mystery to this, and I don't think it's disputed!  If you have more than one combination they wear at different rates, and it's the miss-match between the wear on the chain and the wear on some sprockets which causes problems. It's not uncommon for a worn derailleur drivetrain to be fine in one gear and not another, by that time it's too late and it's the swapping of chains early that avoids it.
Chains are pretty incredible things so commonplace we forget what good engineering they are.  You see them in some industrial settings where they run all day every day, but what we do to them on a derailleur bike really ought to be classed as abuse.