The purpose of a truss rod is to counteract the tension placed on the neck by the strings. This tension is visible as a slight “bow” in the neck as you sight down it. It can be affected by movement of the wood from environmental influences like temperature and humidity. Although some amount of “bow” is normal for your guitar neck, problems can arise when it’s too concave (uneven action) or too convex (fret buzz).
To adjust your truss rod you need a set of automotive feeler gauges (.002 – .025), a Phillips screwdriver and an Allen wrench.
There are two different styles of truss rods found on Fender guitars and basses; the “Standard” truss rod and the “Bi-flex” truss-rod. Most Fender guitars and basses are equipped with a “Standard” truss rod (there are two types of “Standard” truss rod; one which adjusts at the heel of the neck and one which adjusts at the headstock, but both operate on the same principle). The “Standard” truss rod can only counteract concave curvature, for example: in a neck that has too much relief, by generating a force in the neck opposite to that caused by excessive string tension.
Fender also uses a unique “Bi-Flex” truss rod system on some instruments, including most American Deluxe and American Series Strats and Teles. Unlike the “Standard” truss rods, which can only correct a neck that is too concave (under-bowed), the “Bi-Flex” truss rod can compensate for either concave (under-bowed), or convex (over-bowed) curvature, by generating a force in either direction as needed for the correction.
Check your tuning. Install a capo at the 1st fret; depress the 6th string at the last fret.
With a feeler gauge, check the gap between the bottom of the string and the top of the 8th fret – see the specification chart below for the proper gap.
Neck Radius Relief
9.5″ to 12″ .010″
15″ to 17″ .008″
Adjustment at headstock (Allen wrench): If neck is too concave, (the guitar in playing position, looking up the neck towards the keys) turn the truss-rod nut counter clock-wise. If the neck is too convex turn the truss rod clockwise.
Adjustment at neck joint (Phillips screwdriver): If neck is too concave, turn the truss-rod nut clock-wise. If it’s too convex – counter clockwise.
Check your tuning, and then check the gap again with the feeler gauge. In either case, if you meet excessive resistance or need for adjustment, or you’re not comfortable with this adjustment, it might be time to send your guitar to Sweetwater, your authorized Fender Service Center.