Is a matching bridge radius necessary?

Discussion in 'Technical Side of Things' started by Stefan, May 16, 2017.

  1. Stefan

    Stefan Country Gent

    Jan 20, 2016
    After bothering enough about the flawsy Compton bridge, especially about "no return policy" for unusable stuff, I've read interesting statements about fretboard matching bridges on
    The feeling with the matching Tru Arc on the Hot Rod is a bit uncommon to me, since the inner strings are a tad higher.
    One says the bridge should have a wider radius than the neck (Dan Erlewine guitar repair book). On the other hand- the difference between 10" or 12" radius is just about 0.06...
    What's your opinion?
  2. BuddyHollywood

    BuddyHollywood Gretschie

    Sep 11, 2009
    Venice, CA
    I like a matching radius between the bridge and the fretboard. It allows me to get the strings as low as possible without buzz. You can get the best playability out of a guitar when all of the variables are balanced with each other.
    Salsg, ZackyDog and Stefan like this.
  3. Wozob

    Wozob Country Gent

    Jul 6, 2014
    The Netherlands
    I have the action higher on the low E than the high e. I also use strings that have the highest tension on the D and G string. I also like a pretty high action in general. These all add up (from an engineering POV) to a higher radius on the bridge than the fretboard. But like you already stated: the difference is minimal.
    Ricochet and Stefan like this.
  4. Stefan

    Stefan Country Gent

    Jan 20, 2016
    From the gear page:

    "Yeah, the radius at the saddles is routinely set up flatter than at the nut.
    I sometimes call this a "poor man's compound radius".
  5. ZackyDog

    ZackyDog Friend of Fred

    Feb 6, 2015
    In the USA
    In my experience, it only helps. I feel like it facilitates making more complex chords.
  6. Stefan

    Stefan Country Gent

    Jan 20, 2016
    After another hour reading I guess the matching bridge/fretboard radii is a deception since the strings should be conical from nut to bridge.
    On my Guild I like the feeling of the matching bridge, but it feels a bit uncommon on the Hot Rod. If you set up the bridge to the perfect radius both E-strings should have the same height. But this causes a disadvantage on your string action and also a tonal disadvantage (the bass strings should be higher).

    Honestly- there must be a reason why Gretsch uses 12-14" radii on their bridges :) By the way, on GP someone else starts the same discussion.
  7. Hammerhands

    Hammerhands Country Gent

    Aug 26, 2011
    The slots have different depths, the strings have different amplitudes.
  8. Dead Roman

    Dead Roman Country Gent

    Dec 22, 2015
    No, and sometimes it's not even ideal, depends on what you are trying to accomplish.
    Gretschmen65 likes this.
  9. Hammerhands

    Hammerhands Country Gent

    Aug 26, 2011
    Is it that much, or 0.006"? [0.01" over 2.25"]
    Last edited: May 16, 2017
  10. Aymara

    Aymara Friend of Fred

    Jul 6, 2013
    For my preferences a matching radius is a must ... ultra low buzz free action.

    If the E strings will have identical action or if the bass side of the bridge is a bit higher depends on the guitar and the used strings.

    Though I use Gibson Brite Wires in .10 on both, my Penguin and my Les Paul, the later needs a bit higher action on the bass side, the Penguin doesn't.
    Atomic likes this.
  11. mschafft

    mschafft Gretschie

    Jan 19, 2017
    If parts allow I tend to match saddle radius to fretboard radius and use a 0.017 string height at the nut. Anything in that ballpark will be useable for me.
  12. Ricochet

    Ricochet I Bleed Orange

    Nov 13, 2009
    Monkey Island
    I suppose for a 12" radius fretboard I'd want 12.5 or 13", but for practical reasons 12" is fine for me.
  13. Ricochet

    Ricochet I Bleed Orange

    Nov 13, 2009
    Monkey Island
    Sorry to hear your Compton is not up to snuff Stefan. I have about 13 Comptons and most of them are on my guitars. Workmanship and functionality have always been stellar for me.

    What is the context of the quote above?
  14. Stefan

    Stefan Country Gent

    Jan 20, 2016
    In addition to the starting post.
  15. Ricochet

    Ricochet I Bleed Orange

    Nov 13, 2009
    Monkey Island
    Enough to make me squint...;)
  16. benjwri

    benjwri Country Gent

    Oct 27, 2011
    Central ON Can
    From a post April 2015
    So from a 10" to a 12" the total difference would be about .003" ...about the thickness of a piece of paper.
  17. Henry

    Henry Gretschified

    Apr 9, 2014
    Are you sure you can trust that guy?
    benjwri likes this.
  18. benjwri

    benjwri Country Gent

    Oct 27, 2011
    Central ON Can
    The 'math' is simple enough...just plug it into pythagerous...r=the hypoteneus, c/c distance /2 is the opposite side, difference in adjacent sides is the number you're looking for. Can also do it with trig...

  19. Hammerhands

    Hammerhands Country Gent

    Aug 26, 2011
    Here's the math I did, is it right? I put it in a spreadsheet but I can't upload the spreadsheet.

    You need to find out how much of an arc** of the radius of the fretboard you need to fit half the width of the fretboard or bridge, then calculate how much the fretboard would rise.

    (1-cos(arcsin(((2.25"/2)/10")))*10" = 0.06348"
    (1-cos(arcsin(((2.25"/2)/12")))*12" = 0.05285"

    [I see this definition could make it easier.
    cos(arcsin(x)) = (1-x^2)^(1/2)]

    **it's 5.4 and 6.5 degrees, 8.9 degrees for 7.25"
    (1-cos(arcsin(((2.25"/2)/7.25")))*7.25" = 0.08782"
    (1-cos(arcsin(((2.25"/2)/9.5")))*9.5" = 0.06685"
    Last edited: May 17, 2017
  20. hcsterg

    hcsterg Country Gent

    Feb 13, 2012

    I put on my G6119LH Tennessee Rose a Gretsch RBB and the guitar was poorly playable : outer strings were too high and/or center strings buzzed.

    Then I checked the radiuses with radius gauges : the fretboard was 10", and the RBB was 16".

    So with a big vise, with the help of steel and wood shims, I re-radiused the RBB from 16" to 10". The guitar is now perfectly playable and comfortable, with correct action and no more buzzes.

    So yes, it's better if the bridge radius matches as close as possible the fretboard radius. I mean : if you have a 10" radius bridge for a 9.5" fretboard radius, that's also correct. Maybe 12" for 10" would be the limit, but for sure, 16" for 10" was unacceptable by my experience.

    Aymara likes this.
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