A spoke nipple holds a
bicycle wheel's rim to each
spoke.
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
Tension may refer to:
Science
* Psychological stress
* Tension (physics), a force related to the stretching of an object (the opposite of compression)
* Tension (geology), a stress which stretches rocks in two opposite directions
* Voltage or el ...
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 like 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 (Cu) and zinc (Zn), in proportions which can be varied to achieve different mechanical, electrical, and chemical properties. It is a substitutional alloy: atoms of the two constituents may replace each other wit ...
(usually
nickel-plated) and
aluminum
Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It ha ...
. Brass is heavier but more durable and less prone to corrosion, rounding of flats while tightening, breaking and
galling; 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 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 with the Symbol (chemistry), 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, resista ...
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
A spoke wrench or spoke key is a small wrench or tool used to adjust the tension in the spokes of a tension-spoked wheel. A spoke wrench is sometimes called a nipple wrench, as it is the spoke nipple – not the spoke – that is turned in the pr ...
Discusses the three major nipple sizes.
References
External links
DT Swiss - Nipples2012 page
)
Sapim - NipplesSix Union - Nipples
{{Bike equipment
Bicycle wheels