A spoke nipple holds a
bicycle wheel
A bicycle wheel is a wheel, most commonly a wire wheel, designed for a bicycle. A pair is often called a wheelset, especially in the context of ready built "off the shelf" performance-oriented wheels.
Bicycle wheels are typically designed ...
's rim to each
spoke
A spoke is one of some number of rods radiating from the center of a wheel (the hub where the axle connects), connecting the hub with the round traction surface.
The term originally referred to portions of a log that had been riven (split ...
.
The spoke nipple is a headed cylinder with
threading on the inside through part of its length (there is an unthreaded lead-in nearest the "flats"). Traditionally, the nipples fit in holes in the rim, so that the head of the nipple is on the outermost part of the rim, while the other end of the nipple points inwards towards the hub. Many different types of nipples are now available, including internal nipples that sit entirely within the rim and can only be adjusted by removing the tire, as well as externally threaded nipples that thread into the rim (such as those used by Mavic Ksyriums). The threading grasps the spoke, so turning it increases or decreases
tension in the spoke and influences the position of the hub relative to the rim.
Thread pitch can vary with thread size, but is 0.454mm for common spoke thicknesses, which use thread types Fg 2, Fg 2.3 or Fg 2.6.
Since spoke threading and nipple threading must match, boxes of spokes usually include a similar number of nipples. Weight savings or the need for great strength due to building a wheel with few spokes might call for obtaining different nipples from those shipped with the spokes. Standard materials for nipples are
brass
Brass is an alloy of copper and zinc, in proportions which can be varied to achieve different colours and mechanical, electrical, acoustic and chemical properties, but copper typically has the larger proportion, generally copper and zinc. I ...
(usually
nickel-plated) and
aluminum
Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...
. Brass is heavier but more durable and less prone to corrosion, rounding of flats while tightening, breaking and
galling
Galling is a form of wear caused by adhesion between sliding surfaces. When a material galls, some of it is pulled with the contacting surface, especially if there is a large amount of force compressing the surfaces together. Galling is cau ...
; aluminum is far lighter. If using aluminum nipples, the spokes should be long enough to engage the full length of spoke nipple threads so that the load is carried from the spoke to the top of the nipple.
If the spoke is only part way into the nipple, the nipple carries the tension load and is prone to breaking from fatigue failure. Also, with aluminum nipples care and a good spoke wrench are needed to avoid rounding the flats while tightening. Recently,
titanium
Titanium is a chemical element; it has symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength, resistant to corrosion in ...
nipples have become available from both US and Chinese sources. Proponents of titanium nipples suggest that they combine the advantages of brass and aluminum nipples (strength and weight, respectively), while being more
corrosion resistant than either material.
See also
*
Spoke wrench, for a discussion on the three major nipple sizes
References
External links
DT Swiss - Nipples2012 page
)
Sapim - NipplesSix Union - Nipples
{{Bike equipment
Bicycle wheels