Wikipedia says IGH is about 2% less efficient than derailleur gearing. What does that really mean to your riding experience and speed? I guess that for the same effort, you transfer 2% less force to the wheels. But since effort has a nonlinear relationship to speed, as your effort increases from low to medium to high, the actual reduction in speed relative to derailleur gearing is progressively less.

So the actual reduction in speed is less and less as effort increases. Is my thinking correct about this?

https://en.m.wikipedia.org/wiki/Hub_gear

Yes, IGH is also heavier. On a typical commute bike this would seem to have even less influence on speed.

The actual reduction in speed is less and less as speed increases. (not effort). Because power needed relates to the cube of wind speed. (or more precisely ground speed times wind speed squared)

Going up hill for example, or accelerating from a stop, the speed is lower and the linear effect predominates. 2% isn't that insignificant - but it is less than what you could lose from slow tires, loose clothes or poor positions on the bike.

The power you need varies with the cube of your speed, because of wind resistance. So travelling at 30 kph on a flat road requires close to 3.5 times as much power as does 20 kph.

In that context, a 2% loss in efficiency in power transfer is going to be lost in the noise. Looking at the figures on a bike calculator, a loss of 2% in drivetrain efficiency is going to mean I need about 4 watts more to maintain 30kph. Maintaining the same power would cost me about 0.3 kph. If you're racing competitive time trials, significant. Commuting, negligible.

I doubt it's worth worrying about. Most riders could improve efficiency several percent just by properly inflating their tires or bending their elbows more.

I don't doubt the inefficiency built into IGH design, which is meaningless in commuting for me.
The advantage of being able to shift while braking or at a dead stop is the major reason that I use an IGH on my town bike.
Being in the proper gear to launch with unruffled dignity from every traffic control on the route outweighs the drivetrain loss and mass of an IGH.

If I was that concerned about drivetrain efficiency I'd ride my fixed gear instead.....

-Bandera

The big inefficiency is a rear flat

Speaking purely from a mechanical/speed/efficiency viewpoint, the 2% difference isn't that meaningful. But there's a hitch in that most (all?) IGH hubs are lose efficiency with load, so they'll be least efficient in hill climbing, when you need the most help. Some are also less or even least efficient in the lower gears compounding the problem.

But for general cruising around, you'd be very hard pressed to find a difference.

Do you mean they lose more absolute power under load, i.e. 2% of 350W is more then 2% of 200W? Or are you saying the efficiency actually gets worse with higher power?

A good approximations is that the loss in speed will be 1/3 the loss in power. So 2% loss in power translates to .67% loss in speed or not much as others have pointed out.

I would use an IGH with belt drive on my winter bike when they come up with a reliable IGH that can be shifted with normal road shifters. My impression is the only reliable hub is a Rohloff and for that you need to add some type of rotary shifter to the tops of your bars.

I mean that they lose efficiency with increased torque. So the power loss percentage will be highest in hill climbing situations, where you have the least to spare.

Of course actual power loss will always be higher at higher power levels because we're X% of a bigger number is bigger, but that's pretty obvious.

By contrast, derailleur systems are most efficient when larger sprockets are used, so there's a small (not enough to matter) improvement in low vs. high.

In any case, I don't think the differences are all that material in the scheme o things, unless you live on the side of a mountain. Efficiency is only one of a bunch of factors to consider if trying to decide between IGH and derailleur. I use both, and prefer IGH for utility riding, and derailleurs for sport. Because I use IGH mainly in the flats, I would ratehr see 3-5 speeds which are mechanically simpler but with closer spacing, since I don't need the range for my applications. (I currently own a vintage SA 3s ultraclose spaced freewheel hub, which is perfect for flattish terrain, though I'd want something a bit wider (what SA used to call medium spacing BITD) for general riding in lightly rolling terrain.

I use to have an upright Dutch bike with a derailleur as well as a nearly identical one with 5 speed Sturmy IGH. When we were riding with guests I'd ride the derailleur version, otherwise I'd always ride my IGH. I noticed no difference in the two. In an attempt to have a lot of upright IGH bikes for guests we've amassed a collection of about a dozen different IGH's and all work quite well.

There was a very slight noticeable difference with the early Nuvinci's but not nearly as much with the current ones. Even so I still really liked the variable gears and ride one of the new ones today.

Both Netherlands and Copenhagen went through brief periods of derailleur popularity. These didn't last long and people were back to IGH which overwhelmingly dominate. If they were a problem this wouldn't happen. Fixies have lasted longer and are still popular with a small portion of the population but probably make up way less than 1 in 1,000.

Just a guess here: if you were racing and trying for a personal best time, you would notice the difference. Riding to work, probably not.

"in 1929 Jack Rossiter set off from Land's End on a fine August day and covered the 866 miles to John O'Groats in 61 hours, 27 minutes, reducing by nearly 7 hours Harry Green's record and claiming the added distinction of being the first record-breaker to cycle every inch of the End-to-End roacL His Sturmey Archer equipped Raleigh had been more than a match for Shap, the Grampians and the even more dreaded Berriedale. He used a "K" hub, giving variations of 2S per cent. below and 33 1/3 per cent. above normal. A year later he broke the 1,000 miles record, which had also been standing for 21 years, by nearly 4 hours."

Sturmey-Archer-50 Years of Leadership - page 7

I can understand your preference for sti but you're mistaken about reliability. SA 3 and 4 speed hubs have been astonishingly reliable for a long time. The Rohloff is probably more durable than the Shimano hubs, as well as having 14 speeds - but you'd expect that with the price differential.

I've got a Rohloff on a flat-bar heavy-duty tourer. It's an excellent bit of kit and seems absolutely bulletproof.

I have the Shimano "red band" 8 with Versa shifters on one of my commuters. It's probably due to the added weight in the rear but it feels a bit slower overall.

I converted a mountain bike to an 8 speed IGH. While the loss of some higher and lower gears was noticeable, there was no noticeable change within the range of the IGH. Once I changed to road orientate bars, and tires, the overall feeling is that the bike is faster now.
In the big picture, there are things that will have much more influence.

I agree the Rohloff has a good reputation for reliability but it doesn't work with road shifters. I've read a reasonable number of reports of poor reliability with Shimano's hubs for anything other than easy beach strolls. The 3 and 5 speed hubs may be reliable but I need/want more gears. I ride 1x10 now for commuting and wouldn't really want to go with fewer gears.

Maybe Rohloff will add an electronic shift one day.

I've often wondered why they don't. Given how simple the shifting mechanism is it would be much less complex than the electronic derailleur systems.

Old school company with no expertise in electronics. Shimano is unlikely to license them technology so they'd need to come up with something themselves or find someone else to do the work.

The reason I prefer the IGH is that it is more likely to be in-tune than a derailleur system. The efficiency gain that one can, theoretically, gain from a derailleur system is immediately lost when the bike is clicking and clacking in half of the gears.

Another way to think of 98% is that it's one tooth on the big ring in the front. On a MTB or hybrid triple system, the rear shifts are about +-15% and the front shifts are equivalent to two rear shifts. So -2% is equivalent to a lot less than one shift.

My utility bike has a Nexus 8 IGH. If I let my coworker ride my utility bike and he let me ride one of his racing road bikes (at least 15 lbs lighter, wide gear range, etc.), he'd still beat me to work by more than 15 min. We live in the same 'hood. He can get to work in 35-40 min. It takes me 1 hr. to ride the same distance.

He loves racing and trains all the time. Neither is true for me.

Less than air resistance.

Premium, rolling on needle and ball bearing Oil lubricated Rohloff , less than plain bushings and grease lubricated most every thing else..


They dont have to someone in Australia already did. stepper motor and an up/down button

https://www.edsanautomation.com.au/

https://www.edsanautomation.com.au/EdsanProducts.htm

More 3rd party parts > https://www.rohloff.de/en/technology/...rts/index.html

See: https://www.rohbox.com/

Once Again not made By Rohloff But made by other companies to do that which you wish to do.

My bikes have derailleurs because I like them better in general, but the ability to shift while stopped is really nice. Every time I ride an IGH bike, I use that feature and really enjoy it. I ride Citi Bike (the big bike sharing program) which uses 3-speed hubs. The bikes are geared low, so I rarely need 1st gear on the newer model which is geared higher than the older model. I never need 1st gear on the older model.

You want/need gears, SRAM DualDrive is the way to go. 33 speeds with a possible gear-inch range greater than 100 gear-inches, much lower price than Rohloff and very good reliability. SRAM DualDrive.

10 speeds is fine for me. What i would like is to run a belt drive and eliminate chain maintenance during the winter. I don't like coming home in the rain and then having to clean my bike and dry/lube the chain.