Let’s talk about nipples (stop sniggering at the back). Our best nipples buying guide will explain all!
In biking terms – and just to be crystal clear about it, those are the only terms we are going to cover here – ‘nipple’ is the word used for the small nut that secures the end of each spoke to the rim of your wheel. Each nipple is a small brass or aluminium cylinder with an internal thread, a conical or spherical head which sits inside the rim and flattened areas on the outer end of the cylinder (pointing inwards towards the hub) in order that they can be gripped and tightened by a special tool (spoke wrench or ‘key’).
Nipples work by exerting tension on the spokes, the threaded interior of the nipple matching the screw thread on the end of the spoke. Tightening or loosening the nipple increases or decreases the tension on the spoke, and achieving the correct tensions so that the wheel spins ‘true’ is one of the integral skills of wheel building and adjustment.
Which nipple is right for you?
When building wheels from scratch, or replacing broken spokes there are a few things to bear in mind when it comes to picking nipples, these being thread diameter, materials and nipple length.
• Diameter: It’s essential the external diameter of the spoke thread match the internal diameter of the nipple thread (normally 2mm, even in butted spokes). For this reason, most spokes come with nipples included.
• Materials: Nipples are either brass or aluminium. Brass is heavier, but more durable. Aluminium nipples may offer a minor weight saving (not insignificant considering the importance of rotational weight and the cutting-edge carbon construction of many high-end wheels) but they may be more prone to damage so take care not to strip the threads (pay attention to the manufacturer’s max load rating) or round the flats.
• Length: Spoke nipples are usually 12, 14 or 16mm in length. 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.
And once you have the right nipples, have hours of fun tweaking them! (sorry)…