mozad655

So my current BB is an FSA, Mega Exo, BC1. 37'' x 24T, BB-4000, 68mm. Link to retailer: Wiggle | FSA BB-4000 Omega Drive MegaExo Bottom Bracket | Bottom Brackets

Crank arms: FSA CK-4000

After 4 years the BB is showing signs of wear. Reviews are very bad and it is expensive so I'm looking into replacing it with a different brand like Shimano. How do I know if a different BB will fit?

If I've researched correctly, I will also have to replace my crank arms. Are there any rules to what crank arms I have to use if I want to use it with a new BB like Shimano?

Slash5

The BB lasted 4 years and a replacement is $40 and that is expensive?
Both FSA and Shimano spindles are 24 mm so in theory they should be interchangeable. However, FSA cranks can be a very tight fit in Shimano BB's. Some people seem to make them work but I know I could not get a FSA crank to fully seat in a Shimano BB without using excessive force. I was afraid I would never get them apart.

fietsbob

External bearing BB are just exposed to wheel spew , if you go to overseas sellers ,

for their cheaper prices ($40 is cheap, retail)

get the proper installation tool and several bearing sets and .. just replace as needed.

mudguards on the front & rear wheel may help.




I am still running 'old' Square taper Stuff . it is better sealed It seems ,

mozad655

Is it possible to replace an external with old square type bottom brackets?

agenkin

The BB-4000 is the 19mm spindle version of the MegaExo bottom bracket. This means that you would need to replace both the crank and the bottom bracket. I was in exact same situation (except that my BB failed a lot faster) and got an FC-5703 crank set with the HTII bottom bracket for around $100 off eBay, from this seller: Shimano 105 FC 5703 175mm 50 39 30T Road Bike Crankset BB Triple Alloy New | eBay

jimc101

No if keeping the crank, but as you say your going to replace the crank arms, just get whatever you like.

If looking to keep with an external BB, would be looking at the latest Shimano Tiagra 4700 Wiggle | Shimano Tiagra FC4700 Chainset | Chainsets, for the crank, and BB70 Wiggle | Shimano BB-R60 Ultegra 6800/105 5800 Hollowtech ii | Bottom Brackets Have given Wiggel links, as that's what you used, but you may find cheaper buy searching

fietsbob

Threaded frame, yes, but have to buy the Square taper cranks too...
resell the current stuff to someone enamored with newer designs.

Dump the Cranks & buy both again, as a set, to get an adequate BB length match..