This Idéal derailleur is pleasingly elegant. In the style of the times it is a sliding rod mechanism, but its genius is that the sliding rod slopes down at an angle, to allow the derailleur to follow the profile of the freewheel. In this way it maintains a relatively constant chain gap - prefiguring SunTour's 1960s slant parallelogram that is still influential today.

I am aware of two variants of this design:

• A 'racy' model with a single pulley wheel and a flamboyant pusher plate.
• A 'touring' model with two pulley wheels and a longer pulley cage.

I do not know Idéal's model names for these variants - you could guess 'Course' and 'Tourisme' but you might be wrong.

Finally, I would note that the pulley wheels and their associated nuts and chain catchers on these Idéal derailleurs are extremely similar to those on Super Rapid derailleurs. I don't know if Idéal manufactured the Super Rapid derailleurs or vice versa or if both brands shared a third party supplier of these parts.

---

This is an example of the 'touring' double pulley wheel model. In this case the main sliding rod components are manufactured from bronze. I do not know if Idéal made an aluminium version of the touring model. Perhaps not, as on tour, strength tends to trump light weight.

Some other points to note are:

• The mounting bracket clamps onto the chainstay, unlike my other Idéal derailleurs that mount into the dropout.
• The upper part of the sliding rod mechanism is not exactly the same as on my other bronze Idéal derailleur. This is a little surprising and a little hard to explain.
• The pulley wheels are also slightly different from the pulley wheels on my other Idéal derailleurs.
• The bronze parts are finished with a silver coloured metal plating, possibly chrome. A great deal of this plating has gone AWOL.

---

• Derailleur brands: Idéal
• Country: France
• Date of introduction: 1939?
• Date of this example: unknown
• Model no.: unknown
• Weight: 236g
• Maximum cog: unknown
• Total capacity: unknown
• Pulley centre to centre: 75mm
• Index compatibility: friction
• Chain width: 1/8”?
• Logic: low normal
• B pivot: sprung
• P pivot: none
• Materials: the two parts of the sliding rod system are bronze, the mounting bracket, adjuster rod and pulleys are steel.