How to convert non-Boost to Boost
Boost 148, Boost 110 or simply Boost has been around for quite some time. Quick recap on why did come on existence: the 29” wheels. Wider flange spacing for stiffer and stronger 29” builds. There are plus 10 mm of spacing for front hub – 110 mm. Hence Boost 110. And plus 6 mm for the rear – Boost 148 (141).
Alternative is to take the new measures from the centerline to any of the sides. That is plus 5 mm for the front and 3 mm for the rear. Sounds simple. But how exactly to convert to Boost from classic, non-Boost hubs? At first it seems simple. Why not to compensate for that added space by special end caps? Even that this approach defeats the purpose of Boost at first place, let us dig deeper here.
Boost is not only about the Over Locknut Dimensions (OLD). The rotor mount placement is different. The variation is: 5 mm for the front and 3 mm for the rear. Mounting appropriate shims can work, at least technically. But something else changed as well: the chainline. From 49 mm for OLD 142 mm, to 52 mm for Boost 148 (141). Special end caps will not help here. They do not alter the position of a freehub. And this is the case with new 52 mm chainline.
Note the use of another reference to Boost 148 in the parentheses above – 141. This is also Boost, but the different type – Boost QR.
There is neither a conversion kit for classic 142 (135) mm to Boost 148 (141) mm – rear, nor for classic 100 mm to Boost 110 – front. These are different hubs. Although, they have common parts within their model group: freehubs and end caps.