chess.gary

Hello,

I've searched but found conflicting information. I think this may be a result of specifications changing over time. I've also read this: Square Taper Bottom Bracket Interchangeability.

My question is as follows:
I purchased the EighthInch Courier Crankset (EighthInch Fixed Gear/Single Speed Cranks |EighthInch Courier).
The product specifications state the following:
Crank: Chainring BCD 144 BCD
Crank: Recommended Spindle Length 110 mm
Crank: Spindle Interface Type Square Taper JIS
But the box states, "110mm ISO bottom bracket recommended."

I also purchased the EighthInch Square-Taper Bottom Bracket (EighthInch Bottom Brackets | EighthInch Square-Taper Bottom Bracket). I chose a spindle length of 110mm. The website states, "The 110mm works well with our EighthInch Courier crank."
The box states the following:
- 68mm shell width
- ISO/english threading (1.37" x 24tpi)
- JIS square taper spindle
- crank bolts included

Are these two truly compatible? Will 110mm give me the straightest chainline? Should I simply contact EighthInch?

Thank you.

Scrodzilla

My shop stopped carrying that crankset because EighthInch is stupid and couldn't tell me what BB to actually use. I eventually found that using a 107mm JIS spindle works the best.

ufbeans

If I could resurrect an old thread here.......I run my cranks with the 110 mm eighthinch bottom bracket. The chain line looks straight to me but I haven't measured it if its actually 42mm. Even if I did measure it, no guarantees I could get it accurate enough to within a few mm. I like these cranks by the way. They are nice and thick and of course 144 bcd. It's ugly though. I tossed the stock chainring and picked up a 7075 47t and I'm good to go.

ufbeans

So to continue talking to myself and for the sake of Internet posterity I did some more accurate measuring of these cranks. I measured the circumference of my seat tube using a string and calculated its diameter and then placed a ruler against it to find that with the 110 bottom bracket you get a 43.18 mm chain line. With the 107 spindle BB that Scrod suggested you would get a 41.68 chainline. So Scrod is technically closer to the magical 42 mm chainline. Is this guy ever wrong? I'm not changing my BB though as its close enough for me and maybe even closer to my formula hub all city cog combo rear chain line. I can't be exactly sure but we are talking about a minuscule difference only hardcore bike nerds would even care about.

Scrodzilla

No.

chess.gary

Hahaha seriously. I really appreciate both of your responses. So ufbeans, thank you for resurrecting the old thread and no you weren't talking to yourself. I'm impressed by both Scrodzilla's bicycle knowledge (nothing new there) and ufbeans's commitment to finding the answer. I spoke with someone at Eighth Inch, but this is all I got (despite directing them to this thread):

"It is possible you could use a 107 with the courier cranks. Will that provide a stronger chainline? Not in our experience. A 107 spindle with a courier crankset on a Scrambler, Manifest or Dispatch frame puts the crankset too close to the frame. So close it might even hit when heavy pressure is applied to cranks."

I had used the word "straighter" not "stronger" so I believe he simply mistyped in responding. But given that response, are you guys still sticking with the 107mm over the 110mm? Or does it truly not matter and I've already wasted far too much time and energy on this decision?

Thank you!

mrblue

I really hate trying to match square taper bottom brackets, to cranksets, to frames. It always seems like one combo of BB and crankset works great on one frame, but not another, and vice versa... It could be that I am an OCD perfectionist, but I really hate dealing with this sort of issue. I'm actually having the same issue with a Miche crankset, Miche BB, and a Leader 725 frame.

The crankset and BB work great, giving me a perfect 42mm chainline, on the Leader 725. However, the Leader 725 flexes like Silly Putty, and I end up whacking the crankarm against the chainstay whenever I skid, so I need to figure out a longer BB, thus f'ing up the chainline. Anyway, enough of my issues. Just do what I do: Buy a whole bunch of bottom brackets, have them sitting around, then you can choose and experiment with them, all day, all week, all month, all year, for the rest of your life...until you go crazy.

Or, just do what Scrod says. He's usually spot on.


I'm starting to hate my bike. Anyone want a Leader 725 frameset?

Flatulentfox

The rest of the cycling world has moved away from square taper.

Everything about square taper is pain. Two piece crank and outboard bearing are far superior IMO.

I can't figure why the "fixie" scene has such a hard on for them...

Scrodzilla

The cycling world moved away from bikes having fixed gear drivetrains a while back too.

It is? I actually still prefer a square-taper setup.

One theory is that outboard-style bearings can't typically withstand both the back and forth stress put upon them by riding fixed gear bikes on the street. The amount of ****ed up outboard Sram BBs I've seen and replaced for people supports this theory.

mrblue

Just out of curiosity, why is that?

Scrodzilla

See my edited post above.

Flatulentfox

Ha. Good point.

The larger diameter of the spindle allows for a stronger/stiffer/lighter interface between the cranks and bottom bracket, everything else equal. Its also much easier to screw up a tapered interface by over/under torquing. Many splined designs do not require the use of a crank puller. In my experience I have had fewer problems with splined interfaces and outboard bearings vs square taper. ISIS drive was an exception. That was terrible...

How does fixed riding put any more stress on a BB than any other form of riding? The bearings don't care which way they are turning.

Srams outboard BBs are garbage. There are also plenty of good outboard BBs. There are also plenty of garbage square taper BBs that will fail with the same regularity as Sram/Truative outboard junk.


A quality square taper crank and BB will obviously perform very good. A quality two piece set up with outboard bearings at least has the potential to perform better. Does it make much difference for most of us? Probably not.

Scrodzilla

It's not riding fixed that stresses the bearings but I'm fairly certain that riding fast and suddenly locking up the bearings to skid (as most fixed riders do) would put added stress on the way the cartridges fit into the cups in a way that wouldn't occur during normal riding and not necessarily the bearings themselves. I know people who have blown through Sram GXP BBs in under a month on fixed gear bikes ridden on the street (not track bikes) while others who use them on road or mountain bikes have had them for considerably longer.

At any rate, I don't have the trouble you describe with over-torquing or under-torquing my square-taper cranks because I majored in rocket science.

TejanoTrackie 

Technologically, outboard bearing / splined BBs are superior to square taper, just as threadless stems are superior to threaded / quill, but far more important is the quality of the parts. There are plenty of very powerful keirin racers that do just fine on square taper / quill setups. Over/under tightening of a square taper BB won't occur if you use a decent quality torque wrench.

Scrodzilla

And have a degree in rocket science.