Hey I’m looking to get a compact crank for my wife, but I’m confused about the bottom bracket. What size do most bikes uses. She has 105 triple on their now. Plan on getting a new BB with the cranks, but I have no idea what ISIS, octalink, and the dimensions mean.
68mm x 108mm width - Is this what most bikes would use?
Try to read this page.
Bottom Bracket Size Database
http://sheldonbrown.com/bbsize.html
Hey I’m looking to get a compact crank for my wife, but I’m confused about the bottom bracket. What size do most bikes uses. She has 105 triple on their now. Plan on getting a new BB with the cranks, but I have no idea what ISIS, octalink, and the dimensions mean.
68mm x 108mm width - Is this what most bikes would use?
The most common BB in the US is English…which is threaded 68mm. The other most common is Italian which is threaded 70 mm. They are not interchangeable. Check you bicycle’s spec on the companies website.
The spindle length (i.e. in your example 108mm) must be matched to the cranks you are buying which also goes for spindle taper (i.e. ISIS, Octalink…etc)
Hope this helps.
68mm is the shell size, most US bikes are 68mm (english thread), most Italian bikes are 70mm.
108mm is the length from end to end of the spindle and will work with most double cranksets. If your wife allready has a triple, it is probably longer than 108mm. You can measure it by taking the crank arms off and measuring it with a pair of calipers.
ISIS and Octalink are spline standards. These are the splines on the spindle that the crank goes onto. Octalink is Shimano 8 and 9 speed (I’m pretty sure) and ISIS is another popular spline pattern used all over the world. Campagnolo has their own standard too.
Honestly, a good bike shop would be the best option to get the correct bottom bracket for you, even if you buy the crank some place else.
jaretj