Spoke nipples
A spoke nipple - in short: nipple - is a screwable connection from the rim to the spoke in the wheel of a bicycle . The nipple is usually made of brass , less often of aluminum . When the tires are fitted, the best way to adjust the nipple is with a special tool, the nipple spanner . If no tire is fitted, the nipple can be adjusted from the bottom of the rim with a screwdriver.
Technically speaking, nipples are square sleeve nuts, the most common sizes (wrench sizes) are:
- 0.127 "(3.23 mm)
- 0.130 "(3.30 mm)
- 0.136 "(3.45 mm)
The thread must match the spoke. Spoke threads are rolled and therefore have a larger outer diameter than the diameter of the spoke. The most common are spokes with a 2 mm diameter in front of the thread and 2.3 mm thread diameter (DIN 79012, Fg 2.3), especially with sports bikes also 1.8 mm with a 2.1 mm thread (DIN 79012, FG 2) and in Cargo bikes spoke diameter 2.3 mm with thread 2.6 mm (DIN 79012, Fg 2.6). Larger diameters are used in motorized two-wheelers and cars with wire-spoke wheels.
Nipples for spokes with a diameter of 1.8 and 2 mm have the same dimensions of shaft and head diameter for conventional bicycle rims with nipple holes of 4.5 mm diameter. There are adapter nipples with Fg 2.6 for these rims as well as large adapter nipples with Fg 2.3 for the larger holes in rims for cargo bikes.
Nipples are available in different lengths (12 mm, 14 mm, 16 mm). With longer nipples you can - within certain limits - use spokes that are actually a bit too short. Particularly with aluminum nipples, make sure that the entire nipple thread is used right down to the bottom of the slot, otherwise the thread will tear out easily.
Nipples with a conical transition to the head align themselves under load concentrically to the rim bore, and thus radially in unpunched rims. Nipples with a spherical contact surface to the rim allow a limited angular alignment, the spokes bend less.
Recessed spoke nipples are used in deep hollow-wall rims for particularly aerodynamic wheels, which can only be reached from the tire side with special socket wrenches.
literature
- Fritz Winkler, Siegfried Rauch: Bicycle technology repair, construction, production. 10th edition, BVA Bielefelder Verlagsanstalt GmbH & Co. KG, Bielefeld, 1999, ISBN 3-87073-131-1