ss drivetrain questions.... help please- Mtbr.com
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  1. #1
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    ss drivetrain questions.... help please

    i am using a 32T ring on the front, fit to my bontrager race cranks and a 18T cassette ring on the rear (with spacers on a 9 speed hub).
    my chain alignment seems really good, is there a way to check it without buying a tool of some sort, save some cash??
    tension? how tight should i make it?

    dumb questions, i know, new to the ss game - love it.

    i took it for the maiden voyage today and the chain would pop off when i was climbing....

    thank you....

    shaun

  2. #2
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    Usually, it is better to run chainrings and cogs that don't have shifting ramps or pins.

    ..8/9 speed cogs and 3 ring chainrings usually have the ramps and pins, which can make the chain jump off the teeth under the pressure of hard climbing, especially if the chainline isn't really straight, or your chain tension isn't correct.

    However, if you are using the correct SS chainring and SS cog, then it is either the chain is worn, the teeth are worn, the tension isn't correct, or the chainline isn't straight.

    1/2" play in the bottom run of chain with pressure on the pedal to hold the top run tight.

    Usually you can eyeball the teeth of the chainring and cogs to see if they are badly worn...or check them against a new cog.

    You can measure the chain with a good steel foot rule. There should be no more than 1/16" stretch in 12", pin to pin.

    Is your rear wheel alignment correct?


    R.
    It is inevitable ...

  3. #3
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    chainline

    Is the ring and cog strripped from a geared bike? If so, SS specific ones would work better. Ghetto checking chainline. You can use a steel yardstick or something similar just flush it up against the inside of the chainring and cog. Also pedal the bike where you can eyeball how the chain is catching on the ring and cog. The teeth should not rub hard against the chains plates.
    Hope that helps.

  4. #4
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    Bonking ... not feelin' well

    thank you, both of those inputs help.

    i am using a 9 speed cog, as i took it off my xtr der. i should start by checking your other methods, i beleive my wheel is aligned correctly. that too i have eyeballed

    i think i will order a spot 18T cog, that sounds like the right thing to do.

    i will try the others.

    any other help is great. i appreciate the input.

  5. #5
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    Chain alignment to perfection is a simple calculation. Use a small steel rule to determine the centre of the BB shell. Measure from this point to the centre of the front chainwheel (this is your chainline measurement. Somewhere between 45mm to 60mm. (For example say it is A=55mm)

    If your rear hub spacing as normal on an MTB is 135mm then half this (B=67.5mm) to give the centreline of the rear hub.

    Then B - A = 12.5mm

    Thus the centreline of the rear cog needs to sit 12.5mm from the inside face of the driveside dropout (effectively 55mm from the centreline of the rear hub to match the front chainline).

    Or you can measure the thickness of the cog (say 3mm) and half this (to give 1.5mm) then measure to the side of the cog from the dropout which is easier.

    So the 12.5 (to the centre cog) becomes 12.5 - 1.5 = 11.

    So simply set the cog up by adjusting the spacers either side until it is exactly 11mm from the dropout to outer face of cog.

    You can do this off the frame by measuring from the outer locknut of the hub instead and then check it when mounted in the frame.

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