I’m planning to buy a Giant Revolt 1 (2025), which comes with an FSA Mega EXA bottom bracket and an FSA Omega Adventure 48/32 crankset.
I’d like to lower the front gearing, but I’m stuck because I can’t find detailed specs for the BB/crank interface or chainring compatibility. Giant just lists “FSA Mega EXA” and FSA’s documentation isn’t very clear either.
From what I’ve found so far, the bike is spec’d with a 48/32t crank and Mega EXA BB, but no further details on spindle type, chainring BCD, or compatibility limits .
Before I start swapping parts, I’m trying to figure out:
- What exact BB standard this uses (threaded BSA? spindle diameter?)
- Chainring BCD / whether smaller rings are available for this crank
- Whether it’s easier to swap chainrings, crankset, or the whole BB
If anyone owns this bike (or has worked with this crank/BB combo), I’d really appreciate any specifics or upgrade suggestions.
Also, to proceed with the changes, what are my possible options (My region has poor supply of FSA components, Shimano components are far more easily available)?
- Can I replace the FSA crankset with a Shimano one (looking at GRX 46/30) while keeping the BB same ? (I doubt they both share the same spindle diameter)
- Will I have to replace the BB too ? (I came across a video online with a guy facing issues replacing his FSA BB to a Shimano BB)
- Any other options I can explore?
by ShreeshBhan
2 Comments
pretty sure all giants these days are bb86
to use a shimano crank youll need to replace the bb, fsa omega adventure uses a 19mm spindle, shimano is 24.
crank is 120/90 bcd
looking at your link of the revolt specs i see the cassete has max cog of 34. pretty sure that rear derailleur can take a 36 but im going from memory so do your homework.
If you want to get lower gearing, you do have the option to change out the chainrings on the cranks, though I’m not sure how easy or difficult it is for you to source chainrings for a 120/90 BCD crank, FSA does say that they have a 46/30t chainring available for the Omega Megaexo cranks.
If you’re going to go with swapping out the cranks, then you can purchase a set of Shimano GRX 600 cranks with 46/30 chainrings or if they’re available locally, Microshift Sword Cranks have a 48/31 or 46/29t chainring options, though the cranks are a bit heavier than Shimano. Going this route will mean that you would have to swap out the bottom bracket to a 24mm spindle compatible one as the FSA crank uses a 19mm spindle. You would also need to change the FD to a Microshift Sword, Cues U6030, or any GRX FD as the chainline on GRX and Sword cranks are about 2.5mm outboard at 47mm than the FSA one which iirc adopts a 43.5mm chainline.
Btw, last I checked, all Aluminum Giant Revolts use a 68mm BSA Bottom Bracket Standard and only the Carbon Models use Pressfit.