Single Speed on a MTB tech advice

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Single Speed on a MTB tech advice

Postby redcloud » Wed Apr 10, 2013 5:25 pm

Hi all, I apologise if it's been discussed somewhere already but I've been having some trouble with my Single Speed Mountain bike that I use for some single tracks near by. I think i have the gear ratio just right, however the chain has the tendency of falling off. I have a chain tensioner but I find that if it's too tight it comes off and obviously if it's too loose it does the same. It also comes off when i'm putting some torque on going up hills...which doesn't breed much confidence in me!

Any tips or experience with it appreciated.

p.s. the chain tensioner is not spring loaded.

p.s.s It's a liberating experience getting rid of all those gears!!
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by BNA » Wed Apr 10, 2013 6:11 pm

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Re: Single Speed on a MTB tech advice

Postby drubie » Wed Apr 10, 2013 6:11 pm

How straight is your chain line? Are you using the right chain for your cogs?

I abandoned the tensioner on my single speed MTB not for those reasons though.
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Re: Single Speed on a MTB tech advice

Postby redcloud » Wed Apr 10, 2013 6:38 pm

Thanks Drubie, yes it's straight/aligned...not sure about chain though. I just used a sprocket from a cassette lying around and put her on. THink I've just used a similar 'multigear' chain also. WHy did you abandon the SS on the bike? I really like it for the most part but it just seems to fall off randomly. Might stick for 5 kms then it will fall off every 500 mts. Frustrating.
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Re: Single Speed on a MTB tech advice

Postby drubie » Wed Apr 10, 2013 7:16 pm

No I still have it single speed but I managed to find a magic gear that didn't require the tensioner.

If the tensioner is spring loaded and your cog is worn out the chain might be "walking" up the worn teeth. On a multi speed bike you'd feel it catching and releasing. On a single speed its likely the chain is falling to the side of your cog. If the tensioner is fixed then this is less likely. I don't really like them on single speeds for this reason as even the rigid tensioners are hard to get right and on a mountain bike it could cause all sorts of issues on a rocky, uphill section.
So we get the leaders we deserve and we elect, we get the companies and the products that we ask for, right? And we have to ask for different things. – Paul Gilding
but really, that's rubbish. We get none of it because the choices are illusory.
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Re: Single Speed on a MTB tech advice

Postby MoeJoe » Wed Apr 10, 2013 8:17 pm

redcloud wrote: I have a chain tensioner but I find that if it's too tight it comes off and obviously if it's too loose it does the same. It also comes off when i'm putting some torque on going up hills...which doesn't breed much confidence in me!

Any tips or experience with it appreciated.

Mine did the same under load - the chain would slip at the crest of a hill or any high torque moment.

The driveside BB needed a bit more tightening oomph which seems to a have fixed it. I also added a bit more tension on the chain tensioner spring as precaution.

Don't discount this chainline measurement method though.
It is simple which I like and just because it 'looks' aligned doesn't mean it is aligned :?
http://forums.mtbr.com/singlespeed/why- ... ost8417635
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Re: Single Speed on a MTB tech advice

Postby Alistair » Thu Apr 11, 2013 5:27 pm

redcloud wrote:I just used a sprocket from a cassette lying around and put her on.


Get a single speed cog - they aren't ramped so keep the chain on much better.

If you use the right cog, chain tension and chain line it should work fine.
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Re: Single Speed on a MTB tech advice

Postby singlespeedscott » Thu Apr 11, 2013 6:35 pm

Agree. Your problem is your cassette sprocket.

The teeth just aren't long enough. A true single speed sprocket will have longer teeth with no shifting ramps. Also the base of the sprocket will be thicker which will reduce notching to your freehub body.

Also double check your chainline using a engineering ruler. 1/2mm out can be enough to derail it especially if you use to much tension in your chain.
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