Bicycle Mechanics - Why no affordable mtb internal gear hub?

Seems to be an untapped market.

I understand Sram and Shimano don't recommend their internal gear hubs for off-road use, but the question is, what about them is not off-road worthy?. What would they need to improve upon to make these hubs sturdy enough for heavy mtb use?

Could the reason behind them not developing/marketing a mtb internal gear hub be they don't want it to clash with their lucrative derailleur based groupsets?

Maybe someone should build one up and try it. I don't do so much mtb, but I might consider using one of my spare nexus-7 internals next time I build one up --just for grins.

I use them for kids bikes (even adult sized teenage kids) because I got tired of pulling rear derailers out of the rear spokes. My experience has been good. They stand up to kid abuse just fine.

what about them is not off-road worthy?.



the Shimano and Sram cannot be used with a disc brake- that is the main problem for me - I have thought about buying an internal hub for a winter bike but the Rohloff is too expensive and I won´t give up my disc brakes

there is definitely an untapped market though you are right

I'd go for it, for sure. Do they really not recommend the existing hubs for off-road? What is the official reason?

Seems to be an untapped market.

I understand Sram and Shimano don't recommend their internal gear hubs for off-road use, but the question is, what about them is not off-road worthy?. What would they need to improve upon to make these hubs sturdy enough for heavy mtb use?

Could the reason behind them not developing/marketing a mtb internal gear hub be they don't want it to clash with their lucrative derailleur based groupsets?

Sram and Shimano gearhubs as currently offered are unsuitable for MTB use. Don't get me wrong here, I am a big fan of both these units, but only for their intended purpose , that being commuting or bike path use. They are even OK for touring as long as the route is fairly level, and you are not hauling big packs. For one thing, the ratio coverage, at something in the 300% range is seriously inadequate for off road use. Also, gear changing requires a break in pedalling torque, and sometimes even a slight back pedal to make a shift. Do you want to have to cope with that on a technical trail?
Furthermore, the internals are just not up to that kind of punishment. They are not terribly delicate, but having been up close and personal with the interior of the Sram unit at least, I just don't think it is rugged enough for that kind of use.
Now, I am assuming because you used the word "affordable" in your title, you have ruled out the Rohloff Speedhub. This is the one truly off-road capable gear hub. I have one of these as well, and I can tell you that I prefer it to the XT/XTR drive train I replaced with it. Sure it's pricey, but if it lasts as advertized, it will pay for it's self.
There is one other newer option out there, but I know nothing about it. It is the Nupace continuously variable hub. You can check it out here.
http://www.freeridehubs.com/
You will find some negative stuff about Rohloff on that site, but I would advise against taking it too seriously.
Dan

the Shimano and Sram cannot be used with a disc brake- that is the main problem for me - I have thought about buying an internal hub for a winter bike but the Rohloff is too expensive and I won´t give up my disc brakes

I can understand the appeal of a disc brake on the front wheel, but why do you need one on the rear?. Even when the braking surface is covered in all kinds of muck, I can still lock the rear wheel with almost any half decent v-brake.


For one thing, the ratio coverage, at something in the 300% range is seriously inadequate for off road use

Couldn't you just gear it low enough that you spin more on descents, I'm sure that would leave you with a fair amount of range for the uphills. 300% range is still 300% more than singlespeed/fixed mtb'ers have and they seem to enjoy themselves well enough, there's no shame in dismounting every once in a while, is there?


Also, gear changing requires a break in pedalling torque, and sometimes even a slight back pedal to make a shift. Do you want to have to cope with that on a technical trail?

I was under the impression you could shift whilst pedalling with the Shimano units(not stomping, just slight pressure). At any rate, don't you have to ease off the torque when changing up/down with derailleur gears aswell.

Back pedalling to make a shift would be highly annoying, yes. Any idea why you sometimes need to do so to make a shift?(is this Shimano and/or Sram hub you're commenting on?)


Now, I am assuming because you used the word "affordable" in your title, you have ruled out the Rohloff Speedhub. This is the one truly off-road capable gear hub. I have one of these as well, and I can tell you that I prefer it to the XT/XTR drive train I replaced with it. Sure it's pricey, but if it lasts as advertized, it will pay for it's self.

I have no problem with the Rohloff hub, I'm sure it's a fantastic bit of kit,but...

it is very expensive!

and whilst it'll certainly outlast many a XT drivetrain, it's yet to prove itself fully, durability wise, against the likes of Sturmey-Archer hubs. SA hubs generally cost about 1/6 the price of a Rohloff, the point being does it really need to take all that extra expenditure on the consumers part to get an "off-road" worthy hub, are the problems that are preventing the SA/Sram/Shimano hubs from being off-roadable hubs really that expensive to fix?

Now to build an ISO brake adapter for a Nexus hub! who is up for the challenge

I can understand the appeal of a disc brake on the front wheel, but why do you need one on the rear?. Even when the braking surface is covered in all kinds of muck, I can still lock the rear wheel with almost any half decent v-brake.

In freezing temps rim brakes can become worthless. I have had my brake surface covered in ice after riding though water. I was unable to lock up the brakes even when my tire was on a patch of ice.

The reason you can't use those hubs off road is the huge amount of torque low mtb gearing will put on them........it will explode (or possibly implode). If you have skinny girl legs and/or walk up any steep climb then it will probably last. But if you want a usable low gear of 17" like your 22x34 gives you, you will break the hub. Unless it is made by Rohloff.

This is in addition to everything that Mr Burkhart said, and he appeared to know what he was talking about. If you refuse to beleive us by all means try it out and let us know how it goes!

Andrew

BTW just checked shimano's site and crunched some numbers......to get a 17" low gear on a nexus 7 with a 16t cog would require a 15t chainring! Ha! Just spin a little faster on the downhills..........

In freezing temps rim brakes can become worthless. I have had my brake surface covered in ice after riding though water. I was unable to lock up the brakes even when my tire was on a patch of ice.

Yeah?

It never really gets quite that cold round here, so I can't say it's something I've personally experienced. Definitely something to keep in mind though ;)


This is in addition to everything that Mr Burkhart said, and he appeared to know what he was talking about. If you refuse to beleive us by all means try it out and let us know how it goes!

Why so defensive?

Am I out of order by asking these questions?

Like I said previously, I've no doubt the SA/Sram/Shimano hubs have problems, but whether it really needs to take an extra £500/£600 to attain an off-road worthy hub is questionable and something that should be questioned...

Rohloff currently have the run of the market, so it's pretty logical that they can charge whatever they like.

G-Boxx. http://www.nicolai.net/
Internal 24speed gearboxx.
Affordable.....no.

Only now I am building a mtb with an internal geared hub. For several years I abuse internal gear hubs and I am still to find the sort of bicycle riding style they will not fit. German manufacturers are building DH and freeride bicycles with internal gear hubs and I am wondering why ?! An internal gear hub can be shifted when ever the rider wants, even in effort and I dought the strongest of the riders during the hardest of effort will damage such hubs. Try a Nexus 8 with a 22 teeth cog and an ordinary crank with 44, 32, 22 chain rings and you will see your bicycle climbing walls! If you do not believe me, read Sheldon Brown's articles on internal geared hubs or send him an E.mail on the issue and then make your conclusions.

I have no idea of the quality, but a company called Dynamic Bicycles is marketing a couple of Mountain Bikes with Nexus 8 speed hubs and shaft drive. Interesting concept.

Try a Nexus 8 with a 22 teeth cog and an ordinary crank with 44, 32, 22 chain rings and you will see your bicycle climbing walls!

Cool idea, but don't you have trouble keeping a straight enough chainline with 3 chainrings?

One method I think would work really well is to have two sprockets on the hub, one about twice the size of the other[say a 11/22 or 12/24] and a rear derailleur to shift between them. This should double the gear range with very little overlap, the rear derailleur will keep a good chainline and I don't think it'll add too much to the maintenance needed.

What'd you lot think?

The Rohloff hub has a lower gearing limit set to 2.4:1. That means your lowest possible gearing is a 15T sprocket with a 36T chain ring. Go below that, and you void the warranty, and you risk wearing it out much faster, I assume.
That combo gives you a range from a low of 17 gear inches to a high of 90 gear inches.

The setup i wrote about below was aimed at the SA/Shimano/Sram hubs, which sprockets from 14t to 24t are available for. Such a setup for the Rohloff hub would just be unnecessary complication and you can only get sprockets from 15t to 19t anyway(correct?).

I meant above, even ;)

My post wasn't really in response to your last one, just a reply to the thread in general. :)

No probs, do you have a Rohloff equipped bike?.

Nope. Nothing for me, that. I have regular derailer gearing.
Would be fun for a pure inner-city commuter bike, but not for anything else.
And my entire bike doesn't cost as much as the Rohloff by itself... :D

You'd stick a Rohloff on a commuter, you must 'ave a screw loose, mate :)

the Shimano and Sram cannot be used with a disc brake
I give up. How does the geared hub know what mechanical mechanism is being used to slow the wheel?

I give up. How does the geared hub know what mechanical mechanism is being used to slow the wheel?

The hubs are made without any place to attach a brake disc.

If you do try and build a MTB with an internal gear hub, go with the Shimano. While the SRAM hubs work great, the way the shift cable attaches to the hub is through the end of the hub. A small chain screws into the end and is fed through a plastic pulley kind of deal that can break quite easily if hit against something, which can happen alot since it sticks straight out of the end of the nut holding the hub in place. The Shimano nexus does not have this problem. BTW, just wondering if any of the people trashing this idea had ever ridden for a long period of time on an internal gear hub, or if they actually know anyone who has. Even LBS's tend to have misinformation on them...my 2 cents

For those of you missing the disc brake capability, why not go for an internal gear hub with drum brake. Not quite a disc, and somewhat heavier. You can still have a disc on the front, where it really matters.

BTW, just wondering if any of the people trashing this idea had ever ridden for a long period of time on an internal gear hub, or if they actually know anyone who has. Even LBS's tend to have misinformation on them...my 2 cents

Where I live, most people ride internally geared bikes. As did I until my teens. However, I've never used anything with more than a 5-speed hub.
Then, I'm not trashing the idea either. It's just not for me. I'm happy with my regular gearing - it's superior to even the Rohloff hub in terms of gearing range (674% vs the Rohloff's 526%). And everything is easily accessible for service and repairs.

What do you mean, no disk brake set up for internally geared hubs?:

http://www.sturmey-archer.com/hubs_8spd_XRK8.php

What's with direct drive as gear 1 though?

Bizarro

Cool idea, but don't you have trouble keeping a straight enough chainline with 3 chainrings?

One method I think would work really well is to have two sprockets on the hub, one about twice the size of the other[say a 11/22 or 12/24] and a rear derailleur to shift between them. This should double the gear range with very little overlap, the rear derailleur will keep a good chainline and I don't think it'll add too much to the maintenance needed.

What'd you lot think?

With ordinary derailler system, sometimes you have few centimiters out of chainline. If you settle your chain line for the middle chainring, all you need to be concerned about are few milimiters either to the left or to the right. Of course you need a chain tensioner for this sort of drive train.
About assembling a double sproket on the internal gear hub, I think it is not possible because the sproket sits on the hub through 3 grooves and locks with a round spring. that's why you can only assemble a sprocket at a time. Anyhow, if you are a skilled person you can build a double sproket for your internal geared hubs.

Where I live, most people ride internally geared bikes. As did I until my teens. However, I've never used anything with more than a 5-speed hub.
Then, I'm not trashing the idea either. It's just not for me. I'm happy with my regular gearing - it's superior to even the Rohloff hub in terms of gearing range (674% vs the Rohloff's 526%). And everything is easily accessible for service and repairs.

Use a triple chain ring and you have even a greater gearing range.

What I suggest in this case, if riders are afraid of short gearing range, is to play a bit with Sheldon Brown's gain ration calculator and then make your conclusions.

http://www.sheldonbrown.com/gears/internal.html

What do you mean, no disk brake set up for internally geared hubs?:

http://www.sturmey-archer.com/hubs_8spd_XRK8.php


that looks nice but Sturmey Archer stuff often seens to be more theoretical than reality- try and find a shop that sells them :(

If you do try and build a MTB with an internal gear hub, go with the Shimano. While the SRAM hubs work great, the way the shift cable attaches to the hub is through the end of the hub. A small chain screws into the end and is fed through a plastic pulley kind of deal that can break quite easily if hit against something, which can happen alot since it sticks straight out of the end of the nut holding the hub in place. The Shimano nexus does not have this problem. BTW, just wondering if any of the people trashing this idea had ever ridden for a long period of time on an internal gear hub, or if they actually know anyone who has. Even LBS's tend to have misinformation on them...my 2 cents

The shift mechanism on the 7 speed Sram is not exactly as you describe. True, it is mounted on the end of the axle, putting it somewhat in harm's way, but it is totally enclosed and actually quite rugged. Mine has taken a couple of hits that I am sure would have done some damage to a derailleur or it's hanger.
My main concerns with this particular hub are 1) there are only 2 pawls each on the ring gear and the planetary carrier. Given the size of the hub shell, I believe there should be at least 3.
And2), the drive unit engagement within the hub in gears 1 -3. In this hub's design, 4th is a direct lockup with 1-3 being underdrive and 5-7 overdrive. In gears 1-3, the drive unit is in the outward position, transmitting torque to the ring gear which in turn drives the planetary carrier. The clutch teeth engaging these 2 units are quite tiny, and prone to wear. By contrast, the engagement between the drive unit and the planetary carrier, which engages in the high range gears is extremely robust.
I currently have my hub in about a bzillion pieces on my workbench because of skipping in the high gears. After careful study, I concluded that the main problem was worn pawls. After finding no sources for replacement parts, I contacted Sram directly. I talked to a gentleman named Ed who informed me Sram does not import replacement parts to North America. He said they offer an overhaul kit which is essentially a complete replacement hub mechanism which just slides into your old shell. The price for this is very close to that of a complete new hub.
:(

...have two sprockets on the hub, one about twice the size of the other[say a 11/22 or 12/24] and a rear derailleur to shift between them...What'd you lot think?

Sounds like the worst of both worlds - the weight of an internal hub with all the external damage potential of a derailleur. The whole idea of an IG hub is to contain all the shifting! If you externalize part of the shifting mechanism, you'd be lighter and no less reliable using a common cassette/derailleur.

However, with an internal hub, you still have its gearing options left if the derailer goes to pieces... :)

I still don't want one, though. :p

Sheldon Brown has built a bike with an internal 3-speed hub that takes 7-speed cassettes. With a triple in front, that makes 3x7x3 combination for a total of 63!
A whole bunch of the combos are probably duplicates (or triplicates!), so it doesn't have 63 unique gears.
Here it is: http://sheldonbrown.org/otb.html

I currently have my hub in about a bzillion pieces on my workbench because of skipping in the high gears. After careful study, I concluded that the main problem was worn pawls. After finding no sources for replacement parts, I contacted Sram directly. I talked to a gentleman named Ed who informed me Sram does not import replacement parts to North America. He said they offer an overhaul kit which is essentially a complete replacement hub mechanism which just slides into your old shell. The price for this is very close to that of a complete new hub.
:(
Wow, you're braver than I am. I don't have the know-how to take aprt my hub and confidently put it back together again. I'm just glad to hear that there is someone giving advice from direct experience and not from 'what they have heard' about internal hubs. I myself use a dual drive sram hub. I love it and have had no problems with it. Even with what you've added about the shift mechanism, I still think it is a bit more fragile than a regular derailler and would hesitate using it for serious off roading. The shimano's shift mechanism actually sits within the dropouts, so is much more protected than even a conventional derailler set up.

Sounds like the worst of both worlds - the weight of an internal hub with all the external damage potential of a derailleur. The whole idea of an IG hub is to contain all the shifting! If you externalize part of the shifting mechanism, you'd be lighter and no less reliable using a common cassette/derailleur.

I only posed the idea as a way of getting nearly double the gear range with very little overlap, if needed. I think it's potentially more reliable than a 3 x 7/8/9 setup, as you're only shifting between two sprockets, so adjustment doesn't need to be particularly accurate, you could use a friction shifter to good effect.

True, the derailleur will still be exposed, but if worst comes to worst it can always come off. Just think, twice the gear range!!!(gets me salivating)

I can't decide whether this would be a better idea than 2 chainrings instead. 2 chainrings would still need a chain tensioner of some sort...would it even be possible to shift between say a 22/44 or 24/48 combo, how close can you get two chainrings to each other in order to maintain the best chainline possible?

However, with an internal hub, you still have its gearing options left if the derailer goes to pieces... :)

I still don't want one, though. :p

Different strokes for different folks...

Although you seem to be contributing rather a lot for someone whose interests lie elsewhere, schizophrenia perhaps? :p


Sheldon Brown has built a bike with an internal 3-speed hub that takes 7-speed cassettes. With a triple in front, that makes 3x7x3 combination for a total of 63!

Trust the 'don with the shell' to come up with such a contraption, I'm glad someone's out there on the edge, living wildly for the rest of us.

The clutch teeth engaging these 2 units are quite tiny, and prone to wear. By contrast, the engagement between the drive unit and the planetary carrier, which engages in the high range gears is extremely robust.

Do you think this could be a common problem with downgearing in any hub gear?

bump