Spoke Wrench Selection

Preliminary Knowledge

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.

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.

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 2.0 mm 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.

3.17 to 3.24 mm square
Typical examples include DT Swiss, Sapim, Wheelsmith, and others	SW-0, SW-9, or SW-7.2
3.26 to 3.30 mm square
Typical examples include older bicycles using 2mm spokes such as Union and Torrington spokes	SW-1 or SW-7.2
3.36 to 3.46 mm square
Typical examples includes many value-priced bikes	SW-2, SW-9, or SW-7.2
3.7 mm square
Found on some hub-drive e-bikes	SW-6
3.95 to 4 mm square
Typical examples include some Shimano® wheels, hub-driven e-bikes, Campagnolo® Scirocco, and heavy duty bikes with “10g spokes.”	SW-3
3.75 mm square
Shimano® standard 3.75 mm square	SW-14.5
4.2 to 4.3 mm square
Shimano® standard 4.3 mm square	SW-14.5

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 nipples	SW-5
5.5 mm diameter with 6 splines
Mavic® nipples with six splines	SW-13
6.4 mm diameter with 7 splines
Mavic® R-sys spokes	SW-12
9.6 mm diameter rim fitting 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

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 5.5 mm and 6 mm 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.

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.

Closeup of internal nipple inside rim

SW-15 spoke wrench used on an internal nipple wheel