OSBB Confusion,
which bottom bracket
for my Specialized bike?
The term “OSBB” stands for “OverSized Bottom Bracket”. Specialized uses this term to describe a bottom bracket standard on their bicycles.
Before we get into the subject matter of OSBB confusion, one needs to make an initial distinction :
– Specialized carbon ROAD bike 46×61 , where there is still much bottom bracket confusion and what this article is about.
– Specialized aluminium bikes 42×68 such as Allez, which has been BB30 bottom bracket shell of 42×68 mm
– Specialized MTB 46×73, which is with PF30 bottom bracket shell of 46×73.
– Lately , Specialized has been on BSA standard.
OSBB (OverSized Bottom Bracket) – introduced on Specialized CARBON bikes around 2011:
1. Shell Width : The OSBB shell width is 61mm. OSBB is a narrower version of PressFit 30, sharing the same inner diameter of 46mm, but reducing the shell width to 61 versus the PF30 road standard of 68mm.
2. Delrin cups : Bearings installed into Delrin bottom bracket cups which are then installed onto the bikes.
3. Compatibility: OSBB frames are designed to accommodate Specialized Fact cranksets with 30 mm spindle diameters. Typically, they are compatible with cranksets designed for BB30 bottom brackets, which have a 30mm spindle diameter.
At the time, C-bear is the first to come with an effective, affordable and available no creak solution. C-bear pioneer in all its bottom brackets make with cnc-precisioned aluminium cups, higher tolerance and eliminate deformity and flex due to delrin properties. Specialized uses C-Bear bottom brackets. To presence C-Bear is still known as the bottom bracket silencer.
Is osbb the same as BB30?
After a few years, Specialized changed their OSBB road frames by bonding an aluminum insert/ adapter into the bottom bracket shell width of 61mm, converting the OSBB into a BB30 bottom bracket shell. This made the frame essentially a BB30 frame (68mm x 42mm).
Adapters: Specialized provides adapters for OSBB frames to allow compatibility with other cranksets, such as Shimano Hollowtech II. These adapters allow you to use different cranksets without needing to replace the entire bottom bracket.
C-Bear has custom-fit-designed bottom brackets to fit
24 crankset : Shimano, Rotor 24
Sram GXP
Campagnolo
Sram DUB
Rotor 30 ROTOR/EASTON/CANECREEK
FSA EVO 386/THM Clavicula/SRM Origin
without the intermediary of an adapter.
C-bear also developed the PF42-30 as an additional option to those who have experienced with fit and creaking issues with BB30 bearings direct mount inside the bottom bracket shell.
C-Bear solves your BB30 woes with new 42/30 pressfit bottom bracket system (bike rumor).
To clarify the confusion, if someone mentions “OSBB” in the context of a Specialized bike, they could be referring to the original OverSized Bottom Bracket standard with the 61mm shell width.
It’s essential to verify the specific bottom bracket shell on the bike in question, whether you have a
– Specialized carbon road bike of 61mm bottom bracket shell with delrin cups
– or with an aluminium insert expoxied into the bottom bracket shell, thereby converted into a BB30 bottom bracket shell
– or lately Specialized bikes are with BSA threaded bottom bracket shell.
In all cases, C-Bear has the custom-fit-designed bottom bracket for your Specialized bike(s),
all without intermediary adapter. ONE bottom bracket custom-fit-designed to, efficiently and effectively, maximize stability and optimize the power transfer with every pedal stroke.
Still unsure, please contact us and we will help you to select the compatible bottom bracket.