Tuesday, May 1, 2007

Shimano's XT group gets updated for 25th birthday

The new XT — plenty of choice for 2008

photo: Shimano

A quarter of a century is a milestone. It's real history. When someone or something has been around that long it has had a chance to grow into its true being.

In 1981, Yoshi Shimano, president of Shimano's U.S. sales office, noticed a weird new segment of bikes popping up in the U.S. bicycle market and immediately informed corporate headquarters in Japan that Shimano needed to be a part of this new "mountain" bike movement.

The new BL-775 brake lever incorporates Servo-Wave technology

photo: Shimano

The following year, Shimano introduced the Deore XT component group to the world. Since other full component group options were virtually non-existent, both bicycle manufacturers and consumers enthusiastically embraced the new mountain-bike group.

XT turns 25 this year, and to commemorate the occasion it gets a facelift for 2008. While many of the improvements trickle down from last year's revamp of XTR, there are a couple of brand-new technologies in the mix.

"This is an adventure group in the sense that it's designed to be as contemporary as possible in its focus," said Devin Walton, Shimano's PR manager

The ST-M775 Dual Control lever does as well, both feature radial master brake cylinders.

photo: Shimano

"XT, because it has a few more budgetary constraints, comes into a price point where it's going to hit a wider range and a higher volume of mountain bikes, from full, big-suspension trail bikes all the way to a cross-country-race-type bike.

"That's why you're seeing an even wider range and additional options over even what XTR offers. Options are sort of the result of XT's initiative of just being contemporary."

What's old is new again
When it was introduced in 1992, Servo-Wave was a mechanical cam-operated method of changing the XT brake lever's cable-pull ratio throughout the lever's stroke. The design started with a high ratio of cable pull to lever movement, then progressively reversed the mechanical advantage, providing more braking power. In addition to providing powerful braking control, the new system also permitted more rim clearance.

Shimano’s new RD-772 is called the Shadow rear derailleur for its narrow profile.

photo: Shimano

XT's new Servo-Wave disc-brake levers, which are available in stand-alone and Dual Control configurations, offer more brake-pad clearance than the old XT calipers - about the same as the new XTR version - and upwards of 20 percent more stopping power than the old XT disc brakes when paired with the group's new Mono-block brake caliper.

"The reason for even integrating the Servo-Wave is so that you can get the maximum amount of lever travel and leverage to get the most power," said Walton. "It's a blend between those two.

"What the Servo-Wave does is that it gives your pads clearance, but it moves the pads quickly through the first little bit of motion so the pads will contact [the rotor] as quickly as possible, and that's what allows you to get the most power out of the system."

Shimano’s new HB-M776 20mm XT hub hub can be purchased alone or in complete wheelset.

photo: Shimano

The new brake levers use a radial master cylinder and feature a tooled reach adjustment, plus what Shimano calls a lever free-stroke adjustment, commonly referred to as a pad-contact adjustment; no tools are needed for this. The calipers retain compatibility with XT's previous mounting hardware and brake pads.

The XT group adopts XTR's goal of providing choices for all types of riders. Most apparent is the new Shadow rear derailleur, which is new to Shimano's mountain line and meant as an option for technical-trail riders.

The Shadow is based on the top-normal (standard style) spring design. Main features are a slender side profile (15mm narrower than a standard XT derailleur) and a redesigned mounting bolt and B-spring assembly, with a stronger spring, that work together to prevent the derailleur from knocking into the underside of the chainstay on FSR and other suspension designs. Traditional top-normal and low-normal rear derailleurs will be available as well. All three styles come with a choice of medium or long cages.

The new FC-M770 Hollow Tech II crank has a carbon reinforced steel middle chainring.

photo: Shimano

Like last year's XTR redesign, the new XT group includes a 20mm through-axle front hub. But unlike XTR, XT's 20mm hub can be purchased alone or pre-built into a wide-rim (21mm I.D.) XT wheelset meant to accommodate five- and six-inch trail bikes. The 20mm hub features a standard sized Center Lock rotor attachment and regular, adjustable angular contact ball bearings.

The XT rear hub is also upgraded with two extra pawls to quicken the engagement response time. The hub boasts a 10-degree engagement, twice as fast as the old version; it, too, relies on adjustable angular contact bearings. The rear hub has a new 14mm 7075-T6 aluminum axle. A standard quick-release wheelset will also be available. It features a narrower (19mm I.D.) rim in line with cross-country and racing applications.

The new XT cassette has pins that extend rearward to catch a chain before it damages spokes in the event of an over shift.

photo: Shimano

Borrowed but new (to XT)
In the trickle-down category XT's drivetrain incorporates instant and two-way release technologies from XTR. This year's XT transmission featured two-way release shifter technology but not instant release. Instant release lets cable go on the push or pull stroke instead of waiting for the lever to return, while two-way release allows the cable release trigger to toggle for both push and pull operation.

The front derailleur features angled limit screws and a lighter cage with more tire clearance for use with tires sized 2.3 inches and above. It's available in three versions: E-Type and top and bottom swing. Both the top- and bottom-swing derailleurs come with one band size and use adapters to fit 28.6, 31.8 and 34.9 seat tubes.

The XT PD-M770 pedals look like XTR except for their logo and powder coat.

photo: Shimano

XT's 850-gram Hollow Tech II crank retains its four-bolt, 104/64mm bolt circle, but features refined arms, a new carbon-composite-reinforced steel middle chainring and thicker alloy outer chainring.

In final touches, Shimano added external pins to the rear cassette to catch the chain in the event of an over-shift and protect the rear wheel's spokes. The XT also group gets its own branded 352-gram PD-M770 SPD pedal.

The components should be available by mid-June.

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