There are lots of decisions to make when buying a new mountain bike. One of the most crucial is your choice of gearing. The most popular option is Shimano, but their big range varies greatly in price and if you're comparing, say, Deore vs XT it can be difficult to tell what you're getting for the extra money. Read on to find out what the differences are between the groupsets.
Shimano's Alivio groupset is the highest level of their "recreational" range of parts and is designed for keen leisure cyclists. It is best suited to trekking and cross-country bikes and isn't really intended to cope with the rigours of freeride and downhill. It is available in eight- or nine-speed, with a modest choice of crankset and cassette options to suit recreational riding. Alivio is offered only with V-brakes as part of the groupset, but is often found with disc brakes from Shimano's non-series range or from another manufacturer. Alivio is a relatively heavy and simple groupset compared to the others in this review, but is well suited to inexpensive mountain bikes that are mainly used on trails and paths. Alivio offers a choice of Rapidfire Plus or EZ-fire trigger shifters.
Deore is Shimano's least expensive true mountain bike group and is offered in nine-speed only. It offers a great deal of the technology from Shimano's higher-end groupsets but at a lower cost. Shifting performance is much improved over Alivio and weight is significantly reduced. Deore is offered with a choice of V-brakes or two-piston hydraulic disc brakes, the latter with either 160mm, 180mm or 203mm centerlock rotors. Deore features a two-piece crank with an external bottom bracket, a significant improvement over the square-taper bottom bracket featured on Alivio. There are two choices of chainring size and four possible cassette sprocket combinations. Deore also offers a choice of a standard rear derailleur or Shimano's Shadow technology, which reduces the profile of the derailleur to offer better protection for the mech from bumps and crashes.
This is Shimano's all-purpose groupset, designed for cross-country, freeride and light downhill. It is offered in nine- or ten-speed, with disc brakes only. Cranksets are available in double or triple with a range of chainring options. Both cranksets use Hollowtech II construction for reduced weight with forged aluminium crank arms. The double crankset is fitted with an advanced honeycomb composite bash guard to provide maximum protection for the chainring against stumps and rocks. The triple features a steel and composite middle ring, which will last twice as long as a comparable Aluminium ring at no extra weight. The cassette is available in three sets of ratios and uses spider-arm construction on the three largest sprockets for reduced weight. The two-piston hydraulic brake calipers use Servo Wave technology for improved braking power. SLX front hubs are offered in standard QR and 15mm or 20mm through-axle for improved front-end stiffness and durability.
XT is intended as a cross-country groupset, with smooth performance and light weight. Like SLX it is offered in both nine-speed and ten-speed versions. Unlike SLX there is the choice of disc or v-brakes. The hydraulic brake levers offer adjustability for improved ergonomics. The cassette offers a full aluminum spider for reduced weight and better stiffness. The gear shifters feature Instant Release for quicker downshifts. The crankset is only offered in triple with 44-32-22 chainrings, but features a thicker outer chainring for maximum stiffness.
This is the pinnacle of the Shimano MTB range. There are currently two distinct XTR groupsets, the M970 group in 9-speed and the new 10-speed M980 groupset. I'll address these seperately as they are very different groupsets.
The old M970 9-speed groupset is largely similar to XT, but with extensive use of lighter materials. The front derailleur cage is hard-anodized aluminium rather than steel. The cassette includes titanium sprockets for minimum weight. The rear derailleur makes more extensive use of forged aluminium in place of steel. The crankset middle ring uses a mix of carbon fiber and titanium. Shifters are available in either standard rapid-fire format, or an integrated STI unit which further reduces weight over seperate brake and gear levers.
The new M980 group is substantially different. It is a 10-speed groupset, but is offered in Race and Trail formats. The Race components offer absolute minimum weight, while the Trail components are designed to be more suite to all-round use. There are double and triple cranksets in a variety of chainring combinations. Nine different front derailleurs provide a match for all frame and crankset combinations. Both groups feature improved calipers, with ceramic pistons and a finned heatsink for reduced fade. The discs are also made from a steel and aluminium sandwich composite, to reduce fade on long descents. They are offered in 140,160, 180 and 203mm size. Brake levers differ between Race and Trail, with the Trail levers offering more modulation and power for slightly more weight. Brake levers and gear shifters can be mounted to the same I-Spec clamps for reduced weight.
This is not a groupset, but Shimano's range of super-premium upgrade parts for XTR. The range includes lightened titanium sprockets, carbon-fiber rear derailleur plates, a titanium-nitride coated chain, drilled jockey plates, lightweight gear cable and super-rigid brake hose. In addition to these weight-reducing parts, Yumeya includes a number of purely cosmetic components - a range of anodized bolts and a machined and anodised lever clamp. Yumeya is for the most part pure bike bling, offering only marginal improvements over XTR at substantial cost. If you must have the best of everything and have a budget to match then Yumeya is for you, otherwise it's a component set strictly for show bikes.
Hopefully this article will have given you a better picture of the various Shimano groupsets and the technology they feature. The fundamental improvement offered by an upgrade from one groupset to the next is lighter weight and smoother shifting, but all will provide long and reliable service if fitted correctly and kept well-maintained.