Guide to bottom brackets.
How do you choose the correct bottom bracket for your bike?
Een trapas, ook wel bottom bracket genoemd, vormt de verbinding tussen het frame en het crankstel van je fiets. Het kiezen van de juiste trapas hangt dus af van twee factoren: het type frame en het type crankstel dat je gebruikt.
1 (type frame) + 2 (type crankstel) = 3 (bottom bracket)
Om frame type en cranktype te bepalen, hoef je alleen een paar afmetingen op te meten. Deze afmetingen kun je vervolgens gebruiken als filter in onze shop.
Step 1: Determine the type of your frame
Pressfit frames
Pressfit frames have a bottom bracket shell with a smooth inside into which the bottom bracket is pressed.
The type of a pressfit frame is always determined by a combination of 2 dimensions, the width of the bottom bracket shell and the inner diameter of the bottom bracket shell. If you have both of these dimensions, you will always be able to reduce a frame to one specific frame type.
We always recommend measuring both dimensions when multiple inner diameters of the bottom bracket shell are possible in combination with a given bottom bracket width.
Measurement width
Measure the width of the bottom bracket shell with a caliper. Measure only the frame and do not take into account any cups installed.
Inner diameter measurement
Measure the inside of the bottom bracket shell with a caliper.
What types of pressfit frames exist?
BB30
BB30 frames have a bottom bracket housing width of 68 mm (Road) or 73 mm (MTB) and a bottom bracket housing inner diameter of 42 mm.
De BB30 frame standaard werd oorspronkelijk geïntroduceerd door Cannondale, maar wordt later ook gebruikt door andere fabrikanten. Lagers met een buitendiameter van 42 en een binnendiameter van 30mm worden direct in het brackethuis geperst om gebruikt te worden in combinatie met een BB30/PF30 crank. Door gebruik van adapters is het ook mogelijk om andere cranktypes te gebruiken in combinatie met een BB30 frame.
Ontdek het BB30 assortiment
BB30A
De BB30A frame standaard werd oorspronkelijk geïntroduceerd door Cannondale en is een variant op de BB30 frame standaard. Het brackethuis van de BB30A is 5 mm breder dan de BB30 standaard en asymmetrisch aan de niet-aandrijfzijde van het frame.
BB30A frames are road frames with a bottom bracket shell width of 73mm and a bottom bracket inner diameter of 42mm.
Discover the BB30A assortment
BB86-BB92
The BB86-BB92 frame standard was originally developed by Shimano and grew to become the most widely used pressfit frame standard in the bicycle industry. BB86-92 is used by brands such as Giant, Canyon, BMC, Cube and others.
BB86-92 frames have a bottom bracket housing width of 86.5 mm (Road) or 92 mm (MTB) and a bottom bracket housing inner diameter of 41 mm.
Discover the BB86-BB92 assortment
BB89
The BB89 frame standard is a variant of the BB86-BB92 frame standard and is used exclusively on (older) types of MTB.
BB89 frames are mountain bike frames with a bottom bracket shell width of 89.5mm and a bottom bracket shell inner diameter of 41mm.
Discover the BB89 assortment
BB386
The BB386 frame standard combines the width of a BB86 road frame (86.5mm) with a larger 46mm diameter bottom bracket housing.
BB386 frames are road frames with a frame housing width of 86.5mm and a frame housing inner diameter of 46mm.
Discover the BB386 assortment
BB90-BB95
The BB90-BB95 bottom bracket standard was developed by Trek. Bearings with an outer diameter of 37 mm were pressed directly into the bottom bracket shell for use with a Shimano or SRAM GXP crank. Due to the limited diameter of the bottom bracket housing, these frames can only be used with 24 mm cranks.
BB90-BB95 frames have a bottom bracket housing width of 90.5mm (Road) or 95mm (MTB) and a bottom bracket housing inner diameter of 37mm.
Discover the BB90-BB95 assortment
PF30
The PF30 (Pressfit30) frame standard was originally introduced by Cannondale as a variant of the BB30 frame standard. Bearings with an outer diameter of 42mm and an inner diameter of 30mm are installed in a cup after which the cup is pressed into the bottom bracket shell. This frame standard was developed to be used in combination with a BB30/PF30 crank, but by using adapters it is also possible to use other crank types in combination with a PF30 frame.
PF30 frames have a frame housing width of 68mm (Road) or 73mm (MTB) and a frame housing inner diameter of 46mm.
Discover the PF30 assortment
PF30A
The PF30A frame standard was originally introduced by Cannondale and is a variant of the PF30 frame standard. The frame housing of the PF30A is 5 mm wider than the PF30 standard and asymmetrical on the non-drive side of the frame.
PF30A frames zijn wegframes met een brackethuis breedte van 73mm en een brackethuis binnendiameter van 46 mm.
Discover the PF30A assortment
OSBB
The OSBB (Oversized Bottom Bracket) frame standard was developed by Specialized and was only used in Specialized carbon frames for a short period of time.
Specialized OSBB frames are road frames with a frame housing width of 61mm and an inner diameter of 46mm.
Beware of the term “OSBB.
The term OSBB (Oversized Bottom Bracket) is once incorrectly applied to pressfit frames that you can often trace by measurement to another standard such as BB30 or Pressfit30.
Discover the OSBB assortment
BBRIGHT
The BBright bottom bracket standard was developed by Cervélo and focuses on optimizing power transfer and improving frame stiffness. The BBright standard differs from traditional BB30 - PF30 bottom bracket systems by a wider asymmetric design, where the drive-side of the bottom bracket has the same width as traditional BB30 and PF30 frames (68 mm), but the non-drive-side is 11 mm wider resulting in a total bottom bracket shell width of 79 mm.
A distinction is made between a direct fit BBright42 and a pressfit BBright46 frame standard, the difference being in the inner diameter of the bottom bracket shell.
BBright42 frames are road frames with a bracket housing width of 79mm and an inner diameter of 42mm. BBright46 frames are road frames with a bottom bracket shell width of 79 mm and an inside diameter of 46mm.
Ontdek het BBRIGHT assortiment
Wire frames
Wired frames have a bottom bracket housing with an internal thread in which the bottom bracket screws directly into place.
To determine these frame types, it is sufficient to measure the width of the bottom bracket shell. Only if the width is 68 mm, the inside diameter of the thread must be measured. If it is 34 mm then you have a BSA frame, if it is 47 mm then you have a T47 frame.
Measurement width
Measure the width of the bottom bracket shell with a caliper.
What types of wire frames exist?
BSA (1,37" x 24T)
The BSA frame standard is the most commonly used thread standard for attaching bottom brackets in bicycle frames and is marked 1x37” x 24T. The cups have right-hand thread (normal thread) on the non-drive side of the frame and a left-hand thread on the drive side of the frame.
BSA frames have a bracket housing width of 68 mm (Road) or 73 mm (MTB).
Explore our BSA offerings
ITA (36 x 24T)
The Italian frame standard is a threaded standard for attaching bottom brackets in bicycle frames and is characterized by the designation 36 x 24T. This frame standard is mainly used by Italian frame builders. Both cups have right-hand thread (normal thread).
ITA frames are road frames and have a frame housing width of 70 mm.
Explore our ITA offerings
T45 (M45 x 1,0)
The T45 frame stand is a threaded standard for attaching bottom brackets in bicycle frames. This frame standard is mainly used on a number of Colnago brand models. The cups of a T45 bottom bracket have right-hand thread (normal thread) on the non-drive side of the frame and a left-hand thread on the drive side of the frame.
T45 frames are road frames and have a bracket housing width of 82.5 mm.
Explore our T45 offerings
T47 (outboard)
The T47 frame stand is a threaded standard for attaching bottom brackets in bicycle frames. This frame standard is a modern bottom bracket standard that combines the larger 46 mm diameter of an oversized pressfit system with the reliability of a threaded system. With a width of 68 mm (road) and 73 mm (MTB), the bearings are mounted in cups outside the frame (hence outboard). The cups have right-hand thread (normal thread) on the non-drive side of the frame and a left-hand thread on the drive side of the frame.
T47 frames have a bracket housing width of 68 mm (Road) or 73 mm (MTB).
Explore our T47 offerings
T47-Trek (inboard)
The T47-Trek frame stand is a threaded standard for attaching bottom brackets in bicycle frames. This frame standard is a variation of the T47 frame standard. The bearings are mounted in cups inside the bottom bracket shell (hence inboard). The cups have right-hand thread (normal thread) on the non-drive side of the frame and a left-hand thread on the drive side of the frame.
T47-Trek (inboard) frames are road frames and have a bracket housing width of 85.5 mm.
Explore our T47 Trek offerings
T47A
The T47A frame stand is a threaded standard for attaching bottom brackets in bicycle frames. This frame standard is an assymetric variation of the T47 frame standard. The cups have right-hand thread (normal thread) on the non-drive side of the frame and a left-hand thread on the drive side of the frame.
T47A frames are road frames and have a bracket housing width of 77 mm.
Explore our T47A offerings
Step 2: Determine the type of your crank
Determining the crank type of your bike can be done by measuring the axis thickness, but also by identifying the data mentioned on the crank (brand, type).
Axis thickness measurement
Measure the axis thickness of your crank with a caliper.
Schematic overview of crank types
|
BRAND |
AXIS THICKNESS |
|
24 |
|
|
24-22 |
|
|
25 |
|
|
29
|
|
|
30-28
|
|
|
30 |
|
|
30 |
What types of cranks exist?
Shimano
All Shimano cranks (ROAD and MTB) have an axle diameter of 24 mm.
Check out the possibilities with Shimano
SRAM GXP
All SRAM GXP cranks (ROAD and MTB) have an axle diameter of 24 mm with a choke on the non-drive side to 22 mm (hence 24-22).
Check out the possibilities with Sram GXP
SRAM DUB
All SRAM DUB cranks (ROAD and MTB)have an axle diameter of 29 mm.
Check out the possibilities with Sram DUB
386 - Rotor30 - FSA386 - Raceface30
All modern 30 mm cranks are type 386. The axle thickness of these cranks is 30 mm. Some well-known brands of 386-type cranks are Rotor, FSA386 and Raceface.
Check out the possibilities with 386 - Rotor30 - FSA386 - Raceface30
BB30/PF30
Is an older crank standard that you will therefore find mainly on older bikes. These cranks have an axle thickness of 30 mm but these axles are shorter than those of 386 cranks. These cranks can only be used with BB30 or PF30 frames.
Check out the possibilities with BB30/PF30
Praxis M30
All PRAXIS M30 cranks (ROAD and MTB) have an axle thickness of 30 mm with a narrowing on the non-drive side to 28 mm (hence 30-28).
Check out the possibilities with Praxis M30
Campagnolo Ultra Torque
Campagnola Ultra Torque cranks have an axle diameter of 25 mm.
Check out the possibilities with Campagnolo Ultra Torque
CEMA Interlock System
CEMA Interlock bottom brackets are bottom brackets for pressfit frames. The two halves of the bottom bracket are connected inside the frame by means of a thread. This interconnection ensures a strong whole and a perfect alignment of the bearings. Also, the cups will not be able to move separately from each other leading to a stable and crack-free solution. We will always use this interlock construction whenever possible.
Find out how to install an Interlock bracket here:
Bottom bracket chart
Easily find the right bottom bracket for your bike with our easy-to-read bottom bracket chart. This handy guide contains all the specifications and compatibility overviews of the different bottom brackets available. Whether you're looking for threaded or pressfit options, you'll quickly find the right combination of width, diameter and crank type. Use this tool to see exactly which solution fits your frame and crankset for optimal performance.
Download chart
Shop chart pack
Conclusion
Choosing the right bottom bracket is critical to the performance of your bike. With this guide, you'll be well on your way to finding the perfect match for your needs. If you still have questions about this, don't hesitate to contact us. We're always ready to help!
Satisfaction of our customers
At CEMA Bearing, customer satisfaction is paramount. We strive to continuously innovate and improve our products. Our customers can count on products of the highest quality, backed by our commitment to excellence and innovation.
At CEMA Bearing, customer satisfaction is paramount. We strive to continuously innovate and improve our products. Our customers can count on products of the highest quality, backed by our commitment to excellence and innovation.
CEMA Bearing
info@cemabearing.be
+32 (11) 64 71 81