Spoke Wrench Selection

This article will review selecting the correct wrench for bicycle spoke nipples.

1

Preliminary Knowledge

What Tools do I need?

Bicycle wheels rely on opposing tension from the spokes to suspend the rim around the hub. Each spoke acts as a skinny fastener, with the spoke being the “bolt” and the nipple being the “nut”.

As a nipple is turned and tightened, the spoke threads are drawn into the nipple, which increase the pulling or tension of the spoke. The process of adjusting spoke nipples and spoke tension is called “truing”. By adding the right amount of tension to the spokes, the wheel becomes strong and spins straight.

Nipples are commonly made of relatively soft materials such as brass or aluminum, both of which can be easily damaged by the wrong sized spoke wrench. There are many different sizes and even shapes of spoke nipples, and having the correct wrench is important.

Top: an incorrectly fitting wrench that is too large. bottom: The correct fitting wrench with better engagement.
Top: an incorrectly fitting wrench that is too large. bottom: The correct fitting wrench with better engagement.
2

Square-Shaped Nipples

The common bicycle wheel uses a square-shaped nipple. The best method to determine the correct spoke wrench size is to use a caliper and measure the nipple across the wrench flats.

Measure nipple size across the wrench flats
Measure nipple size across the wrench flats

It is important to know that the diameter, or so called “gauge”, of the spoke does not determine the spoke wrench size. For example, spokes that are 2mm in diameter (so-called “14 gauge”) will fit several different sized nipples and require different wrenches.

The table below lists a variety of square shaped nipple sizes, examples where they can be found, and the appropriate Park Tool wrench.

The Park Tool SW-7.2 spoke wrench is made with the three common spoke wrench sizes equal to the SW-0, SW-1 and SW-2.

3.17mm to 3.23mm square
Typical examples include DT Swiss, Sapim, Wheelsmith, and othersSW-0, SW-9, or SW-7.2
3.24mm to 3.30mm square
Typical examples include older bicycles using 2mm spokes such as Union and Torrington spokesSW-1 or SW-7.2
3.31 to 3.44mm square
Typical examples includes many value-priced bikesSW-2, SW-9, or SW-7.2
3.95 to 4mm square
Typical examples include some Shimano® wheels, hub-driven e-bikes, Campagnolo® Scirocco, and heavy duty bikes with “10g spokes”.SW-3
3.70 to 3.75mm square
Shimano® standard 3.75mm square

SW-14.5

4.2mm to 4.3mm square
Shimano® standard 4.3mm square

SW-14.5

3

star-shaped nipples

Nipple wrench fittings can also made to be a series of splines or a “star” pattern. Some patterns are proprietary, and wrenches are available only from the spoke manufacturer. The table below shows the Park Tool spoke wrenches for this style of nipple and lists some examples.

3.3mm diameter with 6 splines.
DT Swiss® Tricon nipplesSW-5
5.5mm diameter with 6 splines
Mavic® nipples with six splinesSW-13
6.4mm diameter with 7 splines
Mavic® R-sys spokesSW-12
9mm diameter with 6 splines
Threaded rim fittings that hold a square nipple. The fitting is installed with the wrench, but truing is done at the nipple. Examples include some Mavic® rims

SW-12 or SW-13

4

Hex-Shaped Nipples

Hex-shaped nipples appear similar in shape to the common six-sided nut. The Park Tool SW-11 is doubled sided, with ends to fit 5.5mm and 6mm hex-shaped nipples.

Examples of wheels using hex shaped nipples include some wheels from Fulcrum® and Campagnolo®. The 5.5mm side is for brass nipples. The 6mm side is for aluminum nipples.

Hex shaped nipple using a 6mm wrench
Hex shaped nipple using a 6mm wrench
5

Internal Nipples

There are wheel designs that place the nipple down inside the rim where they are not accessible from the outside. It is necessary to remove the tire and rim strip to access the nipple.

Manufacturers vary in the size of fitting used for these Internal nipple rims. It is often impossible to reach down inside the rim to measure the wrench flats. Contact the wheel manufacturer for the size of the nipple.

View of internal nipple installed on a bicycle wheel
Internal nipple in wheel
SW-15 spoke wrench used on an internal nipple wheel
SW-15 spoke wrench used on an internal nipple wheel
Internal nipple shapePark Tool spoke wrench
3.2mm SquareSW-16 or SW-15
4.7mm (3/16″) HexSW-16.3
5mm Hex

SW-17 or SW-15

5.5mm Hex

SW-18 or SW-15

6mm Hex

SW-19