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Translate this bottom bracket spec

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Translate this bottom bracket spec

Old 07-21-18, 08:16 PM
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wunderchicken
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Translate this bottom bracket spec

I just bought a Specialized Sequoia Expert and these are from the spec describing the crank set:

- FSA SL-K Light crankset, ABS Compact BB386 EVO, PF30 System Interface, 10-/11-speed, hollow, 147mm Q-factor, 110 BCD crankset
- Megatooth V2 XX1, 42T chainring

I know the crank arms are FSA SL-K Lights (carbon and seem nice). The chainring is also pretty obvious. I have no idea what the rest of that line means.

I was just in the bike shop because I mistook a bottom bracket wave washer with a bunch of dirt on it as a busted bottom bracket puking out a bunch of bearings. I was happy when they told me it was just a wave washer + dirt. I asked them about the BB spec and they told me it was threaded. I thought BB386 Evo were press in bottom brackets. I was too confused to put together a coherant question because the bike mechanic kept showing me wave washers and assuring me my bike was OK.
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Old 07-21-18, 08:47 PM
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BB386EVO is a standard system made to work into basically any frameset. It is the kind of clever solution that all the other post-BSA crank/BB systems should have been.

BB386EVO means this: 30mm crankset spindle. 86.5mm bearing spacing....and ends up using the same cups/bearings as PF30. Because of these properties the cranks and BB can be made to fit everything from BSA/BB30/PF30/PF86. I have an SLK BB386Evo crank/BB in my BSA gravel grinder frameset.

https://problemsolversbike.com/files..._Reference.pdf


If your frame is PF30, then it is PF30. A BB386EVO crak will work fine with it. You'll need a wave washer to supply preload.

Last edited by Marcus_Ti; 07-21-18 at 08:54 PM.
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Old 07-22-18, 07:46 PM
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Thanks - that PDF is very helpful. My understanding is the hole in my frame is complaint with the BB386 Evo spec and Specialized or the bike shop pressed PF30 cups into said hole? The exterior facing side of the PF30 cups are the threaded part then?
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Old 07-22-18, 08:03 PM
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Originally Posted by wunderchicken View Post
Thanks - that PDF is very helpful. My understanding is the hole in my frame is complaint with the BB386 Evo spec and Specialized or the bike shop pressed PF30 cups into said hole? The exterior facing side of the PF30 cups are the threaded part then?
If your frame is threaded (per your LBS, and from what I can gather most all Sequoias use threaded BB shells), the cups are not pressed in. Rather the cups thread in but the bearings themselves are outside the BB-shell. Remember the crank axle is itself 30mm, inside a standard 68mm roadie bottom bracket the internal bore is only 34mm...that PDF? Remember the bearings themselves are 46mm, there's no physical way to press them inside the frame as they're larger in diameter than the shell, so they are outboard in cups that thread in. What is more the bearings are supposed to be 86.5mm apart per the standard and a 68mm BB shell is only 68mm (hence the name).

What you're getting confused by, I think...is the interchangeability of the bearing cartridges themselves, as well as the interoperability of the cranks. Both PF30 and BB386EVO use the same size of bearing cartridges (46mmx30mmx7mm)--but PF30 press-fits them inside a 68mm shell...BB386EVO however is a swiss-army knife, the bearings can either be pressed in or reside in threaded cups outside spaced at 86.5mm (and with spacers the 386EVO cranks can be made to work with narrower BB30/PF30 systems)

https://www.mantel.com/blog/en/botto...-brackets/#BSA

The cups are outboard of the shell, by themselves should itself looks like this by itself:

https://www.maplegrovecycling.com/pr...t-243422-1.htm

Here's what a BB386EVO SLK crank looks like installed in a threaded shell...you can even just see the wavy-washer for bearing preload in this photo of my gravel rig:


Last edited by Marcus_Ti; 07-22-18 at 08:10 PM.
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