This Sachs Plasma derailleur is one of Sachs' famous DI.R.T. designs.

DI.R.T. (note the weird placing of the full stops) stands for DIrect Response Technology. The DI.R.T. designs were extremely innovative, with two composite knuckles, a composite outer parallelogram plate and a composite inner pulley cage plate. That's a lot of composite for the time, and it made these derailleurs fiendishly light. They also had a pretty straight cable run and a groovy curvaceous look. Finally they were Shimano compatible - sounding the death knell on Sachs' proprietary ARIS system.

Did they change gear well? I would say that they did - although many home mechanics, who were not used to the straight outer cable run, were not careful enough about the length of outer cable required. Get this right and these gears worked well, possibly very, very, well. Get it wrong and they were dogs.

Were they a commercial success? Possibly not. They acquired a reputation for being fragile, with numerous macho dudes claiming on the, then newly fashionable, internet that they had smashed their DI.R.T. derailleurs to pieces in this way or that. I have to say that I didn't notice more smashed DI.R.T. derailleurs than smashed Shimano derailleurs, so I am mildly dubious about this claim. I do think that the DI.R.T. derailleurs looked fragile, and that plastic and pressed aluminium possibly does not look as comforting as polished or anodised aluminium forgings.

Most of all these derailleurs were not cheap (particularly the higher end ones). The biggest downside of the DI.R.T. derailleurs was that it was hard to convince customers that a plastic and pressed aluminium derailleur was a luxury item that should cost as much as one constructed of polished or anodised aluminium forgings. These derailleurs were no only light in weight, they were also light on Bling.

The Sachs brand was, of course, taken over by SRAM. And despite the supposed fragility, and despite the fact that it does not chime with SRAM's foundation myth, it might be true to say that there is more of the Sachs DI.R.T. DNA in, say, a SRAM X-0, than DNA from SRAM's own, contemporary, SRAM ESP 900.

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This is an example of a Sachs Plasma, the top model in the Sachs DI.R.T. range. It weighs a terrifying 196g. This example has its aluminium parts badly painted with white enamel. Mystifyingly, I have seen this on a number of Sachs Plasmas - was it a fashion amongst Plasma owners to deface them in this way?

The Sachs Plasma featured:

• an aluminium inner parallelogram plate.
• an allen cable clamp bolt
• an aluminium outer pulley cage plate
• an aluminium b-pivot bolt
• a fully dissassemblable parallelogram that could be readily cleaned and serviced
• two sealed bearing pulley wheels with no float and both are, sensibly, black in colour
• the word 'Plasma' prominently written on the b-knuckle
• no round badge on the p-knuckle to indicate the first letter of the model
• adjustment screws that can be turned with an Allen key or a flat bladed screwdriver
• pulley wheels that are branded 'Sachs'
• an outer pulley cage plate that is branded 'Sachs' and 'DI.R.T.'.

The Sachs branding is notably discreet. Perhaps they knew that the takeover by SRAM was in the offing.

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• Derailleur brands: Sachs
• Categories: Sachs - DI.R.T.
• Themes: Ultra-lightweight - touring/mountain bike
• Country: Germany, manufactured in France
• Date of introduction: 1997
• Date of this example: possibly 1997 - the inner pulley cage plate is stamped ‘Y7’
• Model no.: unknown
• Weight: 196g
• Maximum cog: 32 teeth
• Total capacity: 40 teeth
• Pulley centre to centre: 86mm
• Index compatibility: 8 speed
• Chain width: 3/32”
• Logic: top normal
• B pivot: unsprung
• P pivot: sprung
• Materials: largely plastic (OK - ‘composite’), inner parallelogram plate and outer pulley cage plate aluminium