FarHorizon

Just in case I do have to replace my BB, I think I currently have an FSA Mega Exo (or something like that - the cranks are definitely FSA and the BB spindle is definitely hollow).

The crank arms are currently 170mm, but I scored a crank today called a Shimano Alivio with 175mm arms. Since I got it for $5, I can't complain...

So now for the questions:

1. Can I simply replace the FSA crank with the Alivio, or will I need to change the BB also?
2. If I do need to replace the BB, how do I ensure that the replacement is the same axle width as the original?
3. Since the FSA was intended to be a single-speed, and the Alivio was (I think) intended to be a triple, what will this do to my chain line?
4. If I do need to replace the BB, what's the least-expensive, most-durable, sealed-bearing one I should consider? (weight does NOT matter to me)
5. Are the chain rings of the FSA the same BCD as the Alivio (the latter, I'm pretty sure, is 104mm)?
6. So far as I know, I DO need a single-speed chainwheel and it should be ⅛ inch width?
7. Is the Shimano BB called an "octalink?"

Pardon my ignorance...

SkyDog75

You'll need to change the bottom bracket. Whatever bottom bracket your particular Alivio crankset needs, it isn't MegaEXO.

The bottom bracket doesn't need to be the same width as the original. It needs to be whatever width the Alivio crankset was designed for. Finding the appropriate spindle length for your crankset should be easy once you look closely at the Shimano crankset to find its model number. It's probably stamped on the back side of the crank arm(s).

...unless you've got a two-piece crank whose spindle is permanently attached to the drive side crank arm. In that case, the crankset's spindle length is fixed and needs to be appropriate for the frame's bottom bracket shell width.

If you pick a bottom bracket with the correct spindle length for your crankset, your chainline should be correct for a stock setup. (Again, assuming it's a three-piece crankset.)

That depends on your particular crankset. Alivio cranksets have been square taper, Octalink, and most recently, Hollowtech II. Figure out which interface and size you need, then we can help you pick a model.

I'd need model numbers to tell you for sure.

Octalink is a proprietary bottom bracket/crank arm interface. Do you need an Octalink bottom bracket? That depends on your particular crankset model.

Bottom line: Find your crankset's model number and go from there.

jimc101

Add to that, Octalink comes in 2 version, V1 & V2, the V1 has shallower splines, and was only used on a limited number of cranks. V2 is the more common version, and was used on all MTB versions of Shimano Octalink cranks,

Although a Proprietary design, FSA was one of the few aftermarket manufactures to release cranks with the Octalink BB spec

For all you ever wanted to know about BB's see here Sheldon Brown's Bottom Bracket Size Database

FarHorizon

Thanks, gents. I'll look for numbers on the morrow.

achoo

It seems the latest Alivio cranks use square-taper bottom brackets:

Alivio 9-Speed

Do you know the exact crankset model you have? The Sheldon Brown page seems dated - it has no mention of FSA bottom brackets at all.

FarHorizon

The FSA that's on the bike says: FSA V-Drive - 175C - CK-7060 - DN08F0841 / DN08F5942

The Shimano Alivio says: FC-M410 / FC-M411 - 175

Both cranksets are four-arm and 104 BCD

The FSA bottom bracket that is installed is marked: BC137-X24T

The actual width of the frame's bottom bracket shell (not counting the bottom bracket cups or crank shaft extension) is 75mm wide.

So to summarize, I'd like to switch from the current FSA (which is creaking) to the Shimano Octalink / Alivio combo. But to do so, I need to select the proper Octalink bottom bracket. Since Octalink BBs come in a variety of widths and diameters, which is correct for this frame? Thanks again - FH

jimc101

Thats a previous generation of Alivio, current M4000 is HT2 ALIVIO (M4000) 9-Spd

HillRider

The FC-M410 is a square taper crank, not an Octalink or Hollowtech II. Your bottom bracket markings of BC1.37x24T means the bottom bracket threading is "English". It tells us nothing about the type or width of the spindle. Your bbs shell is most likely 73 mm wide as that is a common MTB width.

SkyDog75

OK, now we've got the info we need to pick a bottom bracket for that Shimano Alivio crankset. Googling the crankset's model number, we can find Shimano TechDocs that tell us it's a square taper crankset designed for use with a 113 mm bottom bracket spindle. As HillRider mentioned, the markings on your FSA bottom bracket indicate English threading. So we need to find a square taper bottom bracket with a 113 mm spindle that'll install into your 73 mm English threaded bottom bracket shell:

Shimano UN55 Bottom Bracket, 113 mm spindle, 73 mm English shell - $24.28 at Niagara Cycle

To remove your FSA crankset, you'll likely need an Allen wrench and a tool like this one to remove the external bearings. Once it's removed, you'll need a Shimano-compatible splined bottom bracket tool like the Park Tool BBT-32 to install your new bottom bracket and a socket wrench to install your crank arms.

I'd strongly recommend using a torque wrench when installing the bottom bracket and crank arms to ensure you get them torqued properly. Installing them too loose or too tight can cause damage. The torque specs, as listed in this Shimano TechDoc, are as follows:

Bottom Bracket: 50 - 70 N·m (435 - 608 in. lbs.)
Crank Arms: 35 - 50 N·m (305 - 435 in. lbs.)

Your Alivio crankset is square taper, not Octalink.

FarHorizon

Gentlemen, I appreciate your comments, but I just looked again. My Alivio FC-M410/M411 pair is not a square taper. It IS a splined type of one persuasion or the other.

For the time being, the need to change the cranks may have disappeared. I took my bike to the local co-op, and the mechanic there noticed something that I hadn't. My current chain has a master link. A very loose, very old master link. The chain itself, additionally, is somewhat worn.

So before changing anything else, I plan to replace the chain and to completely eliminate the master link. I have a chain tool, and know how to use it...

If my noise persists after changing the chain, then I'll explore further options. So thank you all very kindly for the information. I will come back to this thread should I actually need to work on the BB. If the chain does fix the problem, I'll mention it here for the benefit of anyone else with mysterious drive train noise.

Cordially - FH

HillRider

Then either you have given us the wrong model number for your crank or Shimano doesn't know what they are selling. If it's splined and if it's really a Shimano crank than it's an Octalink. If it's really an FC-410, then it's square taper. Otherwise, who knows.

FarHorizon

Well, my eyes aren't what they used to be... I'll look again.

SkyDog75

If you do need to look into these Alivio cranks again... Along with double-checking the model number, a picture would be awfully helpful.

Bezalel

There was a FC-M410-8 that was Octalink, However I don't see any reference to a FC-M411-8 ever being produced. I'm not sure what the difference between the M410 and M411 was but they specified different spindle lengths.

M410-8 118
M410 113
M411 123

But since you're running a single, just use whatever gives you the desired chainline.

The only part that should be stamped FC-M410/FC-M411 is the left square taper crank arm because that part is common to both models. The right crank should only have 1 model number.

FarHorizon

Well, guys, maybe Shimano DOESN'T know what they've made, because here's what I've got:

HillRider

OK, I'm convinced those are really Octalink, perhaps the M410-8 that Bezali referenced. However, I'm not certain if they are V1 or V2. V1 (road) Octalinks were only made in 109 (double) and 118 (triple) crank lengths.

FarHorizon

Hi HillRider - Typically, I thought that road cranks were almost always 5-arm and MTB ones 4-arm, but I may be mistaken. If I'm correct, then this came off a MTB of some type or another. Based on the "depth" of my splines (and matching them to the photos on Sheldon Brown's site), I think that this crankset uses an "Octalink v2" BB, but again, I'm not certain.

Is there any way that I can measure the splines to see? Or might it be easier to drop by the local bike shop & ask?

Thanks - FH

Bezalel

You have a FC-M410-8. It uses an Octalink V2 BB. Shimano's recommendation is a BB-ES25 in 118mm.

https://cycle.shimano.co.kr/media/tec...9830667768.PDF

SkyDog75

Alivio is a mountain bike groupset, so it should be Octalink V2. And although I'm not the Octalink expert, those splines look too deep to be V1. You can compare to the Octalink bottom bracket pics on Sheldon Brown's web site:

Sheldon Brown's Bottom Bracket Size Database

FarHorizon

Problem solved: I put a new chain on, and the drive train is now quieter than a bought-off witness. The Alivio goes in the parts bin until needed. Thanks again to all for the help!

ksisler

FSA Mega Exo has its own BB concept and it comes fully attached to the drive side crank. Consider it "1 Piece". All the ones I have seen (and use with considerable delight) are triples not singles, but who knows...

Overall the FSA Mega Exo gives me all the impression of being an excellent crank and one that can occasionally be found at a killer price (~$79 complete kit about a year back at Nashbar for the last couple I bought) so be sure to shop for price if buying another. Should be findable in 170, 175, and 177.5mm (I remember having difficulty finding one in 180mm and took the closest available to that). The ones I have came with a spacer to use as needed/if needed on left or right side to optimize the chain line, but I never found it was needed (for 9 speed).

Hope that helps
/K

FarHorizon

I think that the FSA that I have is NOT a "Mega-EXO" model. Despite that, it does appear to have the crank-shaft attached to the drive-side crank and the left side is bolted on. I found the bolts on my left crank somewhat loose (probably contributing to the noises) and have tightened them subsequently.

Because the FSA was the "stock" crank on this bike (a Kona "Unit" single speed), I suspect that it may be a special model or one that was custom-produced for Kona. In either case, it seems sturdy and well made, and once the arms were tightened, it works fine.