juan162

I've personally had so many questions about the whole weight issue between internal and external gears that I thought it would be helpful to start a thread where people could actually put down some standard weight differences in hubs. All I could find was for some of the Shimano hubs. If anyone knows the standard weights on the SRAM hubs, please post.

Hub

Nexus 8 speed: 1750 grams: 3.85 lb (Red Band)
Nexus 7 speed: 1465 grams: 3.23 lb
Nexus 3 speed: 1120 grams: 2.47 lb

Ultegra: 347grams: .77 lb
Dura Ace: 264grams: .58 lb

Keep in mind that internally geared hubs don't need deraillers or multi cog cassettes. A cassette and derailleur will generally add anyware from 1-1.5 lbs combined depending on the quality of said components. For example, a 10 speed ultegra setup in the rear would run you a little less than 1.75 lbs total (That includes the hub, cassette, and derailleur). That's a savings of more than 2 lbs over a Nexus Red Band 8 speed! That may not be a big deal to some, but that definitely makes me stop and think.

I am personally interested in the weight of the sram dual drive hubs.

Juan

randya

IMO your being a bit of a weight weenie. Personally, I like internal hubs but recognize the tradeoffs, both ways. Also, more gears = more weight with either system. The Nexus 7 seems like the best deal for the weight; I've used this hub and like it; 5-speed internal might be another consideration, IMO 3 to 5 is enough speeds to work in most situations. Although I don't have the specs, I've got a few Sram internal hubs in 5 and 7 and the weights seem comparable to the Sturmeys. The dual-drive also seems like a good compromise. Have you considered the new Sturmey hubs? I saw a recent post somewhere on the forums w/ link to whole range of newer Sturmey stuff in 3 to 7 or 8 speed.

Wavshrdr

Don't forget you also need a longer chain with a derailleur too. Those links aren't light weight. You also have shorter spokes on an internal hub and it tends to be a very strong hub as well. Also your weight is incorrect for the 8R25 aka redlabel (high efficiency according to Shimano). It is actually 1550grams.

One other big benefit on small wheeled bikes that nobody seems to use, is the option of going with a roller brake. This makes a lot of sense given the accelerated rim wear I've seen on some of my bikes and especially the Bromptons. These small rims are definitely eroded more quickly by the brakes due to the fact they turn more rpms and have less swept area.

I am not saying there isn't a weight disadvantage with the internal hubs as there is. I do love their benefits on a folder. Nothing hanging down to get all over your pant leg. I can shift at a stop. No low chain that sucks in dirt and debris. Very quiet gear changes. The Shimano shifts great under load. I could go on and on. A pound or so weight penalty isn't going to kill me. It is a folder, not a race bike. I can lose the pound in a day if I want.

jur

It would be fair if you listed the exact tradeoff weights, as you yourself have mentioned about cassettes, derailers and the extra chain length. Just to day I looked at an XT hub setup, and it came to 910g without the extra chain, but I don't know what that amounts to.

The SA 8-speed hub, no brakes, no disc, amounts to 1480g. Not sure if that includes the cog.

caotropheus

Hello W. I totally agree with your description of internal gear hubs, and I would like to give one more vote for the advantages of internal gear hubs for folding bicycle. The desadvantage of 0.5 kg or one more kg is not relevant in a bicycle if you are not competing. Now about losing 0.450 kg is easy for you but a guy like me weighting 54 kg is a bit difficult!

Dahon.Steve

Weight is only one of the problems. The major issue with the Nexus 7 or AW-3 is the inefficiency from the internals. This makes it feel like the hub is much heavier than the actual weight and the SRAM dual drive when shifted in 3rd gear is very inefficient.

I also happen to believe when the weight is all shifted to the rear hub, it feels like you're carrying an additional two water bottles!

caotropheus

From the scientific point of view, indeed internal gear drivetrains are less efficient than derrailleur drivetrains. But, I use internal gear drivetrains for several years and I didn't notice a difference on efficiency. From the bicycling science book a scientific comparison gave an average difference of 4 to 5 percentual points between derraileur drivetrains an internal gear drive trains.

EvilV

Maybe you weight sensitive guys are built lean 'n mean yourselves. For me, the fourteen pounds of extra fat I'm carrying over my younger days are a much greater problem. Too much red wine and beer in my early fifties. Still, I'm on the case now. Maybe when I've shed the fat, I'll worry about the three speed SA being a few ounces heavier than a derailleur. I might not feel the need to uprate my brakes either if I wasn't flinging quite so many pounds downhill!!

Seriously though, and racing aside, when you consider the all up weight of a rider and bike, does the odd pound make much difference? If you take my 172 pounds, add it to my Merc at about 27 pounds we come to 199 pounds of fat, muscle, bike and brain.... So how much am I going to notice a 1% weight reduction, and how would that compare with (to put it crudely) taking a dump or emptying my pockets of change before going out on the bike?



Tony

geo8rge

If you are carrying the bike it is important. You might look at the ultra light weight Brompton projects. An interesting question is: does the extra 1.5 lb, and $100, you get from going from 3 to 8 gears get you much extra?

Bacciagalupe

It does, if it's right on the wheel or if you have to carry it up and down stairs.

Long story short is that an internal hub will be a little heavier, a little less efficient, and generally more robust than a derailleur setup. I'm not sure why you'd need to know anything else....

folder fanatic

Never mind the ounces/grams differences between internal hubs and derailleurs. Concern yourselves with the insistance of carrying around huge packages on collapsable or folding bikes which turn into another package eventually.

invisiblehand

I think that the efficiency, weight, and robustness matter. An individual's need will determine the best tradeoff.

I was talking with Peter Reich one day. He said that there is about a one pound difference between the SRAM Dual Drive and Nexus 8 drivetrains with the Nexus-8 being heavier.

WAV ... how much does a link in a chain weigh? And how many links less does an internal hub use?

Note that there have been comments on the location of an internal hub's weight. That is, it puts a lot of weight further back on the bike relative to a gear driven drivetrain.

rhm

Speaking of which, can anyone tell me anything about the current SRAM Spectro P5 five-speed hub? I see from merchants' websites that it has five evenly spaced gears with a wide (303%?) range, but it's not on Sheldon Brown's online gear calculator. What I'm wondering is: which gear is the direct drive?

randya

All Sheldon's got is the 7 speed: https://www.sheldonbrown.com/seven_speed.html#sachs7

My links to SRAM tech info no longer work...

Here's some product info on the SRAM P5: https://www.universalcycles.com/shopp...s.php?id=10697

edit: here's links to SRAM's new tech info site:
https://www.sram24.com/newtechdoc/eng...tions_MY06.pdf
https://www.sram24.com/newtechdoc/eng..._P5_8_2005.pdf

Wavshrdr

First I've never been a fan of any Nexus other than the 8speed ones. They are far more efficient than the other Nexus models and the 8R25 (red label) is the most efficient. Last I read they better internal hubs are now closer to 95-98% efficient. A chain isn't light. Each link can add up pretty quickly when you have an extra 10-20 or so (depends a lot on your biggest chain ring on the back). Keep in mind that this is all rotating mass which requires more energy to move it. You also have additional drag through the little derailleur. Don't forget to add the effects of the chain not being in a straight line.

At first glance it looks like the derailleur should kill the internal hub but it isn't quite as lopsided as you might imagine. I think the vast majority of riders would be very well suited by an internal hub but they are so derailleur centric that they don't think about it. What might be best for a racer might not be best for your normal usage unless you are mostly concerned about speed.

Here is an interesting new Shimano hub, the Alfine, that looks interesting if you haven't already heard about it.

https://cycle.shimano-eu.com/publish/...or_sporty.html

For a good introduction to internal hub efficiency from the perspective of Rohloff see the link at the end. I've owned the Rohloff and still have several 8R25's and I can tell you that in most situations the Nexus feels more efficient and is definitely quiter.

https://www.rohloff.de/en/technical/e...ncy/index.html

juan162

[QUOTE=WavshrdrAlso your weight is incorrect for the 8R25 aka redlabel (high efficiency according to Shimano). It is actually 1550grams.
.[/QUOTE]

Wavshrdr - I pulled the weight off of the Shimano site. They do say it's "about" this weight...I don't exactly understand what that means, but that might explain the difference in your weight, as opposed to what I found at their site.

randya - I AM being a weight weenie, and happily. I haven't ruled out an internal hub nor do I think they are a bad idea, for all the reasons listed in this thread and others. However, rolling weight is a big deal and losing 2 or more lbs from the rotating mass is a huge difference. I currently am running a dual drive on my Twenty. While I'm not planning any changes in the immediate future, I have been thinking of converting my Twenty to a 105 drivetrain. While I know I can't get the weight down anywhere near 20lbs, it currently weighs 32-33 lbs. If I change the drivetrain over to 105 componants and build a lighter set of wheels (I'm also running a 42 spoke front wheel, which is way overbuilt for my style of riding), I can definitely get it south of 30lbs - maybe even 27-28lbs. While this isn't light, It's a whole heck of alot better than 32+lbs. I haven't made up my mind yet.

I have a crescent folder that I currently have set up as a single speed, but would like to change to a multi speed. I will probably go with an internal 7 or 8 speed. It's currently around 24lbs with an all steel front wheel. I figure if I build up a lighter weight front wheel and go with an internal 7 speed shimano hub, I should only pick up an extra 1.5-1.75lbs.

Juan

juan162

It's me again, Juan.

I thought I might add that one of the big reasons I've been thinking of changing my Twenty set up is because I use it regularly on my climbing route, where I have definitely felt a difference in efficiency and weight. I climbed the same hill on my old mountain bike, and it was definitely easier on the mountain bike. I'm trying to find the best compromise for my riding needs.

Juan

jur

Well this is another can of worms.

Why do you ride hills? I assume for general fitness purposes. So from that perspective it doesn't really matter, with the R20 you will be getting slightly more exercise for your money. If this is a commute and you would like to cut the time, well that's different. Perhaps you may need to consider a Swift because the R20 has a 5kg frame and nothing you can do will make it into a lightweight speedbike.

But who cares anyway? Go for it. It's fun, that's why.

invisiblehand

Supposedly, the efficiency loss from cross-line offset and poor lubrication are negligible ... at least in a lab.

https://www.ihpva.org/HParchive/PDF/hp50-2000.pdf

Regarding the Nexus-8 internal hub weight, I find 1550 grams too.

invisiblehand

Hah! That probably is the best solution ... get a lighter bike! Soooooo many choices relative to the R20.

Although if you go that route then you might consider Bike Friday, Airnimal, as well as the Swift.

Jur ... that is some commute. Doubt that I would do it everyday.

By the way, this is in regards to an old post, why are you limited in chainring sizes on your Raleigh 20?

jur

Re my commute: Thanks! It may seem far but I got thoroughly used to it. Then when I was away for 2 weeks without riding, I bonked on the way home a few times before I got the old form back.

Re chainring: I can implement the solutions that exist, but I like the look of the genuine R20 crankset, so I had it replated. So I am kinda "stuck". Plus I am now satisfied I can tour Tasmania with the existing setup, so at his stage I foresee that it will stay that way. Plus I now need any spare money to build my new Swift frame into a bike.

Wavshrdr

The weight you listed is for the 8R20, the NON redlabel version. The 8R25 is the redlabe high efficiency hub that weighs 200 grams less. To a weight weenie that is a huge difference. Go here to see the weight for the 8R25:

https://cycle.shimano-eu.com/catalog/...=1172727229941

invisiblehand - everything is perfect in a lab where everything is well maintained and pristine. Keep in mind that a folder has a shorter chain run, therefore the relative angles between the gears are more significant. They still measured a 0.5% degredation on a normal bike. Additionally any lateral stress on the chain will accelerate chain and sprocket wear.

That report also made hub gears look quite attractive as well. Based on their information, the larger sprockets often used on the internal hub gears would quite likely offset the mechanical losses of the internal hub to a great extent and in some circumstances if I extrapolate their date, the internal hubs could be MORE efficient if you choose the appropriate sprocket sizes front and rear.

I have bikes with both and internal hubs and derailleurs, for 99% of my riding I'll stick with the hub gears.

jur

Which begs the interesting question, what sort of riding is the 1%?

Wavshrdr

When I go riding with a club and they all want to ride their wannabe racebikes. So I keep one wannabe racebike just for these purposes and since they frown on recumbents on these rides. Then it goes back in the garage. I will likely sell it this year and just forget about the club rides. I get tired of people who agonize over every gram as if they could win the Tour by just shaving another 50 grams off their bike.

I have nothing to prove, I just want to have fun. A ride on a recumbent is more enjoyable for me as I can go faster on the flats and not have to deal with a paceline and all the hassle that entails.

DVC45

That's me too! I'm giving my road bike to my brother and just keep my folder as my main bike. I like riding on my own pace and not worry about keeping up with anyone.