Thorn Cycles Forum
Technical => Transmission => Topic started by: ipswichcycler on August 13, 2014, 10:31:01 pm
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If after many miles you have used all the ebb movement up and then the chain goes slack and you remove a link and reset the ebb are you increasing sprocket wear? How do you know when you need to buy a new chain?
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This is a nice puzzle and I expect there are many strategies. I started by switching chains a lot and now I have given up and just ride.
Here is one piece of the puzzle. The chain and sprocket and chain ring seem to need to wear together. A fresh chain on a worn chain ring isn't very happy. Anyway I am still learning but this seems to be one factor in the big equation.
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I am by no means an expert, but here is my understanding: The EBB takes up the slack between the chainring and the sprocket. However, as the chain wears, the critical problem is the wear in the rollers (is that the correct part?) in each link of the chain. When these parts wear, the links do not seat perfectly in the teeth of the sprocket and chainring, and start riding higher on the teeth. With less bearing surface between the chain and the teeth, the teeth start wearing much more quickly, and take the shape of a shark fin. Eventually the chain will skip over the teeth, and the sprocket, chainring, and chain will all need to be replaced.
Once the teeth have worn, if only the chain is replaced, a new chain will not mate smoothly with the worn teeth, resulting in rapid wear in the chain. The chain and teeth are designed so that the teeth "cradle" the chain links, with a large bearing surface. A worn chain on new teeth, or vice versa, has a much smaller bearing surface, resulting in rapid wear on both parts.
The chain should be replaced before it starts to cause the rapid wearing of the teeth. You can tell if the chain is not mating nicely with the teeth by grabbing the link on the foward part of the chainring, and trying to pull the chain away from the teeth (pull towards the front of the bike). Ideally, you should only be able to pull just that link, or maybe not at all. If you can pull a few links away from the chainring, then the chain should be replaced.
Note that tension on the chain (as caused by the position of the EBB) does not affect how many links you can pull away from the front of the chainring. Since the chainring is holding the chain around half of its circumference, any slack in the chain around the chainring is entirely due to wear in the chain. This is good, since it means that you can measure the wear in your chain independently of the tension in the chain caused by the position of the EBB.
This is how I understand chain wear. Please correct me if this isn't right.
- Dave
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I'm no expert either. But everything you say ties in with my experience of my chain skipping totally. It was so bad and came on so suddenly that I almost abandoned my tour. It was only the LBS fitting a new cheapie front ring that got me back on the road again.
Another guy I met later on my tour took a 12 inch ruler and layer it along side my chain and said it wasn't worn. It was a rough way to measure chain wear. Anything more that one eight of an inch is wear, according to him. There are of course proper chain wear guages.
I can still see gaps between the chain and ring so perhaps the chain ring fitted was not new? Or maybe the chain is worn.
I have decided to start from scratch again. And fit new fornt and rear rings plus chain. And also a new EBB.
Since I bought the bike second hand I am not clear as to how long those components have been on the bike.
So I consider it a good move.
Having said that, the new ring got me through 800 miles of loaded touring without skipping a beat.
Tough buggers are there Thorns!
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I just treat my chains and chain rings as I would with any other bike. I've got a Park Tool chain measurer and when the chain is too stretched I change the chain. I work on using three chains before I change the rings. I usually get 3,000-4,000 miles from a chain.
I suspect as has been said above there are many other approaches and all will have their merits.
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I just treat my chains and chain rings as I would with any other bike. I've got a Park Tool chain measurer and when the chain is too stretched I change the chain. I work on using three chains before I change the rings. I usually get 3,000-4,000 miles from a chain.
+1
Apart from the Park Tools chain measurer (I use a 12" ruler), everything you say is what I do as well. By rotating the chains once each I have got ~8,000 kms per chain.
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I run two chains. After about 2000 miles I rotate them. This way they both wear along with the sprocket and chain ring. When all the play is used up on the EBB I remove a link. After about 10,000 miles I change the chainring, sprocket and chains. This is conservative and I could probably get 50% more by rotating the ring and sprocket etc but they're not that expensive.
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il pardrone
Can you clarify your 12 inch ruler measurement method please.
How much over the 12 inch do you allow?
Thanks
Good points about changing rings and chain BTW
Matt
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get rid of those fecking rohloff hubs more hassle than a pk of crisps ::) ::)
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Not yet had my Rohloff bike long enough to worry about chain maintenance. As I have a Chainglider, I expect to at least halve chain maintenance compared to my hub-gear bikes without chain protection, which already needed significantly less maintenance than my derailleur bikes.
On my 5-speed hub gear bike I used to run several chains/rear sprockets in rotation, changing every 500 to 1,500 kms depending on how quickly the chain picked up dirt, then cleaning the chain and storing it to put back on the bike later, flipping the (cheap) rear sprocket to use it with 2 different chains. I scrapped chains/rear sprockets when I reckoned they were too worn, between 4,000 and 8,000 kms per chain, and scrapped the chainring when I finished the last chain.
So with 4 chains, 2 sprockets and 1 chainring I used to get between 16,000 and 32,000 kms of use.
I put a Chainglider on this bike about 2 years ago and haven't done any chain maintenance on it since, except for opening the Chainglider once out of curiosity.
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So with 4 chains, 2 sprockets and 1 chainring I used to get between 16,000 and 32,000 kms of use.
Pretty similar to what I have had - 3 chains, rotated at ~3,000 kms each; finally binned on the second rotation after 8,000kms each. On the last chain now, sprocket and chainring don't look too bad after 21,000 kms, but I have the replacements and will swap all at 24,000 kms.
I put a Chainglider on this bike about 2 years ago and haven't done any chain maintenance on it since, except for opening the Chainglider once out of curiosity.
Now that is really what I wanted to hear ;D
Chainglider waiting for fitting with new drivetrain. What chainring do you use and do you notice any drag from friction with the Chainglider?
Re the 12 inch ruler: I actually use a longer 1m rule to get the over-length measure. I use the generally accepted measures - under 12 1/16" - the chain is unworn; no need to do anything. 12 1/16" - 12 1/8" - the chain is worn; replace it but the sprockets are probably OK. More than 12 1/8" - both the chain and the sprockets are going to be worn; replace all of drivetrain. A caveeat to this is that a chainring will have a longer lifespan than a rear sprocket/cassette, due to the wear spread over many more teeth, so you may get several chain lives before the chainring really needs replacing.
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I buy cheap enough chains that I do not bother to rotate them. I misplaced my Park gauge, so am using the 12 inch ruler to watch for about 3/32 inch of stretch, at which time another chain goes on. I have not changed a chainring or cassette on any of my bikes for over a decade. All five of my bikes that I regularly ride use the same KMC eight speed chains. I do not keep track of when I change a chain, so I can't say how many miles I get to a chain. But since I keep several spares handy, I probably get less miles that most other people because I do not wait for them to get so bad that they damage the chainring or cassette or Rohloff cog.
When my drive train gets noisy, I lube the chain. I only remove the chain to clean it if it is extremely filthy, otherwise just wipe it off with paper towels and add lube. See photo, that was a filthy chain. It is hard to see the chain in the photo because it is the same color as the ground, but you can see how dirty the EX box is, the chain looked that bad too.
I have no idea if this theory will make my Nomad chains last longer or not, but I am using this method since both my rear cog and chainring have an even number of teeth. I put a tiny little slot in one tooth on the chainring and on the rear cog to mark teeth that I make sure I use a link with outer plates. It is a small slot, did not grind it down as much as Sheldon described.
http://sheldonbrown.com/chain-life.html
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And see in Mick's photo how Thorn Yellow just about rejects dirt!
Upon inspection of my zero-added-lube chain-life experiment, and reading the threads here, which all indicate very great reduction of wear-inducing circumstances inside a Chainglider, I've started to wonder if it is really necessary to use a stainless steel chainring. I went to the Surly stainless steel ring because a) I always buy the best (I don't mean boutique brands, I mean the best objective quality), b) it didn't cost all that much more than a TA or Thorn chainring, c) I was deliberately building a bike that would require zero maintenance or the nearest possible equivalent, and d) part of the zero maintenance strategy was to fit components that would not require replacement in my lifetime. There's an additional reason to fit the Surly stainless chainring which appeared on consideration of the Chainglider chain width specification: the Surly fits beautifully, but I'm sure you can get thin aluminium chainrings if you search for them, and you could use cheaper plain steel. I don't intend to swap out my Surly chainring (and in any event I've laid in a spare), but I mention this for those of you who are put off by the initial cost of the Chainglider and associated replacements to make it work on your bike.
I'm no longer even certain that the high quality KMC X8 chain I recommend (or even its theoretically slightly cheaper Z8 single speed sibling of the same high quality) is necessary inside a Chainglider, never mind the expensive Rohloff-specific X1. Inside the Chainglider, after a distance in which I would deplorably have worn out two Shimano chains in the days when I ran Shimano hub gearboxes with Dutch plastic full chain enclosures, the X8 chain, running only in factory lube, no added lube at all, appears good to go indefinitely. In that case, why not fit a KMC single speed chain from down the list at half the price of the X8? I won't do this either, because I have X8 spare chains laid in from when Chainreactioncycles had a sale, but the logic is striking.
I guess, like everyone who doesn't have experience of it (see in particular Dan's thoughtful questions in the Chainglider threads), on consideration of its form and construction, I expected some dirt to enter the Chainglider whereas almost none does, and for it to provide more interior grinding possibilities to wear itself or the transmission while in in use there appears to be none.
Remember though: my purpose is now, and has always been, a bike as near as possible to maintenance-free. Some of you guys already achieve amazing mileages with open chains. I wouldn't expect you high-milers to double or quadruple your mileages just for fitting a Chainglider, because all it will do is replace the cleanliness of regular chain cleaning and swapping with maintenance-free cleanliness. All you'll find is some cycling time that you previously spent cleaning chains.
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Chainglider waiting for fitting with new drivetrain. What chainring do you use and do you notice any drag from friction with the Chainglider?
<snip>
I'm also interested in the response to Pete's question. I've had a Chainglider for some time now, ready to fit to my Nomad (38Tx16T), but every time I have a go, I worry about friction and scoring of the Rohloff hub case. I also had to shorten the Chainglider significantly to get it to fit. Is that normal?
(I probably should have started another thread with this...) ???
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I'm also interested in the response to Pete's question. I've had a Chainglider for some time now, ready to fit to my Nomad (38Tx16T), but every time I have a go, I worry about friction and scoring of the Rohloff hub case. I also had to shorten the Chainglider significantly to get it to fit. Is that normal?
(I probably should have started another thread with this...) ???
There is friction with the chainglider. If you spin it on a stand it will slow the pedals down and makes a low noise. But, when in use you forget about it suggesting that at touring speeds any loss in performance is small. If you have the rohloff specific version it shouldn't scratch the hub. The adjustment needed depends on the length of the chainstays which are a function of the model and frame size. When I changed from RT to RST frame I had to cut an inch off the chainglider.
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Sammy, I believe that you have a yellow Nomad, as I do. (I also am using 38x16.) In order to fit the Chainglider, I had to cut away the part that is closest to the seat stay. Otherwise the seat stay would push the Chainglider to the left of the bike and cause a lot of friction (and noise) between the chain and the Chainglider. It is quite easy to trim the Chainglider with a small knife.
I don't remember shortening the length of the Chainglider. I might have.
It took a bit of fiddling around to get it to fit nicely with a minimum amount of friction, but I have had it now for about a year, and I don't notice it anymore when I am riding (aside from a small amount of noise). I definitely recommend installing it, especially if you ride in the rain.
- Dave
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Yes, you may have to trim the wide part near the seat stay. Julk also has commented on this with his nomad and I'm having an issue with my RST frame. I think the chainglider is the best solution at the moment but it's not perfect. To be fair it's asking a lot given the number of variables involved.
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I must admit I'd given up on getting the CG to work, but I will have another look at it tomorrow.
As much as I like the idea of a clean chain-side, I'm not sure I will tolerate ANY noise, but I really should give it a proper trial (as long as there's no damage to my hub).
Thanks!
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Chainglider waiting for fitting with new drivetrain. What chainring do you use and do you notice any drag from friction with the Chainglider?
On the 5-speed hub geared bike, non-optimal components that were already fairly well used before fitting a Chainglider:
- TA Cyclotouriste 1/8" 44T ring slightly too thick for Chainglider.
- Sturmey-Archer 1/8" 21T sprocket, probably slightly too thick for Chainglider.
- Sedis (SRAM predecessor) 1/8" chain.
At first, I noticed rubbing noises. But no perceptible slowing, and I no longer notice any noise, either it has reduced with use or I have simply got used to it.
On my Thorn Raven, new components chosen to fit the Rohloff-specific Chainglider:
- Surly stainless steel 3/32" 38T ring, narrower than any aluminium rings I had.
- Rohloff 3/32" 16T sprocket.
- SRAM PC890 3/32" chain (I didn't buy a specific KMC chain as I had several SRAM spare from when I used to run several derailleur bikes, which needed frequent chain replacements).
Chaingliders seem to work quite well in my area (South Brittany) and with my type of riding - occasional muddy paths, coastal tracks with sand, wet-weather commuting. Not tried Chaingliders in dry, dusty conditions.
I've only had Chaingliders for 2 years, not done any long trips with one yet, so I don't consider them proven, only promising. But promising enough to fit on 3 of my bikes.
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I must admit I'd given up on getting the CG to work, but I will have another look at it tomorrow.
It seems to me in the light of my experience of several years now that if a Chainglider doesn't work on a Rohloff-equipped bike, the owner has fitted the wrong model of front end (there's a long and a short version to suit various chainstay lengths, and several versions in each length to fit very specific chainring tooth counts) or rear end (there's a specific Rohloff back end it isn't optional, it is essential). It is also important not to try to stuff too wide a chain or chainring into it. You're supposed to cut (especially the long version of) the Chainglider front end to length; that cannot be a criticism; it's a design feature to make it fit many bikes.
Beyond that you can go wrong by fitting it too tight, so the chain drags or (theoretically at least) too loose but this last problem is one of patience: you have to move the notches that lock the thing together in or out one notch at a time until the Chainglider operates silently, litterally by gliding across either the lube or the air inside -- its like magic once you have the thing fitted right..
As much as I like the idea of a clean chain-side, I'm not sure I will tolerate ANY noise, but I really should give it a proper trial
A properly fitted Chainglider makes no noise you will hear over general road noise. You know that sighing noise a Rohloff makes in gears 5-6-7 when it is new, that becomes less obtrusive as it runs in? That's ten times as loud on a run-in Rohloff box as a well-fitted Chainglider. If your Chainglider is audible over the sound of your tyres, you didn't fit it right. Man, I'm maniacal about noise, and I'm happy to stamp the Chainglider "Approved as silent". On the solid white stripe on a smooth road, useful to kill the relative "roar" of the Big Apples (in truth not very loud tyres), my bike, complete with Chainglider, glides like a phantom, zero noise. The four top parameters that persuaded me to spend BMW money on my current everyday bike were low stepover without sacrificing stiffness, steel, lugs (no welding!), utter silence.
(as long as there's no damage to my hub).
This is ancient, ancient street corner gossip being thrown up again and again and again by people who don't pay attention the first ten times they are told. It's been years since Hebie launched the Rohloff-specific rear end for the Chainglider (and equivalents dedicated to several other popular hub gearboxes as well). If a Rohloff pilote damages his hub by fitting the wrong rear end for his Chainglider, he has no one to blame but himself. But the Chainglider damaging a Rohloff hub isn't even a remote possibility, and hasn't been for several year, for cyclists with their brains in gear.
Check your Chainglider rear end against the photos on the Hebie netsite to ensure you have a Rohloff rear end.
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If you don't want the Chainglider because chain-cleaning is your thinking time, or you think only sissies have chain cases, or you don't like the charcoal grey it comes in, or any other aesthetic reason, or plain prejudice, fine. That's a matter of taste. But I sigh when hear technical objections to the Chainglider like noise or damage to particular hubs. The thing, given only that you bought the correct subcomponent specifications for your bike and fitted it right, just plain works, fit and forget.
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All that said, a consideration when fitting a Chainglider to a few particular Thorn models (type and size to be determined in each case -- it may be that all the guys who reported this here have the same size rear triangle) is the possibility that the Chainglider may intersect slightly with the particular geometry of that Thorn frame, and rub paint off the seat stay. But that has been solved by several forum members shaving the Chainglider in the right place with their pocket knives...
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All in all, I think a properly fitted Chainglider is one of those landmark components that everyone should experience at least once in a lifetime.
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Sammy, I believe that you have a yellow Nomad, as I do. (I also am using 38x16.) In order to fit the Chainglider, I had to cut away the part that is closest to the seat stay. Otherwise the seat stay would push the Chainglider to the left of the bike and cause a lot of friction (and noise) between the chain and the Chainglider.
I also have a yellow Nomad Mk2, running 42-17. I fitted the Chainglider and had no such problems. The rear wheel end all fitted fine. My chainring (Thorn double-sided) caused rubbng and friction on the Chainglider as the Thorn ring is extra thick. I rode it for about 3-4 kms on a ride and had to stop and remove it as I would have burned out quick smart. A bit of the anodising on the ring was rubbed off. When this ring is worn out I have a Surly SS ring, which is a good bit thinner, to replace it. I just want to be sure the Surly ring does not cause drag. Seems that it is fine by Andre's account.
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It seems to me in the light of my experience of several years now that if a Chainglider doesn't work on a Rohloff-equipped bike, the owner has fitted the wrong model of front end (there's a long and a short version.
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This is ancient, ancient street corner gossip being thrown up again and again and again by people who don't pay attention the first ten times they are told. It's been years since Hebie launched the Rohloff-specific rear end for the Chainglider (and equivalents dedicated to several other popular hub gearboxes as well). If a Rohloff pilote damages his hub by fitting the wrong rear end for his Chainglider, he has no one to blame but himself. But the Chainglider damaging a Rohloff hub isn't even a remote possibility, and hasn't been for several year, for cyclists with their brains in gear.
Check your Chainglider rear end against the photos on the Hebie netsite to ensure you have a Rohloff rear end.
I have checked my CG and note it very clearly says 350R Speedhub on the inside. My front is also very definitely the correct part. I'm using a Thorn chainring (black), and it does rub. But what really concerns me is the rear rubbing on the hub. It does rub - I have (slightly) marked the hub case already.
I have shortened the "arms" of the CG because the rear wouldn't fit on at all. At Andre's urging, I will continue to play with the setup to try and achieve nirvana, and I have ordered one for my wife's Raven (38-17), so will get a good opportunity to confirm the fitment.
(My wife habitually dismounts on the right-hand side. She claims it feels more natural to her. Of course, she often gets grease on her leg! She's right-handed. Has anyone else had this issue?)
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Sam, the CG should be no problem on your wife's Raven. I've lost track of the references, but the "chain life with rohloff" seems to have morphed into a CG discussion--they're related, obviously--but I recall Matt's queries about fitting CG's to Ravens on another thread, and there's a fair amount of info there. (I did send a fairly detailed note to Matt as a PM, on the sequence of fitting my CG to my Raven, 38 x 17, and am happy to send the same to you if it's helpful -- let me know.
The issue may be some more fiddling required with the Nomad frame, but I recall David Simpson explaining his fitting & experience on his Nomad 2, over the course of a Vancouver winter.
Cheers, John
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Sam, the CG should be no problem on your wife's Raven. I've lost track of the references, but the "chain life with rohloff" seems to have morphed into a CG discussion--they're related, obviously--but I recall Matt's queries about fitting CG's to Ravens on another thread, and there's a fair amount of info there. (I did send a fairly detailed note to Matt as a PM, on the sequence of fitting my CG to my Raven, 38 x 17, and am happy to send the same to you if it's helpful -- let me know.
The issue may be some more fiddling required with the Nomad frame, but I recall David Simpson explaining his fitting & experience on his Nomad 2, over the course of a Vancouver winter.
Cheers, John
Thanks very much, John. I'll take you up on your kind offer, if it's not too much trouble. And I will review David's thread in the next few days while awaiting delivery of the new CG.
Now I suppose we really should return control of the thread back to the topic. :)
Cheers!
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Ha ha. That's me. But I have enjoyed all the posts here about the CG.
If anything, I have received more info. than I expected and I now have a tougher choice to make on the chain ring sizes.
I don't tour too much so without buying x2 set ups I will go with one that allows me to climb walls and then spin away the days until you do tour!
Thanks chaps
Matt
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Please don't stop the chainglider topic on my account. I've got a nomad mk2 590L with 40 and 17 teeth and I'm interested in the possibility of fitting a chain glider. I'm a bit concerned about the fitting of a surly front chainring (?) and the need for spacers and such like.
It seems the 38 and 16 front and rear sprocket have very similar gear inches to my current 40 and 17
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But what really concerns me is the rear rubbing on the hub. It does rub - I have (slightly) marked the hub case already.
I have shortened the "arms" of the CG because the rear wouldn't fit on at all. At Andre's urging, I will continue to play with the setup to try and achieve nirvana, and I have ordered one for my wife's Raven (38-17), so will get a good opportunity to confirm the fitment.
If the Chainglider components are correct but the rear end has actually rubbed on your bike, however slightly, I'd wait until the new one arrives and is fitted to your wife's bike, a fresh start so to speak with new information and experience, and then return to the one on your bike bike and see what can be done.
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I'm a bit concerned about the fitting of a surly front chainring (?) and the need for spacers and such like.
It doesn't have to be a Surly chainring. Any chainring that fits can be used: you could choose steel or possibly thin aluminum (I have some Stronglight ali chainrings that seem like they would fit). But Thorn-level quality ali chainrings intended to last a long time are usually too thick. The reason so many forum members fit the Surly stainless steel ring and be done with it is that it will last forever and an ali chainring will eventually wear away even inside a Chainglider, and steel might even rust. I had a good quality Indian Amar steel chainring in a Utopia Country chain case (similar to but much better sealed than the Chainglider, which is actually sealed better than well enough) and it didn't rust, and didn't show much wear in 4500km either, but that's hardly a lot of miles, nor very hard miles. So people just take the Chainglider concept to its logical conclusion and fit a stainless steel chainring to reduce maintenance and replacement to the minimum. The logic for some fitting the KMC X1 Rohloff-specific chain is the same: reduce or obviate entirely the maintenance/replacement cycle. I've taken this a step further, by not adding any lube to my chain inside the Chainglider, running it only on the factory packing grease it arrived in. The KMC X8 chain currently on my bike has run without any lube added to the factory grease for 3500km without any sign of abnormal wear, indeed with no sign of wear at all. It needs only to make another 1000km to beat the previous well-lubed chain. There's a thread here somewhere about it but it isn't very active because there's nothing to report.
Whether you need spacers depends on what the Surly stainless chainring is replacing. You need a 54mm chainline with the Rohloff gearbox, and it has to be good to within 1mm. If you have that already, no spacers are required. If you're fitting a different bottom bracket, you just buy it to suit (118mm axle width is good with the common Sugino XD2 and rebrands and equivalents). If you're fitting a different crank, ditto. The reason for the necessity of spacers being assumed is that most people on a Thorn forum have a thick Thorn ali chainring fitted, and the thinner Surly has to be centred on the removed chainring's thick edge. But you can achieve the same effect much more conveniently, and with better engineering integrity, with a spacer between the frame and the bottom bracket lockring There are in any event Rohloff spacers available that meet this eventuality precisely and they're pretty cheap.
It seems the 38 and 16 front and rear sprocket have very similar gear inches to my current 40 and 17
Couple of penny-farthing equivalent tables I worked up for forum members at http://coolmainpress.com/BICYCLINGHebieChainglider.html (http://coolmainpress.com/BICYCLINGHebieChainglider.html) include all the permitted Rohloff toothcount combinations for which Chaingliders are available; check the tyre and cadence prefs at the top of each table. If you're a heavy tourer, 38x16 sounds good; Dan Wood, a heavy tourer in heavy, dangerous going, a guy with dud knees but a high cadence, goes all the way down to Rohloff's permitted limit of 36x17 setup. But if you're a light tourer, or a masher rather than a spinner, 38x16 may be too low, because you'll spin out at the top irritatingly often. I live in a town all on hills, in a countryside full of hills, and had two recent turns of cardiac surgery, and find 38x16 just right but I don't mind cruising down hills in exchange for gears low enough never to have to push.
Thing is, if you have a Rohloff 17t sprocket already and still in good nick, it'll take forever to wear out, so you'll be throwing out a good part, or giving it away. 38x17 is also possible under both the Rohloff and Chainglider regimes.
The reason I mentioned Dan above is that he decided on due deliberation that reliable stump-pulling gears are more important to him than low maintenance and ultra-long transmission system life. Something you have to decide for yourself.
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Sam, the CG should be no problem on your wife's Raven. I've lost track of the references, but the "chain life with rohloff" seems to have morphed into a CG discussion--they're related, obviously--but I recall Matt's queries about fitting CG's to Ravens on another thread, and there's a fair amount of info there. (I did send a fairly detailed note to Matt as a PM, on the sequence of fitting my CG to my Raven, 38 x 17, and am happy to send the same to you if it's helpful -- let me know.
The issue may be some more fiddling required with the Nomad frame, but I recall David Simpson explaining his fitting & experience on his Nomad 2, over the course of a Vancouver winter.
Cheers, John
Hi John,
Many thanks for that PM. last June
I just checked it and the Dropbox links don't work now. :( :(
Also, I note you say you fitted it to a 38/17 combo but the SJS page for the CG says 39/18-22.
Is there a guide from Hebie saying that 17 goes with 38?
I am thinking of going for the 38/18 combo.
But when I look on the SJS site, the rear rings are only 13 15 16 & 17 teeth!
What am I missing?
I am about to place my order but will hold off until I hear from you - or someone else.
Surley 38 ring - part 20828
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Here is what I ordered to go from a Thorn setup to a Surly chain ring and Chainglider.
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The Rohloff-specific Chainglider I bought from SJS for my Thorn with Rohloff is designed for a 38T chainring and 15 to 17T rear sprocket. It probably won't work properly with an 18T rear, but I haven't tried.
From the Chainglider design (sitting freely over the top run of the chain) I reckon the largest (17T) sprocket option would keep it furthest from the hub shell, but not noticed any interference with the 16T I have.
I chose 38 x 16 because it was the lowest recommended Rohloff combination at the time I bought my Thorn. Rohloff lowered the permitted gearing shortly afterwards, so I will probably change to 38 x 17 at some stage, as I don't really need the current 89" top gear.
But no hurry as I expect the 16T to last quite a long time.
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As I've said before, I don't yet consider the Chainglider as proven for use on a long tour, in particular how it will cope with dry, dusty conditions.
But unlike some other modifications, it would be easy to remove the Chainglider, chuck it away and revert to a bare transmission if it proves troublesome, so I can't see a valid reason for me not to try it.
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Also, I note you say you fitted it to a 38/17 combo but the SJS page for the CG says 39/18-22.
Is there a guide from Hebie saying that 17 goes with 38?
I am thinking of going for the 38/18 combo.
But when I look on the SJS site, the rear rings are only 13 15 16 & 17 teeth!
What am I missing?
So as not to hijack someone else's thread, I've answered your question at
http://www.thorncycles.co.uk/forums/index.php?topic=6813.msg67901#msg67901 (http://www.thorncycles.co.uk/forums/index.php?topic=6813.msg67901#msg67901)
complete with piccies and parts numbers and links and video.
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Does anyone have any comments on how it copes with winter salt? I try not to ride in snow but there can are longs periods when the wet roads have a significant amount of salt (and grit) that get sprayed over the bikes. (I live in the west of Scotland). At the moment I just rinse it the bikes gently with a watering can.
I'm attracted by the idea of fitting a Chainglider to my Raven, but worry that although it would keep most of the much out, salt would still get in but be difficult to wash out, not a Good Thing in my book.