A New Rohloff Question

[keleher]

My rohloff always has had quite a bit of drag (seals too tight?), but I kept telling myself that it can't be any big deal compared to the energy of a big guy like me moving on the bike. However, I have to say that my surly seems to coast a bit better.

Three data points: 1) grabbing the wheel by hand and giving it a good spin (not a heroic one, just a good one), it only rotates five times before stopping. 2) pedals rotate when coasting, and 3) see the linked movie (if the forum lets me link it). Note how the pedals turn immediately, and how the wheel stops very abruptly at the end.

http://www.youtube.com/watch?v=vbckyINVu84&feature=youtube_gdata_player.

Is this normal?

[Danneaux]

Is this normal?

Not in my experience, Pete. It looks to me like there's a great deal of drag in your Rohloff.

I did notice my new Nomad Mk2 with Rohloff was about 8mph slower descending Green Hill with an identical load in near-identical conditions compared to Sherpa, but it is brand-new, and I descended in Gear 14, which I believe may have considerably more drag while coasting then Gear 11 (direct drive). By the way, that comparison at speed was at high speed 53mph/85kph on the Sherpa, 45mph/73kph on the Nomad. If the dfferential remained proportional, then the difference is much less significant at normal touring speeds of, say, 15mph/24kph. Even if it never equaled the free-running of the derailleur drivetrain, the lower maintenance costs alone would tip the scales toward the Rohloff for long-distance touring for me. Add in the ability pre-select gears on the sequential shifter and the ability to shift while stopped, and it is a pretty terrifc touring drivetrain.

But to return to your original question...no, your rapid spin-down does not appear "normal' in comparison to my brand-new example, which spins very nicely to an eventual stop. I would say (depending on the gear it is in) mine spins comparably to a new sealed (cartridge) bearing derailleur hub with fresh, tight contact seals.

As for the cranks turning while coasting or pushing the bike, the Rohloff manual indicates a drop of the lighter Rohloff "cleaning" oil between the cog and the hub will do wonders at reducing that effect. When I find the page reference, I will post it verbatim.

Could you tell me when you took the video? Was it during the time you had trouble with the oil leaking...before the present trouble wih the plate retention screws? Or, was it when the hub was running well overall? Did changing to another gear result in less drag than shown in the video?

No doubt you've already checked, but could the tire or rim be rubbing on anything (mudguard, brake pad), or perhaps the brake disc might be slightly warped? It certainly looks like there is a lot of drag in the system, and friction in one of these areas might mimic a too-tight Rohloff hub.

Best,

Dan.

[keleher]

No rubbing. I just took the video today, but it is consistent w/ what I've always seen.

Well, I'll definitely mention this on a note when I send my wheel off.

Thanks for all your hope.

[Relayer]

My Rohloff has never coasted as freely as a derailleur and the pedals almost always turn when pushing the bike, however I think it does better than yours in the video.  It looks to me as though your chain tension could be high, which could contribute a whole lot to this effect.

[Hamish]

Dan,

Assuming the hill is 100% coasting, You could try the same decent with your Nomad:

1. Freewheeling normally

2. With the chain removed

That should determine how much drag is due to the freewheeling mechanism and accociated seals, etc.

I think that the slower coasting effect is quite useful in a way and am happy with it
.

Hamish

[rualexander]

The video looks fairly normal for a Rohloff freewheeling to me.
On my Sherpa when I first converted it to Rohloff use I used the chain tensioner, and the pedals did not turn when pushing the bike. After I got rid of the chain tensioner and just use a sprocket and chainring combination which doesn't need it, the pedals now rotate when pushing the bike. So the small amout of extra friction that the chain tensioner puts into the system is enough to stop the pedal rotation. This must be a very small amount of friction.

[Danneaux]

Hi All!

Here is Rohloff's take on coasting, freewheeling drag, and pedals turning:

http://www.rohloff.de/en/service/faq/faq_detail/archive/2005/11/july/article/Crank_rotation_whilst_pushing/index.html

Of particular relevance to Pete's question, "Is this normal?", Rohloff say...

Power independent losses like the friction of the seals will have the same effect as a lightly rubbing brake block. This brings a free spinning wheel to stop but is barely noticeable whilst riding. But it is easy to recognise on a bicycle repair stand.

Perhaps this bit of advice they offer would help...

Crank rotation whilst pushing

Should the bike be pushed, it is possible that the cranks could also start to rotate.

This occurs due to the hub seal automatically activating the sprocket.

Bad seals and a very light running bottom bracket make it easier for the cranks to turn.

A drop of Rohloff cleaning oil (Part No. 8402) through the holes in the sprocket onto the hub seal will reduce this acivating effect.

Best,

Dan. (...who's happy to trade some coasting friction for the other Rohloff advantages but might try a drop of oil if mine tightens up)

[Andre Jute]

My rohloff always has had quite a bit of drag (seals too tight?), but I kept telling myself that it can't be any big deal compared to the energy of a big guy like me moving on the bike. However, I have to say that my surly seems to coast a bit better.

Is this normal?

Yes. My Rohloff is getting on towards 6000 km and still the pedals turn, regardless of which kind of bottom bracket I have in there, currently Shimano 55. I haven't tried the oil through the sprocket holes onto the seal trick and don't know that I'll bother, because that's a place where it is difficult to clean the dirt even a light oil will collect over time.

On coasting. It is a long time since I had a derailleur bike, but my Rohloff's free spin-down, on the work stand, is definitely shorter than I remember from a finely tuned derailleur system, and also shorter than Shimano's Nexus hub gear system. But that's the price of precision engineering that will last almost indefinitely, and more of such precision engineering, 14 gears v the 8 of the Nexus roughly defining the amount of drag that would be acceptable as the factor 14/8 or 1.75 times the drag of a Nexus system. The Rohloff clearly doesn't have nearly twice the drag of a Nexus HGB. All this has been measured and documented but I can't be bothered to look it up, because in these round terms we know the answer, and greater precision would be spurious.

Like many utility bikers and heavy tourers, my Rohloff transmission chain is geared towards the MTB stump-puller end (38x16), and my preferred cadence is only 60rpm, so on even slightly fast downhills I run out of high gear pretty soon and thus coast a lot. I can't say I've noticed my Rohloff-equipped Kranich being wanting in the coasting department -- in fact, it coasts much faster than any of the bikes in my riding party, all derailleur-equipped, even when we swap riders to equalize the weight.

The Rohloff's crank rotating trick is, I think, an anomaly that doesn't necessarily indicate any abnormal amount of drag. Interesting to demonstrate but not necessarily relevant in use.

Andre Jute

[Danneaux]

...my preferred cadence is only 60rpm...

Andre,

I am pleasantly surprised to find operating drag is not noticeable; I find I still fall into my default 110-120RPM pedal cadence, just as I do with my derailleur bikes, and haven't noticed the Rohloff holding me back in any way (my 62-inch Gear 11 keeps me in the 17-21mph/27-34kph range at my preferred hummingbird-like cadence). Keep in mind, my Rohloff is still essentially brand-new and far from broken-in. It can only get better.

Good things await.

Best.

Dan. (...more amazed by the day at the R-box's virtues)

[expr]

Don't forget that depending what gear you are in (if comparing) can make a difference, in my experience I have found a couple of things that affect the freewheeling capabilities of the wheel/hub...

The hub lip seals greatly affect the ability to drive the pedals round..however what I notice in the video is the way in which the hub comes to a stop quite quickly, again in my experience I have found the main cause of this to be main bearing misalignment. The bearing on the non drive side is fixed and the bearing on the drive side is floating only being held in place by the output drive and the drive sprocket. The same symptoms can also be seen if the quick release/ wheel nut have been over tightened.

Initially I would check the later first, then if it still remains "tight" and doesn't freewheel any better then I would take a rubber hammer filled with lead shot and hit the non drive side axle a couple or three times fairly hard, I have had to d this many times on the occasions I have stripped a hub down, what this will do is eliminate any misalignment between the two main bearings causing internal stresses to occur..

Having the pedals turn is a different matter, and to a certain extent no bad thing, it gives a good indication that the lip seal is actually making good contact with the sprocket sealing face, and to some extent a characteristic of certain hubs, some people have noticed that their hub doesn't turn the pedals and others it does, taking into consideration what I have noticed, I would much prefer to know that the oil lip seal is tight on the sprocket, one thing to consider though and I have brought it up before is that people whom turn the sprocket around must check to see that the outboard side of the sprocket that has been exposed to all the elements must be in good "smooth" condition, any pitting or corrosion will greatly reduce the life and sealing abilities of the oil seal lip.

So to conclude,  first check how tight the qr is, then check the bearing alignment only with a rubber hammer, this must be done with the wheel out of the frame.

[keleher]

Andre,

I am pleasantly surprised to find operating drag is not noticeable; I find I still fall into my default 110-120RPM pedal cadence, just as I do with my derailleur bikes, and haven't noticed the Rohloff holding me back in any way (my 62-inch Gear 11 keeps me in the

I went for a ride on derailleur-equipped LHT, and I've got to say that it seemed to have less drag. This could have been because:
- really was drag
- it's all in my head
- LHT is lighter, or
- the LHT has higher gears (109" vs 93-ish" for the thorn) available, and I was able to really get moving for once. My cadence is in the 60 or so range, unlike the hummingbird above.

[swc7916]

Is this normal?

Mine coasts about like yours but doesn't stop so abruptly.

[swc7916]

I find I still fall into my default 110-120RPM pedal cadence, just as I do with my derailleur bikes, and haven't noticed the Rohloff holding me back in any way (my 62-inch Gear 11 keeps me in the 17-21mph/27-34kph range at my preferred hummingbird-like cadence).

I have found that the Rohloff works better at high cadences. 

[pyjamas]

Yes, I was looking for an answer to this question, because, cycling downhill with a friend with derailleurs, we noticed that he was braking while I was still pedalling hard.  As I also have a hub dynamo, I suppose that must add a bit of extra drag, but the hub does feel stiff.

[keleher]

My rohloff is currently w/ Cycle-Monkey (rohloff's US service partner) investigating another issue, and I've asked them to look at this as well. I'll report back their conclusions.

pete