The generic term "press-fit" actually covers several different standards, each with its own dimensions and compatibility. A common source of confusion that can cost you if you buy the wrong part. Here's a precise comparison to help you identify and understand each of these standards.
Discover our range of road bike bottom brackets and road bike drivetrain groups in stock.
1. What is a press-fit standard?
A press-fit bottom bracket works without threading: the cups are pressed directly into the frame's tube, with the mechanical fit providing the retention. For a full reminder of how it works and a comparison with threaded bottom brackets, see our comparison of threaded vs press-fit bottom brackets. What matters here is that the term "press-fit" actually covers several different standards with different dimensions, which are not interchangeable.
2. The BB86 / BB92 standard
BB86 and BB92 are the most common press-fit standards on modern road and mountain bike frames, mainly associated with Shimano. BB86 mostly equips road frames, while BB92 is its mountain bike variant, with a slightly wider shell to accommodate the appropriate bearings. Both standards keep a 24 mm bottom bracket axle, the same as used on Shimano threaded bottom brackets.
3. The BB30 standard
BB30 was popularised by Cannondale before spreading to other manufacturers. Its distinctive feature: the bearings are pressed directly into the frame, with no intermediate cup, and the bottom bracket axle measures 30 mm in diameter, compared with 24 mm for BB86/BB92. This larger axle diameter improves crankset stiffness, an asset sought after for competitive use. On the flip side, the lack of an intermediate cup makes this standard more sensitive to manufacturing imprecision in the frame.
4. The PF30 standard
PF30 uses the same 30 mm axle diameter as BB30, but with one key difference: the bearings sit in intermediate cups made of composite or reinforced plastic, which are themselves pressed into the frame. This intermediate cup absorbs some of the manufacturing tolerances and statistically reduces the risk of creaking compared with a pure BB30 setup, while retaining the stiffness benefits of the larger axle diameter.
5. Comparison table of the 4 standards
| Standard | Frame shell diameter | Shell width | Axle diameter | Associated brand(s) | Main use |
|---|---|---|---|---|---|
| BB86 | 41 mm | 86.5 mm | 24 mm | Shimano | Road |
| BB92 | 41 mm | 92 mm | 24 mm | Shimano | MTB |
| BB30 | 42 mm | 68 mm (road) / 73 mm (MTB) | 30 mm | Cannondale, SRAM | Road / MTB |
| PF30 | 46 mm | 68 mm (road) / 73 mm (MTB) | 30 mm | Multi-brand | Road / MTB |
To verify: the dimensions above are given as a guide. Always check the exact dimension for your frame with the manufacturer or by direct measurement before buying, as tolerances may vary slightly by brand.
6. How do I know which standard fits my frame?
Three reliable methods let you identify the exact standard on your frame:
- Measure the inner diameter of the bottom bracket shell with callipers.
- Check the manufacturer's spec sheet for the frame or complete bike.
- Note down the markings stamped on the old bottom bracket when removing it.
Good to know: if you've never removed a bottom bracket before, our guide to removing a bottom bracket details the procedure step by step, standard by standard.
7. Are these standards interchangeable?
No. Each press-fit standard has its own diameter and width dimensions, which makes them incompatible with one another without an adapter. A frame designed for PF30 cannot directly accept a BB86 bottom bracket, and vice versa. There are, however, adapters for certain specific cases — for example converting a PF30 shell to fit a BB86 bottom bracket — but their exact compatibility must always be checked before purchase.