4mm Allen Nut Hot Rod Truss Rod

  • 113 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
In stock, ready to ship!


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 113 reviews
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Excellent truss rod

(Customer's Reviews)

I've been putting these in my necks for a number of years now and have had no problems at all. I guess the true test will come when one of my necks decides to start warping...


Ordered wrong size.

(Customer's Reviews)

Great rod. I wasn't sure how to determine size. "Fits most guitars" isn't exactly accurate. Measured total neck length 18" and ordered slotted. Instructions that came with rod explained how to measure. Had to return and reorder. Might want to put that explanation on the website??

Response from StewMac

Thank you for the suggestion. I am happy to submit this to our Web Team for review. Thanks again for the review and feedback!

-Spencer, Customer Support


Two way action 

(Customer's Reviews)

Easy and very effective. Way better than a banana boat style.


Problema con esta truss rod

(Customer's Reviews)

He usado estas truss rods por 4 o 5 años, han funcionado de maravilla, instalé una en un bajo de 5 cuerdas y al momento de hacer los ajustes finales el cilindro donde encaja la llave allen se abrió. Trate de girar para que quede suelta y poder sacarla y ya no pude por lo que tuve que retirar el diapason para poder extraer el truss rod. El bajo era un proyecto nuevo de lauderia, no me explico que pudo haber pasado, tal ves el cilindro tenia una cuarteadura, afortunadamente el diapason salio intacto y pude cambiar el truss rod, recomiendo revisar los detalles de la tuerca antes de instalar porque el material es muy blando


Hot Rod Truss Rod

(Customer's Reviews)

Easy to install . Works great !


works great

(Customer's Reviews)

I have used this truss rod several times. One time in particular I had to ask it to do more than I should have and it came through for me. only thing I don't like is 3/32" slot it requires.


Works fine but not necessarily a drop-in replacement.

(Customer's Reviews)

I ordered one with the 4mm Allen nut to replace the broken rod in a Seagull acoustic. I had to make the slot a little deeper as this rod is slightly taller than the original. I also found out that the adjusting nut lies a lot deeper into the body than the original, so it needs a long Allen wrench to adjust it. I thought about having the old longer adjusting nut welded on to extend it to the original position but decided against it because there was a possibility the threads might might weld together as well. (It happened when I tried getting the old rod rewelded).

Other than that, once installed it worked well, double action rods need a lot less turning of the adjusting nut, with less effort, to have an effect. Had to wait a week or so for it to be in stock but once in stock delivery was prompt as always.


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?.

Showing 10 of 113 Read more reviews >>

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.