Rohloff with a Double ?

[Thomas777]

I work part time  in a bike shop a d since I have a Rohloff  on my wife's touring bike I am considered the "expert"!
So a Rohloff equipped bike came in with a double  chainring and a chain tensioner.
Anyone  familiar with this setup?  My wife  is interested because  she spins out on downhill.

[PH]

It isn't uncommon on a recumbent trike, where balance isn't an issue with really low gears, I haven't seen it on a convectional bike, but there's no reason it wouldn't work. I've used a double on an Alfine 8 speed, without problem, not really very different to using a cassette. The Rohloff tensioner has a capacity for 10 chain links, which roughly translates to a 20T chaining difference*, you don't have to use the Rohloff one, though most others don't offer an acceptable chainline without modification.  You'd have to play around with a gear calculator to decide where to put the extra gears, I think realistically it's going to provide an extra three. On the Alfine I set the extra gears at the bottom, it was a mistake, shifting at the top where you can afford to lose some momentum would have been better. Chainline isn't going to be critical, setting it for either of the chainrings or between them isn't going to make much difference. You still have the advantage of the chain only running to one sprocket, lots of ways to shift, I'd choose 8spd, friction shifting and a jump Stop.  You might also consider the Rohloff's maximum ratios, it's up to you whether you treat them as a rule or a guide and that might depend on whether the hub is still in warranty.
I occasionally spin out on a Rholoff, but not often enough to consider doing anything about it, the bottom gear is a low as I can go without falling off and the top gear is high enough that even with more gears it would be a lot of extra effort for marginal gain.  Nor saying someone else might not get the benefit, but the numbers need a proper look at first.

* EDIT - No need to do the sums, there's a choice of chain length calculators, like this one:
https://www.alpinetrek.co.uk/chain-length-calculator/

[martinf]

It worked for me on a Brompton, where for several years I used a double chainring with a 5-speed Sturmey hub to extend the gear range.

No real difference if using a Rohloff, or an Alfine 8 as PH has done.

I have the Rohloff on my Raven Sport Tour geared quite low - 42 x19, which gives a range of 15" to 80" with my tyres. I don't (yet) really need the lowest gear on this bike, 15" gives about 4.4 km/h at a "lazy" cadence of 60 rpm, so about walking speed.

And I could do without the highest gear, which gives 35 km/h at my usual cadence of 90 rpm, not a speed I can maintain on the flat for long. Though I have pedalled that bike up to 50 km/h on a gentle downhill just to see if I could do it (130 rpm, again not sustainable for long periods)

On my heavy tourer, I gear even lower at 13" to 67". My reasoning is that I sometimes use the very low gear when really tired at the end of a long day, and I wont need to (or be able to) go very fast with a full touring load. 67" is about 29 km/h at 90 rpm. 

I don't usually "spin out" on downhills, I just stop pedalling and save my energy for the next uphill.

But if someone does need more range than the Rohloff's 526%, a double chainring should work quite well.

[Andyb1]

If your wife ‘spins out on downhill’ she either likes to ride very fast or the crank / rear wheel sprocket ratio is too low.
Does she ever use first gear on climbs?   If not then maybe it is worth trying one tooth smaller on the rear cog?  As PH says, Rohloff give guidance on acceptable ratios.

I have read someone advising that Rohloff bikes should be set up so that gear 11 is used as the ‘normal’ cruising gear (as it is the most efficient gear) - but this would seem a bit too lowly geared.  On flat roads, no wind, I am usually in gear 9 so have 5 gears left!

[Danneaux]

... a Rohloff equipped bike came in with a double  chainring and a chain tensioner.
Anyone  familiar with this setup?  My wife  is interested because  she spins out on downhill.

Not yet realized but surely in my queue for my tandem update and for reasons similar to what Andyb1 described. So long as the ratio remains within what Rohloff recommends, I don't see a problem. I've got mine planned to deliver essentially duplicate gears throughout most of the range with an extended top range on one chainring and an extended bottom on the other.

My situation us a bit more complicated as I will need to machine and break out my torch to braze in spacers to narrow the dropout OLN spacing from 140mm to 135 and I'll convert my hub with internal shifting from the OEM torque-reaction arm to the longer external version so it can key into the PacMan fitting for my present Arai drum drag brake. The present derailleur will serve to tension the chain as the bike has vertical dropouts and the only eccentric is for the timing chain.

Fun stuff!

[mickeg]

When I first got my Rohloff bike, I thought it would be nice because the 13 percent difference between gears is higher than I like or have on my derailleur bikes.  But, never implimented it and after about a year decided that the 13 percent was not that bad.

For riding around near home where the most luggage weight on my Rohloff bike is one pannier of groceries and a small pannier as a gym bag, I use a 44T chainring and 16T sprocket.  That gives me as low or high a gear as I want.  I add or remove four links when I change chainrings, use a second quick link when I add links.

But for touring, I swap out the 44T chainring for a 36T to get lower gears for the uphills with a heavy load.  Yes, I spin out more often on the downhills, but I just live with it.  Yes, at times I wished I had a 15th gear of another 13 percent for the downhills, but we all want things we can't have.

That is the reason I built up my Rohloff bike with a chain, not belt drive.  I anticipated using two different chainrings, one for touring and one for riding near home.  I expected to be adding or removing links which is easier to do on a chain than on a belt.

[Chris667]

My feeling has always been that a front mech and a rear mech as a tensioner is the worst bit of the technology.

I have ridden bikes with Schlumpf drives. If you can afford a Rohloff, it is not that much more of a leap financially and much more elegant.

But then, I would rather spin out downhill, I think.

[Andre Jute]

My feeling has always been that a front mech and a rear mech as a tensioner is the worst bit of the technology.

The very devil's invention, and worse with the Omega oval chainrings I received on a Peugeot bike c1990, which would fold up and take out the entire drivetrain, and sometimes the wheel too with it, every so often. Bernd Rohloff certainly did the cycling world a huge favour, and a hat-tip to Sturmey-Archer's and Shimano's hub gearboxes which came before.

I've ridden bikes with Schlumpf drives. If you can afford a Rohloff, it is not that much more of a leap financially and much more elegant.

I looked into them I still rode on the Shimano Nexus hub gearboxes (several kinds, including one automatic, see http://coolmainpress.com/BICYCLINGsmover.html) as a means of protecting the gearboxes by giving me a bigger working range because I wrecked a couple of Nexus boxes by mashing on them, but decided the Rohloff was a better deal.

But then, I would rather spin out downhill, I think.

I was once in my gunsmith's shop, checking out the fly-fishing gear, when an American tourist came in and was very finicky about the fishing line. The old chappie behind the counter finally said, "Sir, if you don't have time to stretch your own fishing line, you don't have time to fish."

Personally, I think all cyclists should plan well enough to have time to cruise downhill.

The bottom bracket on my fave bike is now occupied by an electric motor, whose electronics give me another set of gears -- up to nine more -- which, with enough torque from the motor, could give 14x9 gears. After some experimenting I set it to five electronic "gears" but haven't even calculated the ratios (many duplicate, I'm sure), preferring to override the electronics with a manual throttle where necessary, normally at places where I'm already in Rohloff low gear and my legs won't make it to the top of the hill. I further regulate use of the electric motor and the throttle by my heart rate.

I did calculate the ratios with either of the Swiss bottom bracket box types (Mountain and Speed) and decided there was too much duplication and not enough extension of Rohloff's already extraordinary range to justify the expense; the small extra weight of the Schlumpf wasn't a consideration for me, and in my electric setup even its much greater weight doesn't bother me, though its distribution (the placement of the battery) cannot be made optimal because of the frame format of the bike it's on.

I do suggest however that anyone looking into the Schlumpf makes careful calculations of the combo's ratios to determine which are duplicates of ratios already on the Rohloff. To be an effective choice, separations should be at least the half-step that many road cyclists are keen on. The Rohloff is good in this regard in that spinning the rotary control past several stops and then coming back to pick up the next gear but one doesn't throw off the chain or cause other problems native to derailleur transmissions.

You also need to know at which end you need or want to add gears before you start considering the Schlumpf boxes. I mention this because the main complaint one hears from tourers about the Rohloff is that they could do with an extra stump-pulling gear, rather than regretting spinning out on downhills, and for this the original "mountain" Schlumpf is ideal as it was designed to help unicyclists storming up mountains.

As you can see, for a mainly utility bike, I consider a torquey bottom bracket electric motor and the Swiss bottom bracket gearbox as pretty much six of the one and half a dozen of the other.

Admittedly, the electric motor is not as elegantly invisible as Florian Schlumpf's masterpiece...

[PH]

My feeling has always been that a front mech and a rear mech as a tensioner is the worst bit of the technology.

Certainly the ugliest, but I have a tensioner on my folder where there's no other option and really it's fine.  There must be some loss of efficiency, but it isn't of a magnitude I can feel.  It's another thing to collect muck, and wear out, and it's vulnerable to damage, but when it comes to riding it, I don't notice any difference. 

[martinf]

Certainly the ugliest, but I have a tensioner on my folder where there's no other option and really it's fine.  There must be some loss of efficiency, but it isn't of a magnitude I can feel.  It's another thing to collect muck, and wear out, and it's vulnerable to damage, but when it comes to riding it, I don't notice any difference.

Agreed. I have used a rear derailleur as a tensioner on occasion, the main downside is the cleaning. And since I discovered the Chainglider this annoys me more.

A front derailleur on a hub gear bike makes a tensioner necessary. I used this setup for a long time on a Brompton to get a wider than normal gear range. This didn't matter, because the Brompton already requires a tensioner to fold properly.

[mickeg]

My only IGH bike is my Nomad Mk II.  I am glad it has a means to adjust chain that avoids the tensioner, but quite frankly, I do not put a high priority on that.  If it had a tensioner, I would not get upset.

Oops, forgot, my folding bike also has an IGH.  But a Sram Dual Drive of course needs a rear derailleur because that type of IGH also has a cassette.