The Dia-Compe Gran Compe Zero was, in essence, a microSHIFT Arsis, of one type or another, branded up for Dia-Compe. As such they were decent, well constructed, nicely finished derailleurs, if a touch heavy for their price point.

The purpose of these derailleurs is slightly mysterious. Dia-Compe had made derailleurs way back in the 1950s, but for 5 decades had concentrated on is core business of manufacturing brakes. Then, suddenly, in 2010 it decided to get back into the derailleur business. Perhaps Shimano had eaten too much of its brake business and, in a fit of fury, it felt the need to hit back. But I suspect that the nice-but-dim Gran Compe Zero did not strike much fear into Shimano's steely heart (if it even acknowledged its existence).

This is an example of the first generation Dia-Compe Gran Compe Zero with the model no 'RD800'. It is a thinly disguised microSHIFT Arsis (R66S). Some of its features are:

• Its a 10-speed device.
• The outer parallelogram plate is a conventional shape.
• It has a very year-2000-Campagnolo, polished aluminium, Zeppellin shaped p-knuckle.
• The pulley cage is 50mm long.
• The adjustment screws are titanium with Phillips heads.
• The machined aluminium pulley wheels have sealed bearings.
• The cable clamp washer has one tab.

This example is unusual (to my eye) in that the b-pivot Allen bolt and the pulleys are silver. In the publicity shots for this model both are black.

• Derailleur brands: Dia-Compe, manufactured by microSHIFT
• Country: Japan, manufactured in Taiwan
• Date of introduction: 2008?
• Date of this example: unknown
• Model no.: RD800
• Weight: 197g
• Maximum cog: 27 teeth (source: microSHIFT)
• Total capacity: 29 teeth (source: microSHIFT)
• Pulley centre to centre: 50mm
• Index compatibility: 9 & 10 speed Shimano
• Chain width: 3/32”
• Logic: top normal
• B pivot: sprung
• P pivot: sprung
• Materials: aluminium with a carbon wrapped outer parallelogram plate and titanium cable clamp bolt

Ref. 2106