Rohloff on a Dawes Ultra Galaxy

[Brucey]

the torque arm arrangements that suit a Rohloff are somewhat different than those that will work OK with a lot of other IGHs; the reason is that the gear ratios are skewed towards low gears, ranging from 0.28 to 1.47. The high gear is nothing exceptional; basically anything that isn't a two or three-speed gear will have a higher gear ratio than that. However the low gear is very low; by my reckoning the Nexus/Alfine 8 has a low gear of 0.53 and no other IGH has a gear lower than that barring the Rohloff.

The low gear ratio means that there is a considerable torque reaction; supposing that you input 100 ftlbs of torque via the sprocket; in gear #1 the output torque at the hubshell is 357 ftlbs and this means that there must be a torque reaction into the dropout of 257 ftlbs.

By contrast the torque reaction into the dropouts in an N8/A8 hub is (in gear #1 for the same input torque) a mere 88 ftlbs.

So the slightly unintuitive result is that the torque reaction is about three times more with the Rohloff even though the gear ratio is only half. Hence the large reaction arm and the alternative of rather beefy dropouts etc. The torque loads are comparable with braking loads but (in contrast to braking loads), pedalling forces can go on all the time, instead of just occasionally.

In fact -in much the same way as disc brake mountings are not always a good idea- I am very doubtful that lightweight chainstays and seatstays are really strong enough to accept the reaction loads from such low geared hubs if a reaction arm is not used.

In terms of managing the torque reaction loads, a 'gear-up' hub is arguably best; in top gear (same input torque etc, gear ratio of 3.05) an SA8 hub generates 32.8 ftlbs output torque and just 67.2 ftlbs of reaction torque into the dropouts. There are of course other compromises with this approach; notably overall efficiency, increased chain tension loads (using available SA8 sprockets) and associated reaction loads in the frame, BB bearings etc.

cheers

[PH]

I ran my Rohloff in a Surly LHT for a while, with a simple SS tensioner and the torque arm. Worked fine though looked a bit ugly. Treated myself to a custom frame after I was happy with what I wanted, very pleased with that, but I couldn't say it rides any different to being in a standard frame. I know there must be some loss of efficiency using a tensioner but it wasn't enough for me to notice. Cables need some consideration to run in a non specific frame, it's possible of course, though can get messy.
I've had my Rohloff 10 years and done around 70,000 miles on it. It is without doubt the best bit of cycling kit I've ever bought. I bought litre cans of the oils and the other running costs have been peanuts, it's paid back the initial high cost several times over.

[Brucey]

out of interest how many chains and sprockets have you gone through in that time?

I use cheapish 1/8" chains on my SA hubs and I get about 5000 miles (+/- a thousand or two) on an exposed chain and about five or ten times that (it is difficult to be sure!) if I have a chaincase fitted.

cheers

[Tigerbiten]

I go through a chain (2.5 chains as it's a recumbent) a year or around every 7,500 miles.
My 21 tooth sprocket has done around 12,000 miles and I may need to reverse it the next time I change the chain.

[PH]

out of interest how many chains and sprockets have you gone through in that time?

I use cheapish 1/8" chains on my SA hubs and I get about 5000 miles (+/- a thousand or two) on an exposed chain and about five or ten times that (it is difficult to be sure!) if I have a chaincase fitted.

cheers

I haven't been counting, I did for the first few years when it was doing a lot more commuting mileage, it would get a Autumn and Spring service and new chains then, so 4 - 6,000 miles sounds about right. It's usually had really cheap chains, like 4 for £10 from York Rally, or £2.99 from Asda and for the last few years when I've been more particular about maintaining my derailleur bike, the Rohloff has been happy with the cast offs, it's also been getting the used middle ring off the same bike. It's on the first side of it's fourth rear sprocket, these seem to wear well. I'm not that bothered about keeping any of it clean, though it is always well oiled. I like to run the chain fairly slack, I don't know the science but it feels better to me.

[Brucey]

re running the chain slack; once the chain is a bit worn it is stretched. In order for the chain to sit on the sprocket such that the chain pitch matches the tooth pitch, the chain needs to be able to sit outwards on the sprocket (and the chainring) a little (a percentage of the diameter in each case, in accordance the chain stretch). Basically it can't do that so easily if the chain is set too tight. If the chain is a lot too tight then it can't do it at all.

'A lot too tight' is actually still quite slack when the chain is worn! Once the chain is stretched about 1% or so then 1" of 'slack' is a bare minimum and 2" may be just fine with a chain nearing the end of its life (which is a far greater degree of stretch than is acceptable on a derailleur system). When it is really knackered the chain cannot be set so that it both runs smoothly and doesn't stand a chance of derailing over rough ground.

If it is too tight then the chain will run rough; this is not an illusion! I believe that when the chain is too tight the rollers move against the tooth face when they are under load, which is what makes for the roughness.

cheers

[Gearoidmuar]

Rohloff sprocket mileage..

I'm on my fourth Rohloff sprocket, changed fairly recently at about 18,000 miles so that's about 6000 miles a sprocket.
I could get more if I properly cleaned my chain, but when you live in Cork, you realise that there's more to life than cleaning chains.
If I lived in Spain I'd double it, maybe..

I've had to have my Rohloff serviced (free) at about 13000 miles due to a slightly dodgy point in changing, but it's been the most fantastic thing I've ever bought for a bike. If you're into touring, it's mega. You get a really strong wheel as well.

[geocycle]

The rear sprockets do about 10,000 miles for me. I'm on my third. I could have got more with more careful rotation of chains but after 10k it gets harder to seat a new chain IME. Chains are about 6000 miles. This is without running chains and sprockets into the ground, and also without any serious cleaning regime.

[PH]

I'm a bit surprised how little use people are getting from a sprocket, are the figures quoted per side or both?
I'm going to turn my sprocket and replace the chain in the next week or so, I think I'll start mile counting and see how far it goes before giving any trouble.

[jb]

You can make the sprocket last until the bushes fall off the chain, but it will feel and sound rough. Depends what your prepared to put up with.

[AdyJapp]

By way of further wittering whilst I plan this upgrade/change, call it what you will, I initially looked at a few configurations to see what the best option for my frame set was.
My first thoughts were to have an external change as this looked to be the neatest option, but it seems as though this will not work with the torque arm - or rather will not fit - if I want to run the cables along the chainstay (which I do). I therefore decided that the internal change version is the way to go.
Anyone have any alternative thoughts about this?
In terms of cable routing, I'd utilise cable guides where my existing ones are (obviously the cables will be housed for their entire length), get a guide for one of the accessory/bottle mounts (as my Galaxy has them on the underside of the downtube and Shand cycles seem to have something designed for the job that they have on their bikes), and then look to see if I could find a plastic guide to replace my existing front/rear derailleur guide which is mounted underneath my bottom bracket. Haven't found one of these yet.

[syklist]

By way of further wittering whilst I plan this upgrade/change, call it what you will, I initially looked at a few configurations to see what the best option for my frame set was.
My first thoughts were to have an external change as this looked to be the neatest option, but it seems as though this will not work with the torque arm - or rather will not fit - if I want to run the cables along the chainstay (which I do). I therefore decided that the internal change version is the way to go.
Anyone have any alternative thoughts about this?
In terms of cable routing, I'd utilise cable guides where my existing ones are (obviously the cables will be housed for their entire length), get a guide for one of the accessory/bottle mounts (as my Galaxy has them on the underside of the downtube and Shand cycles seem to have something designed for the job that they have on their bikes), and then look to see if I could find a plastic guide to replace my existing front/rear derailleur guide which is mounted underneath my bottom bracket. Haven't found one of these yet.

I bought a standard kit from Rose in Germany when I converted our old derailleur tourers to Rohloffs. I have some pictures of the conversion somewhere. This kit routes the cables along the top tube, down past the rear brakes with a little adaptor that fits on the left hand v-brake bolt. A neat way of doing it but it does have the drawback that you have to disconnect the gear cables to get the V-brake off. At the moment the cables are externally mounted (good old cable ties) although it would be neater to use the bosses built into the frame. The hubs are internal cable changers and both bikes use the long torque arm. I fitted Weber B couplings with stands recently to both bikes and had to bend the torque arms round the Weber mounts. This seems to work fine.

We road tested the bikes this summer on a steep and hilly route in Norway (700km) cycle camping, towing a 10kg child in a heavyish trailer. Currently running a 34 - 16 chainwheel - sprocket (IIRC) with a Rohloff chain tensioner. Rohloffs are great even when retrofitted.

[ukdodger]

also worth noting that you can (apparently) now get 36h rohloffs, which is a better idea than 32h, especially for a 700C wheel.

cheers

Unless they are smaller I'm wondering how they get three crossings on the spokes.

[Brucey]

also worth noting that you can (apparently) now get 36h rohloffs, which is a better idea than 32h, especially for a 700C wheel.

cheers

Unless they are smaller I'm wondering how they get three crossings on the spokes.

eh???

cheers

[ukdodger]

also worth noting that you can (apparently) now get 36h rohloffs, which is a better idea than 32h, especially for a 700C wheel.

cheers

Unless they are smaller I'm wondering how they get three crossings on the spokes.

eh???

cheers

Forget it. I'm getting confused between crossings and holes. The large diameter of the Speedhub wont permit 3X.