How efficient is a bicycle ? Rohloff v derailleur.

…when I’m riding in muddy conditions and all I can hear is the transmission – but is it actually running any less efficiently?

Likewise the rohloff ‘noise’ that people complain about. Does that fact that theres a bit of whirr actually signify a material change in efficiency?

off-road? Wind resistance is a much lower factor, and others may be significant.

Rolling resistance of tyres? Differences between one road tyre and another at 100psi must be pretty minimal. Off road they vary hugely. Theres the soft vs hard thing as well – soft tyres deform over small obstacles, hard tyres bounce off/over them.

Another thought;
If smaller sprockets are less efficient because of the increased friction caused by bending the chain, how much effort is wasted by those tiny jockey wheels ?
Do people notice the difference between a SS and derailleurs in the same gear ?

And what Simons said, there’s a noticeable whirr from a Rohloff in certain gears. This makes it feel like it’s dragging, even though it may not be.

simons_nicolai-uk – Member
Likewise the rohloff ‘noise’ that people complain about. Does that fact that theres a bit of whirr actually signify a material change in efficiency?…

I don’t know if it affects efficiency much, but for the brief period I used my Rohloff the coffee grinding noises in some gears did me in psychologically. So my Rohloff lives in my attic now and I went back to singlespeed.

My brother has done 10s of thousands on his in Oz, usually hauling huge loads, and he swears by Rohloff. As an example on one of his overland trips, his bike ran flawlessly, whereas his mate had to replace a couple of derailleurs and cassettes. He tells me I haven’t used mine long enough to run it in properly.

I may build up a fat bike wheel with it for my bog monstering exploits (need gears for that).

MidlandTrailquestsGraham – Member
Another thought;
Do people notice the difference between a SS and derailleurs in the same gear ?

They may well think or belive they do…

The acoustic output from a transmission is likely to be insignificant. Rolling resistance trumps transmission losses on a MTB, especially in winter when the ground is soft and the tyres more knobbly.

I’m inclined to agree that running a chain through a rear mech will be less efficient than running it without, surely just from a drag point of view?

I do run SS, but of all the benefits I can’t say I’ve noticed reduced drag.

Also, regarding SS ratios – would the benefit of running a 40/20 compared to a 32/16 be outweighed by the additional weight of bigger rings and a longer chain? On of the key reasons I run SS on my racebike is weight and its surprising the amount of weight in a chain.

[list]I’m inclined to agree that running a chain through a rear mech will be less efficient than running it without, surely just from a drag point of view?[/list]

Does that mean a Rohloff is less efficient on a sus bike with a tensioner than on a hardtail with sliding dropouts/ebb?

Dunno, but if the loss of efficiency is caused by the increased friction of having to bend each link of the chain at a sharper angle, then I would guess there’s very little friction at the jockey wheels as the chain is not under significant tension on the bottom run.

that new gearbox bike seems to have a large rear sprocket.
I the nexus I set up on a pompino seemed smoother in with a 20 in the back,panacea maybe.probably.

panacea? suspect you mean, er, placebo?

Likewise the rohloff ‘noise’ that people complain about. Does that fact that theres a bit of whirr actually signify a material change in efficiency?…

well noise (sound) is a form of energy so if sound increases that energy has to come from somewhere..

having said that in the grand scheme of things with mud, dirty chains, dragging brakes etc etc doubt it makes much difference

If smaller sprockets are less efficient because of the increased friction caused by bending the chain, how much effort is wasted by those tiny jockey wheels ?

as the chain passing them is not under load in the same way as the chain is from chainring to sprocket is, the fiction is likely to be less…

Acoustic power is usually measured in mW at most, so the amount of energy wasted as noise is irrelevant. In the case of a few metal bits moving and vibrating (like in a hub gear) you won’t need much wasted energy to make the noise.

The psychological effects can definitely be significant, though.

Years ago, when I first fitted a Rohloff to my demo bike, it definitely felt draggy in some gears. So I tried putting earplugs in and not looking at the shifter, and I could no longer tell which gears had felt draggy before. So for me at least, it seemed to be psychological – the gears which sounded noisier felt less efficient.