Advertise on Bikeforums.net



User Tag List

Page 1 of 2 12 LastLast
Results 1 to 25 of 27
  1. #1
    eternalvoyage
    Join Date
    Feb 2007
    Posts
    2,433
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Rohloff hubs: lowered efficiency negligible or non-negligible?

    There are charts somewhere on the web that show the efficiency losses of the Rohloffs, compared with derailleurs, for each gear.

    For racing, it could be a very legitimate concern. But in other cases -- when you aren't very pressed for time, or trying to keep up with fast riders, or in some other situation where two or three or four percent losses might matter -- it may or may not be significant.

    One percent seems pretty minor. Two percent also seems minor. But when you get up around three or four percent, it starts to make one wonder.

    Then again, maybe it doesn't really matter.

    If anyone has any viewpoints or perspectives on this, please feel free to post them.

  2. #2
    Senior Member DannoXYZ's Avatar
    Join Date
    Jul 2005
    Location
    Saratoga, CA
    Posts
    11,507
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    It only matters if you're riding at LT and time-trialing on all your rides and giving it your all. Otherwise, if you can just push 2-4% harder when using the Rohloff hub.

  3. #3
    Senior Member
    Join Date
    Feb 2006
    Posts
    1,564
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    it depends


    mountain bike racing, negligible

    road racing, noticeable

  4. #4
    Sir Fallalot wroomwroomoops's Avatar
    Join Date
    Jul 2006
    Location
    Helsinki, Finland
    Posts
    5,171
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by DannoXYZ View Post
    It only matters if you're riding at LT and time-trialing on all your rides and giving it your all. Otherwise, if you can just push 2-4% harder when using the Rohloff hub.
    The Rohloff has less transmission efficiency than 2-4%. There was a scientific paper published on Human Power a while ago, and the Rohloff was tested, among other gear hubs and derailleurs. The best transfer efficiency the Rohloff achieved was about 5%, but usually a bit less.

    The gear hubs with best transfer efficiency were the 3-speed Shimano gear hubs, around 4-5%. Where the EFF did I save that .pdf....

  5. #5
    Sir Fallalot wroomwroomoops's Avatar
    Join Date
    Jul 2006
    Location
    Helsinki, Finland
    Posts
    5,171
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I couldn't find the original paper, but I did find a shorter one, that, too, on Human Power, as an answer to Rohloff. This is what the paper concludes:


    Quote Originally Posted by Human Power contributing scientist
    To summarize, we are reasonably
    confident that the rank order between
    transmission efficiencies that we found
    would not change appreciably as load is
    varied within a normal range. In other
    words, transmissions should rank about
    the same at either low or high loads. We
    feel that the loads we tested under are
    typical of the actual conditions under
    which hub gears are used and represent a
    reasonable average efficiency. In our article
    we therefore concluded that hub
    gears are about 2% less efficient that derailleur
    transmissions under typical field
    conditions. We see no reason to change
    that conclusion.

  6. #6
    Senior Member Bill Kapaun's Avatar
    Join Date
    Feb 2007
    Location
    Mid Willamette Valley, Orygun
    My Bikes
    86 RockHopper,2008 Specialized Globe. Both upgraded to 9 speeds.
    Posts
    7,254
    Mentioned
    4 Post(s)
    Tagged
    0 Thread(s)
    A Rohloff will never be in my budget, but if I were...
    I'd optimize the chain ring/cog ratio to use 11th gear as much as possible, since it's direct drive.

  7. #7
    Senior Member Retro Grouch's Avatar
    Join Date
    Feb 2004
    Location
    St Peters, Missouri
    My Bikes
    Rans Enduro Sport, Hase Kettweisel Tandem, Merin Bear Valley beater bike
    Posts
    23,939
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Niles H. View Post
    One percent seems pretty minor. Two percent also seems minor. But when you get up around three or four percent, it starts to make one wonder.

    Then again, maybe it doesn't really matter.
    Suppose you had a commute that takes you exactly 30 minutes with whatever you're using as a base line drive train. A drive line that's 4% less efficient would take you 31 minutes and 12 seconds. Would that bother you? I rather suspect that would drop out into the background noise of weather and traffic conditions. In other words, the normal day-to-day variation in commuting times would exceed any difference that could be attributed to the hub.

  8. #8
    cab horn
    Join Date
    Jun 2004
    Location
    Toronto
    My Bikes
    1987 Bianchi Campione
    Posts
    28,295
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Retro Grouch View Post
    Suppose you had a commute that takes you exactly 30 minutes with whatever you're using as a base line drive train. A drive line that's 4% less efficient would take you 31 minutes and 12 seconds.
    Uh, it doesn't work that way. 4% drivetrain efficiency loss does not equate to 4% time gain.
    Mes compaingnons cui j'amoie et cui j'aim,... Me di, chanson.

  9. #9
    Senior Member
    Join Date
    Oct 2007
    Posts
    66
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by operator View Post
    Uh, it doesn't work that way. 4% drivetrain efficiency loss does not equate to 4% time gain.
    So how does it work?

  10. #10
    Senior Member
    Join Date
    Aug 2005
    Location
    Pittsburgh, PA
    My Bikes
    '''96 Litespeed Catalyst, '05 Litespeed Firenze, '06 Litespeed Tuscany, '12 Surly Pacer, All are 3x8,9 or 10. It is hilly around here!
    Posts
    25,968
    Mentioned
    10 Post(s)
    Tagged
    0 Thread(s)
    One question that I never seem to find an answer for in these tests of internal geared hubs; is the mechanical efficiency number given for the hub just for the hub or for the entire drivetrain?

    Remember, an internal geared hub still has to use a chain,chainring and rear cog so is the "95%" (or whatever number is quoted) efficiency value just for the hub itself or does it include the rest of the required drivetrain parts too?

  11. #11
    Senior Member Retro Grouch's Avatar
    Join Date
    Feb 2004
    Location
    St Peters, Missouri
    My Bikes
    Rans Enduro Sport, Hase Kettweisel Tandem, Merin Bear Valley beater bike
    Posts
    23,939
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by operator View Post
    Uh, it doesn't work that way. 4% drivetrain efficiency loss does not equate to 4% time gain.
    So what is the difference likely to be? I notice that you left out the pertinent point. That being that the difference, whatever it is, is likely to less than normal day-to-day variations.

  12. #12
    Senior member Dan Burkhart's Avatar
    Join Date
    Oct 2004
    Location
    Oakville Ontario
    Posts
    5,090
    Mentioned
    9 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Retro Grouch View Post
    So what is the difference likely to be? I notice that you left out the pertinent point. That being that the difference, whatever it is, is likely to less than normal day-to-day variations.
    Someone posted these efficiency test results over on wreck bicycles.tech some time ago. I seem to remember that the Rohloff did not fare as favorably against derailleur systems as some of the other gearhubs, but there are a few things to consider. The Rohloff is currently the only gearhub that is oil bath lubricated, and must necessarily use seals. In my own experience, these seals do create some drag (which I really only notice in the work stand) which does decrease with use.
    Even so, if I recall correctly, the Rohloff came in somewhere around 94% efficient, which is slightly less than Rohloff's own claim of 96% efficiency. The overall efficiency will be an average over all gears, as it will vary depending on how many steps of gearing the power flow follows in any particular gear. Optimal efficiency, we would expect, should be acheived in direct gear.
    Derailleur gearing efficiency will vary as well any time an absolutely straight chain line is deviated from.
    Speaking as someone who does not, nor never has ridden competitively, nor do I track time/distace or anything like that, I did not notice an appreciable difference in drag with my own Rohloff over the XT/XTR drivetrain it replaced. I do however appreciate the ability to grab as many gears as I want or need, up or down, instaneously, whether the pedals are turning or not.
    Gearhubs demystified and other cool stuff.


    Rule #12: The correct number of bikes to own is n+1

  13. #13
    cab horn
    Join Date
    Jun 2004
    Location
    Toronto
    My Bikes
    1987 Bianchi Campione
    Posts
    28,295
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by bikingbrit View Post
    So how does it work?
    Think of it this way. If you decreased the wattage you produced into the bike by 4% do you go 4% slower? If you increased your wattage by 4%, do you go 4% faster?

    So what is the difference likely to be? I notice that you left out the pertinent point. That being that the difference, whatever it is, is likely to less than normal day-to-day variations.
    The difference to the user is negligible. Once you are riding internally geared hubs like that I don't think you'll be trying to set any TT or climbing records at your local club rides.
    Mes compaingnons cui j'amoie et cui j'aim,... Me di, chanson.

  14. #14
    Senior Member
    Join Date
    Apr 2006
    Posts
    1,024
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    When I was a kid, I had a bike with a generator lighting system where the generator rolled on the side of the tire. When I used the generator I felt like I was going nowhere fast and I only used the generator when going down hill and when I had to have a light. I am guessing that the generator was probably about a 3 to 5 watt drag on my engine. So this should compair with the loses in the hub. If you put a generator light system on your bike and ride you should be able to decide if the hub is right for you.

  15. #15
    cab horn
    Join Date
    Jun 2004
    Location
    Toronto
    My Bikes
    1987 Bianchi Campione
    Posts
    28,295
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by jim p View Post
    When I was a kid, I had a bike with a generator lighting system where the generator rolled on the side of the tire. When I used the generator I felt like I was going nowhere fast and I only used the generator when going down hill and when I had to have a light. I am guessing that the generator was probably about a 3 to 5 watt drag on my engine. So this should compair with the loses in the hub. If you put a generator light system on your bike and ride you should be able to decide if the hub is right for you.
    This is a bad comparison. The tirewall rub generator is consuming much more than 3-5w to produce 3-5w of power. Having ridden both rohloff and a sidewall tire generator, the latter IS going to be noticeable. The rohloff is like riding any other internally geared hub (sturmery archer etc.).

    Maybe someone will do a study where they compare how many watts somebody is losing through the rohloff hub vs a derailleur system. I doubt the loss will be meaningful to anyone who actually rides these.
    Mes compaingnons cui j'amoie et cui j'aim,... Me di, chanson.

  16. #16
    Senior Member Bolo Grubb's Avatar
    Join Date
    Jun 2004
    Location
    Tucson, AZ
    Posts
    1,749
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I just built up an old Trek Steel tour bike with a Nexus red band hub. I don't notice any difference. I am sure there must be a slight difference, but I do not notice it when riding.

    I do notice a big difference when I have to pick up the bike. It is much heavier in the rear end.

  17. #17
    Newbie
    Join Date
    Nov 2007
    Posts
    1
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    IHPVA articles

    Kyle & Berto article about transmission losses etc. (plus other interesting articles)

    http://www.ihpva.org/pubs/HP52.pdf


    Rohloff's answer to Kyle & Berto article

    http://www.ihpva.org/HParchive/PDF/hp55/hp55p11-15.pdf



    Here is Rohloff's own article about transmission efficiency

    http://www.rohloff.de/en/technical/speedhub/efficiency/

  18. #18
    Senior Member
    Join Date
    Sep 2005
    Location
    Ohio
    Posts
    1,819
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Also remember that the measured 3 to 4% difference is under laboratory conditions. Since I rarely ride in a laboratory I think it may not be applicable. I'd like to see a comparison done with a chain at 0.5% stretch, add some dirt, leaves, and grass clippings and use an eye dropper with a saline solution, a single drop on the chain every minute would do nicely.

  19. #19
    Formerly Known as Newbie Juha's Avatar
    Join Date
    Mar 2002
    Location
    Helsinki, Finland
    Posts
    5,848
    Mentioned
    4 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by jim p View Post
    When I was a kid, I had a bike with a generator lighting system where the generator rolled on the side of the tire. When I used the generator I felt like I was going nowhere fast and I only used the generator when going down hill and when I had to have a light. I am guessing that the generator was probably about a 3 to 5 watt drag on my engine. So this should compair with the loses in the hub. If you put a generator light system on your bike and ride you should be able to decide if the hub is right for you.
    I agree with operator, you are guessing wrong. I have a B&M bottle dynamo on my winter bike, and the losses from that are far worse than any transmission inefficiency I've ever experienced. Well, maybe a broken spoke and resulting brake drag are worse.

    Top notch hub dynamos would give a more realistic comparison. The SON dynamo for example operates somewhere around 5 watt loss range when switched on. When switched off, the SON claims a 0,5W loss or so.

    --J
    To err is human. To moo is bovine.

    Who is this General Failure anyway, and why is he reading my drive?


    Become a Registered Member in Bike Forums
    Community guidelines

  20. #20
    Senior Member
    Join Date
    Apr 2006
    Posts
    1,024
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Thanks it is good to know that the sidewall generator system eats up more than 5 watts. If there are any trainers with power meters, then maybe a person could ride at 100 watts for a while and then go to 105 watts and see the precieved difference in the effort required. Going back and forth between the power levels over a period of an hour or two should be helpful. I am not sure but I think that I would notice the difference. But if a person jumped on the trainer and rode for an hour without looking at the power meter they probably could not tell if it was set to 100 watts or 105 watts. But then again I really don't know because I don't have any way to test my guesses.

  21. #21
    Senior Member
    Join Date
    Nov 2006
    Posts
    467
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    A couple of percent diff in drivetrain efficiency is going to make almost no difference to riding speed. You have to recalculate the difference in total drag, and the drivetrain drag is only a small proportion of the total. Imagine you're riding a road bike at about 16mph. That takes about 150Watts. Most of the 150Watts is consumed fighting the air. Some on rolling resistance. A few watts are lost to the drivechain, say its 10W (I'd be surprised if it's this high). 4% of 10W = 0.4W, so a 4% difference in drivetrain efficiency is only going use up 0.4W of your power. Negligible.
    (I made up the figures, so actual ones will be different. Point still stands, 'tho)

  22. #22
    You need a new bike supcom's Avatar
    Join Date
    Aug 2002
    Posts
    5,434
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by hairytoes View Post
    A couple of percent diff in drivetrain efficiency is going to make almost no difference to riding speed. You have to recalculate the difference in total drag, and the drivetrain drag is only a small proportion of the total. Imagine you're riding a road bike at about 16mph. That takes about 150Watts. Most of the 150Watts is consumed fighting the air. Some on rolling resistance. A few watts are lost to the drivechain, say its 10W (I'd be surprised if it's this high). 4% of 10W = 0.4W, so a 4% difference in drivetrain efficiency is only going use up 0.4W of your power. Negligible.
    (I made up the figures, so actual ones will be different. Point still stands, 'tho)
    The 4% loss is applied to the total power at the cranks, not against a derailler system loss. In your example, 4% of 150W would be a loss of 6W. This is actually very good, assuming that the hub really does have this efficiency and that it remains fairly constant over the service life of the hub.

  23. #23
    Senior Member Bill Kapaun's Avatar
    Join Date
    Feb 2007
    Location
    Mid Willamette Valley, Orygun
    My Bikes
    86 RockHopper,2008 Specialized Globe. Both upgraded to 9 speeds.
    Posts
    7,254
    Mentioned
    4 Post(s)
    Tagged
    0 Thread(s)
    I think there are 2 different ways to approach this-
    1. IF I were to exert an additional 5% over my "comfort zone", I would expect my endurance to be MUCH less than 95%.
    2. I exert at the SAME level, my speed will be 95%, except I've got a slightly smaller amount of wind resistance, which would result in an actual speed of 95+%.
    That's my story.....

  24. #24
    Broom Wagon Fodder reverborama's Avatar
    Join Date
    Jul 2006
    Location
    Minnesota
    My Bikes
    Fuji Supreme; Kona Wo; Nashbar road frame custom build; Schwinn Varsity; Nishiki International; Schwinn Premis, Falcon Merckx
    Posts
    1,175
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I ride a road bike fitted with a Nexus-8 hub. It's great. I can and do keep up with everyone. I did 3 century rides on it this year. Efficiency loss? How much does someone with a derailleur lose when they fail to downshift before coming to a stop? With the hub gear you just click it down a couple of gears while stopped and ride right off when the light changes. In 5th, on the Nexus, you're in 1-1 which is as efficient as it gets. Any I never have any loss due to a poor chain line. Maintenance issues are almost non-existant.

    No, it isn't what you'd ride in a time trial, but you wouldn't do well commuting or running errands in a real race car, either.

  25. #25
    tcs
    tcs is offline
    Palmer tcs's Avatar
    Join Date
    Mar 2007
    Location
    Parts unknown
    Posts
    4,291
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Everyone worries about/discusses efficiency of hub gears. Nobody ever worries about or discusses the variable efficiency of derailleur set ups - even different gear combination on the same drive train. The typical comment treats all combinations in derailleur drive trains as the perfect base line to which to compare hub gears; the reality does not agree.

    A 52/15 and a 38/11 are the same ratio, but the 52/15 is significantly (as these things go) more efficient. The gains are worth far, far more than the negligable grams of weight savings that everyone does focus on. In a review of over two dozen cycling books, not a single one mentioned this.

    BTW, modern chains can run significantly out-of-line without meaningful effect on efficiency. The power goes into rotating all those little bushings under load, not flexing the links sideways. See the Kyle/Berto test, above.

    HTH,
    TCS
    "When man first set woman on two wheels with a pair of pedals, did he know, I wonder, that he had rent the veil of the harem in twain? A woman on a bicycle has all the world before her where to choose; she can go where she will, no man hindering." The Typewriter Girl, 1899.

    "Every so often a bird gets up and flies some place it's drawn to. I don't suppose it could tell you why, but it does it anyway." Ian Hibell, 1934-2008

Page 1 of 2 12 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •