# IGH vs. traditional gears/chain....observations on drag.



## _CJ (May 1, 2014)

As a result of my IGH belt drive bike being down for repairs, I had an opportunity to put my backup bike with traditional chain/gears into action and compare it's performance to the IGH bike via Strava.

Both bikes are essentially the same with the exception of the drive mechanism. Both are fully rigid steel 26ers with the same tires. The backup is a 1x8 setup with gearing similar to the Alfine8.

Whenever anyone talks about IGH bikes, or belt drive, somebody always pops up to tell everyone that they're less efficient than traditional gears/chains, so I was kind of curious to see if there really was a difference. Had I gotten used to the drag of the IGH/belt setup? Would the old gear/chain bike be faster?

So, I fired up the Strava and rode the backup bike with it's traditional gears and chain on a couple of rides that I've done a bunch of times on the IGH/belt bike. Rode the rides at an average level of perceived exertion, the same as I ride with the IGH/belt bike most rides.

End result.....the traditional gear/chain setup times over various Strava segments fell right in the middle of the curve for efforts on the IGH/belt bike. No difference. Nada. Well within the variation of trail/road conditions and my fitness for the day.


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## vikb (Sep 7, 2008)

I'm a IGH and derailleur user as well.

Your experiment doesn't compare the same bike with the different drivetrains which is what would be required to draw the conclusions you are making.

There are enough possible variables between bikes that could confound the results.

Even then there are enough issues with a specific IGH or derailleur setup that the results would only be valid for the specific ones you own...not the larger classes of components they are part of. The sample size is just too small.

That said I agree that just from anecdotal experience I don't think IGH drag is generally a big deal and there are lots of of benefits to using IGHs that would make up for as slight power losses even if you experienced it.


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## Varaxis (Mar 16, 2010)

Forgive me for being ignorant to IGH, but doesn't the Alfine use roller bearing clutch instead of pawls? If there's coasting sections, the lack of drag compared to pawls would make up for some time difference.


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## _CJ (May 1, 2014)

Varaxis said:


> Forgive me for being ignorant to IGH, but doesn't the Alfine use roller bearing clutch instead of pawls? If there's coasting sections, the lack of drag compared to pawls would make up for some time difference.


The combined total of the rides in this "test" was about 24 miles, and 4000 ft of climbing covering multiple segments over various terrain. Paved, dirt, singletrack, climbs, downhills, etc. There's not a significant difference under any conditions....or at least not enough difference to say one is better than the other, or that anyone should avoid an IGH because it's "less efficient".

I was actually expecting to get on the gear/chain bike and have it be a rocket ship, but it just didn't happen.


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## fokof (Apr 24, 2006)

+-2% is the difference in theory

http://www.ihpva.org/HParchive/PDF/hp52-2001.pdf

This paper is becoming a bit old but looks thorough.
Rohloff internal hasn't changed since but with advent of 1X11 instead of 3X8 , the chain twists more between the smallest and largest cog so the difference now in 2016 is probably even closer than 2%. 
Now with belts , there is another variable...... I've read somewhere that belt were less efficient than chain.

I'll take my less efficient IGH/belt over any derailleur system in a heartbeat.

A Shimano/Sach/Rohloff user since '00


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