Following a broken rear mech during a ride this week end, when i tried to singlespeed it, the chain refused to stay on after a few turns of the crank. I was riding a full-sus, 1x11, no chain guide, so i guess that's not going to help. So if i was in middle of nowhere, which luckily I was not last Saturday, could I pack a chain tensioner as a backup rear mech to carry on riding? I just spotted that one on Planet X which might do the job:
[url= https://www.planetx.co.uk/i/q/FSOOSSD/on-one-doofer-singlespeed-chain-tensioner ]Doofer chain tensioner[/url]
Any experience? other alternative? not sure i want to pack a whole rear mech.
cheers.
I suppose the question should be how long have you been riding for and is the first rear mech you've broken?
If the answer is a long time, and just the one. Then I suspect it won't happen again for a long time (if ever), so you'll probably be ok.
If however you're a serial mech-smasher then I guess that a tensioner would work. My experience of tensioners like that one is mixed though. They can be a bit fiddly to set up, and I'm not sure how they will cope with chain growth.
A cheapy short cage mech would probably be a better bet as a spare.
If you are trying to ride a FS single speed you will need a sprung tensioner like the doofer.
FS bikes alter the chain length when the swing arm moves so it will never stay on untensioned.
I once fitted a chain tensioner to an old beater rigid mtb when the rear mech was knackered, but it kept trying to change gear and eventually split the rubber wheel on the tensioner.
I then bought a single-speed cog and spacers, and a new sprung tensioner with a cog instead of a rubber wheel, and the chain kept coming off, however long I spent lining it up and shortening/ lengthening the chain etc.
Turns out the mech hanger was bent - worth watching out for!
I'd go with the geared/ sprung tensioner - worked a treat after I replaced the hanger.