Square Taper Headache!
07-12-11 | 02:10 PM
#1
Thread Starter
i smell bacon
Joined: Mar 2010
Posts: 5,574
Likes: 1
Bikes: Geekhouse Deerfield, GT Edge Ti, Spooky Skeletor, TET Track, Ritchey P-650b, Bridgestone MB-3
Square Taper Headache!
I recently bought a set of used Sugino 75 crank arms, which are supposed to be used with a 109mm ISO taper BB. The previous owner used a 111mm JIS BB (Shimano UN72… not sure what kind of chainline this gave). I've read online that using the wrong taper can deform your crank arm spindle hole taper, but I'm confused as to which direction is OK to mix and which isn't. Would it be OK for me to go back to an ISO taper BB (109mm) and still get the a correct chainline?
I'm new to this square taper stuff, as most of my cranks have been splined. Go easy on me!
I'm new to this square taper stuff, as most of my cranks have been splined. Go easy on me!
Last edited by yummygooey; 07-12-11 at 02:14 PM.
07-12-11 | 02:25 PM
#2
Senior Member
Joined: Sep 2007
Posts: 3,741
Likes: 16
From: Gaseous Cloud around Uranus
You not suppose to swap them but in the real world it works.You can swap them around,the difference will be the chainline between the two.The diameters are a little different.Here you go:
https://www.sheldonbrown.com/bbtaper.html
https://www.sheldonbrown.com/bbtaper.html
07-12-11 | 03:26 PM
#3
Thread Starter
i smell bacon
Joined: Mar 2010
Posts: 5,574
Likes: 1
Bikes: Geekhouse Deerfield, GT Edge Ti, Spooky Skeletor, TET Track, Ritchey P-650b, Bridgestone MB-3
Yeap, I saw that article. I just wasn't sure if you could switch back and forth between the two. I've got it now, though! Thanks!
07-12-11 | 05:02 PM
#4
Old fart
Joined: Nov 2004
Posts: 26,378
Likes: 5,297
From: Appleton WI
Bikes: Several, mostly not name brands.
Anything manufactured in the past 25 years or so will have a 2deg taper. ISO and JIS differ only in the length of the taper and overlap over most of the length of the taper. Nothing bad will happen if you put an ISO arm on a JIS spindle, or vice-versa -- only the chainline will suffer.
N.B. back in the 70s and early 80s there were some (mostly low-end) spindles with 2.5deg and 3deg tapers -- these could cause damage if the wrong taper arm was installed. But these have been deprecated for many, many years now and are seldom seen in the wild any more.
N.B. back in the 70s and early 80s there were some (mostly low-end) spindles with 2.5deg and 3deg tapers -- these could cause damage if the wrong taper arm was installed. But these have been deprecated for many, many years now and are seldom seen in the wild any more.
