English threading or BSA/BSC
The English BSC (British Standard Cycle) thread is the most common thread on bicycle parts on the market today. This standard, derived from BSA (Birmingham Small Arms), has become the international ISO standard. The generic name BSA remains very common for this type of thread. Many recent bottom bracket models are threaded to BSC specifications. Examples include Shimano Octalink and Hollowtech II bottom brackets, and Campagnolo Power Torque and Ultra Torque bottom brackets.|>
BSA bottom bracket threading" width="450" height="189" />
The cups of a bottom bracket with English threading are tightened in the opposite direction to the pedalling action.with English threading is done in the opposite direction to the pedalling direction on both the drive side and the left side. As a result, the right side is screwed in a counterclockwise direction, while the left side is screwed in a clockwise direction. The diameter of the thread on this British standard is 1.37 inches for a thread pitch of 24 threads per inch, which gives it the designation 1.37x24. The measurements for BSC threads are as follows: Diameter at the thread: 34.8 mm, or 1.37 inches Number of threads per inch: 24 Pitch: 1.06 mm|>
Italian thread or ITA-24
Italian threading, or ITA-24, is also a very common standard on modern pedal cases. It is very different from BSC threading in terms of both the direction of screw rotation and the thread measurements. Italian threading is found on many models, including FSA MegaExo and SRAM GXP bottom brackets and cartridges such as the Shimano 105 Octalink. Italian threaded cups are tightened clockwise on both sides of the crankset. This means that the right side is tightened in the direction of pedalling, while the left side is tightened in the opposite direction. The diameter of the thread on this Italian standard is 36 mm for a thread pitch of 24 threads per inch, which gives it the designation 36x24. The relevant measurements are summarised as follows: Diameter at the thread: 36 mm Number of pitches per inch: 24 Pitch: 1.06 mm.
French threading
Although French threading was used for a long time on mountain bike and road bike frames, it was abandoned following the standardisation of English and Italian threading. This type of thread is found on older bicycle models and on the few parts manufactured by manufacturers for maintenance purposes. The French standard is quite similar to the Italian standard, except for the thread measurements. To tighten French threaded cups, screw them clockwise on both sides of the cranks, just like Italian threaded cups. This means that tightening is performed in the opposite direction to the pedalling on the left side and in the direction of pedalling on the drive side. The thread diameter on this standard is 35 mm with a pitch of 1 mm. Thread diameter: 35 mm Pitch: 1 mm.|>
Swiss threading
Swiss threading was used in the 1970s and 1980s, and has long since been abandoned by the bicycle industry.This standard is only found on certain older models of bicycle frames. Swiss threading has the same measurements as its French counterpart and the same tightening direction as the BSC standard. Swiss threaded cups are tightened in the opposite direction to the pedalling action on each side of the crankset. Tightening is therefore clockwise on the left side, while it is done counterclockwise on the drive side. The thread diameter on this standard is 35 mm with a pitch of 1 mm. Diameter at the thread: 35 mm Pitch: 1 mm
If recent bike models are configured with English or Italian threading, it is essential to determine precisely the standard according to which the frame was manufactured.. Most bottom brackets on the market are available in both thread types for the same model. Identifying the frame standard therefore ensures that the equipment is compatible and prevents damage during assembly or disassembly.
