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Oddities in relief

Discussion in 'Hardware, Setup & Repair [BG]' started by Theonestarchild, Feb 10, 2006.

  1. Theonestarchild

    Theonestarchild Artfully lost

    Aug 23, 2005
    North Carolina
    This is odd. I suspect it's a bridge adjustment. I adjusted the truss rod for the final time, and the D and G strings are vibrating the frets. But not the E or A. I suspect this means the saddles need to come up a bit on the high side, and could probably be dropped a bit on the low side. Where do I find the allen key? What size is it? Also, is there a way to get the action down high up on the neck? I've heard shimming, but I don't know how or where to do it? :help:
  2. theshadow2001


    Jun 17, 2004
    You could raise the D and G and lower the E and A as you've said but I would try and make another neck adjustment to get the action a bit more to you liking since you obviously have it the way you like now.

    Shimming could be done by removing the nut and sanding down the underside of the nut leaving the grooves intact. This could be difficult enough to do with out doing some damage to the nut or bass. However the bass Im working on at the moment seems like the nut is going to come out failry easily. Alternitavely you could get as set of files from stew Macdonald and file down the grooves in the nut. Either way has its merits and disadvantages.

    Anyways take what I say with a pinch of salt because Im far from an expert on the matter just my two cents
  3. How are you going about checking the relief when you're adjusting the truss?
    Try not to think of the truss as an "action" adjustment. Sure, it will change string height and action across the neck, but it's mostly for setting that small amount of forward bow in the neck to allow room for the strings to vibrate freely.

    The D and G open strings are buzzing at proper tune? Yeah, I'd automatically raise both of those just a touch at the saddles, just enough to get rid of the buzz.

    Different bridge saddles require different tools and allen-wrench sizes. You should have at least the truss wrench, saddle wrench, and screw drivers for setting intonation and pickup heights. A good setup usually requires adjusting all of these.

    How do you get the action down at the higher frets? First it's critical that you have the relief set right. In the past, I would tighten the truss to bring the upper-fret action down, but this doesn't work with all basses and necks. You can easily start to pull a backbow in the neck, and then you'll have lower-fret buzzing problems. So.. get the relief right, set the saddle height to give a good, even action at the lower frets (no buzz), then look at the upper frets. If action is still quite high, then YES , a shim could really help under the neck heel. I've done several basses where this is the only option that helped. It really made an unplayable bass very playable.
    I would not mess with the nut, unless it's the adjustable type, which it probably isn't.

    Let us know how it works out for you..

  4. Theonestarchild

    Theonestarchild Artfully lost

    Aug 23, 2005
    North Carolina
    Ok, I set the relief as tight as it would go, after waiting over a week since the last adjustment. It's dialed in with a backbow (very small) without strings, and a relatively small bow with the tuning dialed in. It still has more relief than say my friends guitars, but it is a bass. It's VERY tight action up at the first frets. Like... close enough that you can kind of put your finger on the strings and it plays it as the first fret. I like it. It seems like the neck is pitched out towards the crowd a bit while I play. In the past, I would have thought it was the relief, but now I realize that it is more than likely the neck pocket angle, or the neck angle. I'll probably make adjustment to the bridge with the small allen key I've yet to find in any store. Shimming from the nut? WHAT?!?! :-\ Why?! Oh, and filing down the nut any further would be a bad idea for me. It's got a sick amount of string groove.
  5. Ok.. sounds like you've got the relief you want. Raise the D and G string saddles until you don't have any open-string or lower fret buzz, and even out the action of all 4 strings until she plays nice at the lower frets.
    If you still have a high action at the upper frets you have a couple of options.
    1. Check the neck again carefully to see if you can tighten the truss a bit more without losing all of your relief at the 8th-9th frets. If it's already a small amount of relief, then a shim is needed.
    2. If you still have a moderate amount of relief, you can experiment with tightening the truss just a touch. Just a small amount will bring the upper-fret action down alot, and you don't really want to try to completely even out the action all the way down the neck. The upper fret action should be slightly higher.
    3. If you go with the shim, you'll only want the shim to fit under the neck heel at the screws closest to the body. This will tilt the neck angle a bit, evening out the action. If you added a shim to the entire neck-pocket area, it would bring the the action down without changing the angle, and you need to change the angle.
    A thin shim goes a long way. I've used an aluminum soda can (easy to cut with scissors) for this, and it worked well. Others might argue that aluminum is soft and might hurt sustain, but it didn't with the basses that I worked on.

    I believe if the bass was engineered right, it should not need a shim, but this isn't always the case..
    Good luck, and let us know how it goes.

  6. about your bridge adustment..

    I too was at a loss for a tool, it looked like an allen wrench would fit but it wasnt quite right and didn't work. I used needlenose for an emergency adjustment (bad idea, stripping the screws I know), but my dad appeared with a very thin screwdriver, and the end was a ....hex nut? or something. The end is a very tiny, flat, hexagon, and the sides angle up. It works perfectly.
  7. jeffhigh


    May 16, 2005
    Sure it will lower the action, but you will then need to raise the bridge saddles even more to get rid of the buzz.
    If the relief is right (about a business card thickness) then just get the right allen key and adust the saddles.
    That is all you need to do.
  8. Yes, the saddles will have to be raised if you shim. This is something to keep in mind if your saddles are already high. If they are, you might not be able to raise them enough. I did not have this problem on the 2 basses that I decided to shim. It depends on how much shim you use (or need to use).
    Remember that some basses (older Peaveys come to mind) had a micro-tilt screw at the neck plate for adjusting the neck angle in the pocket.

    If you have neck relief set good, action is nice at the lower frets, but action is high at the upper frets, a SHIM is the way to go.. It's not a complicated project, and if you can always go back if it doesn't work for you.

    Bridge Saddle tool: Keep in mind that allen-wrenches come in both SAE and Metric sizes. Many basses use the Metric size. I had 3 different SAE sets and I still had to run out and buy a Metric set for my ESP-LTD.

  9. jeffhigh


    May 16, 2005
    I am not anti shim. I have a bass and a several guitars that I have shimmed, but I use it only where the bridge saddles have bottomed out or the break angle on the saddles is insufficient.
    It does not miraculously achieve a better action high on the neck any better than dropping the saddles
  10. No offense, but I disagree in this case. Tilting the neck (that's the kinda shimming we're talking about) can substantially lower the action at the upper frets without changing action much at the lower frets. When you add a shim to the end of the neck heel, closest to the body, you tilt the neck. This is what I'm suggesting. If you added an even shim to the entire pocket, you wouldn't be changing the angle, but simply raising the entire neck evenly. This is what one might do if their saddles were bottoming out as you've described.
    It's surprising just how thin a shim is actually needed. On one bass, I went with a thin piece of plastic as a test, and it was WAY TOO MUCH.. The thin aluminum was just right.

    Many basses never require a shim. Most of them are engineered to have a decent action at the higher frets when the truss is adjusted properly. Some bassists that need more relief due to heavier playing style might find that this leads to a higher action at upper frets. The tilt shim works for this.


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