In terms of performance, these Shimano XT Ice Tech Disc Brake Rotors are the functional equivalent of the XTR units. However, as you might expect, they aren't as sculpted and take on a few extra grams in comparison. The big headline is Ice Tech, and it's the result of some forward thinking by the folks at Shimano.

Technically these XT Ice Tech Rotors are a composite. Two layers of stainless steel are bonded to an aluminum core. So you get the benefits of both -- the durability and powerful braking properties of stainless and the lightness and heat dissipation of aluminum. If you've ever boiled your brake fluid and experienced serious fade, enough to scare you, then you'll appreciate that heat related fade has been reduced by 35%. And cooler running rotors will help your brake pads last longer as well.

Aluminum also gets the nod for the spider. This type of construction typically saves a few grams over one piece stainless rotors, but the biggest advantage is that the aluminum spider, again, dissipates more heat and adds rigidity, so your rotors will warp less and be less susceptible to getting dinged out of shape.

The Shimano XT Ice Tech 6-Bolt Disc Brake Rotor SM-RT86 is available in three sizes -- 160, 180, and 203mm. Even with the Ice Tech sandwich construction, they're the same thickness as Shimano's other rotors at 1.9mm, and they're available to fit 6-bolt hubs.