Singlespeed & Fixed Gear - SS mtb chain tension question

Bikeforums.net is a forum about nothing but bikes. Our community can help you find information about hard-to-find and localized information like bicycle tours, specialties like where in your area to have your recumbent bike serviced, or what are the best bicycle tires and seats for the activities you use your bike for.



PDA

View Full Version : SS mtb chain tension question

mack_turtle
03-11-09, 07:33 AM
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.

AngryScientist
03-11-09, 07:52 AM
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.
stet
03-11-09, 08:23 AM
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.

dookie
03-11-09, 10:48 AM
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).