Double single speed

[PIGEON]

Right, I've been thinking about doing a single speed. The thing that's been holding me back is that I don't exactly live in the middle of a mountain range and the nearest bit of trail is a 30 minute ride away from my house, which I don't really fancy doing on an ultra spinny bike.
Today I've come up with a possible solution and I'm curious to know if someone on here has done the same.
The idea is to use a double chainwheel and two rear sprockets, for example 42 & 48 up front and 20 & 14 in the back. That way I can ride to the trail on 48x14, manually change the chain to the other set of sprockets without having to lengthen or shorten it because the total number of teeth is the same, and then ride the trail on 42x20.
This might be pretty common but I haven't seen it done before but then again, I haven't been into single speed mountainbikes.
So has anyone tried this? Any thoughts or experiences?

 

[ededwards]

White Industries do a double freewheel so the possibility is definitely there.

 

[IDB1]

Well.. it'll be quad speed, not single, but there's no rules . . and not much to lose by trying it to find out either

 

[highlandsflyer]

Na, it will a manual change dual speed.

Seems like it would be fine.

Me, I would use a changer rather than manually adjust.

While adding one, how about a full cassette of say 8 sprockets?

 

[PIGEON]

You're right, it wouldn't be a true single speed. In fact it would be a two speed with no means of shifting on the fly. Running the chain diagonally won't work because that would require a different chain length.
I've looked up the White Industries freewheel, looks very nice but $120 is a bit steep and I think a cassette hub with spacers and two sprockets from a cassette would be more versatile, both in sprocket size and chain line. Good to know it is very much possible though!

So I guess I need to figure out a usable off road ratio and work from there, maybe 5 teeth larger up front and 5 teeth smaller in the back for the road setup. The local trail does have a couple of decent climbs, what would be a good ratio for semi-serious off road singlespeeding?

 

[choppstar10]

you could get a Schlumpf!! internally geared crank!! google it!

http://www.youtube.com/watch?v=p_9CRMgD ... _embedded#!

 

[PIGEON]

Haha I knew someone would say just put gears on it. But I already have a geared mountainbike, and in my experience when I have two bikes that do the same thing, I'll always ride my favourite one and never the other. Plus I like doing something different just for the sake of it

 

[Crum]

I had one of these on a BMX bike back in the day...
http://cgi.ebay.com/SUNTOUR-FREEWHEEL-2 ... 519509eec2

It is spring loaded... High gear normally, but a lower gear when you squeze the lever. It was supposed to be for faster starts at races...

You could do the same thing with a short cage derailleur and a shorty lever...

 

[andrewl]

White Industries do a double freewheel so the possibility is definitely there.

What he said.

I have the a set and it works great except that I hate having to stop to change the chain (lazy I know), so I went back to a conventional Single Speed setup.

38/35 up front 16/19 at the back works pretty well.

 

[jimihendrix]

I think a cassette hub with spacers and two sprockets from a cassette would be more versatile, both in sprocket size and chain line. Good to know it is very much possible though!

So I guess I need to figure out a usable off road ratio and work from there, maybe 5 teeth larger up front and 5 teeth smaller in the back for the road setup. The local trail does have a couple of decent climbs, what would be a good ratio for semi-serious off road singlespeeding?

You could look out for an old nackered XTR cassette or a normal cassette and knock the rivets out, the middle sprockets tend to wear the least anyway, failing that i dont see why a couple of different size SS sprockets (maybe 16-20) wont work, as long as you get the spacing between them right, shifting wont be smoth as they are not ramped and the teeth are big but it should still go, of course the mech will be no problem, just a short cage with the stop screws wound in.

I found 2 to 1 ideal offroad, 32 on the front 16 on the back, i recon having 32 - 20 for climbing and 42 or 44 - 16 as a tall gear would work pretty well.

Be interested to see if you get this to work as i love single speed off road but found it a bit frustrating when twiddling away a tiny gear on the road or a flat fire road.