I have a FSA Gossamer SRM crank with mega-exo. For my first two bottom brackets I went with the cheap FSA bottom bracket recommended by SRM but it was incredible how fast those things would start to grind. About a month ago I decided to grab a Dura-ace 7900 BB and toss it on instead. 2 things to note: it feels noticeably better and will supposedly last much longer which is the important thing here. The tolerances are, as I had read online and you saw, absurdly tight. It took smacking my cranks with a rubber mallet to a level most probably wouldn't feel comfortable with to get it fully seated in there. Frankly it seems worth it to me as the FSA BB was such crap that I would have been replacing it every 2-3 months. My SRM still works and the cranks spin better than ever before (though still not as well as my wife's GXP cranks).

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Benjamin Deal - Professional - Instagram - TriRig - Lodi Cyclery
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So, I found this on Wheels Manufacturing's site: https://wheelsmfg.com/enduro-24-07x37-ceramic-hybrid-sealed-bearing.html

They've just recently stopped carrying this 24mm "overbore" bearing set. Maybe a now-discontinued Wheels Manufacturing BB with these bearings is what I originally saw.

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"They're made of latex, not nitroglycerin"

I used to have a FSA Gossamer SRM MegaExo spindle and what I did was use an Shimano BB (the new BBR60 aka Ultegra 6800) with it. The way I got it to fit not so "snug" (without having to resort to the mallet) is to sand the living daylights out of the spindle to get it to match the same rough diameter of a Shimano axle. You don't have to sand the entire thing just the portion closest to the drive side spider and the opposite NDS closest to the splines for the crank arm mating splines.

I used a caliper to gauge roughly how much I needed to take off. The reference Shimano I used (7800 crankset) measured something close to 23.98mm or so (don't recall exactly) and the FSA was coming in at a tick over 24 (like 24.02 or 24.04 range from my cheapo "tool shop" caliper). The middle portion of either spindle tapered off to well below <23.95 or lower (so you weren't stuck sanding the entire FSA spindle). Went with coarse sandpaper (200 or 400, I forget exactly what I had available at the time) until the fit was snug but the crank could be removed by hand then used a fine mesh sandpaper to clean up the finish (something like 1800 or 2000 grit). Took me forever to do this by hand but it worked. A lathe would've been faster but then you'd probably have to build a fixture to ensure the spindle is mounted properly prior to removing material.

I forget the exact numbers but you get the idea.

So, those overbore Enduro ceramic bearings for Megaexo spindles are still available elsewhere, and can apparently be pressed into a Wheels Manufacturing thread-together BB86/92 sleeve, but they're ~$80 a pair.

Found a more budget friendly option from Rulla with ABEC-3 chromoly bearings for ~$10/pair, but you have to have them shipped from the UK.

I think I'll try a standard 24mm Wheels Mfg BB, first. If the fit is too tight, I'll order a set of overbore bearings from one of the two sources.

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"They're made of latex, not nitroglycerin"

Friend of mine had the stuck crank axle probelm original megaexo BB failed in months. LBS (Cervelo dealer not just BSOs) put Shimano BB in.
All ok for 2 months... then that BB failed. Had to be VERY brutal to remove the crank. Luckily it was on an overbuilt Alu bike, not carbon. And threaded BB shell.
Would be bad for a strain-gauged power meter !

Suspect the Shimano BB failed as I bet the LBS had to whack the crank in fiercely too, causing the bearings to Brinell in the process.

Bought a quality BB aftet that (made by Hope in the UK). And I fitted it for him. No problems since.

I put a new BB in my old Cervelo P2. At the time it came with MegaExo FSA SLK-light cranks which I later replaced with a Rotor 3D... but now I switched it back. I got a Kogel ceramic BB, easy installation, reinstalled the FSA crank, easy as pie. Only ridden it on the trainer because I'm in the process of doing a bigger overhaul which includes replacing the Vision stock bars with a TriRig front.

Interestingly, Hope recommends against using their 24mm BB for Megaexo cranks. But it looks like their BB86/92 sleeve takes the same size bearings as the Wheels Mfg, (OD 37mm x 7mm wide), so either 24.07mm ID replacement cartridge option I mentioned above could be installed.

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"They're made of latex, not nitroglycerin"

I'll check back with what was bought / done for the set up i describe. It was earlier this year, but may have some wattsapp back and forth from when the parts were bought.

Your logic sounds... sound from a 1st read.

I did see that Kogel had an FSA specific 24mm BB86/92 bottom bracket, with a different P/N than the 24mm they recommend for Rotor/Shimano. Those are press-fit, though, right? I was looking for a BB where the two sides thread together in hopes of reducing the chances of future creaking.

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"They're made of latex, not nitroglycerin"

No it's threaded, not pressfit. Oldschool BSA thread bottom bracket standard. https://www.kogel.cc/...d-24w-for-fsa-cranks

I have a BB86 shell, that won't work. This one will, but it looks press-fit, only, unlike the Wheels Mfg & Hope versions in which the two sides thread together.



Alas, I was ready to order the Wheels Manufacturing Shimano BB and the replacement over-bore bearings, but the close out deal on the Power2Max Type S that prompted this wild goose chase has sold out :(.

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"They're made of latex, not nitroglycerin"