SRAM’s commitment to innovation was demonstrated by the one-to-one actuation and radical use of composites in their original SRAM ESP 900 model. But with the X-0 they took a further step and introduced a radically new ‘look’ for a derailleur. This has only been carried off a few times; notably by the Simplex Tour de France, the Campagnolo Gran Sport and by the SunTour Competition. The X-0 stands a chance of joining that hallowed list.

The X-0's look is all skeletal forms and open spaces. It's lovingly rendered in silky, forged, aluminium with natty circlips on the removable stainless steel pivot pins. The main parallelogram spring is both prominently displayed and matte grey Titanium. Overall, it's an interesting object, it's a classy object, and, most surprising of all, it's an object that functions superbly well.

Like many of the best derailleurs, the first basic design of X-0 had a long production run including many technical variants. The timeline of these variants may go something like this:

• SRAM often claims to have launched the X-0 in 2001. The 2002 Technical Manual, published in August 2001, lists the X-0 derailleur, showing a choice of 'long' or 'short' pulley cage and with the outer parallelogram plate made of Magnesium. I have a strange feeling that this fine object never actually hit the market.
• The very earliest models that I knew of (2002?) had aluminium pulley cage plates, sealed bearing pulleys with large aluminium dust covers, a distinct 'weave' pattern printed on the composite p-knuckle and cable guide and, most distinctively, 'SRD' and 'SRAM Racing Development' etched on the b-knuckle. The choice of pulley cages was now 'long' or 'medium'. Critically, the outer parallelogram plate was made of aluminium, although it did have a silver 'spackled' finish rather than being smoothly anodised.
• In 2005, the finish on the composite p-knuckle and cable guide was changed to a discreet metal-flake grey and the etching on the b-knuckle was changed to simply say 'SRAM'. The outer parallelogram plate was now smoothly anodised. The choice of pulley cage lengths was increased to 'long', 'medium' and 'short'. The 'medium' and 'short' versions had a full carbon pulley cage with screwed cylindrical chain traps.
• In 2007 a 20th Anniversary edition was released with gold lettering and a gold b-pivot bolt. The pulley cage was changed again, with all three lengths having a machined carbon outer plate and an aluminium inner plate with conventional chain traps. The sealed bearing pulley wheels were changed to have smaller, black, dust covers.
• In 2008 The pulley wheels were changed again to have racy cut outs in them.
• Also in 2008 5 models were released in anodised colours called Tango (orange), Cash (green), Nugget (gold), Pinkslip (pink) and Redwin (red). 'Tango and Cash', starring Sylvester Stallone and Kurt Russell was one of the worst movies that I ever had the pleasure of sitting through. I hope, upon hope, that it is not also relevant that Lindsay Lohan played in a band called Pink Slip in the equally terrible movie 'Freaky Friday'. Sylvester Stallone, Kurt Russell and Lindsay Lohan - it's like being trapped in the Blockbuster video store from hell.
• In 2010, for the 2011 model year, the X-0 was upgraded to 'X0' and from a 9-speed to a 10-speed. To celebrate, it got a new p-knuckle and was presented in either silver with silver graphics or black with graphics in a choice of black, red, gold, blue or green.
• Then in 2011 the X0' got a new pulley cage, with an offset guide pulley. As a result, the maximum allowed sprocket size was increased from 34T to 36T.
• Also in 2011 a new 'DH' model was introduced. This 'DH' model reverted to the old-design, 9-speed, p-knuckle and concentric guide pulley. This allowed it to better track close-ratio Downhill sprocket clusters. I believe that it was only offered with a short cage. The maximum sprocket size was 28T, which does not quite make sense, as the 9-speed design could handle 34T, but hey-ho. The DH model was offered in either silver with silver graphics or black with graphics in a choice of black or red.
• Then in 2012 came the 'X0 Type 2' - with the now-obligatory clutch. This was offered in three cage lengths. It also came in either silver with silver graphics or black with graphics in a choice of black or red. Finally the pulleys were upgraded to have 'faux' cutouts in them that did not go all the way through.
• In 2012 the standard, clutch-free, X0 10-speed derailleur also got the new pulleys with faux cutouts.
• Finally (I hope!) in 2014 we were privileged to enjoy the 'X0 Type 2.1'. The X0 Type 2 had been lambasted on various seething internet fora for the unreliability of its clutch (surely a benefit?). And so we got an improved version. As with the Type 2, it was offered in three cage lengths and came in either silver with silver graphics or black with graphics in a choice of black or red. Goddam these colour options - they make my head explode!

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This is a, very battered, 2005 version of the SRAM X-0 with a medium length, full carbon, pulley cage. Some of its attributes are:

• It is anodised silver.
• The logo on the p-knuckle is in SRAM's classic red and white.
• The p-knuckle is entirely free of any clutch-type nonsense.
• The b-knuckle has 'SRAM' etched on it.
• The both pulley cage plates are, exquisitely shaped, carbon.
• The pulley cage is 75mm centre to centre.
• The sealed bearing pulley wheels have no cutouts and one large silver dust cover each. The other dust cover is cast into the pulley cage plate.

This derailleur has put in the miles. The teeth on the pulleys are worn to points. It bears the scars of several crashes. Some less than clever user appears to have routed the chain incorrectly through the pulley cage for an extended period. etc. etc.... And yet it is still light, tight, bright and totally usable. A credit to the derailleur race.

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• Derailleur brands: SRAM
• Categories: SRAM - X marks the spot where ESP meets DI.R.T.
• Country: USA, manufactured in Taiwan?
• Date of introduction: late 2005?
• Date of this example: June 2006 (written on inner piulley cage plate in yellow dots)
• Model no.: unknown
• Weight: 195g
• Maximum cog: 34 teeth
• Total capacity: 37 teeth
• Pulley centre to centre: 75mm
• Index compatibility: 9 speed
• Chain width: 3/32”
• Logic: top normal
• B pivot: unsprung
• P pivot: sprung
• Materials: aluminium, with a carbon composite p-knuckle and pulley cage plates

Ref. 2187