U.S. Built Custom Bicycles in Titanium and Titanium-Carbon Mix

Bottom Bracket Options

Seven offers a wide array of bottom bracket shells in our frames. As with every feature of your new bike, we will recommend the standards and technologies we believe will give you the best ride experience for many years to come.

English 1.37" x 24 Threaded Bottom Brackets

This has been the standard for many years. Sometimes called BSA standard. We offer this type of shell in these lengths:

68 mm: For road bikes, touring bikes, most gravel bikes, and tandems
73 mm: The standard for mountain bikes of all kinds
100 mm: For fat bikes

T47 Bottom Brackets

T47 is the standard for larger bikes where stiffness is paramount. Ideal and sometimes required for any type of internal routing. T47 mimics the frame dimensions of pressfit style shells. T47 has the advantages of pressfit — oversized, stiffer, and helpful for internal cable routing — with none of the downsides — including creaking, premature wear, and numerous fit issues. We offer the T47 shell in these lengths:

68 mm: For road bikes, touring bikes, most gravel bikes, and tandems
73 mm: The standard for mountain bikes of all kinds
100 mm: For fat bikes

When to Choose T47 or Standard English

Bottom Bracket Type	English 1.37" x 24 thread	T47 Chris King design
Internal cable routing	Not compatible with Seven's internal cable routing sytem	Required for internal routing
Compatibilty	Not compatible with a few of the newest progressive cranksets. This list is ever evolving. Check with the crankset manufacturer to confirm compatibilty.	Not compatible with some specialty cranksets. This list is constantly evolving. Check with the crankset manufacturer to confirm compatibilty. Generally more compatible with road systems.
Weight of entire system	A 73 mm length shell is lighter by an average of 22 grams depending on the frame model. The entire crank system may or may not be lighter than a T47 system.	A 73 mm length shell is heavier by an average of 22 grams depending on the frame model. The entire system of shell, cartridge, and crankset can be slightly lighter than the entire English threaded entire bottom bracket system.
System stiffness	Plenty stiff for nearly any rider in any situation. Crankset systems are significantly stiffer than they were five years ago.	For a given crankset and bottom bracket, the T47 setup will nearly always be stiffer than its English shell counterpart. However, it can be difficult to objectively compare both systems on a one-to-one basis.

Eccentric Bottom Brackets

This is a specialty item for single speed and internally geared bikes only. An eccentric bottom bracket, or EBB, is a device used to add tension to a bike chain or belt. A traditional bottom bracket threads into a cartridge in the EBB, which allows tension to be increased or decreased by swiveling the EBB clockwise or counterclockwise. For more details about Seven's EBB system, visit our eccentric bottom bracket page. We offer the EBB system in these lengths:

68 mm: For road bikes, touring bikes, most gravel bikes, and required on tandems
73 mm: The standard for mountain bikes of all kinds
100 mm: For fat bikes

A note about pressfit systems

We don't offer any type of pressfit system anymore. This includes pressfit 30, BB30, and every other numbered system. They creak, squeak, wear prematurely, and generally have constant issues for serious riding. A much better alternative to the perceived stiffness gains that oversized pressfit systems provide is the T47 system that Seven offers.