GTRO 3 Speed Crankset

Installation of GTRO into Eccentric BB

We first heard about this crankset a few months ago and we immediately recognised its potential.  We contacted the manufacturer EFNEO in Poland and ordered 2 sets then looked for a suitable frame that would suit as a demonstrator.   We settled upon a Charge Bikes Mixer hybrid as a demonstrator for the GTRO 3 speed gear box coupled with a standard 8 Speed Shimano Alfine hub to provide 24 speed in total with a vast range of gears suitable for touring and adventure.  This frame has an eccentric bottom bracket allowing the chain to be correctly tensioned.

The GTRO comes with either a grip shift or trigger shifter.  we chose the latter as we already had a trigger shifter for the Alfine.

The installation was easy.  Although working with an eccentric bottom bracket required some careful adjustment, I was able to find a ‘sweet spot’ that gave a good chain line, chain tension and allowed the anchor to sit correctly.  If the BB is rotated forward in the eccentric fitting then the anchor will not fit.

There is a good installation video at that provides decent instructions.

Care needed to be taken with a eccentric BB as the protruding screws can foul on the BB shell.  The main issue is with the length of cable.  I used a small frame which produced a large loop of cable at the front of the bike. We have since been told by EFNEO that a solution that uses cable splitting will be incorporated into future models.   This would allow the cable length to be tailored and would also allow installation on Moulton bikes or bikes that use S&S couplings.  I think this is key point that would increase the systems flexibility.

The installation job was completed after 45 minutes.  The rest of the bike took a further 3 hours to complete but included the Alfine 8 speed hub and Avid hydraulic disc brakes.  I used Sputnik Rims for strength.

Charge Mixer with GTRO Alfine gears just built

The inaugural ride proved to be a revelation.

Being use to derailleur gears, I was initially baffled as to which gear to be in.  There was almost too much choice and I need to think about the what I was doing.  The new Shimano Alfine hub that was used was operated by an outdated thumb shifter where the pull is in the reverse direction. This complicated the situation however after a few miles I thinks settled down.

I noticed that gears could be changed on steep hills which is a great a advantage.  I was also taken by the quick shift of the GTRO which seems to be a very robust piece of kit.   When I got back to the shop I installed mudguards and a rack with some Carradice panniers for effect.

In conclusion the ‘do anything’ bike has a new incarnation that uses hub gears, GTRO and a 1/8” chain for durability.  The following table shows the gear chart in inches based on a 17 tooth sprocket.  I may change this to a 25 tooth sprocket for lower gears.

Alfine/GTRO 28 40 50
1 23.6 33.7 42.1
2 28.8 41.2 51.5
3 33.5 47.8 59.8
4 38.1 54.4 68.0
5 44.8 63.9 79.9
6 54.7 78.2 97.7
7 63.5 90.7 113.4
8 72.3 103.2 129.1


The applications are endless from Cargo bikes and Tricycles, folders, single speeds to mountain bikes with derailleurs.  I have not checked if there is a width limitation on the chain ring.  EFNEO tell me that the cable pull is the same as a Shimano Deore 3 speed but in reverse.  This would allow operation using a STI shifter which would be another worthy setup to undertake.  It also makes the Rohloff 14 speed obsolete.

Touring/Adventure configuration

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