Originally Posted by
kingston
^This post doesn't make any sense to me. Lots of people have already done the 650b conversion on the Grand Jubilee. There's no mystery as to whether or not it will work.
I don't get what's hard to understand.
I didn't say it was impossible. Just that the change will require brakes with significantly longer reach. Specifically the 19mm difference between the 311mm and 292mm rim radii id starting from 700c, or 23mm if starting from 27".
The necessary calipers exist, so it can be done, but the longer reach, comes at a cost in performance, as I described earlier, plus the OP may not be able to find comparably high quality calipers with the necessary reach.
Of course it's the OP's choice, but he might start by measuring the current reach, adding the correction and seeing what his brake caliper options will be.
BTW - if wider tires are the desired outcome, there may be another option. The OP can switch to wide 700c (29r) rims, and shop from a wide selection of tires in that size. This option probably won't call for new brakes, but he'll be limited by fork and stay clearance, so here too measuring is called for before committing.