Chain wear gauge
A chain gauge is a gauge for checking the wear- related elongation of bicycle chains . Manufacturers such as B. Parktool and Rohloff with the Caliber 2 produce such gauges. The elongation of the chain can be determined with a chain wear measurement with a caliper or a gauge .
Reason for measurement
Even if a gear chain is still fully functional, it no longer fits exactly to the teeth of the sprockets and pinions after a certain degree of wear . During the use of the drive unit “chain - chainring / sprocket ”, the chain elongates with the duration and quality of the stress by the driver. If the chain is not exchanged for a new one, the "old" chain with its rollers grooves the chainrings and sprocket, ie the "grooves" of the gears are widened and the chain begins to run on a slightly larger diameter. If a new chain is now put on, it is too short for the new diameter on which it now runs and it can happen that the small rollers of the chain touch the tips of the chainrings and finally jump at least one tooth further. Depending on the load, circuit chains should be replaced after 1500 km to 2500 km of service life. Most manufacturers recommend a chain change if the elongation of the chain exceeds 0.75 or 1%, depending on the type of chain. Accordingly, chain measuring gauges are used to check whether the elongation is within the tolerance range 0.75% (for light metal cassettes) or 1% (for steel cassettes) elongation.
alternative
The chain length can also be measured with a 30 cm ruler. You measure the distance between two head pins that are ten chain links apart. When new it is 254 mm. From a distance of 256 mm, the chain should be replaced. Here, an outer and an inner chain link are added together, so actually 20 chain links are meant, because the division of a bicycle chain is 12.7 mm (1/2 "). It is easier to use the Measure the edges of the outer brackets The reference point at which the measurement is made is basically irrelevant - it just has to be the same point.
literature
- Richard Hallet: Bicycle - maintenance, care, repair. BVA Bielefelder Verlag, Bielefeld, 2003, ISBN 3-87073-308-X .