4mm Allen Nut Hot Rod Truss Rod

  • 106 Reviews
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12-1/4" overall length

Item # 2550
In stock, ready to ship!


6 or more $13.74
12 or more $12.95

14-1/4" overall length

Item # 2551
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6 or more $13.91
12 or more $13.11

18" overall length

Item # 2552
In stock, ready to ship!


6 or more $14.78
12 or more $13.93

24" overall length

Item # 2553
In stock, ready to ship!


6 or more $18.26
12 or more $17.21
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4mm Allen Nut Hot Rod Truss Rod

About This Item

A smaller 4mm (5/32") Allen nut for most instruments. Smooth two-way action corrects upbow and backbow, giving complete control over the neck.

Easy to install. The Hot Rod® fits in a straight channel. For proper operation, this truss rod must be installed so that the active rod (the rod with the adjustment nut) is below the passive rod. A wooden filler stick is not required.

Smooth 2-way action with superior strength for stubborn necks.
Our Hot Rod neck adjustment system features twin rods in threaded brass collars. The stainless steel active rod turns for smooth neck alignment, with 2-way action to correct upbow and backbow.

The Hot Rod requires an access cavity for the adjustment nut, and a straight 7/32"-wide x 7/16"-deep slot (measured from the bottom of the fretboard) for installation.

Pick the Hot Rod Truss Rod size you'll need:
(overall length includes the nut)

Resonator guitar
Acoustic guitar with 12th fret at the body
Acoustic guitar with 14th fret at the body
Electric guitar

We've designed the Router Bit for Hot Rod Truss Rods especially for routing your neck to fit our truss rods.


Product Instructions

Hot Rod Adjustable Truss Rods

Installation and adjustment instructions for Hot Rod Adjustable Truss Rod.

    • Item #
    • Weight
    • 2550
    • 0.1970 lbs. (0.09 kg)
    • 2551
    • 0.2320 lbs. (0.11 kg)
    • 2552
    • 0.2960 lbs. (0.13 kg)
    • 2553
    • 0.3850 lbs. (0.17 kg)

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  • 4.46 average rating from 106 reviews
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Positive first experience

(Customer's Reviews)

This is my first time installing the Hot Rods. Up until now I've been using a fairly typical welded two way truss rod, but had heard many good things about these Hot Rods.
Installation was a bit fiddly compared to my previous installs, but I think that comes down more to the fact I didn't have the correct size router bit, so I made do with a 5mm and made two passes.
They require a deeper slot than I'm used to, which initially concerned me, but I don't see that it will be a problem unless a super slim profile is required (which I don't do)
Overall they seem to be well made and work smoothly


Easy to Use and Install If You Know What You're Doing

(Customer's Reviews)

I bought two of these for a few guitars I'm building from scratch. I have installed one so far in a fender-style neck. The rod works great, especially when installed in a truss rod cavity routed by the specialized hot rod router bit. I am very pleased with my purchase.


4mm Allen Nut Hot Rod Truss Rod

(Customer's Reviews)

I've used these rods for a long time, no failures.
what more could you ask for?.


Wouldn't build without them.

(Customer's Reviews)

I have used several of the allen headed Hot Rod truss rods and they work extremely well.
I would highly recommend getting the router bit designed for them because the better they fit the slot the better the truss rods work.


The Best !

(Customer's Reviews)

really good quality ! the best on the market
I use Them for all my builds !


Truss rod

(Customer's Reviews)

Building a new guitar but haven't installed the truss rod yet...looks like a quality part.


Good quality truss Rod.

(Customer's Reviews)

I like using the Hot Rod Truss Rod with the 4mm Allen Nut. I can make a small access hole by extending the truss rod channel buy about an 1'' and have enough room to use a allen wrench with a ball end for easy access. I would recommend using the longest truss rod as possible to cover the entire fret board. It takes very little pressure to make an adjustment.


Does the job

(Customer's Reviews)

This isn't my favorite truss rod, but it does the job. It isn't as stiff as I prefer, but I've used it occasionally and haven't had one fail.


Truss rods

(Customer's Reviews)

I use these on acoustic and electric and they work great! Easy to install, have not had any issues to date!


It Broke Again!

(Customer's Reviews)

OK - I had one of these break with the nut shearing off the rod while doing final set-up on the last guitar I built. StewMac was great about sending me a repair kit and they assured me that this issue was not unprecedented, but very rare. I like the design so I decided to take my chances and use one of these again.

Shame on me...The exact same failure happened again!! Looking at a my experience plus a couple of recent reviews with the exact same problem it looks like there was a bad batch from the manufacturer or something.

Stewmac has good stuff and I'll continue using them for a lot of other parts and tools, but I strongly advise that you do not buy this truss rod.

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StewMac PDF Catalog, page 74 See 4mm Allen Nut Hot Rod Truss Rod
on page 74 of our StewMac Catalog PDF

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  • Hot Rod® is a registered trademark of Stewart-MacDonald Manufacturing Company, Inc.