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Double Bass Moving bridge

Rocktometrist

Rocktometrist

Oct 3, 2012
479
521
Seattle
#1
I got a new bass about a year ago, and have a had a consistent issue--the bridge slowly but steadily slides laterally toward the G-string, and about once a month I have to knock it about a 1/4" or more back toward center.

I can't figure out why this happens. I though it might be the bass bag--maybe grabbing some combination of handles applies pressure to the bridge--but after looking it over, I think the bag is in the clear(?).

Any ideas on why this happens, or how I might stop it? Seems like the constant moving and adjustments might be harmful to the health of the bass. Is putting something slightly tacky under the bridge an option, or is that crazy?
 
#5
The tailpiece appears to be centered, and to my eye, at least, everything appears to be straight and true. Still hoping it's the bag or maybe something that occurs when I load the car (there is some Tetris involved when my guitarist buddy needs a ride)...guess its time for a trip to the luthier to make sure. :hmm:

Here're pics of the bass from when I first got it:

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#7
As I see it in the photo, neither the fingerboard nor the bridge appears to be centered between the f-holes. Note the overlap between the bridge and the E-side f-hole, but not on the G side. In the photo, the bridge now appears to be correctly aligned with the fingerboard, but if it tends to slide more toward the G side, then it's probably trying to center itself on the top plate. Just my guess.
 
#11
It looks to me like the bridge is centered on the fingerboard - but the fingerboard and bridge are too far to the bass or E string side.

When I look at the tailpiece and saddle - it looks like the saddle may be in the right place and that (at the time the photo was taken) the tailpiece is leading off toward the bass or E string side to align with the bridge.

This could explain why, over time the bridge shifts right (toward the G string side) because the strings are trying to align themselves in a straight line from nut to tailpiece - thereby dragging the bridge over.
 
#12
Judging from the pictures, your neck is definitely pointed off to the bass side. This may or not be what's actually causing your bridge to move, but I doubt it's helping. Especially if it consistently only moves to the trebly side. As mentioned, when your bridge is aligned with the fingerboard, it's not truly centered between the f-holes. It's possible to have a new fingerboard installed that's cheated a little bit to help realign your bass. It's also possible to have a bridge fitted with one leg cut shorter than the other. This allows the bridge feet to be centered between the f-holes, but still have the top of the bridge aligned with the fingerboard. The bridge will be leaning into the strings a little bit and hopefully stay put.
 
#13
I think it's virtually impossible to tell from photos. Looking at the pegbox/scroll, the photo is taken at a slight angle, so I would be suspicious of any guesses about how the bridge is centered. Not to mention that cameras have a tendency to warp the image, so you can't really tell if something is actually straight or not. That said, it does look a little off to me.

I'd take it in and have a qualified luthier take a look at it so you're not guessing as to what's wrong with it.
 
#14
A LOT of necks are misaligned on double basses;a lot of bridges also tend to move due to alignment or tension issues. In basses of this type, slick nitrocellulose or such finishes allow things to move pretty easy. A simple solution is to take a little bit of 220 grit sandpaper and slightly rough up the bottom of the bridge; it will give it just a touch more "bite" and won't slip around as much. At times I've also been known to take a little bit of steel wool and also rough up the finish under where the bridge sits.

Good luck!

j.
www.condino.com
www.kaybassrepair.com
 
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#16
Thanks for the responses. I think the photographs are taken at slight angles that accentuate the misalignment of the neck--but after looking at the bass again carefully, it does appear it could be be ever-so-slightly off-kilter. That said, it's very slight, and the bass plays and sounds great, so I'm not really inclined to do a neck reset unless it's an instrument health issue.

It's currently strung with Pirastro Obligatos with relatively low action, so the string tension is pretty low I'd guess--and the finish is indeed pretty slick. Roughing up the bottom of the bridge might just do it. Thanks for the tip, James.
 
#18
james condino said:
A LOT of necks are misaligned on double basses;a lot of bridges also tend to move due to alignment or tension issues. In basses of this type, slick nitrocellulose or such finishes allow things to move pretty easy. A simple solution is to take a little bit of 220 grit sandpaper and slightly rough up the bottom of the bridge; it will give it just a touch more "bite" and won't slip around as much. At times I've also been known to take a little bit of steel wool and also rough up the finish under where the bridge sits.

Good luck!

j.
www.condino.com
www.kaybassrepair.com
Click to expand...

James, would a bit of rosin dust under the feet be a good idea?
 

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