Thorn Cycles Forum
Community => Rohloff Internal Hub Gears => Topic started by: mickeg on January 05, 2022, 11:17:53 PM
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There currently is a short debate on a different thread about the Nomad Mk II bottom bracket eccentric. I thought I would start a new thread on how I adjust the chain tension on my Nomad Mk II in case others are curious, or they may buy a used Mk II and are unsure how to do it, or perhaps they have a different bike with that type of eccentric. This way there is a new thread that can easily be found in the future. I own a Nomad Mk II, but no other Thorn Rohloff bikes, thus I can't cite a list of other bike models that this applies to.
The Nomad Mk II has two set screws that tighten to hold the eccentric in place, these set screws are conical where they press into the eccentric and leave a permanent small conical depression (I call that a divot) in the eccentric. Thorn has been clear in their instructions that you should avoid putting the divots too close to each other, as a groove can result. And a groove could allow the eccentric to rotate, which would allow the chain to loosen when you do not want it to.
Years ago on this forum, someone described how he did it, he removed one eccentric bolt so he could see where the divot in the aluminum eccentric was before he adjusted it. I have been using that method ever since and I think that is the key to adjusting the eccentric on the Nomad Mk II eccentric. I built up my Nomad Mk II in 2013, or about eight years ago. This method has worked well for me for most of those years.
When it is time to adjust the chain, I remove one of the pinch bolts and loosen the other. I can see inside where the divot into the eccentric is, that divot is centered in the hole where you removed the pinch bolt.
This is the pinch bolt:
https://www.sjscycles.co.uk/bottom-brackets/thorn-m8-extra-fine-conepointed-screw-for-eccentric-bottom-bracket-shell/
The diameter of the pinch bolt is 8mm. Thus the radius of the pinch bolt hole is slightly less than 4mm. I always look inside the hole and rotate the eccentric so that the divot from the last adjustment is on the edge of that hole and then tighten one pinch bolt there. Thus I put the new divot slightly less than 4mm from the previous divot, not closer. That prevents a groove from forming because all divots are well spaced out on the eccentric.
And after you wear a few chains out, you have put several well spaced divots into your eccentric at distances that should match all of the adjustments you need for your chain. If however you change a chainring or sprocket size you may find you will be adding more divots to the eccentric.
My complaint about the eccentric design is that I would prefer infinite adjustability, but I have learned to live with the lack of that on my Nomad Mk II. There have been a few times I started to adjust my chain and found that I could not move the eccentric as far as I wanted to for optimum adjustment without putting a new divot closer to an existing one than I wanted to do. In that case, I restored the chain to the previous adjustment instead of tightening the chain. One result of that is that I no longer attempt to adjust the chain as often as I used to.
Several years ago one of my pinch bolts was a bit loose and I noticed that before it could fall out. Since then I have wrapped a rubber band around the two eccentric bolts so that the bolts can't rotate unless the band is removed. The band became a good cable guide too.
I do not use a torque wrench on the pinch bolt, perhaps if someone knows the correct torque setting to use, they could cite that in a comment below.
ADDENDUM, August 16, 2023, added bold font to one paragraph above.
ADDENDUM, January 20, 2025, added a photo of the divot in the eccentric when looking through the pinch bolt hole.
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...perhaps if someone knows the correct torque setting to use, they could cite that in a comment below...
Per Thorn's Bike Owner's Manual PDF available for viewing or download at http://www.sjscycles.com/thornpdf/ThornBikeOwnerManual2Web.pdf ...
Retighten the eccentric screws to 10 – 17 Newton meter (torque) 7.38 to 12.54 foot-pound-force.
Best,
Dan.
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I do use a torque wrench and so far have found that tightening to max 12Nm is sufficient. I normally wait for chain wear slack to reach at least 60mm (ie T1-T2 on page 12 of the Thorn guide referred to above). On one occasion I left tensioning until there was about 65mm slack, the one occasion the chain jumped off the chain ring when I was freewheeling slowly over a patch of poor road surface.
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Just resurrecting this as my Raven pinch bolts came loose yesterday on my way back from SJS (possibly due to ACF50 in the frame?). I was surprised how slack the eccentric was in the frame with the bolts loose - definitely not seizing! Earlier in this thread mickeg’s suggestion of using pieces of innertubes to lock the bolts sounds good, Thorn have suggested locktite, what (if anything) do others use to keep the pinch bolts tight?
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No tips from me, but I’m pleased you have highlighted a very useful older post that I couldn’t find - thank you!
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One of my bolts came loose early on after I bought my Nomad Mk II, which is in the bold text in the first post. I tried a thread locker like Locktite (blue, removable) but did not like it because as noted above I remove one screw completely when I make an adjustment. And reinstall it later. With thread locker, that made the removal and reinstallation process longer by several minutes.
So, I cleaned off the thread locker, use grease, chose the rubber binders instead. I usually use two (as in the photo), just in case one breaks.
I have had no trouble with my eccentric seizing up in place. My bottom bracket shell is painted, the eccentric is anodized, I should not have any dissimilar metal corrosion occurring. I do not add grease in between, have kept it clean. If I get any grit in there, I do not want that to get stuck there, and it could get stuck in there if I had grease in there. Also by keeping it clean, it is not water tight. If any water gets into my seat tube, it will drain out of the bottom in the gap between the bottom bracket shell and eccentric.
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...what (if anything) do others use to keep the pinch bolts tight?
I use thin jam nuts with great success. For size and specifics, see...
https://thorncyclesforum.co.uk/index.php?topic=14551.msg109035#msg109035
Best, Dan.
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The pinch bolts on my bike have hex heads and do not have enough free thread to add locking nuts (I assume that is what jam nuts are?). Perhaps bolts with grub screw ends would be better?
I will try mickeg’s inner tube binder solution as that obviously works for him. I must also carry a 15mm spanner!
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... I must also carry a 15mm spanner!
Get one narrow enough that it will also fit on your pedals in case you have to remove or install pedals as part of your shipping. Most pedals can be installed or removed with that size wrench.
Pedals can be really tight, but if you do not tighten them too tight, a 15mm cone wrench might also suffice.
I later bought one of those eccentric bolts to carry as a spare on tour, just in case I lost one. Odds are I never will lose one, especially with two rubber bands preventing them from unthreading, but it would be nearly impossible for me to find one other than from SJS so it was worth the cost to me since I later placed a few orders with SJS.
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I must also carry a 15mm spanner!
The Thorn 3 in 1 spanner might be worth considering except you’ll need to check that the pin spanner end of it is right for the eccentric BB on your early Raven Tour.
https://www.sjscycles.co.uk/tools/thorn-3-in-1-bottom-bracket-eccentric-tool-for-73-mm-shell-raven-bikes/
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Thanks Tony, my EBB has ‘teeth’ around the outside so a small peg spanner works fine as the EBB rotates easily. I carry a pedal spanner when on tour abroad but not when local - I will have to modify my toolkit.
Mickeg - a couple of times you have said you are keeping your Sherpa - for tours when a derailleur bike might be best? I can understand you keeping the bike - but I just wondered what would decide you to use the Sherpa on a Tour?
For me, for my 2 Indian trips, it was simple - cost.
My secondhand Sherpa in good running condition (new bearings, transmission etc etc) stood me £500 while my other Rohloff bike (Oxford BikeWorks) cost me nearer £4000 new and I did not want to risk it on planes and trains. If the Sherpa had got stolen or damaged I could have psychologically walked away and shrugged my shoulders. I would have felt very different loosing a £4000 bike. As it was the Sherpa did not get damaged - it just needed a new chain.
My Raven once all set up will stand me at under £1000 so a bigger investment but I think the Rohloff hub is worth the extra. I hope to go to Sri Lanka next winter and there is always a risk (mattmatt’s Raven got fork damage on his flight out there a few years ago).
Sadly I think the Sherpa will have to go as I just can not see why I would use it and two bikes is enough!
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Teeth around the outside of your EBB insert, indicate it was designed to be turned with a C-Type spanner, the advantage of that design is it can be turned without special tools, Just stick something like an allen key or screwdriver in an indent and use the crank as a lever. Having said that, I have never had to adjust my EBB at the roadside, though I don't do long tours either (Max 3 weeks). If you're already carrying a pedal spanner, you're sorted. But if you do want to carry at other times, there's plenty of lightweight 15mm options intended for wheelnuts.
Sadly I think the Sherpa will have to go as I just can not see why I would use it and two bikes is enough!
I'd never question the number of bikes anyone has, but I wouldn't consider keeping two bikes that are so similar.
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Since I ride a belt drive on my Nomad Mk3 these days, and my pedals take a hex key, I wonder if I can safely leave the Thorn 3-in-1 spanner at home. Since belt drives do not get re-tensioned after after a Gates-authorized bike shop has determined the correct tension, I shouldn't need to ever adjust the EBB on the road.
And while we’re on the subject of the 3-in-1 spanner, has anyone else destroyed the spanner part of one? I tried to remove some pedals on my city bike that had seized, and I rounded-out one of my Thorn spanners from the effort. These are apparently made from very soft metal.
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And while we’re on the subject of the 3-in-1 spanner, has anyone else destroyed the spanner part of one? I tried to remove some pedals on my city bike that had seized, and I rounded-out one of my Thorn spanners from the effort. These are apparently made from very soft metal.
Yes in exactly the same way. OTOH it could be described as a feature rather than a fault, the EBB screws shouldn't be tightened anything like that much, it might be a good thing for the spanner to break before the frame.
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My Thorn S&S wrench (photo attached), I have never had any problem with it being soft metal, I was unaware it was soft metal.
I have loaned it to someone a couple times that needed a pedal wrench, no problem.
Maybe mine is different metal?
On mine, it also has an 8mm hex shaped socket. I cut a short piece of 8mm allen wrench to use with that socket to turn my wrench into a high torque allen wrench for crank arm bolts and crank removal tool. If it was too soft, I would expect that 8mm socket to deform.
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My Thorn S&S wrench (photo attached)
That’s not the spanner I was talking about, the one that came included with two Thorn framesets I ordered, and once I ordered one separately from the webshop. This (https://www.sjscycles.co.uk/tools/thorn-3-in-1-bottom-bracket-eccentric-tool-for-73-mm-shell-raven-bikes/) is what my spanner looks like.
I wouldn’t expect the metal to quickly deform under normal use. As I said, I was trying to remove pedals that had seized, so I was applying more force and for longer than ordinarily.
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Why do I keep both my Nomad Mk II and Sherpa? I will try to keep this short. But first, I have enough storage room that I do not feel a need to get rid of any bikes. And financially if I sold one, that money would just go into savings, I would not spend the money on something else, so there is no financial reason to sell one.
I worked in a bike shop in the early 1970s. By 2004 I had decided I needed a newer bike, my newest bike was a 1972 Raleigh Grand Prix I bought at the bike shop under employee discount.
Here is where the story gets long. I have thought of bike touring for decades. When looking for a new bike, I did not see a lot of touring bikes available. Looked at a Trek 520, looked at a Fuji, chose to not spend a lot on one of the custom bikes out there. Ended up buying a Surly LHT which had good reviews, that was its first year of production, they only sold frames, not complete bikes. Built it up. Since my level of bike knowledge was three decades old, had to learn about indexed shifting, cassettes instead of freewheels, threadless headsets, etc. But this new invention called the internet helped greatly. And I had not laced up a wheel for a few decades, the internet was great in that I learned a lot about wheel building that I had not previously known.
Unfortunately, got a defective frame, very soft due to bad welding, would shimmy like crazy. Surly refused to warranty it, said my description was "normal". Tried to do a couple tours on it, gave up, put the frame in the recycle bin. No more Surly bikes for me.
Before I bought the Surly, I had traded a few e-mails with SJS about the Sherpa, and from that knew the size I wanted. I asked them a question by e-mail, they did not respond. Investing a lot in a bike that you have never seen to be shipped from overseas means you need a lot of trust. If they chose not to respond to my e-mail, that was enough to make my trust level dip, I decided not to buy it. Bought the Surly instead.
I saw a Sherpa of my size on Ebay. Seller was in Canada. I did not like the parts on it and it looked too expensive, so did not bid. But I checked later, was curious about the price it went for. It did not sell. I sent a message to the seller that if the frame and fork were available, I was interested. I bought the frame and fork from him. (He also included the fenders.) Built it up. Compared to my Surly, it handled like a dream, I could load it up and it worked great. Also rode nice unladen. This was in 2010. Did a bike tour on it that year, and one in 2012, and in 2013. Used it with 50mm tires on predominantly gravel trips, 40mm on pavement trips.
I was interested in an S&S coupled bike, and also in a Rohloff. Considered the Nomad Mk II and the Co-Motion Pangea. The Nomad won on cost, even when I had to pay customs duty on it. (The Co-Motion is made in USA, no duty.) Bought it in 2013, built that up for heavy touring. In 2014, a friend organized a mountain bike trip in a neat location. Others that I knew were also going. I decided to go too. The ones in the group that did not own mountain bikes rented, I instead decided to try my Nomad, and since it could take a 100mm suspension fork, I bought a Rockshox for it at a great price on Ebay. Was very happy with it. That was unladen, no panniers, simply mountain biking.
First tour I did on the Nomad was in 2016, Iceland for a month. Worked great.
Comparing the Nomad with the Sherpa, the Sherpa is much lighter. The Sherpa was rated for 30 or 35kg for luggage, the Nomad rated at 62kg. And with my derailleur drive train (3X8) I had wider gearing with more gears on the Sherpa than the Nomad. The Sherpa is half step plus granny gearing. So, if I am planning a fairly flat trip, I would much prefer the derailleur gearing on a lighter bike. And a trip mostly on pavement with narrower tires, then I see an advantage to the lighter bike. But if I need to haul a couple weeks of food on the bike or go on very rough terrain, then the Nomad is the preferred bike.
In 2017 did a tour, pavement, fairly flat, narrower (40mm) tires, took the Sherpa and it was perfect for that trip. I would have felt that the Nomad was unduly heavy if I had brought it, and the wider gear spacing would have been a disappointment on fairly flat ground.
And the Nomad Mk II has S&S couplers. If I am flying, that is the bike to take.
I have always wanted a Titanium bike. No, I did not need one, but it was just one of those things you lust over. I got lucky in 2017, saw a titanium touring frame, brand new on Ebay, company is Lynskey. Did some research on it and the company. Learned that the company that made the frame, that when they got a frame returned from a dealer, they put it on Ebay instead of back in inventory. It was brand new and my size. I decided to bid a hair more than half of new price, and I won the auction. The fork for it was not included, they wanted $300 for the fork. But I still had my LHT fork, and that was nearly identical to the specifications for the fork that they sold with the frame, so I could build it up without buying their fork which saved me more. So, got a great titanium touring bike at a fantastic price. I really liked my Sherpa drivetrain, 3X8 with half step and granny, so I replicated that on my new titanium bike.
Typically I think of a titanium touring bike as pure bling, a titanium frame which cuts a few kg off of the weight is not a cost effective choice for touring because your bike is going to be heavy anyway. So, I would never dream of buying a full price titanium touring bike. But, in total I probably paid less for the titanium bike than I would have paid for a comparable fully built steel bike. Plus, I picked the specifications, so it was custom to my needs.
So, I consider my titanium bike to be my light touring bike, the Sherpa to be medium touring, and the Nomad for heavy touring.
I did a bike tour in 2019, brought the Nomad because I flew with it, that is the only bike I have with S&S couplers. I think the Sherpa would have done as well, but the couplers was the key decision maker. I liked the sequential shifter of the Nomad on that trip, but I think that the derailleur drive train would have worked well too. Part of that tour, I carried over a week of food on the bike. For that reason, if I brought a derailleur bike, I think I would have preferred the Sherpa over the titanium bike.
Did a tour with a friend in 2023 and a solo tour in 2024, both with the titanium bike. Grocery stores were frequent enough that did not have to carry a lot of weight in food. And both of these tours were reasonably flat, so the titanium bike with 700c wheels which meant a slightly higher gearing than the Sherpa with 26 inch wheel was not a problem.
I think that explains why I keep three touring bikes in the fleet. I have not used the Sherpa since I built up my titanium bike. But I started to plan a tour for this summer and planned to bring the Sherpa on that. But, to make a long story short, canceled my trip for this year.
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My Thorn S&S wrench (photo attached)
That’s not the spanner I was talking about, the one that came included with two Thorn framesets I ordered, and once I ordered one separately from the webshop. This (https://www.sjscycles.co.uk/tools/thorn-3-in-1-bottom-bracket-eccentric-tool-for-73-mm-shell-raven-bikes/) is what my spanner looks like.
I wouldn’t expect the metal to quickly deform under normal use. As I said, I was trying to remove pedals that had seized, so I was applying more force and for longer than ordinarily.
Since mine is S&S, I knew they would be different. But, I assumed they were made of the same steel in the same shop with a punch press to stamp them out.
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Thanks for taking the time to make such a detailed reply Mickeg. For Nomad vs Sherpa, particularly a Nomad with S@S couplings, there is a big difference in their carrying ability and ease of transportation. So I can understand your logic.
Much less difference for me with a Sherpa and Raven and as my aim was to move from derailleur to rohloff, the Sherpa will have to go. I guess I could store it but I prefer to move things on nowadays. Cycles are easy enough to store compared with motor vehicles and deteriorate very little so if it does not sell I would be happy to keep it……but to ride it seriously I would need to change pedals from flatties and add toe clips and get a third Conquest saddle and Karrimore pannier clips, or steal them from the other bikes which I don’t like doing.
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Thanks for taking the time to make such a detailed reply Mickeg. For Nomad vs Sherpa, particularly a Nomad with S@S couplings, there is a big difference in their carrying ability and ease of transportation. So I can understand your logic.
Much less difference for me with a Sherpa and Raven and as my aim was to move from derailleur to rohloff, the Sherpa will have to go. I guess I could store it but I prefer to move things on nowadays. Cycles are easy enough to store compared with motor vehicles and deteriorate very little so if it does not sell I would be happy to keep it……but to ride it seriously I would need to change pedals from flatties and add toe clips and get a third Conquest saddle and Karrimore pannier clips, or steal them from the other bikes which I don’t like doing.
Got it. Just in case you find some reason you are not happy with the Raven on your trip, you could wait until after trip to sell the Sherpa.
Conquest fell off of the Brooks website again a couple years ago. Conquest was taken out of production years ago, then brought back for a few years, then now gone again. I just checked, not listed. I am in USA, so maybe it is still available in UK??? This is the link for my search.
https://www.brooksengland.com/en_us/catalogsearch/result/?q=conquest
I have a Conquest on several bikes, but could not buy one when I bought my road bike, so bought a Brooks Pro.
Then last year put a suspension seatpost on my light touring bike. That did not play well with the Conquest, so I swapped the Pro for the Conquest. The Conquest is now on my road bike.