Shim dimensions question.

pbassist · #1 11-26-2008, 05:56 PM

Hi,

I just got a Gotoh 201b bridge for my MIM p-bass, and I need to add a shim, as with the current fender vintage bridge the saddle is right on the bridge plate. I have calculated that I would need to raise the strings 7'5mm (around 0.3 inches) in the bridge position, including some margin to play with the action.

I have a piece of alder around here that I can use. The question is, which dimensions would you suggest for the shim?

Thanks (and please excuse my bad English).

Turnaround · #2 11-26-2008, 06:47 PM

A thin shim can make a big difference. My advice is to start by using a bit of a business card and fit it in the space between the end of the neck pocket nearest the bridge and the nearest set of screw holes. Once in place, re-attach the neck, string it up, tune and adjust the bridge height to suit. One business card thickness ought to be enough, but if it isn't, add a second piece. Then if you want, you can substitue wood pieces for the total thickness of the business card(s).

JustDavid · #3 11-26-2008, 07:48 PM

Lots of neck relief has the saddles want to be higher. A good source suggested I try a neck relief of 10 to 15 thousands of an inch.

Did so. VERY glad I did; sweet low action.

pbassist · #4 11-26-2008, 09:10 PM

Quote:

Originally Posted by JustDavid

Lots of neck relief has the saddles want to be higher. A good source suggested I try a neck relief of 10 to 15 thousands of an inch.

Did so. VERY glad I did; sweet low action.

Thanks, but in fact I have my neck almost straight to have lower action, I have not other choice than shimming (I would have shimmed the bass even keeping the fender bridge). Currently I have some buzzes in the first frets so there is not much that can be done here.

pbassist · #5 11-26-2008, 09:14 PM

Quote:

Originally Posted by Turnaround

A thin shim can make a big difference. My advice is to start by using a bit of a business card and fit it in the space between the end of the neck pocket nearest the bridge and the nearest set of screw holes. Once in place, re-attach the neck, string it up, tune and adjust the bridge height to suit. One business card thickness ought to be enough, but if it isn't, add a second piece. Then if you want, you can substitue wood pieces for the total thickness of the business card(s).

Thanks. One question will be any sonic difference between using a paper business card and wood? The piece of wood I have is 3mm (0.12 inches) thick, and I would need to cut it, sand it...

202dy · #6 11-26-2008, 09:30 PM

There will be little, if any sonic difference. Paper used to be wood. The sound will be similar. It is doubtful that anyone, including the player, will be able to hear it in a mix.

JustDavid · #7 11-27-2008, 08:59 AM

Quote:

Originally Posted by pbassist

Thanks, but in fact I have my neck almost straight to have lower action, I have not other choice than shimming (I would have shimmed the bass even keeping the fender bridge). Currently I have some buzzes in the first fret so there is not much that can be done here.

Yep, shim time.

I'm thinking that 1st fret buzz might be nut height &/or low neck relief (anyone smarter than I on this, chime on in). I flattened an ABG neck to get past a massively high bridge saddle & found the 1st fret buzz issue, as well as some weird 'back-buzz'. Issues went away upon restoration of a very modest neck relief.

Turnaround · #8 11-27-2008, 03:43 PM

If the buzz occurs when fretting at the first fret, then the nut is not the issue. The nut is not part of the equation in that position. Check your relief - itt may not be enough.

pbassist · #9 11-27-2008, 03:54 PM

Thanks for the advice, but was an errata, it should say "in the first frets". It's due to I have my neck almost flat in order to have low action.

Turnaround · #10 11-27-2008, 04:02 PM

OK - if it's in the first frets positions, then it is almost certainly a problem of not enough relief.

pbassist · #11 11-30-2008, 11:35 AM

Finally I shimmed the bass, and I had to use 3 business cards (around 3*0.05mm =1.5mm ~ 0.06 inches total), around 2cm (0.8 inches) long and the width of neck pocket. That raised the height of the strings only 0.5cm (0.2 inches) at the saddles position. I think that I should have done the shim longer (now looks fine but maybe I will change the shim in the future).

Thanks to everybody for the advice.

JustDavid · #12 11-30-2008, 02:46 PM

I haven't a lot of experience but 3 card thicknesses seems like a LOT of shim height to me.

0.8" long shim seems plenty long. My shims usually end up 1/2 to 1" narrower than the neck pocket & about 3/8" long. I'm eager to find out others' opinions & experiences on this, but I don't think a really long shim is needed.

Still have the buzzing in the frets near the nut?

pbassist · #13 11-30-2008, 07:02 PM

Well, I forgot to tell this: I cleaned a bit the neck pocket (it has some paint on it and was not very well finished) and I removed part of a QC decal that was on the neck (my original idea was using a wood shim, so I removed it to have better wood to wood contact), so this could count for 1 of the 3 cards.

I think that a longer shim makes the body/neck angle higher than a short one with the same height, as the border of the shim is closer to the end of the neck pocket... maybe 2cm is bit more that the length I really have (I did not measured it), but it has at least 1.5cm (0.6inches) for sure.

About the buzzes, I added some neck relief (around 0.01" at the 8th fret) and I lowered the action a bit (around 0.75mm (0.03 inches) at the 12th fret (while pressing the 1st one)), now I just get an uniform and small buzz between the 1st-15th frets (I could lower the strings even a bit more), but lots of buzzes between the 16th-20th frets (just above the neck pocket, I think that these frets are not affected by the truss rod). I opened another thread about this issue here:

http://www.talkbass.com/forum/f30/heads-up-ebay-rickenbacker-scam-59334/#post659481