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1x conversion thoughts

Stephen Carson2026-09-02 15:43:09

Hi,

I'm thinking of converting the winter tandem to a 1x12 setup

46 or 48 chainring

11-50 12 speed cassette on the back

I know I would be happy with an 11-50 (or at least the initial 10 sporkets), I've had a couple of 10 speed 11-36 cassettes, the ratios on the 12 speed match the 10 speed plus 2 extra large sprockets to make up the 12 speeds.

Both my current tandems run 2x12 with cross over timing chain / belt, they are reliable systems so I am more than happy with 12 speed setups.

My thoughts turn to the timing chain.

What I would like to do is use a standard road double for me (the Stoker), using the inner chain wheel for the timing chain, and then have another standard road chain set on the front with just the inner ring mounted.  I like the idea of keeping everything on the drive side and also opens up the use of much more commonly available chain sets.

Has anyone done this?

My main thoughts are can I put a wide narrow 1x chainwheel in the outside position of a standard road double? Is there something that I haven't thought about?

I know there are divided opinions on 1x Vs 2x (Vs 3x). I'm happy to have the experiment and Iive and learn,

Thanks,

Steve

Mark Tipping2026-09-02 16:32:11

Steve

Great plan, I have done much experimenting and it often works - after fettling a bit.  Most likely issues will be chain line, I know 1x12 setup are the vogue but unless change bb axle length you will be running that 50t sprocket from the big ring position, thats a hell of an angle when masking on a steep slope.  I would favour mounting the drive chainring in the middle ring spot on a triple or inner on a double and put the timing chain outside.  Try it anyway and let us know how you got it working.

Mark 

Mark Tipping2026-09-02 16:39:32
Masking?  Mashing.....
Stephen Todd2026-09-02 18:30:42

One comment coming from a very different tandem setup; electric Ecosmo 1x7 for the odd 10 mile pootle. This may make it irrelevant, but it does have the chain setup you mention. 

If one of the chains comes off at the stoker position, the chains can jam very tightly together. Separating them is a really awkward. This is made worse on the Ecosmo as the bottom brackets contain freewheels to allow independent pedalling. You cannot turn the cranks backwards to help release the chains.

Michael Brooks2026-09-03 08:20:02
I was given one if these tandems a non electric one, the freewheel is actually built into the chainsets which weigh a tonne. I replaced the chainsets and fitted narrow wide chainrings and have never had a jam up. 
Graeme Knott2026-09-03 07:07:00

Check chain clearance around the back of the inner ring with the chain stay for the timing chain

ive done this on 11spd and all good.

 

Will Sillar2026-09-03 07:42:38
Hallo Steve.  I've tried a similar setup in the past and seemed to work fine, albeit only 1x11.  I used FSA 130mm BCD doubles with a 42t drive and a 36t timing chainring.  No problems with chain deflection, but my tandem has 18 1/2" chain stays which makes life easier for the gear set.  I put the timing chainring on the inside, FWIW.  I prioritised the drive chainline and the most important factor in sorting that was BB axle length (or spacers if you use an external bearing setup). 
Good luck and hope it goes well.
Stephen Carson2026-09-06 09:49:17

Some really interesting points and positive feedback.nI asked whether there is anything I haven't thought about, all the points raised really helpful - certainly some things that handy occured to me. 

I think I'm going to give this a go on the winter tandem. This bike currently has 105 12 speed.  Likely plan is that I will keep the sisters, purchase a cable operated GRX rear mech and probably convert the rear hub to micro spline. For now I think I'll keep the cross over drive as I experiment, before committing to standard bicycle chain sets with single sided drives. I'll post my gear inch calculations below for anyone who is interested, I found working these out really interesting.  Still not 100% sure on front chainwheel size.  My current set up is 50/34 + 11-36. We live in the Pennines and spend our rides on long (for UK)climbs and descents so gear range is essential.

 

Stephen Carson2026-09-06 09:58:40
10 =
11-13-15-17-19-21-24-28-32-36T
12 =
Sunrace 540g
11-13-15-17-19-21-24-28-32-36-42-50
11-13-15-17-19-21-24-28-33-39-45-51
Shimano XT 470g
10-12-14-16-18-21-24-28-33-39-45-51
10-12-14-16-18-21-24-28-32-36-40-45

46x11 = 113 to 46x50 = 25
46x10 = 123 to 46x51 = 24
44x10 = 119 to 44x51 = 23.3
42x10 = 117 to 42x51 = 22
42x10 = 117 to 42x45 = 26


36x36 = 28
34x36 = 25.5
50x11 = 123
50x12 = 110

Shimano 105 11 to 36 391g