Bottom Bracket compatibilty question

[Pravda]

Afternoon chaps,
I've got a frankenbike/pubbike project I'm trying to build out of an old Hillman MTB frame for as cheap as possible.
My question is, will the old shimano bottom bracket - English threaded 137x24t be interchangeable with my FSA megaexo BB and crankset? (I told you it was a frankenbike).
My research online tells me both are 68mm wide however my knowledge doesn't extend to whether this will make them compatible.
Can post pics of the existing BB if that helps.
Cheers.

[HappyHumber]

If the intended BB & crank is a road double - you may have issues with with the chainline with any front derailleur you're wanting to use. Maybe also possible clearance of the big ring against the seat stay as well, being that MTBs only generally run upto mid 40s tooth counts

That said - you have bits at hand. It's not going to cost you to try.

[Pravda]

Chainline hopefully won't be too much of a problem as it'll be running to singlespeed on the rear with a 10spd campag freehub. I've got plenty of spacers so should be able to sort that out.
The chain stay clearance is the main concern. The crank will be a road double however I'll be removing the little ring which will hopefully solve some problems.

[familyguy]

Both are english BB sizes (TPI and 68mm width), so it will screw straight in. Then the fun begins.

Jim

[Summernight]

Don't know if it helps, but my FSA MegaExo BB (Omega) (road bike) broke recently on the way to work and the local bike handyman came to my work and installed a Shimano 105 BB that was supposedly the correct specs (and I believe him as I saw the numbers and they all matched up with the old BB, although I'm pretty clueless with these things). He installed it with my FSA Omega crankset that was already on the bike.

Everything looked fine and tightened fine into the bike, but when you hopped on there was a noticeable problem - the part of the crank going through the frame just didn't fit snugly in the Shimano BB and it felt like I was riding a clown bike (I felt like I couldn't put any power through the pedals as the arms would shift around sideways). The handyman then tried to fine-tune it with the Shimano BB but it just wasn't happening. The FSA crank wasn't compatible with the Shimano BB.

While reading up online to see what the problem was there seems to be consensus that FSA cranks require FSA BB. However this problem was with a road bike, so not sure about a mountain bike.