autoshifting (read FAQ and Sheldon's)

Discussion in 'Cycling Equipment' started by Derek King, Jan 29, 2004.

Thread Status:
Not open for further replies.
  1. Derek King

    Derek King Guest

    This is on an older Specialized Sirrus, of unknown year using Suntour derailers. I cleaned and
    lubricated the cable guide on the bottom bracket, according to suggestions on Sheldon Brown's page.
    I also adjusted the rear derailer according to his guidlines, and tightened up the shift lever
    (which helped briefly though it quickly loosens after use). I noticed the rear wheel seems loose on
    its bearings... I can easily wobble it by hand. Would this contribute to upshifting during hard
    pedaling? Someone at a bike shop said it could be that the gears are worn out. Not expecting more
    than $100 in selling this bike, would it be cost effective to replace any parts causing this
    problem? To this end, could someone recommend any reading so I can make the appropriate choices on
    replacement parts? Thanks, Derek
     
    Tags:


  2. A Muzi

    A Muzi Guest

    Derek King wrote:

    > This is on an older Specialized Sirrus, of unknown year using Suntour derailers. I cleaned and
    > lubricated the cable guide on the bottom bracket, according to suggestions on Sheldon Brown's
    > page. I also adjusted the rear derailer according to his guidlines, and tightened up the shift
    > lever (which helped briefly though it quickly loosens after use). I noticed the rear wheel seems
    > loose on its bearings... I can easily wobble it by hand. Would this contribute to upshifting
    > during hard pedaling? Someone at a bike shop said it could be that the gears are worn out. Not
    > expecting more than $100 in selling this bike, would it be cost effective to replace any parts
    > causing this problem? To this end, could someone recommend any reading so I can make the
    > appropriate choices on replacement parts?

    Huh? "the gears are worn out" is not a technical analysis.

    Yes, correct the wheel bearing problem before you have uneven wear of the cones. A loose bearing
    touches only one ball at a time and so wears unevenly and more quickly.

    Most friction downtube levers work better with a bit of oil on all the internal parts. Beyond that,
    three possible solutions which come to mind.

    1.Friction shifters need a mechanism to keep the parts from unscrewing when you move the lever.

    Campagnolo's classic design has a (originally chromed steel but later nylon) washer just outboard of
    the lever that engages two flats on the supporting post. Some Suntours use that design also. Early
    with steel and late models with nylon. The flats in a nylon washer can be worn such that the washer
    rocks and the outer screw loosens after a few shifts. That washer's replaceable.

    2.Other designs use a tab on a cover plate just under the screw head. That tab must engage a slot
    connected to something on the frame side of the lever. Suntour used that design as well. Look
    closely and see if there is such a tab that is not properly engaged. Compare to the left side as
    they are usually symmetric.

    3.One of Suntour's many nice gifts to cyclists was the Power Shifter which incorporated a small very
    effective ratchet. That ratchet pulled easily against the derailleur spring for a shift, yet
    engaged with some resistance such that, when shifting the other way, the derailleur spring pulls
    with you. Net result is a shifter that needs about equal force in both directions and almost never
    slips. Until the ratchet cracks. Listen to the left shifter. If it clicks when pulled back there
    is a ratchet. On disassembly not only the parts order, but the _ orientation_ is important. That
    is, do not flip the washers when you reinstall. Ratchets may be found in discarded shifters. All
    Suntour Power Shifts , road and MTB, used the same internal parts.

    If not one of those three things, write back with the shifter model.

    You asked about parts. If it is a down tube friction shifter, a new set with cables is $19.95 but
    should not be necessary
    --
    Andrew Muzi www.yellowjersey.org Open every day since 1 April, 1971
     
  3. Dianne_1234

    Dianne_1234 Guest

    On Wed, 28 Jan 2004 23:24:34 -0600, "Derek King"
    <[email protected]> wrote:

    >This is on an older Specialized Sirrus, of unknown year using Suntour derailers. I cleaned and
    >lubricated the cable guide on the bottom bracket, according to suggestions on Sheldon Brown's page.
    >I also adjusted the rear derailer according to his guidlines, and tightened up the shift lever
    >(which helped briefly though it quickly loosens after use).

    This is the whole problem. Keep it tight somehow or replace it with an indexed lever so it
    stays put.

    > I noticed the rear wheel seems loose on its bearings... I can easily wobble it by hand. Would this
    > contribute to upshifting during hard pedaling? Someone at a bike shop said it could be that the
    > gears are worn out. Not expecting more than $100 in selling this bike, would it be cost effective
    > to replace any parts causing this problem? To this end, could someone recommend any reading so I
    > can make the appropriate choices on replacement parts? Thanks, Derek
     
Loading...
Thread Status:
Not open for further replies.
Loading...