Having got you up to speed with the new Deore XT transmission components, here's the rest of it.
Brakes
Shimano's Servo Wave system was introduced for cable brakes many years ago, but the new Deore XT marks the first appearance of the design on a hydraulic disc brake. The idea is pretty simple. With the usual linear relationship between lever movement and pad movement, you have to strike a compromise between pad clearance and power. You've only got so much lever travel to play with (limited by your ability to reach the lever at one end and the lever hitting the bars at the other). Using lots of lever travel to move the pads a very small distance gives heaps of power, but limits pad clearance. Boost the pad clearance and the pads have to travel further to reach the rotor, limiting power. Servo Wave introduces variable leverage into the lever, so the first part of the lever travel moves the pads quickly until they hit the rotor before "gearing down" to increase the power. In this way you get a claimed 20% extra brake power but without having the pads running really close to the rotor all the time.
Servo Wave will be found on both the standalone XT disc levers and the Dual Control units. The levers also feature tool-free reach adjustment and adjustable "free stroke" - the amount of lever pull that doesn't actually do anything. This effectively alters the position of the lever when the pads engage.
The XT calipers follow the now-familiar sleek Shimano style, with two opposing pistons in a one-piece forged caliper body. Resin and sintered pads will be available (although we don't know which will be supplied as standard) with the lifespan of the resin pads said to have been improved by at least 100%. Someone will be along shortly to suggest that that'll mean you'll now manage two wet rides in Wales, no doubt. The Centerlock rotors will be available in 160, 180 or 203mm sizes.
Lightweight fanatics will be reassured to hear that V-brakes and cable brakes will be available too.
Chainset, hubs and pedals
XT's existing Hollowtech II chainset has proved to be a popular option, but most riders have found that the alloy chainrings (particularly the middle one) don't last all that well. To improve durability without adding weight, Shimano has borrowed the chainring technology from XTR. While the flagship group has a composite/titanium middle ring, XT gets a composite/steel one - comparable in weight to aluminium, but said to last twice as long.
The non-drive-side crank sticks with the twin opposing pinch bolts to hold it on, rather than the single bolt into the axle that the current XTR uses. Two versions will be available, one with 44/32/22 tooth rings for MTB use and a "Trekking" version with 48/36/26.
Shimano adds to its growing range of 20mm through-axle front hubs with XT's HB-M776 unit with Centerlock rotor mount. The rest of the hub range is now lighter (50g a pair compared to the current models) with options including Centerlock or non-disc, black or silver and 32 or 36 spoke holes. The freehub bodies on the rear hubs are steel and share the quick engagement mechanism from XTR. There's also an internal grease sleeve to help to maintain proper lubrication levels.
One option that we don't see is six-bolt rotor mounts, although Shimano is now making adaptors to allow you to fit six-bolt rotors to Centerlock hubs.
The XT pedals use the familiar mud-shedding design seen on plenty of SPDs, but finished in black and with a Deore XT logo.
Wheels
Shimano has been expanding its range of wheels considerably over the last few years, and the new XT will have three wheel systems to its name. The most interesting is the WH-M776 XT All Mountain wheelset, with a 20mm through-axle hub in the front wheel, standard 135mm QR at the rear, 24 plain-gauge 2.0mm spokes both ends and 28mm wide, UST-compatible rims. Both hubs have Centerlock disc mounts. Overall weight is claimed to be 2,050g.
There's also the M775 XC wheelset for disc brakes, with butted 2.0-1.8-2.0mm stainless spokes and 23mm UST-ready rims. As with the separate XT hubs, the wheelset freehubs use XTR's quick engagement mechanism for faster pickup, and there's an internal grease sleeve for enhanced lubrication. The XC wheels are 1,680g/pair. You can save an extra 10g (steady, now...) with the M770 XC V-brake wheelset - no Centerlock, 20 spokes in the front and rims with braking surfaces.
