External-type bottom brackets are notorious for having so-so durability, along with often-marginal levels of seal drag. Enduro's XD-15 doesn't just buck the trend – it flat-out obliterates it with an incredibly low-friction feel plus phenomenal all weather toughness. We did everything we could to kill it but this thing is simply incredible.
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Video: Enduro XD-15 bottom bracket review
Enduro strays from the standard formula in two major areas in order to achieve the XD-15's remarkable longevity.
For one, it uses angular contact bearings that not only happily handle much more axial loading than typical radial cartridges but actually need it to function properly. Whereas radial cartridges normally function best with virtually zero preload, the recommended preload on Enduro's XD-15 is a fairly substantial 2-3Nm.
Secondly, Enduro surrounds the silicon carbide ceramic balls with races made of a special high-nitrogen steel alloy that Enduro claims is more corrosion resistant than 440C stainless but also much harder than SAE52100 tool steel in order to hold up to the ceramic. Also helping things along here is the angular contact design, which spreads the load out over a larger area than in a radial setup.
The result is a level of all-weather durability we've never experienced before in an external-type bottom bracket. In fact, we had one tester run an XD-15 on his everyday commuter bike through an entire Colorado winter – snow, ice, sand, magnesium chloride, and all.
As if that weren't demanding enough, we ran the entirety of the test with all of the seals removed. Despite the fact that we could readily see the fully exposed, naked ball bearings, the XD-15 merely laughed it off, spinning as smoothly after months of intentional abuse as it did when new, even with no lubricant whatsoever aside from pulverized sand and grit.
We tested one bottom bracket with no seals whatsoever
Even better, the XD-15 also rotates with incredibly low friction for an external-type bottom bracket, thanks to light-pressure silicone rubber seals and the minimal, low-viscosity lube. We haven't subjected the XD-15 to a lab test but even a casual observer can tell the difference here.
So what's the catch? Well, the XD-15 is pretty expensive given the materials involved, plus the fact that everything is machined in-house at Enduro's California headquarters. Also, the preload required makes it a little tougher (but not impossible) to set up on cranksets that don't have adjustable arm spacing, such as most SRAM, Campagnolo, and FSA models.
Otherwise, though, there are simply no downsides that we can find. Simply put: buy one. The Enduro XD-15 costs US$180-210/£119-140 depending on fitment.
Many thanks to Brian Hannon at Elevation Cycles for logging the extra test miles for us.