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Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

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Old 03-11-09, 07:33 AM   #1
mack_turtle
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SS mtb chain tension question

I have a a Gunnar Rockhound frame (415mm chainstays) with vertical dropouts and and a Paul Word hub. it's geared at 32/18, which is a bit spinny even for a noob like me. the old chain was stretched to hell so i got a new KMC 710 "kool" chain and it's way too tight. i can never get the tension just right. if i put a half-link on it, it will flop all over the place. currently, i took the shouldered centering washers off the hub bolts and i am running the axle slightly below the center of the dropout. it doesnt seem like a very solid way to set up a bike.

i am considering two options:

1. add a half-link to the chain (i have one in my toolbox) and put a chain tensioner on it. i can get a tensioner from my LBS for $20. i think it's that DMR tensioner, but i'll have to double check.

2. get a 17t freewheel, which would bring my gearing up a bit and should fit just about right according to my calculations on this site: http://eehouse.org/fixin/javafmu.php

the problem with (2) is that, once the chain starts to stretch, it will be loose and i will have to buy a new chain again or get a tensioner anyways. but i want that higher ratio at some point, might as well start now.
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Old 03-11-09, 07:52 AM   #2
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i have heard some great things about surly's singleator, thought its a little more than $20, thats the option i would pursue, then, no matter how much your chain stretches, you should be good.

the reliability of that alone would convince me, though a tensioner hurts the "clean" look a little, i think its worth it.
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Old 03-11-09, 08:23 AM   #3
stet
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chains stretch as cog teeth pit. if you've only replaced the chain, you'll find it difficult to set tension because your freewheel's teeth are worn (and probably the chainring as well). new chain different tolerances. on singlespeed mountain bikes you usually have to replace the whole drivetrain more often as compared to street geared bikes because the load of you pedaling is distributed over less surface area.
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Old 03-11-09, 10:48 AM   #4
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my experience, in ~5 years of SSing on a conversion:

half-link will break (so will a SRAM PC1 chain).
spring-loaded tensioners will drop the chain on really rough terrain.
use an eno hub (preferred), or a bolt-on tensioner (i like rennen).
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