Shimano Bottom Bracket BB ES51 BB-ES51 113 x 73 Splined ULTIMATE SPORTS

Shimano BB-ES51 Sealed Cartrige Bearing Splined Bottom
Bracket

Description
-Octalink BB interface
-Oversized BB spndle
-113mm Spindle Length
-Hollow Chrome-Moly Steel Spindle Material
-OCTALINK splined axle crank arm interface
-Sealed cartridge assembly
-Threading: BSC English
-Mfg weight: 262g
-Shell Width: 73mm
– Spindle Length:113mm

UPC: 689228132184

Bottom Brackets:
A bottom bracket has to fit both your chainset and your frame. There
are currently four chainset/bottom bracket interfaces that you’re
likely to come across. If your chainset is made by Shimano and it has
splines, then you need an Octalink bottom bracket. If your chainset is
NOT made by Shimano and it has splines, it’s almost certainly ISIS.
There are a very few non-Shimano chainsets with Shimano Octalink
interfaces so, to be sure, count the splines – ISIS has 10, Octalink
has 8. No matter which brand of chainset you have, if it has a square
interface, it will require a traditional square taper bottom bracket.
If you have one of the new Hollowtech II systems, you will need to
choose the exact bottom bracket that matches your chainsets.

The other information you’ll need is the shell width and axle length.
To find the shell width, measure the distance accross the outside of
the bottom bracket tube on the frame. Correct axle length is crucial to
your chain line and the function of your front derailleur. It is very
hard to determine without reference to the bottom bracket supplied with
the frame. In short, the easiest way to work out what shell width and
axle length you require is to choose the same as was originally fitted
to the frame although, if you’re changing chainset at the same time,
this may not be perfect! Stick to the same interface type and brand and
you should be OK.