kmcrawford111

Hey everyone. I just bought a Salsa Timberjack 20 non-suspension for my son. It's a great bike, and he loves it, but I've noticed that the derailleur sits very low, just a few inches off the ground. It's a Shimano Altus with large pulley wheels.

This got me thinking: why don't more (any?) MTBs come with internally geared hubs? They solve the issue of the derailleur/hanger getting whacked. I'm fairly new to proper mountain biking, but this seems to be a constant concern off-road. IGHs use a wider chain, which might be more durable. They do weigh more than a derailleur, but with the advent of these huge wide-ratio cassettes today (that also place the derailleur even lower) I'd think the weight difference isn't as much now, if at all. The gear teeth don't need to be designed with ramps for shifting either, which helps with chain retention.

So what's the issue? Are they just not robust enough? Strong enough? Not enough tension?

dabac

IGHs are not rated for the drops, jumps and general abuse that a MTB is expected to put up with.

It doesn’t have to be instant death for an IGH to be used for MTB, but it does take an understanding rider, and an adapted use.

Kapusta

Rohloff makes a 14 speed IGH that is reliable and totally MTB capable and has been available for a very long time.

The are a few reasons they have never really caught on more for MTB:

1- They are VERY expensive. (north of $1,300)

2- They are heavy.

3- They introduces some internal drag.

It may well be that #2 and #3 are not really big issues in practice, but certainly they are perceived as such in performance-oriented aspects of the sport. So even people (like me), who would love one on their commuter don’t want one on their mtb or road bike.

For me personally, I just don’t see a benefit over an RD system that is worth the cost, weight, and drag.

qclabrat

I've tried this with a Nuvinci 360 IGH. In short, not enough gear range for mtbing. I have not measured it but its appears to be equivalent to 26-30 teeth rear. Besides like others have said its an expensive test. I've kept it on my commuter with a Gates system instead.
For your son's bike, if the pulley is lowish, try a mid-cage, its likely that it's using a standard mtb derailleur which are usually long cage. Though, you may need to change to an 1X system if it doesn't shift well. Most DH bikes have short cages for this reason as well. It is part of the reason I've stated away from SRAM Eagle and the new Shimano. The derailleur hangs so long at the lowest gear. I bend cages fairly often, so try to stay away from the longs.

Also forgot to confirm Kapusta's comment, it's really heavy, like 10+ pounds heavy. Your kid will hate you for doing this....

ThermionicScott 

I've often wondered why IGHs haven't made more inroads in cyclocross. A modern 3-speed hub wouldn't add a lot of weight, but would get rid of the derailleurs while allowing multiple gears. It'd be a step up from single-speed 'cross.

base2 

One common solution with the IGH on a standard bike is a standard short cage derailleur for chain slack and a double crankset. The Nuvinci will require a wider than you are used to, 6 speed chain though...So you won't be using a modern 11 speed crankset.

Many IGH's also have a 2:1 ratio restriction so you don't over torque the innards or the anti-rotation washers in your dropouts ruining the frame. In short, if you want a lower bottom gear than 30-32-ish gear inches with an IGH you'll be in smaller wheel territory...& nobody runs 20 inch wheels on mountain bikes.

As far as conventional IGH's: they don't shift all that well under load either. The shifting dogs on the axle tends to peel off as a matter of design. As mentioned, a knowledgable & capable operator can go a long ways with that, but you still have the problem of aside from the über expensive & differently designed Rolhoff, usually IGH's don't have the range to be useful in mountain bike conditions.

Or, solving the range issue (crankset/derailleur above,) the durability for an errant misshift under high load like would be easily done on trails in the woods poses a high risk of walking.

That being said, I own all the IGH's mentioned. For street/commuter use, they are fantastic. I wouldn't even hesitate to take any of them on gravel or fire service roads. So, like anything, your intended use determines what is suitable.

c_m_shooter

I have had a Nuvinci on my Pugsley for a few years and like it. It is heavy, but so is the rest of the bike.

Darth Lefty 

The lower jockey wheel is not really in any danger, it's protected by the tire when extended/inboard/low gear and it's high when retracted/outboard/high gear.

Shadow style derailleurs are available for SIS and they really tuck the pantrograph and knuckles inboard, so if you are worried about whacking you could check that out.

Alternatively, you can get a derailleur guard like old Schwinns used to have.
https://www.amazon.com/Stylrtop-Bicy.../dp/B07JZFDTPH

My single igh experience with a Shimano Nexus 3-speed did not make me want another

tallbikeman

During the Klunker era of MTB (1970's early 1980"s) I saw Sturmey Archer 3 speed AW hubs in use on all kinds of frames at the Klunker/MTB races. I raced in Northern California and saw all the pioneers of the sport riding the early MTB designs. The advantage of the 3 speed hub was it wasn't a derailleur and had 2 more speeds that the one speed crowd. One speeds and 3 speeds had no chain problems during racing whereas derailleurs specialized in throwing their chains off the sprockets during racing events. The bicycle manufacturers made sure that NORBA got rid of the one speeders on the podium with the derailleur equipped bicycles by reclassifying them and not counting them in their actual placings, but by class. One speeders and 3 speeders were always in the top 10 finishers at MTB races in those days but they were not sexy nor were they going to make the manufacturers a lot of money. In other words they fell out of fashion. I believe that one speed/3 speed MTB's are as fast as multi speed MTB's on courses that feature uphill and downhill and some bicycle carrying along the way. Some of the problems of IGH MTB's have been mentioned. The chief problem is that you cannot gear an IGH too low or you will break the hub from over torque. However in my experience racing in those early races the uphills often favored who could push, not ride, their bike uphill the fastest. We did a lot of carrying of bicycles in some of those early races. Races are different today and meant to showcase suspensions usually in some sort of downhill format. If you are not racing stick to the derailleur setup you have.

bikebikebike

There's an old motorcycling line that says "We only have transmissions because there are no perfect engines."
I love IGH's, and have or have tried just about one of everything.
It is just impossible to beat conventional derailleurs on weight, accessibility and just flat ass simplicity.
They are just the best general solution, faced with so many operator and situational variables.
That being said, there are some pretty kick ass specific answers to many questions.

Carrying your bike, every now and then, is one of the parts of asking interesting questions.

prj71

Maybe the pinion will be common one of these days. Appears better than the IGH.

https://pinion.eu/en/mtb/

https://www.singletracks.com/mtb-gea...t-ride-review/