Hi all I have a short scale Samick Baby bass. It's around 660mm, this is fret 5 on standard scale bass. It is smaller than a standard short scale bass. It had custom set of strings .80, .60, .40, .20. These were fairly hard to get, loose and never sounded resonant and lush like bass should. After some research online people said to get a 5 string bass set at .125 and cut the BEAD strings down to size. This works well. I have fitted the strings and trying to adjust the truss rod. Now I know these strings being thicker have more tension on them. So I am slowly tightening the truss rod. With a capo on fret 1 placing my finger on fret 16 where it joins the body checking around fret 7-12 for a credit card thickness. After 2 weeks tightening the truss rod every day or 2 slowly 1/2 turn, does not seem to be raising the action. I don't want to break the truss rod. Is there anything I have missed or can do to get this right? Note I have adjusted my 5 string bass and acoustic guitars when needed so am not new to this.
14 days of a half turn a day would be 7 full turns. Either the rod is broken or you're turning it the wrong way. Don't wait a day or two between half turns. That's silly. The neck will move as much as it's going to move from an adjustment in a few minutes or less.
The truss rod is not where you want to adjust the action. Use the truss rod to get the correct relief in the neck, then you can adjust the saddle height if you want higher action. If necessary, you can also adjust the nut to get the action where you want it. MonetBass is right, if you want more relief, you'd need to loosen the truss rod, not tighten it, but if you're going from 80s to 125s*, you don't want more relief. If you've turned the truss rod seven complete turns and it's not doing anything, there's a problem with the truss rod. * Which is a very bad idea. It's true that the same set of strings will have less string tension on a shorter scale length than they will on a proper scale instrument, but 125s are huge strings on any four-string bass, and the sub-short scale bass you're messing with was designed to be used with 80s. To give an example of how much string tension you're looking at, on a standard scale bass tuned to standard pitch, an average 80 GA string is at about 23 pounds. A 125 GA string is at about 55 pounds, more than double the string tension. Keep in mind that the scale length of your Samick extra-short scale bass is the same scale length as a Fender Stratocaster. Samick also makes lots of strat-scale guitars (including Squier Stratocasters). Unless the bass in question is a very high end instrument, they did not have a custom truss rod designed, engineered and manufactured specifically for that bass. They used what they had on hand, which in this case is a guitar truss rod. The heaviest gauge string on a stock Stratocaster is 42. It simply was not designed to handle a 125 gauge string. Want to know why you've turned the truss rod seven full turns and it hasn't done anything? .
All is good now. Truss rod loosened and enough gap is now there. Now adjusted the action at the bridge all seems good now.
You'll want to reset the intonation after tweaking the truss rod and saddle height. Glad you got the action where you want it!
