Need help understanding JIS Square taper specs for new crankset
 

Hello, I have a new crankset on the way - FSA Vero Compact (50/34) 10 speed JIS Square taper. Installing in a 68mm BB shell. Can someone help me understand what B.B. I need? I found a Shimano JIS Square taper 68 x 127mm BC1.37 x 24. I’ve also found 68 x 118 and 68 x 134 and 68 x 103/107. How do I know which bottom bracket is correct? I haven’t received the crankset yet, and I’m trying to collect all of my parts in advance. I’ve looked, but can’t find the crankset install docs online (assuming they would contain the B.B. spec). Appreciate any help!

Believe correct size spindle for this crankset is 68 X 110mm. English threading which is 1.37 x 24.

Unless some one here posts a manufacture's or user's suggestion the way to find out the BB length is by trial and error.

The bike industry isn't a simple plug and play one often:) Andy

https://www.treefortbikes.com/FSA-Ve...0-JIS-Crankset

https://www.bikewagon.com/fsa-vero-c...crankset-black

Couple of resellers say 110mm.

Keep a couple of cheap Shimano BBs on hand to test, then buy the (correct?) one.

I am seeing that as well. Guessing the Spindle length for the 10 speed version is the same as the 9?

There isn't any info on FSA website that I could find for this crankset.

I know, strange, like it doesn’t exist. I have an email in to FSA tech support to see if they can help.

It will be whatever the design of the crankset requires, the 10-speed may or may not be the same as 9-speed, not way to tell except from the manufacturer or trial-and-error.

Somewhat common when the part is meant for OEM or otherwise isn't in one of their "prestige" lines. ;)

I'd be pretty comfortable ordering a 110mm BB, measuring the chainline and getting a different one if anything is off or doesn't clear. Square-taper cartridge BBs are pretty cheap and some of us end up with a variety in our parts stashes before we know it.

I'm getting an education. Just got off the phone with FSA. They said if this was a typical road frame then 110, BUT, since it has 135mm dropouts, they suggest a 68 x 113 to keep the chainline right. Doesn't seem like a big difference, but I'll go with it.

Any thoughts on quality of a Shimano UN-26 (Tourney) versus UN-55 versus an FSA TH Industries?

Any of those would do the job well. My preference, since you have advice from the horse's mouth, would be to go straight for the UN55 in 113mm. :thumb:

cool, I appreciate that. The frame I’m using was a complete bike parted out. Just saw a pic of the breakdown. Looks like the original crankset was 7/8 speed with a 68x110.5. Is moving to a 10 speed cassette the reason to go 113 I wonder?

Your 135mm rear end has more to do with it than that. When Shimano went from 7-speed to 8-speed, the cassette only got about 3.5mm wider, with the remainder going onto the non-drive side. That works out to less than a 2mm difference in the chainline, and my preference is to keep the crankset in as far as possible so that the big ring works cleanly with the whole cassette.

In your opinion then, does the 113 seem right, or if 110.5 worked with the manufacturers build at 7/8 speed should it be fine for 10speed?

Can you sent it straight back, and order an external BB (i.e Shimano HT2 spec crank)?

Confused about what you are trying to do, order some parts, then do the research on other essential parts to make the original purchase fit/work, it doesn't really make sense to do it like this, make sure you have got all your parts/specs down before ordering anything and make sure that you can get everything in for the same time (so you aren't waiting months for that last essential part).

Going with the external BB type crank eliminates all issue with compatibility & chainlines as, as long as you stick with the same brand, there is only one possible spindle width which is fixed. and it eliminates any of this trial and error craziness (and if your going do do that, the cost will be far higher in time and money buying unnecessary BB's than just buying a decent Shimano HT2 crank/BB in the first place).

Pfft, where's the fun and learning in that? :p

FYI

Exploded diagram and part numbers including bottom brackets...

• Vero Pro 1x crankset - https://shop.fullspeedahead.com/en/f...5709617aa6129/
• Vero Pro 2x crankset - https://shop.fullspeedahead.com/en/f...d1b7799ac9128/

The FSA documentation website is at https://www.fullspeedahead.com/en/su.../documentation.


-Tim-

"7/8 speed" refers to the intended cog and chain width, not the rear spacing. 7-speed is usually 126mm, 8-speed is usually 130mm, same as 10-speed.

I stand by trying the 113mm first, since that's what FSA themselves recommend for your bike. It's not going to make a huge difference either way.

This isn't an exact science. Different bikes have different chainstays with different clearance issues. (Dropout spacing, chainstay diameter and derails like the attachment at the bottom bracket and (sometimes) chainstay curvature all make a difference. So does the shape of the crank.) So no one really knows what the minimum BB width is until you actually try everything. And even then, remember this is a fit of a very shallow taper over an equally shallow taper, done by hand. Very small differences in size on either the crank of spindle will affect how far in the crank slides. Now Shimano is pretty consistent with their spindles. But different crank manufactures adhere to spec to varying degrees.

So the end result is that we are all guessing. Everyone here and FSA. The advice of buying a best guess Shimano BB and trying it out is excellent. Then you know what you really want/need.

Aside - I have recently set up two bikes as triples with absolute minimum Q-factors for my knees. Went first to the Shimano BBs I had on hand, measured, calculated and ordered from Phil Wood the perfect bottom brackets. Worked like a charm. My frame clearances are in single widths of cardboard. My knees love it.

Edit: there is also chainline. Some consider the exact, proper chainline to be the word of God but face it, chainlines are a lot more like pant sizes. Perfect is nice but we can wear an inch bigger or smaller. Being off with your chainline will cost you a little an reduced chain life but so will using your rear derailleur and any combination that isn't perfect. Other issues get worse with poor chainlines, but still others get better. Crankset too far in? Small-small is worse for chain stretch and interference with the large chainring but the chain is happier in the low gears and there is less friction in the highest chain tensions. Too far out? Reverse all that I just said.

Ben

Perfectly fair question. I had the major drivetrain components in my spare parts bin already (shifters, derailleurs, crankset). I was going external, but my frames outer B.B. shell is rough, and upon examination, the old crankset was pretty worn. Just happened to see the new FSA 10 speed crank on sale/closeout marked down to $30. Hard to pass up. Since it’s Square taper I moved in that direction. All other parts are sourced and fitted, so it’s just the crank B.B. I’m fiddling with. I figure if I wind up with a new 10 speed crank and new B.B. on this project for less than $50 I’ve done alright. Anyway, that’s my rationale.

That makes sense, if you can get parts crazy cheap it's worth grabbing them and working around any compatibility issues (and yes I have done that, may take a while to use the part, but it will get used eventually)

Thanks Ben. I’m guessing that whichever way I went (110 vs 113) a 3mm difference isn’t going to make a huge swing in the chain line over the distance of a longish chainstay (430mm) anyway. I’m in the “saving knees” camp with you. I prefer a close to frame approach until it negatively impacts shifting performance.

The real issue is chainline. The biggest factor is the amount of offset in the crank, but other factors, like rear triangle spacing will also have an effect. I think that's why nobody wants to say for sure for every application. Derailleur bikes, fortunately, are a little more forgiving regarding chainline than single speeds.

If I don't know, I'll install the longest spindle bottom bracket I have on hand, install the crankset, and see how it looks. Old bikes tended to have real long BB spindles compared to modern bike standards so, wherever I happen to be working, I can usually find a big old bottom bracket for test fitting. Once I know how much I need to move the crankset in toward the centerline of the bike and I know the spindle length of my test fit BB, determining the best spindle length is easy.

RG- Chain line is a wonderful spec to hit spot on. But chain ring clearance with the chain stays and the ability for the ft der to travel far enough in or out are more direct to the system's working.

Although it sounds like we overlap a lot in our understanding. Andy

Loving this conversation. For those willing to continue to indulge me here (and I may very well wind up with an extra B.B. or 2 after all if this), I got an update from FSA today. The proper (by spec) B.B. is supposed to be a 68 x 103. The Q factor on this crank is supposed to be 143. Here is what I’m thinking...

I have this frame to build as a winter trainer because it was cheap and came close to matching my regular roadie (except for having 135mm dropouts). My current bike also has shorter chainstays, 130mm dropouts, and a Q factor of 147, which gives me no issues. I’m sketching this up to play with the math, but it seems that if I tried a 68 x 107 B.B. I would add 4mm to the Q factor, matching what I currently ride. As an added benefit, I’ll pick up 2mm of the 2.5mm difference between a 130 and a 135 dropout on the drivetrain side. Given the longer chaintays on this frame, my conjecture is that chainline and therefore shifting should be pretty similar between the two bikes since I’m theory I’ll only be .5mm off from what would be expected with 130mm dropouts, but Im stretching the distance to the cassette so flattening the chainline a bit. Sound reasonable? A fun experiment anyway.