Having finally got round to fitting and using the Shimano Hollowtech II-compatible CK Ceramics bottom bracket sent in recently for test, I can pronounce myself impressed.
The bare bones of the difference between it and a conventional version with steel balls are a saving in weight – silicon nitride (Si3N4) balls are about 30percent lighter than steel – and a smoother feel. Since the balls are harder than steel, they also roll more efficiently and should last longer.
Comparing the two types side by side is more impressive, the differences in weight and rotational drag more noticeable in the hand than might be expected when riding.
Fitment is a straight swap, the two sets having the same width so front mech adjustment is unaffected. I used a Truvativ GXP splined fitting tool for the job. It fits the Shimano cups perfectly but proved a tight fit on the CK Ceramics ones, only passing partly over the splines. Another tool might fit more freely.
Otherwise, tolerances are exceedingly close, the crank axle needing a slightly harder push to press through both sides than with a Shimano bearing. This, of course, is a good thing, since it minimises flex and the possibility of water or dirt ingress.
The cranks spin very freely when installed. Ride feel is probably indistinguishable through the feet but the bike, my Roberts PBP Special, certainly felt pleasantly fast and responsive on my aborted coast ride and on the commute this morning.
The bracket assembly will now get some serious usage to see how it holds up under daily riding conditions. More soon.
CK Ceramics Shimano Hollowtech II-compatible bottom bracket £99.99 including insured postage.
