We've often commented in the past on the somewhat arbitrary nature of the bike industry's calendar, and the increasing randomness of the model year. The announcement of Shimano's all-new SLX groupset chucks yet another spanner in the already somewhat clattery works - the parts you see here in final prototype form will be on sale in July.

We'd speculate that Shimano is anticipating heavy demand from bike manufacturers for this new kit, and wishes to avoid the supply issues that it's had with other new groups over the last couple of years (most notably the Ultegra road group) by cranking up production of ostensibly 2009 model year parts with plenty of time in hand. And based on what we've seen, it's right to expect packed order books - SLX looks set to raise the mid-level component bar quite considerably.

The current Shimano line-up has Deore LX and Hone running roughly parallel in price terms, with LX being the XCish group and Hone being a kind of pocket Saint for more robust applications (although many of the Hone parts are effectively the same as LX with a different finish). For 2009, Deore LX becomes a "trekking" group (think upright riding positions, comfy saddles, the Netherlands) with the new SLX group coming with a myriad of options to cover all persuasions of MTBing from XC to freeride. The line is drawn at "extreme freeride", although where exactly that line is is open to debate...

Shimano has styled the SLX parts with a distinctive angular look - it's clearly a lot more "ggrr!" than LX. The brake levers follow the general layout of the existing XTR and XT units, and like XT they get Servo-Wave variable leverage gubbinses that promise 20% more power. The levers also feature tool-free reach adjustment, although XT's free-stroke adjustment is missing here.

Also quite XTesque are the shifters. We're big fans of the 2-Way Release triggers that let you upshift (and it'll always be upshift with SLX - there's no low-normal derailleur option, and no Dual Control either) with either thumb or index finger. The shifter pods also share XT's removable gear display, with a cover plate tucked away inside. Take the gear display off and you can mount the shifters outboard of the levers, an option that lets you use one finger on the very tip of the brake lever and still be able to reach the shifters without moving your hands.

The shifters drive a pair of new derailleurs. Shimano's Shadow tucked-in rear mech design renders Hone's axle-mount derailleur redundant, and its been reinterpreted for SLX. The new mech will be available in medium and long-cage models and weighs 260g.

Up front things get quite interesting. As part of SLX's "most things to most riders" ethos, two flavours of crankset will be available. The outboard-bearing bottom bracket and hollow forged crank arms are used on both, complete with steel pedal thread insert. The crankset in the picture is the conventional triple-ring setup, which features a composite/steel middle ring like that found on XT and promising the durability of a steel ring at the weight of aluminium and better stiffness than either. Chainring sizes for the triple are 44/32/22.

For those all-mountain types there's a new double chainrign and bashguard option. Shimano has offered twin-and-bash options before, but has always just taken the outer ring off and put a bashguard on, leaving a not-all-that-useful 22/32 combination. SLX, however, gives you a bigger 36T ring sitting inboard of a "honeycomb" bashguard - it's moulded with lots of hollows inside to reduce weight.

One of the frustrations of running two chainrings is that MTB front derailleurs are designed for three - the radius of the cage follows that of a 42 or 44T chainring. SLX has the option of a unique front mech optimised for the 22/36 double chainrings, with a much smaller radius and shorter cage. Without an outer ring to worry about, the double mech can be run lower and the shorter cage helps to reduce chain drop. Another benefit is considerably increased tyre and frame clearance, particularly important with fat tyres and full suspension. As well as the conventional band-mounted derailleur, Shimano has devised a direct-mount version that bolts on to a specific boss on the frame, giving frame designers more freedom by letting them do without a conventional seat tube (or stub thereof) at the bottom bracket.

SLX is finished off by the hubs. As is Shimano's way, they all run on good old serviceable, adjustable and side-load friendly cup-and-cone bearings. The rear hub has a quick-engagement freehub and there'll be a 20mm through-axle front hub alongside the regular 9mm QR option.

No word on exact pricing yet, but SLX will be in the current LX/Hone ballpark. We're pretty impressed by what we've seen so far - the new parts have all the key features from the higher-end groups plus a few useful things all of their own. Shimano's probably right to get the forges running quickly - we expect to see this stuff everywhere on next year's bikes...