i was being deliberatly ambiguous. does that clear things up? :p

the sugino and shimano are both JIS, but there is a difference in the tapers. take measurements. they're different. QBP recommends using the sugino, i asked them, they verifed it.

your statement is contradictory.
how can they both be JIS, yet have different tapers?
does not compute

The UN73 is better than the UN53... hollow spindle, and in the 107mm length, the non-driveside cup is metal instead of plastic.

finally someone got this right. JIS is JIS is JIS. Your cranks won't fit any better with a sugino bb than they will with a JIS Shimano. In fact, if QC happens to be tighter in the tange factory (making those UN xx's) than in the Sugino factory, the Shimano will fit better. They are designed to a standard, and it's all about how close they fit to that standard.

OneTinSloth, have you looked at the two recently. This has been argued 1,000 times in past threads. Some people say this, some people say that. You guys can ride what ever you want. But I prefer to ride what was intended for the actual cranks. Not only because I believe that the taper is different, but also because of chainline. While I may be wrong, I am wrong with hundreds of other people. But look at them, they are definately different. I do believe the Sugino spindle is a tad stiffer, like uh, yes.

I am to Gangsta for this, PEACE.

to gangsta, or not to gangsta? that is the question.

hey look, both JIS, not exactly the same. dunno if you can tell by the pic, but for one, the taper length is longer on the FSA. i can get out the micrometer and really nit-pick, but i wont.

Very, very interesting. Now please do me a favor and mount them both on the same JIS crank and see how far they insert given same torque values. Then measure that length and let us know if there still is a difference.

Don't forget, just because you follow the same standard, there still are manufacturer's tolerances. The way a manufacturer manages this tolerance can be very important. one manufacturer may decide that their variance from the mean (i.e. pre tolerance dimension target) is .00X while another manufacturer will use the same standard but decide that their variance shall be .00Z (Z= X/2). The result is that using the same standard the second manufacturer will have a better more reliable, lower variance product than manufacturer 1. Prime example, dodge vs. mitsubishi, engines and chasis built from the same drawings, but one is a piece of junk.

that is actually a very good experiment. i think i will do that sometime in the near future.

Yes, please get out the "mike". this will prove that there is variance in products built to the same standard. The length of the taper does not matter, the angle and starting dimensions are important.

please do.

In the meantime get your micrometer and measuer the spindle tip on both cranks and then move in at the same distance on both bbs and measure again. Are the numbers different from bb to bb? If they are we can assume that one bb spindle will insert deeper than the other.

okay heres some quick measurements (in mm)
syncros / fsa
starting width 7.60 / 7.75
ending width 8.90 / 8.95
hypotenuse length 16.30 / 15.65

on the FSA, the taper does not begin and the very end of the spindle, its a bit rounded on the end. i measured from where the taper begins, which is apparent, not the very end of the BB. on the syncros, the very end of the spindle is the start of the taper. easy to see which is better...

that should be enough data to find the angles...

awesome!

Now someone please figure out how much of a difference 5/100 of a mm in diameter will make in terms of insertion dept.

I'll throw some more fuel for this fire we got going on here. Use BMX sqaure tapered cranks instead of standard road cranks if you want to get every inch of that square tapered lovin'

Read response number 12 in THIS POST

Or..... numbers 2, 4, 6, 10, 12 and 14 in THIS POST
Now, go back and read 4 and 6 one more time. :D :D

Dogbait

you need to re do the measurements, they can not be right. Or rather, they do not serve the goal you are trying to reach. Start width, end width and Hypot length are good measurements, but by simple inspection they do not add up. Forget Hypot length, it is not relavant here. distance between your measurements are more important. However, don't mess with this method.

recommend the following:

the drive side cup has a flange, the backside of the flange (touches the BBshell) is the datum. Now pick a measurement, i.e. 8.80mm. Find the spot on the spindle that is 8.80mm on each BB and measure that distance to the datum. If there is a difference between the 2, the chainline when a crank is inserted will be equally affected. Trust me, I do stuff like this in my sleep. :P

that's similar to what i did when i was trying to determine if my phil wood BB was ISO or JIS: here.

if it's true that the tapers are the same length but begin and end with different cross sectional dimensions, one should be able to find differences in the cross sections at the spot where the tapers begin (or end). i measured a cross-section of the spindle where the tapers begin on my PW, miche, and shimano BBs and found the PW to be much closer to the miche (ISO) than the shimano (JIS). brent at PW later confirmed that the BB was in fact ISO.

How much was closer in mm?

BTW Brent recommends the BRS08 bb (JIS) with the Sugino 75s.

miche: 13.46mm
PW: 13.46mm
shimano: 13.97mm

i have miche cranks so i was going for ISO.

Thank you! Now if only someone would measure a Sugino 75 BB and compare it to a Phil Wook BRS08 or even a Shimano UN 72, that would be "awesomest"

Also, if it makes any one feel better American Cyclery in SF builds their Soma Rush bikes with Sugino 75 cranks and UN72 bbs.

whew! complicated thread.

hey chicagodream, did you get that frame yet?