Utility Cycling - IGH weight limit

I was curious about this. It was touched upon in the other IGH (http://www.bikeforums.net/showthread.php?t=468387), and I was going to ask there, but they seem to have forgotten what the original topic was. ;-)

I've been thinking of replacing my rear derrailleur set up with an IGH. The bike will mostly be used for commuting, and for that, I expect any 8-speed set up will be sufficient, but I do tend to try and load up my bike from time to time with a little weight, and I'd like to take a short tour or two in the future, so I'd like to know that I can carry some weight if I want to. Probably not Big Dummy type loads, but fully loaded touring loads at least. Not to mention that I'm sitting just a few pounds over the Clydesdale line myself.

I gather that the Rolhoff doesn't have much in the way of weight issues, and has enough of a gear range that I could ditch my front derrailleur as well, but it's also more than I'm able to spend right now.

I had been thinking one the Shimano 8-speeds would do the trick, but it seems that these were the ones mentioned as having some weight issues/limitations?

The middle ground would be the NuVinci. Admittedly I'd love to get the NuVinci just because I like the concept of the continuously variable transmission, or whatever they call it, but it is pricey, and heavy. I can handle the weight, I imagine (although this bike will/does make daily trips to and from a 2nd floor apartment), but probably the only way I can justify the purchase is if the cheaper models are not likely to hold up to a full load.

So, weight limits on IGHs ... what are your thoughts/experiences?

According to Velo-Vision in their sample review (http://www.velovision.com/mag/issue29/vv29hubgears.pdf) mention that the maximum input torque rating of the Nuvinci is 130Nm as opposed to 100Nm for the Rohloff... as long as your back wheel can take it, the Nuvinci ought to take it just fine.

Lessee...working backwards from that- 100 Nm at the wheel = 200 Nm at the crank with my 2:1 gearing. Assuming 165mm (not sure what they really are) crank arms, that's 200/0.165m = 1,212 N maximum. Now, a kg weighs 9.8 N, so that's 124 kg or 273 lbs. In other words, if I stand on my pedal, I'm right at (but not necessarily over) the torque limit.

On my trike with 32:21 gearing, that works out to 208 lbs.

But those calculations only work out if the pedals are level and the bike doesn't start moving as you apply force...so either you have your brakes on and are putting your full weight on the pedal in an effort to move or you are trying to pedal up a wall. I find up unlikely that a single rider is going to put out enough force to break either when the hub is properly maintained.

I have to say that I really don't have a firm grasp of the physics involved, which is one reason for this thread. I have definitely heard that the Rolhoff is a very hardy hub. If a 208 lb rider could trash it, with no load at all, then I don't see how it could have that reputation at all. OTH, if rider weight is the biggest factor in hub durability, then, as a heavier rider, I guess I better be trying to choose the hardiest hub I can, rather than finding the one that's just "strong enough." I was hoping that the Shimano would be "strong enough" because that's far closer to being in my budget, but I may have to give the NuVinci a more serious look.

The Shimano 8 should be fine. Do a search in the forum, IGH`s are being discussed both for touring and commuting bikes and should be more than strong enough. I think somebody said that there is a minimum size for the crank wheel. Was it 33 teeth?

On my Giant Twist/Xtracycle, which weighs a ton (well, 60+), I went through a series of hubs and the only two that held up were the Rohloff and the NuVinci. As far a price goes the NuVinci is 1/3-1/4 the price of the Rohloff and the NuVinci can handle heavier loads and larger amounts of torque.

The Shimano 8 and the NuVinci have about the same amount of gear range (the NuVinci having a slight edge). Unless you are in hill city you should be able to ditch the front derailer with either. The NuVinci is made of sterner stuff than the Shimano, and can handle heavier loads without issue.

I've actually been thinking about this a bit lately. I think the Shimano Nexus hub is a lot better than people give it credit for. Maybe it's because it's so much cheaper than the Rohloff that it's assumed it's not going to hold up (and there may have been issues with past hubs - in particular the 7 speed.) I've been riding my Nexus equipped bike for over 2 years with some pretty decent loads without a problem. In comparison, I've also used a Sturmey Archer 8 speed hub (admittedly on a cargo bike with an illegal gear ratio) and it's just awful - it shifts nastily and has the scary habit of suddenly dropping out of high gears into the lowest :eek:

If you're happy with the range of the Nexus, I would highly recommend the premium Nexus or Alfine given the price and the beautiful shifting - just keep the gear ratio legal if you're carrying reasonable loads (at least 1:2) and you should be fine. There's surely a reason they're the hub of choice for bakfietsen (http://www.workcycles.com/workbike/bicycles/bakfiets.nl/bakfiets.nl-cargobike-long-child-transport-bike.html).

Otherwise I've also heard good things about the NuVinci and the Sram 9 speed. But they are a bit more expensive.

Those numbers are pretty conservative, I think. Very few actual bicycles have gearing like that trike does, which limits me to about 10 mph with a single-speed. I've never actually stood on a single pedal on either bike, but have probably come close to it on a few occasions. It's also not obvious from the torque limit as to whether that's the failure point, or maximum torque for prolonged use or what.

Having spent many years (and many miles) on IGH equipped bikes, I have had a few thoughts about this specific topic. In my experience, most of these hubs (of any brand) are strong enough to withstand much more force than the stated limit, out of the box. The problem arises when subjecting them to extreme forces on a daily basis, over an extended period. While the hub may not "break" immediately under a heavy load, regualr use of this type will accellerate the wear on the gear teeth, resulting in sloppy engagement , metal shards in the lube, and thinner teeth that will eventually start breaking off under even normal loads. Basically, given a hub that would normally last 8-10 years without service, running it with lower ratios or higher loads than recommended will shorten the lifespan drastically. I switched to a NuVinci when it became obvious that I would be replacing the internals of my rear hub every year if I kept using it the way that I was. The advantage of the NuVinci is that there are no gear teeth to break or wear down, thus eliminating that failure mode. The impression I have gotten from many conversations with the folks at Fallbrook (NuVinci manufacturer) is that most of the stated limits on their hub are intended to keep it within a range of efficiency that is most acceptable to bicycle riders. Because of the method of torque transfer within the hub, the efficiency starts to drop off as more torque is applied. I myself am using the hub with chainring/cog ratios well beyond the recommended limit, and they did not have any warnings for me in that regard - the sentiment seems to be that if I can push it, the hub will take it. So far, I have almost 4000 miles on this hub, and it has functioned flawlessly, even in extreme situations. I am not sure if the reduced efficiency in the lower ratios has any effect that I can notice; while I have had to walk a few slopes, it has always been at the end of a hard, long day with a large load, on a long, steep hill. At that point, I would feel like a real scrub to blame the hub.
To actually adress the original post: the type of riding described by Rob E should be well within the capabilities of the Nexus 8, the Rohloff, or the NuVinci. In the case of the Nexus, the lifespan of the hub may be shortened somewhat, but it should still last several years before needing an overhaul (especially if grease is added when the wheel is built - the factory rarely includes enough), and this hub is intended to be overhauled, unlike earlier Nexus hubs. The Rohloff needs to have its oil changed yearly (at least), but this is easy and quick, and the hub should have no problems in this application. The NuVinci has the advantage of the continuously variable ratio (which is truly nice and extremely useful once you learn to take advantage of it), and is completely sealed and warranteed for six years. Choose your weapon, and get some miles in.

For durability, as mentioned previously, Nuvinci is the best.

After Nuvinci, the second best option is the Sram Cargo series in both 5 and 7 speed, followed closely by the i-Motion 9 speed.

The staged systems used in Shimano Nexus/Alfine and particularly Sturmey 8 are more fragile and make less sense for strenuous cargo application.

For durability, as mentioned previously, Nuvinci is the best.

After Nuvinci, the second best option is the Sram Cargo series in both 5 and 7 speed, followed closely by the i-Motion 9 speed.

The staged systems used in Shimano Nexus/Alfine and particularly Sturmey 8 are more fragile and make less sense for strenuous cargo application.

And where does a Rolhoff come on this continuum?

For durability, as mentioned previously, Nuvinci is the best.

After Nuvinci, the second best option is the Sram Cargo series in both 5 and 7 speed, followed closely by the i-Motion 9 speed.

The staged systems used in Shimano Nexus/Alfine and particularly Sturmey 8 are more fragile and make less sense for strenuous cargo application.

Caution on the SRAM Cargo and P5, make sure they will fit a 135mm rear end AND still shift correctly. SRAM confirmed that the P5 wouldn't, even though I could space it so. The "clickbox" shifting mechanism needs enough exposed axle to shift properly. Price was my primary driver for choosing the Nexus7. If price weren't an issue, I'd have gone with a Nuvincci.

I have a Giant Lite/Xtracycle build similar to AllenG, and built a Nexus7/Sun RhynoLite rear wheel for it. It shifts flawlessly even with 120lbs of passenger, and hasn't needed adjustment since install. I have a more difficult time keeping my standard grade Nexus8 in proper adjustment. In fairness, it's a winter bike and gets sees some cold temps.

And where does a Rolhoff come on this continuum?

Durability? Right after NuVinci, not that my Rolhoff is not bomb-proof, but the NuVinci can handle larger torque loads.

Durability? Right after NuVinci, not that my Rolhoff is not bomb-proof, but the NuVinci can handle larger torque loads.

Durability to me implies lifespan/service life. Has the NuVinci's service life been established by users or by the manufacturer? Rohloff hubs seem to be [based on reports I've read] exceeding 100,000kms...the longest serving one over 200,000kms.

Durability to me implies lifespan/service life. Has the NuVinci's service life been established by users or by the manufacturer? Rohloff hubs seem to be [based on reports I've read] exceeding 100,000kms...the longest serving one over 200,000kms.

There isn't a maximum service life that has been shown yet, however Nuvinci offers a longer warrantee than any other IGH... 6 years or XXX miles (can't remember the number of miles)

Durability to me implies lifespan/service life. Has the NuVinci's service life been established by users or by the manufacturer? Rohloff hubs seem to be [based on reports I've read] exceeding 100,000kms...the longest serving one over 200,000kms.

I've had no issue with either of the Rohloffs or the NuVinci. None have done anything other than work perfectly, however the NuVinci is rated for higher weights and torque than the Rohloffs, and it subjectively feels like it can take more of both. Both are bomb proof, and no other IGH I've owned are in their class.

15k+ miles on one of the Rohloffs, 10k+ on the NuVinci. The NuVinci has had to two more weight and torque for longer than the Rohloff. The NuVinci has seen it's entire life on the Xtra-Giant, and one of the Rohloffs is on my commuter and one is currently back in the parts bin.

There has been a discussion on the Thorn discussion forum recently regarding a tandem owner who has had spoke flange failures on two Rohloff hubs. Last time I checked there was claimed to be an ongoing discussion between Thorn and Rohloff over how the wheels were built.

Also mentioned that the normal riding pair are in the 200KG+ range so quite a load. Heard of axle failures from many derailleur hubs due to bending, or flange failures, at lesser weights than that too. For tandem or heavy utility bike use you need strong parts, not just the internal gear mechanism.

In addition to questions of torque loads through a gear hub actual axle loads need to be considered too. Many designs use a hollow axle with the shifting mechanism operating through it. Internally the axle has slots to allow movement of the shifting dogs too in these designs. I have read of older hubs using this design of shifting bending or breaking axles if the weight carried is too great.