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Вот еще из того же Гугля (+)

Entered by GDT on January 14, 2005 at 02:32:31:

В ответ на: Я в FSA полный профан. Но есть ведь Гугль :-) +++ отправлено GDT on January 14, 2005 at 02:07:34:

Как всегда, наоткрывал окошек, и теперь никак не могу закрыть -- зачитался :-)

Мда, если есть хоть какой "small chance", я почему-то всегда именно на него попадаю. :-)


When bike manufacturers and consumers are free to mix-and-match cranks and BB's, there is the small chance that a crank will be installed on a BB it was not intended for, which can in turn cause problems for chainline (shifting performance), crank-arm clearance and q-factor.

There are 2 major problems with square taper BB's in that there is no standard axle length for cranks and the taper dimensions can be made to either Japanese dimension (which follow JIS) or European dimension (which follow ISO), so even if you get the right axle length then you may have the wrong taper size.

ISIS-Drive cleverly addressed this problem by assigning standard lengths (i.e. 108mm for road double, 113mm for MTB, 118mm for road triple, etc.), so you (almost) always know which length of axle you need for your cranks, and by using chainline control shoulders, so your chainline would always be as intended. The great power of ISIS-Drive's open standard is also it's weakness - the tapered spline requires great care to produce and the ISIS standard leaves manufacturing open to interpretation in some respects. In some instances early on, manufacturers found that their in-spec products would not work with another's in-spec product...exactly what was not supposed to happen with ISIS-Drive. Fortunately, many ISIS-Drive competitors have cooperated together to hammer out the manufacturing kinks.


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