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Pressfit bottom bracket standards, one page
Pressfit is not one standard, it is a family, and the names collide constantly. This page lays the common pressfit shells side by side by the only numbers that matter: bore diameter, shell width and the spindle they were built for.
Why pressfit exists
Pressfit shells replace machined threads with a smooth bore, so the frame can be moulded in carbon without a threaded metal insert, and the shell can be made wider and stiffer. The bearings or their cups are pressed in under force rather than screwed. The trade-off is that a smooth bore relies on tight tolerances, so a shell that is a fraction oversize or unevenly faced can creak, which is the reputation pressfit has earned.
Every pressfit standard below is defined by three numbers: the bore the shell presents, how wide the shell is, and the crank spindle diameter the system was designed around.
The 41 mm family: BB86, BB92, BB90, BB95
BB86 (86.5 mm road) and BB92 (91.5 mm mountain) use a 41 mm bore and press cups that carry a 24 mm spindle. Trek's BB90 (road) and BB95 (mountain) press the bearings straight into the carbon with no cups, using their own widths, and are also built for a 24 mm spindle. All four are 24 mm systems at heart.
The 46 mm and 42 mm families: PF30, BB30, BBRight, BB386EVO, OSBB
PF30 uses a 46 mm bore with pressed cups for a 30 mm spindle. BB30 uses a 42 mm bore with bearings direct in the frame for a 30 mm spindle. BBRight and BB386EVO widen the shell for a longer 30 mm spindle and greater stiffness, with BB386EVO running a 46 mm bore 86.5 mm wide. Specialized OSBB is a frame-specific 42 mm or 46 mm interpretation depending on model, which is why OSBB always needs checking against the exact frame.
The pattern is clear: 42 mm and 46 mm bores are the 30 mm spindle world, 41 mm bores are the 24 mm spindle world, and mixing across them needs a reducer bottom bracket.
| Standard | Bore | Width | Spindle | Bearing sits in |
|---|---|---|---|---|
| BB86 (road) | 41 mm | 86.5 mm | 24 mm | cups |
| BB92 (MTB) | 41 mm | 91.5 mm | 24 mm | cups |
| BB90 / BB95 (Trek) | 37 mm seat | 90.5 / 95.5 mm | 24 mm | frame |
| PF30 | 46 mm | 68 / 73 mm | 30 mm | cups |
| BB30 | 42 mm | 68 / 73 mm | 30 mm | frame |
| BB386EVO | 46 mm | 86.5 mm | 30 mm | cups |
Figures compiled from Park Tool, Wheels Manufacturing and BikeGremlin references.
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Sources: Park Tool: Bottom Bracket Standards · Wheels Manufacturing bottom bracket fitment reference · BikeGremlin: Bottom bracket standards explained · Bottom bracket (Wikipedia, CC BY-SA)