Seasonal Truss Adjustment

Discussion in 'Hardware, Setup & Repair [BG]' started by CharlieC, Mar 4, 2014.

  1. CharlieC

    CharlieC Supporting Member

    Aug 20, 2010
    New York, NY
    To maintain the very slight relief I prefer in my bass necks, here in New York I need to perform a 1/4 turn or so truss adjustment, seasonally, every 6 months.

    To be honest, I do not recall which seasons requires tightening and the others, loosening, as I simply measure the gap at the 8th fret and do the necessary.

    To help educate and also predict the required adjustment, my question is:

    When going from dry/cold to moist/warm, what is happening to the neck wood to affect the relief and how does it relate to the necessary truss adjustment, and vice-versa, from moist/warm to dry/cold?

    Thanks in advance!
  2. Turnaround

    Turnaround Commercial User

    May 6, 2004
    Toronto Canada
    Independent Instrument Technician, and Contractor to Club Bass and Guitar - Toronto
    As the relative humidity lowers, wood looses moisture and shrinks. Most of the shrinkage is across the grain (in the width of a typical board), but there is some end-to-end shrinkage as well.

    The truss rod does not change in length with changes in humidity. So as the weather dries out, the neck of you bass shrinks a tiny bit, but the truss rod doesn't. That's effectively the same thing as loosening the trussrod. And as we know, if you loosen the truss rod, it will be counteracting the pull of the strings less, so the neck will bow away from the strings a bit.

    The opposite occurs when the humidity increases.

    Hope this is clear.
  3. CharlieC

    CharlieC Supporting Member

    Aug 20, 2010
    New York, NY

    Thank you, your explanation is very clear