Fuzzy_Dunlop

fietsbob

"hollowtech" .. a tube is part of the right crankarm , not separate...

they may share the same bolt circle diameter standard chainring mount ..

What is that? measure and report back..

Jeff Wills

No. As Bob says, you'll need an FSA BB to match your crank. If it's second hand, ask the seller if it comes with the bottom bracket bearings. If it does you're OK, if not steer clear.

jimc101

Bit confused with what your planning, sounds like you want to use the double crank on a triple set up, this may cause issue with the FR, as if your currently have a triple FD, it may not play well with a double crank your also be left with an additional shift on the front shifter, you will need to set up so it doesn't over/under shift.

For the BB compatibility, Shimano HT2 and FSA MegaEXO technically aren't compatible, but Google search this, and plenty of people have got FSA cranks to work with Shimano HT2 BB's (I haven't tried this myself)

For the BCD, your your still left with the missing 3rd chaining if you swap, guessing the FSA is a 50/34, have you worked out if you need the low 30t gear you currently have, or where you spend most of your time, as your loosing a lot in the middle going from triple to double, which you may or may not use,

Fuzzy_Dunlop

Just to clarify, I am not looking to change to a double crank yet, just the crank arms on my existing triple crank. I understand I will need to change my rear cassette, FD and crankset in order to go to a double crank. Left shifter should still work afaik, as long as I set the limit screw to prevent it shifting to a non-existent third ring.

to answer the previous question, the FSA crank I have the chance to buy does not include the BB, just the crank. My current BB is a Shimano tiagra 1.37x24 road BB. From what I understand, the FSA K Light crank will fit on a hollowtech ii compatible BB. My question is whether those FSA crank arms will fit on my existing chain rings and BB.

Kontact 

What you're talking about doesn't make sense. You don't need to change you cassette with the crank, for instance.

And the "crank arms" are "the crank". A crankset is the crank arms with the chainring/chainwheels. If you change the "crank arms" you are changing the crank.

Figure out what the terms mean and then what you want to do.
These are crank arms:


These are chainrings:

Fuzzy_Dunlop

Kontact 

That's the first time you mentioned the chainrings.

Generally, yes, you can switch if they are the same BCD. There is often a chain catcher pin on the large ring that goes under the arm, make sure it can be installed in the right spot.

Fuzzy_Dunlop

mitchmellow62

If you are attempting to change the FSA double into a triple it won't work. I believe the Shimano crankset has a 130 bcd for the larger rings and a 74 bcd for the smallest ring. The smallest ring that can have 130 bcd is a 38 tooth, if my recollection is correct. Since the FSA is a double, it will only have the 130 bcd for the two larger rings and will be missing the 74 bcd for the small ring.

dsaul

As Mitchmellow62 said, you can't make that crankset into a triple. However, it should work fine as a double, if you lock out the 3rd shift. There is no need to change anything else on the bike.

Litespud

Not quite - the last sentence of the original post is: "My question is, will the FSA crank arms fit on my Shimano chain rings/BB as-is?"

T Stew

Well when I researched this a couple years ago I found that the FSA used slightly different sizes in their carbon cranks vs alloy cranks and that only the alloy 24mm spindle ones where compatible with Shimano Hollowtech II, the carbon ones were slightly bigger and a few that tried had to be hammered in IIRC they were too tight, but I didn't try this. I ended up getting the 30mm version and had to buy their special bottom bracket to fit standard English threaded bb bike.

But that poses the question... Which type of SL-K light crank are you getting... they are available in multiple styles to fit different bb's. I have two SL-K lights and both are 30mm spindle, obviously won't fit a 24mm hole in Hollowtech II - you probably are aware of this just making sure.

Shouldn't be an issue putting on different co. chainrings as long as BCD same... I actually converted an SL-K light to a 1X chainring. Some companies claim to optimize their chainrings to their own chains so there could be slight noise or quirky shifting but I am not sure if this is really a problem.