The bottom bracket is where the bearings for the cranks that your pedals attach to are located. To install a mid-drive motor you remove the cranks and bottom bracket spindle and bearings. The mid-drive motor then slides into the bottom bracket shell and replaces all of that except for the pedals. Before 2013 most bottom brackets were the BSA/JIT English threaded standard. This is still the most popular type and is the type that mid-drive motors are designed for. Most bikes that originally sold for less than $1500 or are older than 2013 have English threaded bottom brackets and the motors will slide right in. If you have a square tapered spindle for your cranks then you have the required threaded bottom bracket.
Around 2012 many higher-end bikes started being fitted with various press-fit bottom brackets many of which can be adapted to English threaded so you can still do a mid-drive motor conversion on them. However, there are some exceptions. For an in depth article on adapting various bottom brackets and the exceptions see this thorough article by Matt Hughes
Electrify Bike Company carries threaded one piece adapters for 68 & 73mm BB30, 68 &73mm PF30. We also carry a 2 piece BB30 and PF30 for wider bottom brackets that use those standards. We also stock a 2 piece PF41/BB92 that works with a variety of bottom bracket widths that use that standard.
Some newer bikes and almost all fat tire bikes use a bottom bracket that is wider than the 68/73mm standard. In this case only the BBSHD comes in wider widths to accommodate this EBC stocks the BBSHD in 68/73mm, 100mm, and 120mm. Other widths can be accommodated with these 3 types by using bottom bracket spacers when required. TSDZ2 and BBS02 motors have after market extensions available for them to allow them to fit wider bottom brackets but these can be very difficult to install.
If you have an older style Schwinn or cruiser bike with a one piece crank and American style bottom brackets we have something for you as well. Give us a call.
We recommend using sleeve Loctite like Loctite 641 when installing the adapter into your press-fit bottom bracket. This is like thread lock but is specifically for sleeve inserts like these adapters.
The 2-piece adapters can be tapped in with a soft mallet. Tap all the way around and ensure that it goes in straight. A bottom bracket press can also be used. For the one piece adapter we recommend using a bottom bracket press. Ensure that it does not get crooked or it can bind up and be very difficult to straighten up or remove. If you do not have access to a bottom bracket press you can make one with hardware available at a hardware store. An example can be found on YouTube here.