XTR gets the same "Dyna-sys drivetrain" upgrade as XT and SLX. The highlight is the jump to a 10-speed
cassette, which Shimano says is also more efficient and more stable than
its nine-speed drivetrain.
PHOTO: This 10-speed cassette puts the "X" in XTR.
The "efficient" claim comes from the revised cog and ring sizes that
are physically bigger at the low end: the 22-tooth ring becomes a 24;
the biggest cassette cog jumps from 34 to 36. By wrapping the chain
around a larger circle, chain tension is reduced, which reduces
friction. For example: the 32/front x 36/rear combo with Dyna-Sys
provides the same ratio as a 22 (granny) x 26/rear combo on a 9-speed
drivetrain, but reduces chain tension by a third. "Bigger rings and cogs
are more efficient" isn't new math. XTR was Shimano's last group to go
"compact" (it downsized with the 960 group). It's now taken a sort of
half step away from compact and back towards "standard" gearing.
More on efficiency
- Dyna-Sys triple cranks have bigger small rings (24t) and smaller
big rings (42t), but the middle ring remains a 32. That's because the
pedaling characteristics of most modern bicycle suspension systems were
designed around a 32-tooth ring and Shimano didn't want to mess with
that. As a side benefit, because the big and small rings are now closer
in size to the 32, there's less variation in pedaling performance in
those rings. Shimano also says the 24t ring provides less pedal feedback
than a 22t ring on full-suspension bikes.
PHOTO: XTR front derailleurs come in 3x and 2x, direct mount and clamp-on.
- For double cranks, small rings are offered in 26, 28 and 30.
Following the logic, these are less efficient than a 32, but more
efficient than a 24. Big rings for double are offered in 38, 40, 42 and
44: All of which are more efficient than a 32. Coupled with the 36 cog,
the double-cranks narrower Q-Factor and chainline (both of which are
claimed to provide additional efficiency benefits), and in the right
situations strong riders can roll their big rings more often, for
increased efficiency. Note this change carefully; In a two-chainring
scenario your big ring is like a middle chainring in a three-chainring
- You want to run the big ring most often, because it's more
efficient. So if you choose the wrong big ring (something too big to
churn easily) you could wind up spending more time in a (less efficient)
smaller-than-32t inner ring.
- Shimano is also pushing the notion that Dyna-Sys requires fewer
"recovery shifts," which is a little tricky to grasp. The point Shimano
is trying to make is that the dump to the small ring from the middle
ring/big cog isn't as jarring with 10s, and the first couple shifts down
the cassette are a little tighter as well. This means your cadence
changes aren't as abrupt and fewer shifts are required to find that
next-lower gear from the middle ring/big cog combo.
PHOTO: XTR rear derailleurs are only offered in the low profile shadow style.
- Because the big and small ring are closer in size to the middle
ring, the chain does not have to lift or drop as far when shifting,
making front shifts smoother, faster and more precise.
When Shimano uses the word "stability," engineers are essentially
referring to the drivetrain's ability to stay in tune and shift
consistently. The increased stability of the system comes from a longer
housing stop arm on the rear derailleur, which, Shimano claims,
increases the mechanical advantage of the derailleur spring, but
decreases the tension on the cable. In turn, this makes the system less
sensitive to contamination, housing deflection and routing, and also
reduces housing compression and cable stretch. Additionally, the exposed
cable between the housing stop and anchor bolt bends less as the
derailleur moves through the range, which makes shift effort more linear
across the range.
About the Chain
Shimano won't shut up about its 10-speed chain. We'll explain why in a
moment, but first, this tip: the Shimano 10-speed chain is directional:
always assemble it so the logo can be read from the right (drive) side
of the bicycle. If you don't see the logo from the drive side, your
chain is on backwards. Each of the four plates are designed to do a
specific job: put the chain on backwards and it'll still shift, but not
as well as it should.
PHOTO: The chain is directional. The Shimano logo needs to be visible from the drivetrain side.
Now, why is the chain so important? The chain is traditionally the
weakest part of a modern bicycle drivetrain. Every time a gear is added
to a drivetrain it’s always the chain that takes the longest to sort
out. If you've been around long enough, you probably remember the eight-
to nine-speed transition and how piss-poor the first nine-speed
mountain bike chains where compared to how smooth they run today.
Shimano seems determined to be sure it has its 10-speed mountain bike
chains well sorted from the beginning, and went so far as to design a
specific chain for the mountain groups that are not interchangeable with
its 10-speed road chains.
Shimano claims its 10-speed MTB chain is as strong at the pin
connection as its nine-speed chain, lasts as long as its nine-speed
chain (perhaps longer, because, Shimano postulates, there is less
tension on the chain) and beats the nine-speed chain at handling
contamination. Time will tell of course, but we're optimistic. The XTR
launch featured more than 20 riders riding brand new, just installed,
XTR drivetrains on demanding technical terrain near Downieville, CA, and
there wasn't a broken chain. In fact, there was hardly a drivetrain
hiccup to speak of.
Vivid indexing refers to XTR's shift feel, and is broken into two
parts. First: consistent effort. Shimano's nine-speed drivetrains had
noticeably different lever effort in higher gears than lower gears. With
Vivid, Shimano not only reduced effort overall, but the effort is more
linear across the range. A shift from the 11 to 13 feels almost
identical to a shift from the 32 to 26. Second: click feel. The
difference between initial lever effort and the effort necessary to
"click" the shifter is bigger than before, for improved feedback.
More Shifter Details
- The front shifter has a mode converter switch to switch between double and triple shifting function.
- XTR shifters are still Shimano's only shifters with Multi-Release.
The rear may be upshifted (down the cassette) one or two gears at a
More Drivetrain Details
- Shifters are available with I-Spec mounts, which allows them to
mount directly to XTR brake levers. Non-I-Spec XTR 980 shifters can be
upgraded: Shimano will sell the mounts aftermarket.
- The XTR 980 rear derailleur is only offered in the low-profile Shadow style (which tucks in closer to the frame). - Medium (GS) and long cage (SGS) rear derailleurs are offered.
- Both pulleys now use sealed bearings.
- The pulley cage is carbon on the outside, but aluminum on the
inside. This gives the cage more of a fighting chance if it happens to
contact the spokes.
- Front derailleurs are 2x and 3x specific. A 3x front derailleur
would probably work with a 2x crank, but it would not be "optimized."
- The 42/30 and 40/28 cranks use a Bolt Circle Diameter (88mm) that's
specific to double rings and not swappable to the triple rings. These
doubles have a narrower Q-factor than the triple cranks. The 38/26
double uses the arms from the triple as well as the same BCD with
cosmetic guards on the spider to cover up the gap left by the absence of
a "big" ring. The 44t ring is only available aftermarket, and only
works with the double-specific arms.
- The left crank attachment system is the same as XT. The bearing
preload adjuster and proprietary crankarm puller tool are gone.
Shimano offers two different XTR brakes. The caliper bodies and
rotors are the same, but the levers and pads are different. The Trail
brake features Servo-Wave, which changes the piston movement relative to
lever travel through the stroke. Shimano says it allows the pads to sit
further from the rotor, for more clearance (without requiring a long
lever throw), and provides a power increase once the pads contact the
rotor. The Trail brake also has tool-free reach adjust and tooled stroke
adjustment. The 980 Trail brake is the same weight, but 25 percent more
powerful than the previous XTR brake, and a few percent more powerful
than an XT brake.
The Race brake lever does not have Servo Wave, external reach-adjust
or free-stroke adjustment. The Race brake is 15 percent less powerful
than the Trail brake (due to the lack of Servo Wave), but the Race lever
is 40 grams lighter (each) than the Trail lever.
Shimano is offering four different XTR pads. Two traditional pads are
offered: a resin pad with aluminum backplate, the stock Race pad, and a
sintered metal pad with titanium backplate. Radiator pads, which come
with the Trail brake, have integrated fins that rise above the caliper
body and are claimed to draw heat from the pads and reduce heat by 50
degrees Celsius. They're offered in both sintered and resin compounds.
The Radiator pads are one part of the XTR brakes ICE heat management
system. Another part is the three layer disc rotors: a stainless steel
braking surface sandwiches an aluminum core. Shimano says the ICE rotors
reduce heat a further 100 degrees Celsius (for a total reduction of 150
degrees Celsius when combined with Radiator pads). The third part of
ICE is the aluminum rotor spider, which sinks heat better than a steel
spider. The heat reduction reduces fade and promotes longer pad life,
according to Shimano. A side benefit is your brake-side bearing grease
More brake bits:
- This is the first XTR group without a rim brake option.
- The hydraulic line attaches to the caliper with a banjo fitting
which provides more routing options than the 970 style direct-route.
Trivia: the first XTR discs, 965, had a banjo fitting; Shimano went
direct with 970 because it was lighter. With 980, they've found a way to
use the banjo, AND save weight.
- Included with the disc calipers is a small threaded plug, which you
can install in place of the bleed nipples. It saves 10g per caliper,
but makes bleeding a bit more labor intensive.
- XTR brakes use 22mm full-ceramic pistons.
- The hydraulic line has three layers, with a woven center material
that increases the stiffness of the hose for better response.
- Shimano's words: "The caliper fasteners are sexier."
- The levers have split clamps, so they can be installed and removed without pulling grips.
- The brake levers are short, and have a pivot placed to prevent finger tug if you like to place them close to the bar.
- The Trail brake has a 14mm-wide lever; the Race brake lever is 13mm.
- Rotors are offered in 140, 160, 180, and 203mm.
- Rotors are Centerlock only. They may be used with any Shimano brake.
- Shimano lightened their brake adapters slightly.
Shimano offers XTR wheels in Race and Trail versions. The Race wheel
is fairly similar to the previous XTR wheel, though there is now a 15QR
front option. The Trail wheels use much of the same technology (Scandium
rims, UST compatible, titanium freehub, cup and cone bearings,
Centerlock brake mounting), but have a wider rim (21mm internal/24.2mm
external width versus 19/23.3mm) and thicker spokes. The trail wheels
are only offered in a 15QR front; the rear is offered in standard 135mm
QR and 142x12 E-Thru, through-axle system (see below). Whether the 135
wheel can be converted to 142x12 (and vice-versa) is a bit of a mystery.
If it is, it's not just a matter of changing the rear wheel's QR hub
end caps: it would require a new axle and freehub body. Weights: Race
(QR front and rear) 1480g; Trail (QR front and rear)1670g. At this time,
there are no XTR 29er wheels. Shimano hinted that they're developing
more 29er options, but did not offer specifics.
E-Thru is Shimano's 142x12 rear thru axle system. Shimano's version
works a lot like the 15QR system found on Fox forks (and co-developed by
Shimano): the QR lever is the same and the nut can be clocked and
secured so the lever is always oriented in the same position. Right now,
the axle is solid, but Shimano is working on a lighter hollow version.
Like wheels and brakes, XTR pedals are offered in Race and Trail
versions. Compared to the 970 XTR pedal, the 980 Race pedal has a lot
more shoe to pedal contact: 227mm squared compared to 61mm squared. That
should provide more stability, and reduce unwanted pedal ejections.
Shimano also reduced the platform height 2mm, and opened up the body so
mud can flow through more easily. Weight is claimed at 310 grams.
Essentially, the Trail is the Race pedal with a minimalist cage. It
weighs a bit more, 389g, and it has even more shoe to pedal contact:
That's it for our second run at the all-new 2011 XTR. But stay tuned
to Mountain Bike magazine and MountainBike.com in the upcoming months.
We plan to get a ton more time on this system (especially 2 X 10) to see
how it stacks up against SRAM XX