seen a few threads on this but they’re now 1.5 years old. I’m wondering if I can use a ‘Mega Exo 24mm’ BB with a Shimano Hollowtech Crankset (105’s…).
Mega Exo BB Says “BC 1.37x24T” on the outer bearings, and “BB-73E” on the inner plastic piece. Anyone care to translate what those mean for my own curiosity?
I don’t have an answer, but I’m curious too. I recently changed from an FSA crankset to a SRAM crankset and I swapped out the BBs too because I wasn’t 100% confident that they would be compatible.
But… there is some evidence to show that the FSA BB should be compatible with Shimano… see below
http://www.probikekit.com/display.php?code=k3101
**FSA Mega Exo Ceramic Bearings Bottom Bracket Cups (BB-8000)**This product can be used with all current Shimano 10-speed chainsets.English threading - 68mm width (1.37 x 24T) I think that the “BC” refers to the specs of the ‘bracket cups’ (like thread pitch and size), and “BB” refers to the kinds of bearings in the bottom bracket.
I used an older (2006 or so) FSA Mega-Exo with Shimano no problem. I just tried to use a newer (2008) Mega-Exo with Shimano and the FSA BB was narrower so the crank wouldn’t tighten up fully. There was some sort of curvy washer that came with the BB, and if I used that then it seemed to work fine. But, in the end, I just went back to a Shimano specific BB. There must be 2 different Mega-Exo BBs out there.
wow that’s annoying… I guess i should just buy a new shimano BB.
yes it’ll work (but the plastic part my not)
I think that the BB shell (in your frame) is 1.37" with 24 threads per inch. I would guess that the BB-73 refers to the width. Usually road frames are 68. Some MTB frames are 73mm wide…
Awesome reply…from which I am inferring the following:
24 = diameter of crank spindle in milimeters
1.37 = diameter of BB threads in inches
24 = threads per inch BB shell (and cups)
68 = length from outermost thread to outermost thread of shell (and cups)
I guess the only question is if the shimano and FSA BB’s are the same ‘length’ from the outermost part of the BB to the outermost threads.
Thanks
A quick check of the FSA Site seems to show that the 8000 model should work. It says it won’t, but my experience is that it will. There is another model that likely will not work, the 8200 series.
Yup. Not sure on an FSA BB, but on a shimano one, the plastic part is separate from the bearings, so it could just be removed if its too long and wont fit into your frame.
I know that FSA takes a lot of crap for their BBs, so there are a lot of people with FSA cranks that run Shimano BBs.
If you install the BB cups on the frame, and measure outermost surface to outermost surface, that will be the same for shimano, sram and fsa.
Yup, I just tore the plastic piece off. I think you’re right and it was an MTB BB before…
I’ll compare the outermost-outermost distances from my other ride, but given a cursory measurement of the outermost-outermost thread it seems like it’s the same.
Thanks everyone for the replies.