Bottom Brackets vs. Tire Valves
Comparing 2 standards across 19 specifications. 19 key differences identified.
Bicycle bottom bracket (BB) shells connect the frame to the rotating crankset spindle. Traditional standards include BSA English Threaded (68/73 mm shell width, 1.37" × 24 TPI, reverse left-hand thread on drive side) and Italian Threaded (70 mm shell, 36 mm × 24 TPI right-hand both sides). Modern press-fit and oversized standards include BB30 (68/73 mm × 42 mm press-fit), PF30 (68/73 mm × 46 mm), BB86/92 (86.5/91.5 mm × 41 mm), and T47 (threaded M47 × 1.0 mm).
Bicycle inner tubes and tubeless systems utilize three primary valve standards: Presta (Sclaverand / French valve; 6 mm stem diameter, manual locknut tip, rated up to 15 bar / 220 psi), Schrader (American / Auto valve; 8 mm stem diameter, spring-loaded central pin, ISO 4570 thread, 0.305"-32 TPI), and Dunlop (Woods / English valve; 8 mm stem diameter, drop-in core).
Specification Comparison Table
19 Parameters| Parameter / Spec | ||
|---|---|---|
|
BSA English Threaded Shell Width
|
68.0 (Road) / 73.0 (MTB) mm shell width | — |
|
BSA Thread Specification
|
1.37 in × 24 TPI (ISO 6698) Left-hand drive side / Right-hand non-drive | — |
|
Italian Threaded Shell
|
70.0 mm width / 36 mm × 24 TPI Right-hand thread on both sides | — |
|
T47 Threaded Standard
|
68.0 / 73.0 / 86.5 mm width M47 × 1.0 mm internal thread (fits 30 mm & DUB) | — |
|
BB30 Press-Fit Standard
|
68.0 (Road) / 73.0 (MTB) × 42.0 mm (42 mm bore, bearings pressed directly into shell) | — |
|
PF30 Press-Fit Standard
|
68.0 (Road) / 73.0 (MTB) × 46.0 mm (46 mm bore with composite bearing cups) | — |
|
BB86 (Road) / BB92 (MTB) Press-Fit
|
86.5 (Road) / 91.5 (MTB) × 41.0 mm (41 mm bore, designed for 24 mm spindles) | — |
|
Shimano Hollowtech II Spindle Diameter
|
24.0 mm chromoly steel spindle | — |
|
SRAM DUB Spindle Diameter
|
28.99 mm aluminum alloy universal spindle | — |
|
BB30 / 30mm Spindle Diameter
|
30.0 mm oversized alloy spindle | — |
|
Presta Valve Stem Diameter
|
— | 6.0 mm (0.236 in / narrow drilling for narrow road rims) |
|
Presta Operating Mechanism
|
— | External Threaded Locknut with captive brass plunger pin Manual Lock |
|
Presta Maximum Pressure
|
— | 15.0 bar (217.5 psi high-pressure road tolerance) |
|
Presta Rim Hole Requirement
|
— | 6.5 mm (0.256 in diameter hole in rim) |
|
Schrader Valve Stem Diameter
|
— | 8.0 mm (0.315 in / identical to automotive tire valves) |
|
Schrader Thread Specification
|
— | 0.305-32 UNEF (ISO 4570 8V1 thread) Standard |
|
Schrader Rim Hole Requirement
|
— | 8.5 mm (0.335 in diameter hole in rim) |
|
Dunlop (Woods) Stem Diameter
|
— | 8.0 mm (uses 8.5 mm rim hole, manual rubber sleeve / core) |
|
Common Valve Stem Lengths
|
— | 32, 40, 48, 60, 80 mm (extended for deep-section carbon aero rims) |