Thorn Cycles Forum
Technical => General Technical => Topic started by: Templogin on March 23, 2018, 08:20:34 pm
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Hi Folks
After a long absence here I am back to ask for some advice.
After years of saying that she was going to buy a Thorn, my partner and I sat down to look at the latest mega brochure to find which would be the best for her daily riding and moderate weight cycle touring. The extra short Raven looked to be the right size and spec, so we were about to order a new one when one came up on eBay, and we ended up winning it for an excellent price. Cycle Sent managed to get it from North Wales to Shetland in 2 days at a very reasonable price. I would recommend them. This is the second time that we have used them, once as sender, once as recipient.
The Thorn will be replacing a Dawes Karakum that has been used almost every day, and only got any love when I gave the other half a withering look. The frame, chain and brakes were normally black with filth, and was one of the reasons we went for a Rohloff hub.
There are two issues which are of concern. SJS used to sell a fully enclosed chainguard, but I can't find it in the online shop, or remember the manufacturer. Can someone please remaind me please? I have one on my bike, but am elsewhere at the moment. It may not fit on a frame this small though. Secondly, the cables to the Rohloff travel along the top tube, then when they travel along the chain stays they are partially exposed. Partially exposed brake cables were one of the things that caused problems on the Dawes. If you have covered the exposed cables, what did you use as a solution?
Thanks a lot in advance
Andy
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Chainglider? Made by Hebie.
https://www.sjscycles.co.uk/search/?term=chainglider
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Hi Andy
Your looking for the Hebie Chainglider, comes in 2 parts now rear roholff specific and front depending on tooth size (38, 42, 44, 48 I think they are)- can't say anything over covering brake cables as I use disc brakes so this is standard
Carlos
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Thanks a lot folks. Very useful. My search in the online shop was for chainguard.
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Hi Andy
Yep, the Chainglider will be your friend.
I've had one on for 3 years now.
I'd never be without it now.
I bit tricky at first to fit but there's a knack.
Just make sure you check your front and rear rings before purchasing.
Matt
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Thanks a lot Matt.
I put a new chain on the bike, then the chainglider and haven't looked at it since. I had to change the chainring though for a thinner one, 3mm. I should have just taken a file to the chainglider.
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I have a Chainglider on my Nomad, and I use Surly stainless steel chainrings. They work great with the Chainglider.
https://www.sjscycles.co.uk/search/?term=surly chainring (https://www.sjscycles.co.uk/search/?term=surly chainring)
- DaveS
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Thanks Dave. Looking back on the posts now that I know the name of the chainglider, I found that I had bought a Mountain Goat chainring.
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Regarding your Rohloff shifting cables... You say that the cables run along the chainstays. Does that mean you have the disc-brake version of the Rohloff hub (also called the "external shifting" version)?
The "external shifting" version looks like this (perhaps different colour):
https://www.sjscycles.co.uk/hubs-internal-hub-gear-brake/retrofit-rohloff-speedhub-50014-cc-14-speed-gear-hub-32-hole-with-disc-fitting-8022-black
This is the "internal shifting" version:
https://www.sjscycles.co.uk/hubs-internal-hub-gear-brake/retrofit-rohloff-speedhub-50014-cc-14-speed-gear-hub-32-hole-8000-anodised-silver
I have the disc-brake version on my Nomad, and the shifting cables run under the downtube and under the left-side chainstay. I thought that the Raven used the internal shifting version, and the shifting cables ran along the top tube, then down the seatstay. Can you confirm?
I've never heard of the "external shifting" version using exposed shifting cables. You can buy new cables and housing here:
https://www.sjscycles.co.uk/cables/rohloff-shifter-cable-set-18m-2-x-11-mm-inners-housing-8268
[Edit: After re-reading your original post, I suspect that you meant "seatstay" when you said "chainstay", and therefore you have the internal shifting Rohloff. In that case, I have no advice to offer.]
- DaveS
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Perhaps chainstays isn't the correct word. I mean the thin tubes that go from beneath the saddle to the plate into which the back wheel fits. From that plate thin tubes (chainstays?) go to the bottom bracket.
The second link seems to be the right one. Well, her cable have the bellows on them. There is a post that the rear brake caliper fits onto (left hand side) that is extended and drilled so that two cable adjusters can go in there. The rohloff cables from the handlebars, come along the top tube and then through the cable adjusters, where the inner cables are intentionally exposed before they are attached to the bellows by way of a small interface piece.
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I remember the names by "chainstays go along the chain (horizontal)" and "seatstays go up to the seat".
Yeah, you have the different kind of shifting mechanism than I have, so I can't help you. But other helpful people will be along shortly.
- DaveS
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Thanks a lot.
Page 18 of the latest mega brochure (Spring 2018) shows the mechanism. It's in the second picture. Internal gear cables.
Thanks again
Andy
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Andy,
Based on my own experience with the same cable routing, I don't think the exposed portion of the cable runs on your wife's bike will pose any problems. The Raven Tour kindly loaned to me by AndyBG for my 2014 tour had this configuration and it was trouble-free over ~9,000km and four months' use in sun, rain, and deep mud. The little concertina bellows covering on the portion of the cable runs entering the hub's internal shifter mechanism below the bayonet connectors proved good at preventing water and dirt from entering and the exposed part between the cable stop at the v-brake boss and the bayonet connectors was similarly trouble-free. The cable adjusters serve as rain bonnets for the exposed cables over the length of their travel. The passage inside the adjuster is a bit larger than the cable so there is room for some dirt before the cable could carry it into the housing where it could increase friction; gravity helps drain any water and grit with it. Perhaps if the bike were inverted water and grit could enter the cable runs...but that is an unlikely scenario.
If you are concerned about it, then some v-brake cable bellows could be fitted over the exposed ends of the adjusters and the other end secured 'round the cables with small cable (zip) ties allowing minimal cable passage (the travel is a bit more than you would have on a well-adjusted v-brake, so a little slippage is necessary; the bellows will squeegee off any debris). This would nicely prevent the entry of moisture or grit over time. I have done this on exposed derailleur cable runs with success as it is quick, easy, and effective at minimal cost. I prefer the Jagwire brand of bellows, as I have found Shimanos, Dia-Compe/Cane Creek/Tektro bellows to degrade more quickly with continued UV exposure.
All the best,
Dan.
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When fitting a Chainglider to a short frame it may be necessary to shorten the front part.
I have just fitted a Chainglider to the Raven 390 step-through frame I bought a couple of weeks ago. Using a Stanley knife, I cut off 5 notches from the rear of the front part.
I am building this frame up as a low-maintenance bike for use by my wife and by visitors at our island flat.
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When fitting a Chainglider to a short frame it may be necessary to shorten the front part.
I imagine that on most bikes the Chainglider "arms" will need to be shortened. Finding a bike on which either factory length of Chainglider fits out of the box would be mainly a matter of luck.
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Thanks, Dan, Martin and Andre. There is some very useful information in there. I will add it to the notes I am keeping so far, in the section Words of Wisdom!
Thanks again
Andy
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Andy,
Based on my own experience with the same cable routing, I don't think the exposed portion of the cable runs on your wife's bike will pose any problems.
I had the same cable routing for more than a decade and it was never a problem, the cables won't attract much dirt, assuming you're using mudguards. A tip to make disconnecting the cables easier when removing the wheel is to replace one of the grub screws in both the male and female sections of each connector with a cap head screw. This makes no difference to the connection but makes it a lot easier to get hold of and disconnect, particularly on the roadside, in the freezing rain...
I have since had my hub converted to external shifting (In order to use a disc brake) and have to say I preferred the internal in all respects other than wheel removal.
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Thanks PH. More useful infon in there, which I will add to my notes.
Andy
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I imagine that on most bikes the Chainglider "arms" will need to be shortened. Finding a bike on which either factory length of Chainglider fits out of the box would be mainly a matter of luck.
I was lucky on my first 3 Chainglider installations - 2 large Thorn Raven Tour frames and an old 650B frame with reasonably generous clearances.
No shortening of the Chainglider needed, but I did need to remove the red button on the rear part of the Chainglider on the 650B frame to prevent the Chainglider from rubbing on the seatstay.
4th and 5th installations needed shortening. Both these bikes were small "ladies" frames - the Raven 390 step through that I am currently building, and an old 700C twin-lateral frame with fairly close clearances for 28 mm tyres.
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Sent you a p m . . . .
Lewis
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Back to the OP's second question...
the cables to the Rohloff travel along the top tube, then when they travel along the chain stays they are partially exposed. Partially exposed brake cables were one of the things that caused problems on the Dawes. If you have covered the exposed cables, what did you use as a solution?
Andy Blance addresses the matter of cable protection with Rohloff internal gearboxes in the latest Thorn Mega brochure on page 18 [emphasis mine]: http://www.sjscycles.com/thornpdf/thorn_mega_brochure.pdf
Above and Left, the original and still current, Rohloff Hub, with internal gear cables. We fit this to our Ravens. The Rohloff-specific gear wire, which runs from the quick release bayonet fittings, to the hub is 0.9mm stainless steel and is sealed from the elements by concertina tubes. The cables above the bayonet fitting, are conventional 1.1mm stainless steel gear wires, which run in brake outer above the adjusters. Between the bayonet and the adjusters, the gear wires are unprotected from the elements, water runs downhill, which is why the perfect cable routing for this hub runs under the top tube.
All the best,
Dan.