The BPR jockey wheels make a noticeable performance improvement in the smoothness of the
drive train.
I
was also surprised to find out
that they also make a significant improvement to the
shifting responsiveness and chain tracking. I attribute both
these improvements to replacing
the standard upper jockey wheel sideways floating bearing with a
fixed upper jockey wheel. The fixed upper jockey wheel
allows you to adjust the rear derailleur to perfectly
align the upper jockey wheel
with the cluster sprockets.
