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Tandem Chainsets

Kevin Smith2019-03-20 09:14:17

Hi, I'm looking for a chainset 175mm front crank and 165 rear. Without opting for very high end expensive sets, it appears I can buy seperates but need to get the threads changed over left/right etc. this can be done by helicoiling and is offered on the web. anyone have any experience with this or solved such a problem in other ways please? For the cross overs, I'd buy doubles and use only the inner only, while giving me spare outers for the rear triple. I could get a nice stronglight set-up for around £200 this way, just the threading on top or buy the tap set my self. I am an engineer BTW.

Stuart Hibberd2019-03-20 12:07:40
Thorn do tandem chainsets in different lengths. I use the 160mm on the back of our tandems.
Rear £89.99
https://www.sjscycles.co.uk/cranks/155-thorn-tandem-triple-crankset-for-xover-drive-rear/
Front on Sale at £39.99 currently
https://www.sjscycles.co.uk/cranks/150-thorn-tandem-crankset-for-xover-drive-front/
These don't include rings. A set of thorn or stronlight rings would be about £100.
So £230 all in.
 
Stuart
Michael Hughes2019-03-20 12:26:19

Is there no simpler way

Assuming that the 11mm difference is wanted for the comfort of the stoker, or to enable the stoker to be able to reach the pedals would it not be easier to find shoes with thicker soles or a means of altering the pedals.

I am assuming that the stoker's saddle is as close to the frame as possible and that a shallower profile saddle would not suit the rider.

Stuart Hibberd2019-03-20 12:48:04
Michael
Thicker soles do not decrease the crank length, as your foot rotates the total travel up and down is the same. People used to put blocks on pedals so their kids could reach them then wondered why they were complaining of knee problems.
 
The longer the crank the more the knee bends when pedalling.
 
So, it makes sense for shorter people ride with shorter cranks. I know that the major manufacturers would disagree with this and sell us all 175mm cranks regardless of how long your legs are.
Stuart
Kevin Smith2019-03-20 12:50:04

Thanks for the links, i'll check these out. For clarification, the length difference is about cadence. i'm comfortable at 100rpm, but my wife around 85-90rpm. Reducing the crank length, does not reduce cadence, but it does reduce the pedal circle and as such the speed, making it more manageable when there is a mismatch. 

Chris Bishop2019-03-20 15:37:41

Why do you need to change threads, can't you just put axle other way round in cups?

Kevin Smith2019-03-22 10:05:13

Need to chenge the pedal threads or they'll come unscrewed. But the Thorn Cranks link above has solved the issue, along with SPA chainreings. 

Thanks to Stuart above.