Engineering:British Standard Cycle

Cycle thread in ​⁷⁄₁₆ and ​¹⁄₂ inch sizes also come in 20 tpi and 24 tpi options.

Traditionally the parts it would be found on are:

• Front axle and seat pin clamp bolt ⁵⁄₁₆ inch (7.94 mm) diameter, 24 or 26 tpi threading
• Rear axle ³⁄₈ inch (9.53 mm) diameter, 26 tpi
• GB Stems using ⁵⁄₁₆ inch (7.94 mm) diameter, 26 tpi for the handlebar clamp

Note that M8 × 1.00 metric threaded parts can interchange with ⁵⁄₁₆ inch (7.94 mm) diameter × 26 tpi parts with a "Class B fit", meaning you should not go back and forth between threadings.

British Bicycle standards for other parts which are not strictly BSC but come in similar fine threads include:

• Bottom Bracket cups diameter with a 24 tpi ISO standard or a 26 tpi Raleigh (now obsolete) standard

History

The thread was defined to meet a requirement for a thread form for bicycles and motorcycles, originally specified by the Cycle Engineering Institute. Before being adopted as a British Standard it was known as the CEI thread.

See also

• Raleigh Bicycle Company