trekking_TW

All machines have an efficiency associated with them. Is there an efficiency difference between a triple and double on a road bike? I ask because I changed out my 105 Triple for a DA double... changed the BB, front der., and crankset... I've done 3 rides on the new setup and seem stronger. I'm either getting my riding legs back or this setup is optimized better.

Any thoughts on the efficiency difference?

TallRider

I doubt there's much efficiency difference, and if there is, it's probably not between the double vs. triple. Maybe the D/A crank and BB combo is stiffer (it is, although I'm not sure that it's enough stiffer for you to notice). Also, it's possible that your chainline is a bit better now, though again I'm not sure you could notice that unless it's a larger diff. Finally, the new crank and BB are a bit ligher, partly because they're D/A and partly because there's one less chainring.

ridesoldtrek

You are probably riding with a different set of gear ratios now, which will affect the feel, but wouldn't necessarily make the gear train more "efficient." Consider that you the rider are the engine on the machine, and you may be better matched with the new gearing - you are part of the mechanical system (that sounds a little out-there, but oh well.) One thing that will make a very small difference is the crank arm length. I say small because most crank arms are 170mm or 171mm. The longer the crank arm, the longer the lever you are pushing against with your feet. It will be easier to exert more force through the crank arm when using a longer lever. 1mm seems too small to make a difference though, in fact a 171mm would only give you 1/170 more torque than a 170mm crank, which is 0.59%. Each additional mm adds an additional 0.59%, so it adds up, but I'd be surprised if your new crank arms are longer than 171mm. This argument will look really silly if the new crank arms are actually shorter! But look at that to see what the difference is, I'd be interested in hearing.

grolby

No difference that you would notice. A triple could put the chain at a greater angle in some gear combinations, but this doesn't happen consistently or even often, I don't think. You're already in the upper 90's range for efficiency, you aren't going to notice a .5% difference due to a slightly better chainline in some gears. Most people can't detect the difference between derailer and internal gears in terms of efficiency, so I doubt that you'd feel any change in efficiency if it even existed, which I rather doubt.

supcom

Placebo effect. You spent a bunch of time and money to make the swap and you don't want to admit to yourself that it was all for vanity.

ridesoldtrek

Placebo is good!!!

GrannyGear

DuraAce riders automatically have stronger legs, deeper lungs, and more dignity than 105 geeks (especially on triples)....or so the industry would have us believe.

supcom

No side effects either - except for a lighter wallet.

ridesoldtrek

Nothing is free - except Arnold Schwarzenager was once heard to say (referring to health/fitness clubs) "I never paid anyone a dollar to do a pushup."

San Rensho 

To sum up what others have posted. There is absolutely no difference in efficiency between a double and a triple. A gear is a gear. An 88 inch gear with a 170mm crank will always feel the same to your legs no matter if you have a fixed gear bike or a quadruple chain ring, 12 cog cassette.

There is a big difference in efficiency in different gear sizes, however.

wagathon

To the extent that with a triple, for any given range of gears, you would have more gears, that are more closely spaced, it seems to me that, theoretically, you would have a better chance of translating the given amount of power in your legs into forward motion on a bike in the most efficient manner, e.g., sort of like having a 10-spd instead of a 3-spd.

trekking_TW

I've considered this and believe it's somewhat true. Perhaps my body (engine) works better at climbing in a bigger gear ratio such as the new setup. The triple was a 52/42/30 with a 12-25 cassette and I often used the 30/25 with a cadence of 90. The double is a 53/39 with a 11-23 cassette and I climb with a cadence of 70-80. I've looked at gain ratios, gear charts, and speed vs. gear ratios at certain cadences, but the fact is that my HR is lower by 10bpm on my climbs with the double!

So here's my efficiency summary:
170mm to 172.5mm crankarm length change = 1% gain
stiffer BB and crankset = .25%
12-25 to 11-23 cassette change = 1%
personal efficiency on double vs. triple = 17.75%
placebo effect = 80% (includes DA vs. 105 expectations)

Little Darwin

Your mentioning the gear ratio and heart rate is likely to be the basis of the answer you are seeking.

It is my understanding that to balance the use of leg strength with cardi-vascular effort, the process is to change gears.

I read somewhere that to switch to a lower gear is easier on the legs, but uses more cardio-vascular effort... In my case, it was an issue because I was pushing too low a gear and causing leg issues while not getting the level of cardio benefits I had been hoping for.

r-dub

I mostly agree, except the part about the fixed gear. On a single speed setup, you're dropping the (not completely insignificant) drag of spinning the rd gears. You also (ideally) always have a perfectly straight chainline.

Don Cook

I may be wrong, but it's my inderstanding that when speaking of mechanical efficiency, it's largely a reference to the loss of energy (power, watts) between input and output. If this is the case, the system of tansferring your input power into locomotion is the same whether you're cranking a double or a tripple. It would seem logical that there might be some miniscule difference in the overall drive system resistance to the input power that's required to operate it, due to the potentailly greater chain angles that are achievable with a tripple. But then that is rider dependent.

When speaking of various gear ratios and differences between tripple and double, it strikes me that whatever an individuals most efficient ratios are, they are completely independent of whether you have a double or a tripple.

wagathon

Except that, assuming the rider's weight does not change, the most efficient gear will change depending the slope of the course and/or how fast the rider wants to travel a particular distance. Since a triple setup offers more gears, that should make it easier to obtain the individuals most efficient ratios compared to a double. Just a thought.