I am putting together an extra cycle and have a chain rub issue so wondering if anyone else had something similar and how they solved it
I dont have nay pics of it but where the top run of the chain runs over the chainstay in almost very gear the chain is in contact with the chainstay itself. I was therefore hoping I might be able to use something like this upside down [img] 
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to keep the chain off but it needs to be pretty solid. Or maybe a chain tensioner upside down in the bike frame mech hanger?
Thanks
a) tighten the b tension screw on your rear mech.
b) run your chain round big sprocket/big chainring and make sure it's as tight as it can be without binding.
c) pedal harder - if the chain is slack on the top run whilst you're pedalling you have legs like my 2 year old 😉
WHen you freewheel, then yes, it's quite likely the chain will drop on to the top of the chainstay. Especially if you are in small/small rings.
I run my xtracycle as 1x8 which helps.
I am not quite at the stage of being able to ride it yet. I have only fitted the additional frame in and lengthened the chain (so not sorted the cabling or lengthened the hose to the rear brake) but even playing with the mech it didnt seem to be clearing the chainstay by much even in big/big (I am running it as 2x8).
But thanks for noticing my legs... 😆
anything like the above run above chainstay is going to put the entire force you're putting through the chain downwards onto the stay itself as the chain tries to take the shortest path between chainring and rear cog.
Does sound more like a geomtery issue with the way the back end is attached to the main bike - is ther anyway of making it so the chainstay is closer to the line between the BB axle and wheel one?
The free radical has a "tongue" which sits on top of the chainstay bridge. Unless I put the "tongue" under the chainstay then not really but then it is not used as intended and I would worry about the strength of the connection if I did that
[img] 
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this bit
looking through Google images it seems "they're all like that".
I'd just wrap the stay in an old inner tube and put zip ties at the point of most contact for a slippery finish to run the chain on.
Indeed they are "all like that". It would need a hefty spring in the rear mech to keep such a long length of chain taught enough to stay clear of the chainstay all the time.
I'll go get a pic of mine...
This is when first built
[img] 
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I now have a small chain device to stop the chain dropping off the top of the front ring.
That's a 30T ring BTW.
Mine's a bit 'slappy', but I don't worry about it. It's a massively long chain so it's bound to happen and stays on just as much as on my other bikes.
Here's a pic during construction - shows the saggy chain quite well
[url= http://farm4.staticflickr.com/3010/2661849356_7ca720138d.jp g" target="_blank">
[url= http://www.flickr.com/photos/cheesyfeet/2661849356/ ]Nearly there[/url] by [url= http://www.flickr.com/people/cheesyfeet/ ]gary_foulger[/url], on Flickr
More pics here http://www.flickr.com/photos/cheesyfeet/sets/72157606127561119/
One other question, can you get away with a standard new rear mech cable or did you all buy a tendem length one?
Kit came with a super long one and an rollamajig too. Normal rear mech cable won't be long enough
EDIT - also longer rear brake cable too
Yeah the brake hose def needs to be longer if I ever want to go straight ahead or turn right without going left, left and left again!
you might need to get your self a 203mm rotor too.
I use shimano brakes so can just get OEM hose off the roll.
Rolamjig is recommended for cable routing, but I guess a SRAM mech might not need one?[img] 
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Why the 203? I have 185 disks front and back ready for it or is the tab set for a 203 already? I have a 203 in the shed too already
get bigger chainings, you pansies !
The FreeRadical will work with either disc brakes or linear pull rim brakes. If you are using disc brakes, you will need a 203mm rotor and a caliper mounted on a 160mm bracket. If you are using rim brakes you will need a linear pull (often called a V) brake. Cantilever brakes are not compatible. 700C wheels using rim brakes will require an adapter.
http://www.xtracycle.com/faq-frequently-asked-questions
I see,a frequently asked question...sorry
Just get it built and join the wonderful (if a bit flexy) world of riding around with massive loads on the back, fighting the desire it has to not go round corners and the scary speeds you can attain on a good downhill road.
They are ace fun!