For the ultimate in speed, corrosion resistance, and long bearing life, this
is the best option for your Trek BB90 or BB95 frame. These are the frames with the "net molded sockets" that
the BB bearings fit directly into. Most Madone road frames, and many of the full-carbon Trek mountain frames (Top Fuel,
Fuel EX, Remedy, Carbon Hardtail) and many of the Gary Fisher carbon frames (Superfly 100, etc.) use this bottom bracket.
Note that many of the mountain carbon frames switched to BB92 press fit systems in 2016. Includes two (2) XD-15 CERAMIC HYBRID RADIAL sealed cartridge bearings. Ceramic balls are matched with
high nitrogen XD-15 steel for 3.5 times the corrosion resistance of stainless steel. These special races are made from
the longest-wearing bearing steel produced today. Packed with top-of-the-line RLBC1 grease.
"XD-15" RADIAL CERAMIC HYBRID CARTRIDGE BEARINGS
HAVE SPECIAL HIGH-NITROGEN STAINLESS RACES WITH GRADE 3 CERAMIC BALLS
steel alloy used in the construction of XD-15 bearings makes them the best ceramic hybrids in the world.
XD-15 High Nitrogen Steel Alloy is 3.5 times more corrosion
resistant than 440C Stainless Steel. In the past, ceramic hybrid bearing manufacturers were faced with
a choice in bearing race material: 1) The longer fatigue life of SAE52100
bearing steel when paired with the extremely hard ceramic balls, or
2) The corrosion resistance of 440C stainless steel for use in harsh environments. If they opted for the longer fatigue life of 52100 bearing steel, the intrusion of water
would always be a threat to the races. If they opted for 440C Stainless, corrosion would become less of a threat
at the expense of longevity. The XD-15 steel not only combines the benefits of both, but EXCEEDS them on both
counts. Yes, much greater corrosion resistance than 440C and longer fatigue life than 52100 bearing steel.
Nitrogen Steel Alloy has a 40 percent higher load rating than SAE52100 bearing steel. Ceramic
hybrids made with 52100 steel races, while having a longer fatigue life than stainless, were still subject to premature
wear when used with ceramic balls. Of course the main claim of ceramic hybrids was less rolling resistance, resulting
in greater speed and a more efficient transfer of the rider's output to actual forward momentum. Wouldn't it
be great to get this superior rolling quality while actually increasing longevity of the bearing? Now you can.
XD-15 has an extremely fine grain structure which dramatically reduces the risk of failure under mechanical loading,
lowers noise and vibration, and makes a perfect interface with ceramic balls. Weak spots in bearing
races due to grain structure flaws in traditional bearing metals are not present in XD-15, which has a homogeneous structure
of finely dispersed carbonitrides, as opposed to large carbides concentrated at grain boundaries (which are vulnerable to
corrosion and mechanical stressing).
Grade 3 pure silicon nitride (SI3N4) ceramic balls are the best available. These
made-in-USA balls are Hot Isostatically Pressed (HIP) for a pore-free microstructure with micron-sized grains.
Reduced bearing friction from ceramic balls is a function of smooth surface finish. The balls used in the XD-15
bottom bracket boast a surface finish of < 0.10 micro inch (< 0.003 micron).
BB90/BB95 BOTTOM BRACKET CENTER SLEEVE
Used in TREK Carbon Road and MTB Frames with BB90 and BB95 Bottom Brackets
Used to shield the crank spindle and BB bearings from water that may enter the frame.
Also protects electronic shifting wires from the rotating spindle. This sleeve is usually included with a new bike or
frame. However, if lost, this part can be very hard to find.