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 Post subject: Two speed.
PostPosted: Tue Nov 13, 2007 9:51 am 
Gold Trader
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Location: Somerset
I was thinking of maybe building a 'single' speed.

However I would like to have a different gear for off road than on the road, so I was wondering if the Single speed tension adjusters on the market will take up the slack from a less than 10 tooth difference on the chain set.

I am thinking that 30 - 18 off road and 38 - 18 for the road would be cool, front mech only.

If not then I have some ideas how to make my own, but it would be nice to know if it is an original idea also! :D


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 Post subject:
PostPosted: Tue Nov 13, 2007 10:14 am 
East Midlands AEC
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I have a 2 speed on my Dave Yates using a Rohloff 2 wheel tensioner I run a 44 and a 34 up front and a 16 at the back (I think - may need to check on that!). I did it for the reasons you are doing it: I have a long rtoad run-in to the nearest off-road so didn't want to twiddle the whole way there!!


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 Post subject:
PostPosted: Tue Nov 13, 2007 10:51 am 
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Joined: Sun May 14, 2006 5:38 pm
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Don't really go with the idea personally - either go for a SS or don't... ;)

But many people do use a two speed set up. Usual way is a cassette hub with two cogs and a double front ring. Keep the tooth count the same and the chain length is the same. No need for a derailleur - just manually swop the chain over when you get there...

30/18 (a 43 inch gear) is very low. Most people settle on something around 50 - 55 inches as an all round off-road gear. Your 38/18 will be ok off-road. For the road a 65 - 70 inch gear is more like it ie 42/16.


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 Post subject:
PostPosted: Tue Nov 13, 2007 11:41 am 
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Thanks for the tips guys.

I was just plucking ratios out of my head then TBH.

The Rholoff thing sounds good though. :D


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 Post subject:
PostPosted: Tue Nov 13, 2007 11:43 am 
East Midlands AEC
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one of these:

Image


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 Post subject:
PostPosted: Tue Nov 13, 2007 11:50 am 
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That looks exactly like what I was going to make!

Only I was using bits of an old 500ex road mech. :lol:


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 Post subject:
PostPosted: Tue Nov 13, 2007 11:53 am 
East Midlands AEC
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Well that will work too. I used an old LX derailleur at first before the Rohloff. You just need to put a bit of cable between the cable crimp bolt and the bit where the cable goes into the barrel adjuster at the back of the mech to adjust the derailleur to the correct chainline position. I used a bit of brake cable which had the lump of metal at the end of it so the cable doesn't pull through. Hard to describe!!


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 Post subject:
PostPosted: Tue Nov 13, 2007 11:58 am 
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Joined: Sun May 14, 2006 5:38 pm
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Or you can make a super cheap one like this, one piece of mild steel, bent, shaped, drilled + one old pulley and a bolt. Cost? Nothing!


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 Post subject:
PostPosted: Tue Nov 13, 2007 11:58 am 
East Midlands AEC
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here's a dodgy picture I knocked up!

Image


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 Post subject:
PostPosted: Tue Nov 13, 2007 12:00 pm 
Retro Guru

Joined: Sun May 14, 2006 5:38 pm
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Location: Sussex
Back shot:



More ideas here:

http://forums.mtbr.com/showthread.php?p=2234257&mode=linear#post2234257


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