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-   -   IGH vs Derailleur on folding bike (http://www.bikeforums.net/folding-bikes/940021-igh-vs-derailleur-folding-bike.html)

adlai 03-25-14 05:19 PM

IGH vs Derailleur on folding bike
 
So I have this debate with myself...

IGH will be less maintinence but will also be heavier.

Derailleur is more maintinance but is lighter.

The thing is, folding bikes are carried more often than regular bikes, and so being light for a folder is much more important than being light for a regular bike.

So are IGH's on folders the best idea? Benefits of IGH seem to be most for heavy commuter bikes

Sixty Fiver 03-25-14 05:34 PM

An IGH also solves the gearing issues on small wheels.

ratdog 03-25-14 05:34 PM

Derailleur is also more prone to get knocked out of alignment from folding, carrying and putting the bike in the trunk of a car than an IGH would be.

fietsbob 03-25-14 05:37 PM

a low gear can be achieved within an IGH without the need for a long cage derailleur
hanging down near the dirt

and big cassette sprocket to have a low drive ratio..
can be without any chain tesioner like a single speed ..

my Brompton.. plus the Schlumpf Mountain drive crank... the hub gears are used a second time in a low range
for 6 distinct ratios.


or the Rohloff Hubs, which do something similar , a 7 speed gear-set used twice, for 14..
but the shift sequence is all sorted out inside the hub.

Oh and the Gates belt drive systems are only for IGH or single speeds..

triple crank + hub cassette, or the Hybrid, like Dual Drive: 3 speed IGH + a cassette driver on the right end.
are some of the other options ..

BUT with a derailleur you have a choice of the cassette ratio spread ..wide or 'corncob' straight.
(except Shimano Caprio only the special 9t to 26t works)

Paul Braithwait 03-25-14 05:40 PM

It's a good question and one that I too have pondered over. My folder has a derailleur. I understand derailleurs because I've had them on various bikes over many years. I don't have a problem adjusting or working on them and very rarely have any trouble with them.

The negatives of a derailleur on a small wheeled folder are that the mechanism sits very close to the ground and could be damaged by debris on the road and it could also be bent out of alignment when the folded bike is laid down or packed away somewhere. On the other hand a derailleur is easy to work on (you can get at all the bits!) and is lighter than a IGH. I'm not sure about the modern IGHs but they used to make rear wheel removal (to fix a flat tyre) a bit difficult - not just a case of opening the QR and dropping the wheel out.

I like to work on my bikes and the inside of a closed gear system is a complete mystery to me. If anything went wrong with the IGH, I wouldn't know where to start to fix it or what tools I would need.

There is no doubt that for some riders a IGH is ideal but for me the derailleur is still king.

wahoonc 03-25-14 06:18 PM

The weight difference may not be as great as you think it is...

I prefer IGH on just about everything. I have a couple of derailleur bikes but they are the exception. ALL of my folders are IGH and will continue to be, as are my city bikes. The only derailleur bikes are own are a couple of MTB's and my road tour bikes.

Aaron :)

adlai 03-25-14 08:23 PM

Well, I am contemplating building a NuVinci into a folder...but the darn thing is sooo very heavy that it is giving me second thoughts. It is probably the heaviest IGH in existence right now.

HGR3inOK 03-25-14 08:47 PM

Quote:

Originally Posted by adlai (Post 16611612)
... I am contemplating building a NuVinci into a folder...

You might consider buying a brand new Dahon Mu N360. See:
Dahon MU N 360
That way you would have a bike you could resell if you decide you don't like it. :)

-HANK RYAN-
Norman, Oklahoma USA

ThorUSA 03-25-14 09:02 PM

Igh versus derailleur is a question of taste
many pro and cons are above

Nuvinci is a very cool hub ... its soo amazing when you ride it..... and sooo heavy when you need to carry the bike .... lol
but considering the close out pricing of the whole bike ..its a steal for what it is ...

I really like both systems ...for different bikes :-)
thor

fietsbob 03-25-14 09:19 PM

RE CVR .. read the data yesterday one in a box, owners manual ..

gear range is .. 1.8x over drive , 0.5x reduction gear .

cog to chainring minimum .. 1: 1.8 so like a 16:30 , any bigger chainring is fine ..

DrBeet 03-26-14 05:33 AM

Efficiency is an Issue with IGH
 
One issue that has not been raised is efficiency. I designed the drivetrain on the Xootr Swift Folder. We considered a variety of IGH options and derailleur options. We made some measurements of efficiency. (This turns out to be quite hard, but we ended up running a series of human experiments in a hill climb -- about 10 trials with each set-up and fitting an implied efficiency to the performance data.) Some of the "speeds" in an IGH are very bad, as bad as 85% efficiency. By comparison a derailleur with a clean chain should be in the high 90s, and even with the grungiest chain is still probably better than 95%. A 10 percent difference in efficiency is a really big deal. You won't notice it on a flat bike path commuting 2 miles to work. On a brisk ride with your friends, you'll really suffer.

One important caveat. Most iGH have one "Speed" that is a direct drive -- just locks the sprocket to the hub. That one is very efficient, even slightly better because there are no derailleur idler pulleys. However, I found it was often an inconvenient speed. (On some three speeds it's the middle one, though, which is great.) Conversely, some speeds are really, really bad as they involve all the possible planetary gear pairings to achieve the target ratio.

Note that the poor efficiency is intrinsic to the planetary gear design -- each gear mating is 95% efficient or so, but they are stacked up on each other multiplying that loss twice or three times. The quality of the hub matters only a little bit -- a Rohloff might be marginally better than some anonymous inexpensive hub, but that difference might be a couple of percent, not 10 percent.

An option worth considering if you ride mostly modest terrain is a single speed. We created that option for the Swift as it simplifies everything and makes the bike a lot lighter.

Quote:

Originally Posted by adlai (Post 16611017)
So I have this debate with myself...

IGH will be less maintinence but will also be heavier.

Derailleur is more maintinance but is lighter.

The thing is, folding bikes are carried more often than regular bikes, and so being light for a folder is much more important than being light for a regular bike.

So are IGH's on folders the best idea? Benefits of IGH seem to be most for heavy commuter bikes


ratdog 03-26-14 06:30 AM

Quote:

Originally Posted by adlai (Post 16611612)
Well, I am contemplating building a NuVinci into a folder...but the darn thing is sooo very heavy that it is giving me second thoughts. It is probably the heaviest IGH in existence right now.


I would advise that you check your gear ratios before you decide. Years ago I was playing around with the idea of installing a Nuvinci onto a 16" folder. If I remember correctly the gearing persuaded me to drop the idea.

cplager 03-26-14 06:32 AM

Some IGHs are not fully efficient until they are broken in. This does confused the issue some what.

It is true that most (pretty much all) IGHs are not as efficient as derailleur systems

tcs 03-26-14 06:34 AM

There's a lot of old significant other's tales and conventional wisdom/a.k.a. BS floating around on the subject of bicycle drivetrain efficiency. Here are some actual instrumented IGH and derailleur drivetrain efficiency tests by respected people in the cycling world:

(beginning on page three of) HP52/2001
(in German, try google translate) Fahrrad Zukunft no. 17

cplager 03-26-14 06:34 AM

Quote:

Originally Posted by ratdog (Post 16612438)
I would advise that you check your gear ratios before you decide. Years ago I was playing around with the idea of installing a Nuvinci onto a 16" folder. If I remember correctly the gearing persuaded me to drop the idea.

I think you have this pretty much backwards. By changing either the size of the chainring up front or the cog in the back, you can get most IGHs to work well with small wheels. That's one of the major points of them

bmac.to 03-26-14 07:17 AM

As for efficiency, most IGHs are less efficient than the derailleur equivalent in some gears. BTW, efficiencies go up and down in a derailleur system as well depending upon the gear - the swing is not as great.

However, please check out Rohloff's web site for a full study of their hub's efficiencies in all the gears - their IGH meets or exceeds the efficiency of a derailleur system in all gears (hence, the high cost).

wilfried 03-26-14 08:50 AM

I carry my three speed Brompton up and down four flights of stairs pretty much every day, often more than once, and I don't find it terribly onerous. I'm a slightly built 150 lbs., so I'm no kind of he-man either. I wouldn't mind if it were lighter of course, but I'm not sure a pound or two would make a huge difference.

ThorUSA 03-26-14 08:57 AM

Quote:

Originally Posted by bmac.to (Post 16612536)
As for efficiency, most IGHs are less efficient than the derailleur equivalent in some gears. BTW, efficiencies go up and down in a derailleur system as well depending upon the gear - the swing is not as great.

However, please check out Rohloff's web site for a full study of their hub's efficiencies in all the gears - their IGH meets or exceeds the efficiency of a derailleur system in all gears (hence, the high cost).

sure......... and I have this bridge for sale

thor

ThorUSA 03-26-14 09:12 AM

Quote:

Originally Posted by tcs (Post 16612446)
There's a lot of old significant other's tales and conventional wisdom/a.k.a. BS floating around on the subject of bicycle drivetrain efficiency. Here are some actual instrumented IGH and derailleur drivetrain efficiency tests by respected people in the cycling world:

(beginning on page three of) HP52/2001
(in German, try google translate) Fahrrad Zukunft no. 17

thanks tcs
interesting read..... interesting also that the rohloff was tested without a chain tensioner ... and being the german " wunderkind" tested by a german ... i tend to wonder .. just a little bit ...
also interesting and somewhat almost expected that the Nuvinci is better for weaker riders, than stronger riders ...

Rob_E 03-26-14 10:36 AM

I hear about efficiency, and those numbers and studies are interesting, but I can't say that I've ever felt efficiency. I went from a traditional drive train to a Nuvinci. The negatives on the Nuvinci have been the weight, the slightly too high low gear, and the difficulty removing the wheel due to the shifting attachment (which has been vastly improved in the N360). I've never thought, "and it's just too inefficient." But that's probably my riding style, as well. I don't try and keep up with anyone or break any records. I just go where I'm going, taking as long as I need, and having fun getting there. But I certainly didn't notice a change in my commuting times when I switched.

As for gearing: There is a minimum recommended gearing set up for the Nuvinci. It's not recommended that the chainring be less than 1.8 times larger than the cog. This has been an issue on my touring bike where a little lower gear might make some of the steeper hills more manageable, but my understanding of gear calculations is that on a smaller wheel, you would have a lower effective gear for the same cog/chainring combination. I'm preparing to try a 20" Nuvinci wheel, so I guess I'll find out.

As for gears vs. hub. I always go hub. It is a personal preference, but I can see some solid reasons to go that route in a folder. No derailler parts to get knocked around in transport being a big one. I feel like it simplifies the fold, not as much as single speed, but enough to be worthwhile. The Nuvinci in particular is heavier than, well, any other drive train, but it's not something I notice unless I'm carrying my bike. That would be more noticeable on a folder that you carry often, but I like folding bikes for their ease in transporting (in luggage, in the trunk of a car) rather than their ease of carrying, and I think an IGH is less likely to to suffer from getting knocked about in transport. Also, not related to folding bikes specifically, I just love the shifting of a gear hub as compared to a derailler system. And the Nuvinci is a step above any gear hub I've tried, too.

If I were carrying the bike all over town, I might change my tune, but as it stands now, I carry my Nuvinci bike up and down the stairs to my apartment daily. It is heavier than my other bike, for sure, but once I set it on ground and start pedaling, I don't notice. Also if you want it to seem light, start out with the previous Nuvinci model and then upgrade to the N360. I got so used to that back heavy feeling when I picked it up, that the first few times after the upgrade, I tipped the whole bike forward when picking it up because I was used to counterbalancing the weight of the rear wheel.

It's impossible to say whether the trade-offs are worth it to someone else. It depends on your use and your priorities. Figure out what matters. And don't throw out your old wheel. You can always change back.

adlai 03-26-14 01:26 PM

There's still time I suppose to put in a lighter IGH at least...now the folder that I have in mind I envision being akin to a touring bike, used for exploring distant city streets.

nuVinci has a 360 range. Any lighter hubs with comparable ranges?

fietsbob 03-26-14 02:01 PM

Rohloff is 526%

my AW3 + MD crank would be 177% x 2 roughly 354 + the gap between the 2 ranges

think theres 33% between them in the hub, and 40% between 3rd & 4th.

but as % is always relative to the next ratio above it, always a smaller difference as you go down the gears.

Rob_E 03-26-14 03:35 PM

Quote:

Originally Posted by adlai (Post 16613895)
There's still time I suppose to put in a lighter IGH at least...now the folder that I have in mind I envision being akin to a touring bike, used for exploring distant city streets.

nuVinci has a 360 range. Any lighter hubs with comparable ranges?

Every hub with a comparable range is lighter. Unfortunately there are only two hubs that are even close. The Rohloff has a wider range and is much more expensive. The Alfine 11 has a narrower range and is also more expensive, if I remember correctly.

Personally, if I could get an Alfine 11 or a Nuvinci for the same price, I'd go Nuvinci because the higher range and the continuous shifting far outweigh any weight concerns.

If the Rohloff were more in my price range, it'd be a temptation, but as it is, I'd really worry that I wouldn't enjoy the boost in range and drop in weight as much as I enjoy Nuvinci's shifting.

A lot is made of the weight, and I mention it because it is noticeable when you pick up the bike, but I don't consider the weight to be a serious detriment when compared to the hub's good quality. I have had the previous, heavier version on my commuter/touring bike for 5 years. In addition to getting me home from work most days, that bike has also taken me on a number of short, fully-self-supported tours. I just upgraded to the N360, and I'm really enjoying that one, too. And there's a plan to get a folding bike rolling with a Nuvinci hub soon. As soon as I find my missing right crank arm.

fietsbob 03-26-14 03:53 PM

It is a clever bit of engineering .. the circumference of 2 different latitudes on a rotating Ball

is the ratio difference .

and a fluid that is a lubricant until compressed then it provides the traction,
between the parts.

dynaryder 03-26-14 04:53 PM

Lots of good points have already been made so I'll only comment on three. As far as weight;the 20" rear wheel w/Nexus 8 on my old FlyBy weighed 5 lbs 6oz(no tire). The 20" wheel w/3spd DualDrive hub and 9spd cassette on my SPTT weighs 3lbs 11oz.

As far as wheel removal;almost all hubs are nutted and require a 15mm wrench. Removing the shifter cable can be easy to a PITA. Rohloff uses two pop-off connectors,current Shimano 3spds use a side mounted box that comes off with a 3mm hex,other Shimano hubs have a nutted cable that has to be threaded around the hub into a slot.

As for gearing;remember,when you change the gearing on an IGH,you change the entire range. You can replace a 12-26 cassette with an 11-28 and both raise and lower the gearing at the same time.


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