Bottom bracket standards and electric bike conversion kits
Bottom Bracket Standards and Electric Bike Conversion Kits
The bottom bracket is an important component on a bicycle
that connects the crank arms and chainrings to the frame. It allows the
crankset to rotate freely and with less friction, making pedalling easier.
Bottom brackets come in different sizes and types, depending on the bicycle
frame and crankset.
There are two main types of bottom brackets: threaded and pressfit bottom
brackets. Threaded bottom brackets screw into threads on the inside of the
frame. Pressfit bottom brackets are pressed into the frame and held in place
with friction. The most common size for road bikes is 68mm, while mountain
bikes use a 73mm bottom bracket.
There are two types of threaded bottom bracket: cartridge and cup-and-cone. The
former is the newer standard and uses bearings that are sealed inside a
cartridge. The latter have loose ball bearings that sit in cups which are
screwed into the frame. Pressfit bottom brackets are more difficult to identify
as there are many different standards.
Threaded and Press Fit
If you have a threaded bottom bracket, then it is simply a
case of removing the old bottom bracket and replacing it with the new one that
comes on the motor. You will however need to check that the spindle length is
correct for your bike. As such, it’s important to look at your existing bottom
bracket and check that the new one will fit. The good news is that most bikes
made before 2012 using a BSA type square taper bottom bracket which these
motors will fit. If however you have a later bike, especially if it is a more
expensive one, please check the type of bottom bracket and then read on for
advice.
If you have a press-fit bottom bracket, then the good news is that aftermarket
conversion adaptors are available for Bafang. As for CYC they offer different spindles
for different types of press fit standards out of the box. These adaptors are
quite universal so it’s likely that if you change bikes in the future, the
motor will still fit.
It’s important to note that if you do have a press-fit bottom bracket, you will
need to check the size. The most common sizes are BB92, BB89.5, BB86 and BB30.
If you’re unsure of the size, then simply measure the internal width of the
bottom bracket shell on your frame. This should be between 41-46mm for a BB92,
between 37-42mm for a BB89.5, between 33-38mm for a BB86 and 30mm for a BB30.
If you have a bike with an even larger bottom bracket shell (up to 50mm), then
you can still use a Bafang, TongSheng or CYC motor, but you will need to get an
adaptor made for your bike by a machine shop.
Get in touch if you are unsure what kit is best suited for
your bicycle
BSA / Square Taper / Threaded / Sealed / Cup and Cone
This is the most common bottom bracket standard and one that
we see on 90% of bikes that we convert. It’s also the easiest to work with
because the bottom bracket is typically threaded into the frame. This makes it
easy to remove and install. The bottom brackets of this type found on most
bikes are 67 or 73mm long.
The good news is that the Bafang BBSHD motor is designed to be a direct
replacement for these. The BBSHD is also available in 100 and 120mm variations,
generally found on fat bikes.
For front or rear while drives that use a dedicated PAS sensor, externally
threaded bottom brackets will require some DIY to make the plastic PAS disc fit
the crank. If you are unsure about how to do this, please get in touch. Generally,
if you do have an externally threaded bottom bracket then a mid mounted motor
is the best way to go.
For this type of bottom bracket the follow kits will fit:
Press Fit Bottom Brackets
Unlike square taper / threaded bottom brackets, these use
bearings that are pressed directly into the shell (ie frame). The BB30
and PF30 are the only press fit bearings that a Tongsheng or Bafang BBSHD
motors will fit. You will need to purchase a BB30 or PF30 to BSA adaptor which
shrinks down the bottom bracket diameter to a BSA size. Without this the Bafang
or Tongsheng motor would be loose.
The CYC motor (both the stealth and X1 Pro) offer a motor than can fit into
BB92 and BB107-109 standards. This is the only motor that offers this out of
the box without the need for any adaptors.
E-mail if you are unsure what motor is best for your bike. Don’t order a kit if you are unsure what motor is the best for your bike and use
Other Press Fit Standards
There are many exotic style of bottom bracket fittings. If
you are unsure what you have or what motor will fit best. Please get in touch.
As the unsupported bottom brackets will require a specialist adaptor to allow
any of the motors we offer to fit.
Please note that you will need to find an engineering company to have an
adaptor milled to convert your bicycle to a BSA standard.
Do send us photos of your bike and we can advise on the best
kit for your ride
Get your kit on the Cyclescheme!
The Cycle to Work Scheme is a Government-backed initiative to encourage people to cycle to their place of work, and consequently reduce environmental pollution. It's also a way for you to save money on the cost of your cycle and spread the cost over a number of months, through your pay packet.
How do you get a conversion kit through Cycle to Work? The paperwork required differs for each scheme and should be available from your employer or from the links below for each scheme:
Due to the cost of running the Cycle To Work Schemes we have to add a 10% fee on top of the kit price to maintain profitability, otherwise we cannot afford to be apart of the scheme.
You can make savings up to 40% by using a Cycle To Work Scheme!
Shop by brand
