- Welcome to 128.bike channel
- In this blog we will be talking about bicycle frames, one point in particular and that is bb housing.
- Until recently bottom bracket housings were pretty much a standardized affair. There were few other options but dominant one was the threaded shells version which was 68mm wide, with 34.8mm inside diameter and with 24 threads per inch thread ,more commonly known as English thread.
- With new possibilities in frame tubing and e-bikes entering the scene changes had to be made.
- So what was the problem?
- Firstly new designs with much wider down tubes and seat tubes as well as fatter tires becoming fashionable demanded wider rear forks. All of this meant that welding of the tubes was taking place at the edges of the bb housing. This often caused the edges of the bb housing to become oval due to heat being generated on its edges. BB housings like these are out of standard and cause huge problems later in production and even have to be discarded. This is making a lot of waste in production with the frame you have already painted and transported it to the assembly line, after the initial problem was made.
- Second e-bike frames are often being made with integrated batteries in the down tube or positioned behind the seat tube as well. This demands wider tubes as well to be functional and could accommodate the batteries.
- The most simple and fastest solution was to make the BB housings wider, first it was 73mm but recently there are more and more versions with 83mm housings.
- So with additional 15mm of space to accommodate wide tubes above mentioned problems are avoided and production could go on carefree.
- One important point to mention here is that one has to be careful when calculating the chainline! We will talk about this and more solutions in detail in another video.
- Thank you for your attention and if you are looking for more details please feel free to write in comments or send me an email.
