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Bottom Brackets

Specialized OSBB – Engineering Guide

A question that crops up frequently is with regards to Specialized's OSBB bottom bracket and what size it is exactly. The short answer is OSBB comes in 3 variants which are all called OSBB. 46x61, 42x68 and 46x73. A summary table is below, with the detailed drawings below that. Variant (Diameter x Width) (mm)ApplicationDescription46 x 61RoadFrame tolerances are the same as PF30. It is extremely narrow42 x 68RoadThis has exactly the same dimensions as BB30 and is designed for 6806 or 61806 bearings…

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24 December 2019
Bearings / Bottom Brackets

Bottom Bracket Pressfit and Creaking, an Engineering Analysis

If you are reading this you will have probably already come across the numerous posts by various individuals in Internet forums across the web. The issue of creaking bottom brackets has been blamed on the introduction of pressfit and directfit bottom bracket standards, where bearings either push directly into the bike frame or push into cups which are then pushed into the bike frame. General guidance varies from taking everything out and regreasing it to installing with extreme measures such as epoxy resin.…

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11 December 2019
Bottom Bracket Pressfit and Creaking, an Engineering Analysis
Bearings / Wheels

Testing to Find the Fastest Bicycle Wheel Hubs

The aerodynamic performance of wheels often grabs the headlines and the marketing budget but the reality is the hubs and the bearings within them will have more of a performance differential for the average cyclist. As an example, the power differential between wheels of an equivalent depth at speeds of less than 35km/h will only be 1-2W, the difference in bearing friction can easily exceed that. Wheel hubs and freehubs account for around 60% of the rotational friction in a bicycle drivetrain. The…

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11 December 2019
Bearings / Bottom Brackets / Wheels

Ceramic Bearings vs Steel Bearings… An Engineering Analysis

One of the most controversial topics in the cycling industry is with regards the topic of Ceramic bearings and whether they do or do not reduce friction dramatically in riding. This article will address some of the concerns and topics associated with this debate and quantify the numbers. Internal Bearing construction - Ceramic bearings are not 100% ceramic Ceramic bearings are in actual fact hybrid. They use ceramic balls and usually a steel inner and outer race. The ceramic balls are often silicon…

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11 December 2019
Ceramic Bearings vs Steel Bearings… An Engineering Analysis
Bottom Brackets

BB86 Bottom Brackets with a 30mm or SRAM DUB Crankset

30mm cranks into BB86 bike frames - Avoid if you can... A common question I am often emailed about is asking if I can supply a bottom bracket that will allow a 30mm crank to be fitted into a BB86 bike frame. This post will talk through the many problems associated with this. BB86 uses a bottom bracket with a diameter of 41mm and a width of 86.5mm (Drawing shown below). In practice these are nominal dimensions and have a tolerance on them…

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10 December 2019
BB86 Bottom Brackets with a 30mm or SRAM DUB Crankset