10 watts difference in drivetrain friction between singlespeed and geared?- Mtbr.com

# Thread: 10 watts difference in drivetrain friction between singlespeed and geared?

1. ## 10 watts difference in drivetrain friction between singlespeed and geared?

10 watts difference in drivetrain friction between singlespeed and geared?

a buddy tells that using power meters on both bottom bracket/cranks and rear hub at same time, there is a 10 watt difference on geared bikes (with new well lubed drive train), and that singlespeeds would be 10 watts more efficient.

based on Analytical Cycling calculator, that would mean for a geared bike using, for example 32:16, and a single speed using 32:16, going up a hill where that gear would be the best choice, that the singlespeed would be 20 seconds faster per kilometre

does that make sense?

2. Sounds reasonable, but there may be too much information available these days.

No question a SS is more efficient. Why not leave it at that?

3. Seems unlikely. A chain is designed to be quite efficient.

P

4. I think to really find out how much faster per kilometer/mile whatever distance you are measuring in, you would have to compare the DIFFERENCE in percentage of total sustainable watts available. i.e.; Take two riders of the same size and weight/build. One rider puts out 250 watts sustained for the kilo, one can put out 320 watts for a kilo. The 250-watt rider will feel that 10 watts more than a rider that can put out 320 watts sustained. Put the stronger rider on "gears" with the same ratio, and he'll still be faster, but only a 60 watt advantage instead of 70. 20 seconds over a kilo? Depends on the rider weight and gradient, to see how much 10 watts will do to the climb time.

5. That's only a 3.33% difference for a 300 w rider.
Also, the SS cannot be 100% efficient, so what does the SS loose from BB to hub, and what does the geared loose from BB to hub?
Everything on bike setup, rider, rider effort, and course has to be the same for these numbers to be meaningful.

6. I don't mean to mock you, but a power meter on a one speed? Someone is missing the point.

7. Same goes for a heart rate monitor!!

Originally Posted by Loudpawlz
I don't mean to mock you, but a power meter on a one speed? Someone is missing the point.

8. I still have old light bulbs that say 60W on them.

9. Originally Posted by Loudpawlz
I don't mean to mock you, but a power meter on a one speed? Someone is missing the point.
you wouldn't understand
my buddie races on the track/velodrome
gear freak not geared freak

10. Does anyone have a graph comparing power, torque, and cadence for a typical mountain biker? I suspect the single gear causes a much wider swing than 10 watts.

11. If you can notice 10w on even a road bike under power up a hill, you're a far better rider than I. Seriously, ride your bike.

12. If that is true and for fun we will say it is acurate, how much of that 10w is from drivetrain efficiency or from lack of weight of the drivetrain?

13. Originally Posted by benwitt11
If you can notice 10w on even a road bike under power up a hill, you're a far better rider than I. Seriously, ride your bike.
You can easily notice a 3W hub generator when it is engaged. Humans only put out ~100W, 10% is significant and noticeable.

However, a geared drivetrain only adds 2 idler pulleys, and they along with the extra bends in the chain are not dissipating 10Ws of heat. Only if you take the extra weight and calculate the extra energy you need to carry it up a hill will you approach 10Ws.

14. Originally Posted by ccm
you wouldn't understand
my buddie races on the track/velodrome
gear freak not geared freak
I challenge you both to a ride off and beer drinking, but on mountain bikes 'cause this is a mountain bike forum. And no PBR or chain wallets just in case he is a cross over fixie rider too.

15. Originally Posted by itsdoable
You can easily notice a 3W hub generator when it is engaged. Humans only put out ~100W, 10% is significant and noticeable.
Humans that exercse can put out way over 100 watts. For a long-term period, yes 100 watts (or less) is probably what most of us average on a trail ride. For a few minutes, fit cyclists can put out 250 - 350 watts or more - and the ellite pros can put out hundreds of watts for hours at a time. In a sprint, top cyclists can put out near the 2 Kw mark for a number of seconds. When I was a teen and racing road, and a decent sprinter, they had a display at the Space science museum in San Diego - a generator-equipped bike attached to a bar with a bunch of auto hi-beam headlights. If they all lit up it was about 650 watts. I could get them all going for nearly a minute - but that was a hard effort. Boonen, Cancellara or some of the other fast boys could probably burn the thing out.

16. There's no doubt that a straight chainline and the absence of derailleur idler pulleys makes a noticeable difference in effort for a singlespeed with horizontal drops, silders, EBB than for a hardtail in exactly the same gear with a new 1x9 or 3x9 setup.

How much, I don't really care, but I know that even shifting from vertical drops and a Rennen tensioner to horizontal drops I could feel the difference in reduced drag.

17. God and i thought i was boring sometimes.

18. ??????? this whole thread is pretty mystifying.... If you take a 3X9 mountainbike and put it in the middle ring and the middle of the cassette and RIDE IT.... there is absolutely NOTHING at work in that drivetrain that is any different than a singlespeed with the same gear combination.
The only possibility would be that it might take less than a single watt to turn deraileur pullies, but beyond that a ring pulling a chain to turn a cog to turn a wheel .....same old thing

19. Beg to differ based on personal experience.

20. Originally Posted by scyule
??????? this whole thread is pretty mystifying.... If you take a 3X9 mountainbike and put it in the middle ring and the middle of the cassette and RIDE IT.... there is absolutely NOTHING at work in that drivetrain that is any different than a singlespeed with the same gear combination.
The only possibility would be that it might take less than a single watt to turn deraileur pullies, but beyond that a ring pulling a chain to turn a cog to turn a wheel .....same old thing
I'm thinking the tension on the chain through those pulleys would require more than 1 extra watt. You've also got extra chain, which adds a little bit of weight, but a bunch more friction. And that's assuming everything is clean.

As you said though, that's only when the multispeed rider is in the exact same gear a ss rider. The multispeed rider is rarely going to be in that one gear, they're going to be shifting through their range, making them more efficient....

21. Originally Posted by Loudpawlz
I challenge you both to a ride off and beer drinking, but on mountain bikes 'cause this is a mountain bike forum. And no PBR or chain wallets just in case he is a cross over fixie rider too.

I get the chain wallet slam, but what's with the slight oh PBR? That was uncalled for

22. It does sound plausible to me, but I also wonder how precisely the two different power-meters were calibrated.

23. Im going to take a differnt stand here, and not question the geekiness into this matter but say , pretty cool info ! Talk about scientific proof...

24. Originally Posted by sean salach
I'm thinking the tension on the chain through those pulleys would require more than 1 extra watt. You've also got extra chain, which adds a little bit of weight, but a bunch more friction. And that's assuming everything is clean.

As you said though, that's only when the multispeed rider is in the exact same gear a ss rider. The multispeed rider is rarely going to be in that one gear, they're going to be shifting through their range, making them more efficient....
I beg to differ. Shifting through the range doesn't neccessarily make you more efficient. AND it doesn't negate the difference friction might make. No matter what the gear ration, you are still delivering the same amount of power to the wheel, it's just either faster spin power, or slower harder push power. Your legs still deliver the same amount of energy they just deliver it by either pushing harder (working one type of muscle) or spinning faster (working different muscles). Whatever energy isn't taken up by friction gets to the wheel eventually.
This means that change in gearing doesn't cause a net loss of energy, but friction does.

Anyway, all the numbers etc. in this thread made me go cross-eyed in thirty seconds...

Here's my take:
Just today, by coincidence, I was doing some maintenance, and compared the inherent resistance in drive trains between my SS, my geared commuter (cyclocross bike) and my geared full suspension. By far the winner was my SS, with absolutely the least resistance.

My test wasn't very scientific or technical at all.... I simply put them up in the stand, and spun the crankset both forward and backward in several different gears... The difference in how far the crankset spun under its own weight after I released it was significant. I could lightly tap the SS crank and it would easily do 360 degrees, where as the other two stopped almost immediately on release unless I spun SIGNIFICANTLY harder.

YUP I know, not very scientific, but it convinced me that more energy is ultimately delivered to the wheel through a single speed.

25. Originally Posted by Jonesy33
I beg to differ. Shifting through the range doesn't neccessarily make you more efficient. AND it doesn't negate the difference friction might make. No matter what the gear ration, you are still delivering the same amount of power to the wheel, it's just either faster spin power, or slower harder push power. Your legs still deliver the same amount of energy they just deliver it by either pushing harder (working one type of muscle) or spinning faster (working different muscles). Whatever energy isn't taken up by friction gets to the wheel eventually.
This means that change in gearing doesn't cause a net loss of energy, but friction does.

Anyway, all the numbers etc. in this thread made me go cross-eyed in thirty seconds...

Here's my take:
Just today, by coincidence, I was doing some maintenance, and compared the inherent resistance in drive trains between my SS, my geared commuter (cyclocross bike) and my geared full suspension. By far the winner was my SS, with absolutely the least resistance.

My test wasn't very scientific or technical at all.... I simply put them up in the stand, and spun the crankset both forward and backward in several different gears... The difference in how far the crankset spun under its own weight after I released it was significant. I could lightly tap the SS crank and it would easily do 360 degrees, where as the other two stopped almost immediately on release unless I spun SIGNIFICANTLY harder.

YUP I know, not very scientific, but it convinced me that more energy is ultimately delivered to the wheel through a single speed.
Until you run out of gear and find yourself watching the backsides of strong multispeed riders pedaling away in either an easier gear uphill(more efficient) or a bigger gear on flats and slight downhills(more efficient).

I prefer singlespeed, and it's all I ride, but until I see one winning a national or world cup xc race, I'm not going to believe that they're as efficient on the trail as a well tuned multispeed.

26. Originally Posted by sean salach
Until you run out of gear and find yourself watching the backsides of strong multispeed riders pedaling away in either an easier gear uphill(more efficient) or a bigger gear on flats and slight downhills(more efficient).

I prefer singlespeed, and it's all I ride, but until I see one winning a national or world cup xc race, I'm not going to believe that they're as efficient on the trail as a well tuned multispeed.
Oh I'll conceed that when it comes to practical trail use, the geared bike overall is more efficient. You can make better use of downhills through higher gearing and you can spin up steeper climbs without having to blow your muscles open cranking at 2 RPM! Adn there is a certain point on the flats where on a SS you spin out and can't really speed up any more (especially if you're geared for any decent climbing at all).

But, if you're talking strictly amount of energy delivered from the source (legs) to the outlet (wheels) the system with less friction in between the two is unquestionably more efficient in a scientific sense.

Don't get me wrong I don't ride my singlespeed because it's faster I ride it cause I'm stupid and don't always feel like thinking about gears etc. I just wanna get out and ride.

27. One thing that would be interesting to test (if anybody REALLY cared...) was to see how much extra friction there was at different RPM. I would bet that at low crank revs, the friction is pretty low on the wattage scale, but as the rider rev'd up the watts required would be measurable. Regardless, I prefer SS, but if I was really racing or wanting to get somewhere the quickest, gearing of some sort would be the ticket. SS is just more challenging for some rides, and there is something about it - in addition to the simplicity and silence - that appeals to me.

28. Originally Posted by scyule
??????? this whole thread is pretty mystifying.... If you take a 3X9 mountainbike and put it in the middle ring and the middle of the cassette and RIDE IT.... there is absolutely NOTHING at work in that drivetrain that is any different than a singlespeed with the same gear combination.
The only possibility would be that it might take less than a single watt to turn deraileur pullies, but beyond that a ring pulling a chain to turn a cog to turn a wheel .....same old thing
Even with a straight chain the drivetrains are different in the tension in the lower run of the chain.

Geared: there is tension on the lower half of the chain caused by the derailleur spring. The same tension is applied across the pulley bearings.
SS: the only tension in the lower half chain is caused by gravity. (An SS with a tensioner feels like it has some drag.)

When the chainline is not perfectly straight there's friction of side-plates on teeth. The bottom run of the chain is pulled sideways by the derailleur, the bottom pulley get pulled sideways too.
SS none of the above.

Bonus difference, SS with 1/8" chain has less force per surface = more efficient.

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