By 1994 SRAM was a seven year old company with single, very successful product - the Grip Shift range of twist grip derailleur controllers. As Stan Day recounts in SRAM's 25th Anniversary book;

"We had to decide whether we'd ride Grip Shift through a normal S-curve product cycle, where growth tapers and then sales start to decline. It was that or reinvest profits and become a full-line supplier."

This decision to merely take on the all-conquering, extraordinarily competent, Shimano, in its very heartland, sounds almost off-hand.

The first product in this world changing programme was this derailleur - the 1995 SRAM ESP 900.

In some ways it was quite conventional, with its unsprung b-pivot, slant parallelogram and p-pivot that was concentric with the guide pulley. In some ways it was classily high-end, with sealed bearing in the pulleys, removable parallelogram pivots, aluminium b-pivot bolt and very impressive weight of 191g. And in some ways it was impressively radical, with that funky cable route, carbon composite knuckles, 1:1 actuation ratio and its trail-blazing manufacturing location - Taiwan. I can't immediately think of anyone else making very high-end components in Taiwan in 1995.

SRAM promoted the ESP 900 heavily - and a mixture of its technical virtues and, in its biggest market, a patriotic instinct to buy an 'American' derailleur - made it an instant success. But almost immediately a problem emerged - the b-knuckle had an alarming tendency to snap in half. It turns out that mass-producing small, stress-critical, carbon composite components is not as simple as it seems. But, to their credit, SRAM stuck with it and solved the technical (if not the reputational) problems and released the redesigned SRAM ESP 9.0 in 1997.

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I am aware of a number of slightly different variants of the ESP 900, but I do not know in exactly what sequence they were produced. This example has the following distinctive features:

• A b-pivot adjustment screw with a Phillips head screwing into quite a slim plastic piece that is glued and pinned to the b-knuckle.
• A, notably odd, outer pulley cage plate with no chain pusher flange around the guide pulley. I can't think of another modern derailleur with an outer pulley cage plate like this.

Note that this example has a visible moulding defect which appears to be where the sprue was cut away from the p-knuckle. The p-knuckle also has a lot of shaping that does not obviously match the profile of the outer parallelogram plate at the p-pivot. It's a production unit, but it all looks a touch unresolved and pre-production. Move fast and (have your customers) break things.

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• Derailleur brands: SRAM
• Categories: SRAM - ESP and all that
• Themes: Ultra-lightweight - touring/mountain bike
• Country: USA, manufactured in Taiwan
• Date of introduction: 1995
• Date of this example: unknown
• Model no.: ESP 900
• Weight: 191g
• Maximum cog: 32 teeth (based on SRAM ESP 9.0)
• Total capacity: 33 teeth (based on SRAM ESP 9.0)
• Pulley centre to centre: 85mm
• Index compatibility: 8 speed
• Chain width: 3/32”
• Logic: top normal
• B pivot: unsprung
• P pivot: sprung
• Materials: carbon composite (plastic) knuckles, aluminium parallelogram plates and pulley cage plates.

Ref. 617