Rohloff pedalling resistance

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Artfularry
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Rohloff pedalling resistance

Postby Artfularry » 9 Apr 2009, 7:05am

I've owned my Rohloff hub for about 3 years and find myself riding it less and less. Why - because it seems so much harder to pedal to achieve a given speed. The weight is not the issue, I,m about 120kg fully kitted, so a few grams is nothing. To me if feels as if I'm having to overcome something other than the resistance of the road and the wind. Also, and more importantly for me is freewheeling -on my other bikes' good hubs whilst on the maintenance stand I turn pedals and they will freewheel for minutes, the Rohloff is measured in seconds *probably <20 seconds. Is there something wrong with it or is it a "design feature".

FYI - the lower 7 gears also still make lots of noise. The top 7 are pretty quiet.

The hub has already been to Germany for a free repair when the fool who owned it before me overtightened the sprocket, it came back in a few days with new oil. Oil has been chnaged since but no effect.

rogerzilla
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Re: Rohloff pedalling resistance

Postby rogerzilla » 9 Apr 2009, 8:11am

In some gears it puts the drive through multiple planetary geartrains so you'd expect more drag.

What is gear 11 like? This is the most efficient, because it's "direct drive". If this is bad, then there is a fundamental problem.

steve climpson
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Re: Rohloff pedalling resistance

Postby steve climpson » 9 Apr 2009, 9:19am

Artfularry wrote:I've owned my Rohloff hub for about 3 years and find myself riding it less and less. Why - because it seems so much harder to pedal to achieve a given speed. The weight is not the issue, I,m about 120kg fully kitted, so a few grams is nothing. To me if feels as if I'm having to overcome something other than the resistance of the road and the wind. Also, and more importantly for me is freewheeling -on my other bikes' good hubs whilst on the maintenance stand I turn pedals and they will freewheel for minutes, the Rohloff is measured in seconds *probably <20 seconds. Is there something wrong with it or is it a "design feature".

FYI - the lower 7 gears also still make lots of noise. The top 7 are pretty quiet.

The hub has already been to Germany for a free repair when the fool who owned it before me overtightened the sprocket, it came back in a few days with new oil. Oil has been chnaged since but no effect.


I also have a rohloff hub and find that gears 1-7 are irritatingly noisy and seem relatively harder than their counterparts from 7-14. In other words moving from 9 to 8 has a greater advantage than 7 to 6 when they should be exactly evenly spaced. It's a though I'm pushing against something more than the hill in 1-7. I hope that makes sense.
It's probably me expecting too much of my legs :(

Overall though I find the hub to be good.

gilesjuk
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Re: Rohloff pedalling resistance

Postby gilesjuk » 9 Apr 2009, 10:30am

I built a bike with an SRAM iMotion9 hub. I've ridden it about twice. Built a bike with a fixed gear and I ride that all the time.

Acceleration and pedalling is smooth and easy on the fixed gear, even with the wind blowing against you.

I suppose I've not worn in the geared hub. But it's so damned heavy compared to a fixed hub which is lighter than a normal freehub.

Artfularry
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Joined: 9 Apr 2009, 6:51am

Re: Rohloff pedalling resistance

Postby Artfularry » 12 Apr 2009, 7:29am

Gear 11 is fine, but like all the rest has very poor freewheeling. I guess it is down to the fact that unlike a car gear box there is no neutral - therefore it is always 'in gear', therefore there is always somethng rubbing causing resistance and hence inefficient use of energy?

Will it last a lifetime? - probably because I only use it as an on-road turbo trainer! Would I recommend it? - probably not -depends on what weightings you give to cash v time v effort.

PH
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Re: Rohloff pedalling resistance

Postby PH » 12 Apr 2009, 5:24pm

The average speed of my Thorn Rohloff is consistently 0.5 - 0.7 mph slower than on my Hewitt tourer. Considering it's around a kilo heavier, 26" wheels and wider tyres that's not a significant penalty and about what I'd expect.
The spinning an unloaded wheel is a poor test, ask anyone with a hub dynamo. A better test would be to roil down a hill on two similar bikes. I'd expect the Rohloff to stop first, I wouldn't expect it to be by much.
I recently rode the Pennine Cycleway on mine, I know on some of the long drags I'd have been better off on a derailleur bike, but on those stretches with constantly changing gradients, the Rohloff ability to always be in the right gear made it faster.
As your experience seems very different, try a test ride another one to see if your hub is at fault. Or maybe it just doesn't suite you, in which case the good news is they hold their value well, so you could get a good price for it.

rogerzilla
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Re: Rohloff pedalling resistance

Postby rogerzilla » 12 Apr 2009, 5:29pm

I'm not sure why spinning is a bad test. Unless Rohloffs are different to other hubs, the planetary gears don't turn when freewheeling, so the drag is purely from the axle bearings. Maybe the seals are exceptionally tight; I think Rohloff use lip seals rather than (or as well as) labyrinth seals, the latter being completely drag-free.

PH
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Re: Rohloff pedalling resistance

Postby PH » 12 Apr 2009, 5:52pm

rogerzilla wrote:I'm not sure why spinning is a bad test.

Because it doesn't reflect the forces at work in cycling conditions. Turning a dynamo light on when spinning a wheel on the workstand is like putting the brake on, yet when riding that resistance is minor. It's not a denial that it exists, just an opinion that it's a poor way to measure it.
Unless Rohloffs are different to other hubs, the planetary gears don't turn when freewheeling, so the drag is purely from the axle bearings.

I know bugger all about the working of hub gears. My Rohloff sounds different freewheeling in different gears, so something is moving.

rogerzilla
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Re: Rohloff pedalling resistance

Postby rogerzilla » 12 Apr 2009, 7:19pm

It may have multiple sets of freewheel pawls like a SA hub. They sound slightly different when coasting in low gear (although this is something you rarely do!) because the right-hand pawls are disabled by the clutch in that gear and only the left set of pawls is making the clicks. The drag of a very lightly-sprung pair of pawls is insignificant though.

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ersakus
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Re: Rohloff pedalling resistance

Postby ersakus » 12 Apr 2009, 7:27pm

I have experience with shimano nexus 8 and share the drag and noise concerns(and the weight). I have sold that bike with hub gears and adopted the Buddhist way and I now feel great with my single speed road bike. Minimal drag and weight really makes a difference. I can do 100 miles a day without complaints, day after day. What more can I want from a bike? Nothing.. (I only carry a small pannier though). For a pannier laden ride I'm not sure how I'd cope with single speed though :roll:

rogerzilla
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Re: Rohloff pedalling resistance

Postby rogerzilla » 12 Apr 2009, 7:39pm

There are some interesting efficiency measurements here for hub gears and derailleur systems:

http://www.ihpva.org/HParchive/PDF/hp52-2001.pdf

Rohloff weren't very happy; their response is in issue 55, which is currently unavailable due to "copyright issues".

An oiled, well-used Sturmey-Archer 3-speed was measured at over 95% efficient in direct drive (93% in low gear, just under 92% in high). That's slightly better than the Shimano derailleur system in its best, least cross-chained gear (the jockey wheels, or the need for the chain to bend tightly round them, are the main culprits). A footnote suggests that the measured efficiencies could be about 2% higher in reality due to the ergometer drive used in the test setup.

glueman
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Re: Rohloff pedalling resistance

Postby glueman » 12 Apr 2009, 8:19pm

Interesting. That would bear out my seat-of-the-pants judgements on SA 3 and 4 speeds, i.e. a very good idea and pretty reliable, especially before they became sealed units. The Rolhoff, from a position of complete user ignorance, seems like a lot of gubbins - before you get to flange breaking under heavy use.

Too clever by at least half. I picked one up once. It weighed about the same as my fixed bike*

* Allowing some increment for hyperbole.

rogerzilla
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Re: Rohloff pedalling resistance

Postby rogerzilla » 12 Apr 2009, 10:48pm

I know someone who's just dropped £2,500 on a new Rohloff bike without ever trying one. I hope he's happy; although it's a Thorn it was ordered through the LBS and their 100-day satisfaction guarantee may not apply.

geocycle
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Re: Rohloff pedalling resistance

Postby geocycle » 13 Apr 2009, 12:44pm

Rohloff's response to that article by Kyle and Berto which unfortunately has vanished from the ihpva site and the original article suggests to me that there is no additional drag, even when comparing the hub with a mythically clean (except those maintained by some senior forum members!)derailleur system. As I recall, Rohloff suggested hub gears (all) were about 2% less efficient than (clean) derailleurs

Efficiency (%) (from Kyle +Berto)
Derailleurs 87-97
Gear Hubs 86-95
Note: Test performed with 80W, 150W, 200W input.

Rohloff's article showed how complex it is to measure. They seemed to demonstrate better results for their direct drive gear 11 relative to a derailleur, but inferior performance in gears 1-3, with the rest being broadly equivalent. In reply to the Rohloff article, the original authors stood by their results but acknowledged the quality of the rohloff relative to other hub gears.

While there is some noise in 6 and 7 on my 3 year old hub the other gears are now silent . I'd agree that its not the lightest system and I am not convinced its not heavier (by up to 400g) than a similar xt drive chain despite the claims made, and built into my thorn it is not the fastest as PH suggests. Nevertheless I find it ideal for my major use (slow touring and commuting) and would never go back.

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ersakus
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Re: Rohloff pedalling resistance

Postby ersakus » 13 Apr 2009, 2:32pm

I wonder how a single speed with perfectly aligned chain would compare. No mentioning of single speeds on that chart as far as I see :? It can't be worse than a hub gear!
May be I am imagining that the my new SS bike feels like it is flying compared to my (ex) hub geared bike? May be due to the fact that I'm able to use the thin 700x25C tyres on the SS.


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