Using just 1 chain ring without a front deraillier

[cyberknight]

I will be doing up a bike frame i will be getting free from a CTC member and it needs a front chain ring, i intended to just run 1 front chain ring but i was wondering if i got a double then i assume without a front mech it would act as a single chain ring ?

 

[MacB]

yep and it gives you the added benefit of being able to use both chainrings assuming chainlength and rear derailleur are appropriate. Easy to manually recreate the action of a front derailleur though I wouldn't want to do it on the hoof.

 

[cyberknight]

yep and it gives you the added benefit of being able to use both chainrings assuming chainlength and rear derailleur are appropriate. Easy to manually recreate the action of a front derailleur though I wouldn't want to do it on the hoof.

I thought so but you can bet if i did not ask and assumed it would not work

 

[TheDoctor]

I expect you're aware that it's not a good idea to use the big-big or small-small combinations on a double, and this would apply even without a front mech!
If you're going to buy a double, why not buy a front mech as well?
Failing that, on my Ribble I run a single ring, but it's a purpose made single chainset with a wide-ratio cassette.
Looks bonkers, but I've been touring on it and it works for me...

 

[cyberknight]

I intend to run a single , i was just pondering if a double was doable
Might be looking at a 40 ish front depending on what i can knab on flea bay with a 13-26 cassette i have in stock .

 

[Andy_R]

If you use a double, make sure you use a bb short enough to recreate the chainline you would have on a single ring setup otherwise, as has been mentioned, youll have chainline issues with big ring to big ring.

 

[TheDoctor]

The one I linked to is £20 new. But, yes, a double is perfectly doable.
It's not going to know what's moving the chain about, after all!!
IIRC, the Crane brothers did a major trip with doubles and no front mechs. No end of other stuff, too, all in the name of lightness.

 

[GlenBen]

On my previous bike I managed to run a triple with no FD , didnt want to spend any money on it so when it broke I just removed the whole mech. Using mainly the middle or outer ring ,I did get the occasional problem where it would shift between the two by itseld if the chainline was too far off, it also had a habit of jumping off the big ring when i went for the big ring small cassette combo. Was never anything you cant pop back on with your feet though mid stroke.

 

[GlenBen]

Just a point, this bike wasnt used on the road, Im not sure how safe Id feel doing that...

 

[MacB]

I'd cover all bases and buy a Shimano square taper Alivio chainset, get the 48/38/28 combo, FCM411 I think. I've used these chainsets on most of the bikes in the garage running some as hub gear single chainrings, 1x9, 1x8, triples, super compact doubles. They cost about £25 delivered and a square taper BB up to about £15 for a UN55 or about £7 for a UN26.

You need to be aware that there are two versions, in the above example it would be FCM410/411 the former with smaller chainrings. They take 10mm different in BB length for the same chainline, so for 50mm MTB recommendation then the FCM410 needs 113mm and the FCM411 122.5mm. For example I use:-

FCM410 with a 118mm BB and add a 1mm spacer to the driveside to give a 53.5mm chainline in the middle ring for a Rohloff. This allows me to fit my preferred option of a bashguard in the outer position.

Whereas I use an FCM411 with a 118mm BB to give a 47.5mm middle ring chainline for use with an Alfine hub, again the bashguard replacing the outer ring.

Apologies if this is all obvious but I got caught out assuming the same BB lengths for any Alivio chainset and do have some spare square taper BBs, didn't feel I could return them as I'd fitted them

If you decide on square taper, have a 73mm BB shell and need either a 110 or 113mm BB then you're welcome to one free of charge.

 

[palinurus]

I've done this a few times- four different bikes now- both with and without using a chainguard in place of the outer ring (and on the 'cross bike with a dog fang to keep it from going the other way). On the road I've run it naked without issue.

 

[cyberknight]

i assume this shifter will work, listed as an 8 speed shifter i would like to mate to a 2300 rear mech and 8 speed cassette ?

 

[cyberknight]

I

If you decide on square taper, have a 73mm BB shell and need either a 110 or 113mm BB then you're welcome to one free of charge.

Apparantly its an english BB, thats all i know atm .Guy i am getting the bike off is chucking in a BB but not sure what length .

 

[cyberknight]

was looking at ..
http://www.ebay.co.uk/itm/261156834499?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649
http://www.ebay.co.uk/itm/121054579548?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649
http://www.ebay.co.uk/itm/230881138441?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

 

[RecordAceFromNew]

i assume this shifter will work, listed as an 8 speed shifter i would like to mate to a 2300 rear mech and 8 speed cassette ?

Yes, assuming you are using flat bars.

was looking at ..
http://www.ebay.co.uk/itm/261156834499?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649
http://www.ebay.co.uk/itm/121054579548?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649
http://www.ebay.co.uk/itm/230881138441?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

I am a bit surprised by your selection of ebay chainsets from 36T to 48T - if I were you I would use a gear calculator to try to work out what is the smallest front ring I would be happy with a 11T rear sprocket, and search for a chainset from that. This will give you a decent shot for a light, tight setup. Some sort of logic is here.

I have been advocating and running the same Stronglight 55 Doc suggested above for some time. It is a remarkably light piece of kit (strong enough for anything on the road other than a fixie imho) for peanuts - my 40T is only 465g. Coupled with a UN72/73 (alas unfortunately these things are increasingly rare in decent shape) you will have a ~700g chainset+bb combo, which for the princely sum of c£35 in total is simply astonishing (ok let me put it this way, it is impossible to achieve same currently with Shimano kit without going all the way to DuraAce...). Incidentally, I use a 115mm JIS spindle to achieve 43mm chainline with the 55, so a 118mm JIS will give you 45mm.