Sure, XT now comes in 2×10 and has new brakes and more elegant pedals, in two shapes. And there’s a orange-anodized mode switch on the XTR Shadow rear derailleur. But it’s the tiny details that really make the difference in the updates for 2012 to Shimano’s XTR and XT groups.
On XTR there is one significant change, and that’s to the rear derailleur. The XTR Shadow Plus rear derailleur now has a little switch on the lower (“P”) knuckle to greatly reduce chain slap when riding bumpy trails. It’s called a “one-way friction pivot” when the switch is in the “ON” position. When ON, the switch makes it very hard to rotate the jockey wheel cage forward (counterclockwise), whereas the (clockwise) twist back that pulls up chain slack remains free and unchanged.
Amazingly, Shimano has no name or acronym for the little switch; it recommends leaving the switch in the ON position when riding and only switching it OFF to remove the rear wheel. When shifting to larger cogs, the shifting force is enough to overcome the stiff pivot, and when shifting to smaller cogs, the derailleur behaves normally and quickly pulls up chain slack.
XT now comes with either a double or triple crank, but there is only one set of shifters. That’s right, the same left shifter works for either a double or a triple – a feature that riders with mismatched SRAM levers (in order to use a triple) can appreciate. When a shop needs to change an XT-equipped bike over from, say, 3X10 to 2X10 for a customer, all it needs to do is change the crank and the front derailleur; it doesn’t need to mess with the shifters other than to turn a little plastic switch on the left shifter from 3 to 2. I should note that YOU MUST NOT HAVE THE DERAILLEUR ON THE TRIPLE’S GRANNY RING WHEN YOU TURN THE LITTLE PLASTIC SCREW; since that granny-gear position is not allowed with a double, you will break the screw, and then you WILL be getting a different left shifter. The screw can be turned with your fingernail; there is no need for a screwdriver, and if you can’t turn it with your fingernail, you’d better ask yourself why before you grab the screwdriver.
The new XT group gets reworked brakes with polished, reservoir-free master cylinders, tool-free lever-position adjustment and free-stroke adjustment, flow-through calipers, hinged lever clamps and the same Ice Tech heat-removing features to the caliper and rotor that XTR got this year. But what’s all that mean?
Well, first, due to the lack of a reservoir and the flow-through caliper, the system is super easy to bleed and does not require removing a master cylinder reservoir cover. Now, you simply put a funnel into the bleed hole atop the lever, fill it with (Shimano) hydraulic oil, put a catch bottle on the caliper bleed fitting and let gravity do the work. That’s right—no squeezing the lever or performing incantations to get air bubbles out; just leave it to sit and gravity-flush the system through with clean fluid. As long as you don’t let all of the fluid run out of the funnel and thus let air in, you will have a clean, air-free system with a minimum of muss, fuss and special tools. (One detail; you might as well remove the caliper and let it hang down free to facilitate gravity.)
Also due to the flow-through caliper, simple gravity bleeding removes crud, and perhaps air, that could otherwise collect in the caliper and stay there despite bleeding. The intake port is at the top of the caliper on the outboard side (as before), but now the bleed nipple is at the bottom of the caliper, on the inboard side. So when you let the clean oil flow by gravity, it will flow from the top outboard end of the caliper out the bottom inboard end and will pick up and carry out dirt that might be sitting in the bottom of the caliper.
Unless a hose or a connection fails, dirt and air realistically only enter around the piston and hence collect initially in the caliper, trapped in the spaces below the pistons. With a system requiring pumping of the lever or forcing oil up from the caliper with a syringe or squirt bottle, you can move that crud upward from the caliper throughout the system. Furthermore, if both the bleed and intake ports are above the pistons, crud will also not be easily rinsed out from below the pistons. But the likelihood of either scenario is greatly reduced if the fresh oil only flows downward and drains out below the crud-collection point.
The lever-position adjustment changes the distance from the grip to the lever. On XTR, it requires a screwdriver, but on XT, it’s a big knob you can turn with your fingers, even while riding. And the free-stroke adjustment? That adjusts point at which a roller attached to the base of the lever (inside the lever body) rolls around the corner in the ServoWave mechanism — in other words, it changes the point at which the brake goes from low-power/high-pad-movement to high power/low-pad-movement.
The hinged lever clamp, to which the shifter is also attached, obviously makes switching out parts on the handlebar easier. But there are a couple of safety details that Shimano added to the clamp and the shifter that could be very important to some rider eventually.
I can’t say I’ve ever worried about this happening, but Shimano engineers have clearly worried about a shift-lever or brake-lever mounting bolt breaking or falling out, causing either the brake lever or the shifter pod to swing down into the front wheel. So, Shimano’s hinge on the brake lever clamp has a pin in it that holds the clamp closed unless you push that pin with a thin nail or the like. And if the shifter pod mounting bolt were to fall out or fail, there is an additional screw from the back that keeps it attached to the brake lever.
The Ice Tech brake-cooling system, for which there is an increased need due to decreased oil volume with elimination of the reservoir, consists of three different cooling features. First, the rotor is a sandwich construction, with highly heat-conducting aluminum in the center in between thin steel pad-contact layers. Secondly, the resin pads, which already run cooler, are mounted on steel backing plates that in turn are attached to large aluminum cooling fins that stand up outside of the caliper body. And finally, the piston is oversized, ceramic and hollow on the back. It tends to not absorb heat, and it only contacts the pad around the edges, leaving a cooling air space under the pad.
There are two new XT pedals, both a cross-country/cyclocross model and a trail version with a larger platform. Both get a new, thinner axle, and the tubular section of the body through which it passes is now oval in cross section with the horizontal dimension being considerably narrower than the old round cross-sectional diameter, allowing mud to pass through the pedal body more easily.
Like on XTR, the platform sections of the pedal have been enlarged and are machined flat, giving more pedaling surface. The bearings now have a wider stance, with the inboard one now being much closer to the crankarm to offer more support to the axle.
The XT double crank has the same Q-factor as the triple crank, unlike XTR, where two of the three doubles offer lower Q. Since XT is often used on trail bikes with a swingarm requiring wide clearance, this makes sense for the same reason that the XTR double with the smallest chainrings has the same Q as the XTR triple crank.
The XT double front derailleur is different from the triple, but the triple one will shift a double, too. The front derailleur has an outboard bulge at the front outside tip of the cage, allowing it to be set lower to the rings without hitting the outer one.
Actually, there is another XTR technology change — to the 985 Trail wheel. On the 12mm through/142mm overlock axle, each hub bearing cone is now a “hybrid;” it’s aluminum with a steel bearing race adhered to the end to save weight over an all-steel cone. The cones on the 135mm QR axle remain unchanged (i.e., steel), since the threads are too small to hold up if they were aluminum. Also, the 985 Trail wheel gets a wider rim — to 21mm inner rim width, and it of course is still UST tubeless.
Also, both XT and XTR Ice Tech sandwich-construction rotors will be available in 6-bolt as well as CenterLock mounting.
I get a lot of questions on my Q & A column regarding differences between Shimano chains and two primary ones are about distinctions between road and mountain asymmetrical chains, and between 9-speed and 10-speed chains. So here goes.
Shimano made its current 10-speed chains asymmetrical since the requirements of inboard plates for climbing up and down cogs are different than those for climbing up and down chainrings. These oversized aluminum links highlight the differences between Shimano 10-speed asymmetrical road and mountain-bike chains.
1. There are no cutouts in links of mountain-bike chains to better resist link twisting as well as mud collection. 2. Also to better clear mud as well as engage muddy teeth, the inner surface of the center of each outer plate is relieved. 3. There is different beveling on the ends of the outer plates on the two chains; the road chain has some flat-cut corners, whereas the mountain chain does not, and the locations of the bevels are different.
And no, the inner-link spacing as well as the plates themselves (save for the center thinned section of mountain-bike outer plates) are not thinner on 10-speed Shimano chains than on 9-speed ones. You can see in the photo that the main difference between the two chains is the elimination of the bowed center section of the 9-speed chain’s outer plates. More subtle is the elimination of some space and lateral freedom of movement at the rollers. But the inner links are the same distance apart, and the plates are made of the same gauge of steel.