DIPLO TYRES

The front wheels are the ones that most influence the dynamic characteristics of a model car.
A good control of the front wheels guarantees very good dynamic behaviour in bends, which, however, turns into unstable behaviour in straights: the car reacts immediately to the slightest stress and runs the risk of not being able to go straight, but rather zigzagging.
The Tamiya “Diplo Tyre” set number SP-1075 is called “Tyre set Front A with wheel”; it is installed as standard on several models:

– Lamborghini Countach LP500S CS model number 58008,
– Toyota Celica LB Turbo model number 58009,
– Ligier JS9 Matra CS model number 58012,
– Williams FW-07 model number 58019,
– J.P.S. Lotus 79 model number 58020,
– VW Golf CS model number 58025,
– Renault 5 Turbo model number 58026,
– Honda F-2 model number 58030 and
– Brabham BT50 BMW Turbo model number 58031.

The set includes two complete front wheels:
– two rims
– two circular bands of soft rubber and
– two sponge wheels with a central groove in which to install the soft rubber band.

List of steps to assemble a wheel correctly:

– join the soft rubber band (highlighted in red) to the sponge part (highlighted in black) by applying a thin layer of epoxy glue (highlighted in orange),
– install the resulting rubber on the rim (highlighted in green) and
– join the two parts with a thin layer of epoxy glue (highlighted in orange).

The resulting Diplo wheel has two different grip zones:

– the central zone is more elastic, but less grippy and
– the two side zones are softer, but more grippy.

This configuration is what differentiates this Diplo wheel from all other all-foam or all-soft rubber wheels. The Diplo wheel is designed to combine the characteristics of sponge and rubber wheels.
Rubber wheels offer better straight-line behaviour by absorbing bumps, but have less grip when cornering than sponge wheels.
When the car is travelling in a straight line, the wheels are parallel to each other with the centre plane of the wheels perpendicular to the bearing surface (the centre plane is highlighted in red in the image below).

In these conditions the front Diplo wheels touch the road surface on the soft rubber strip absorbing the roughness, offering less grip and better straight-line handling; in these conditions grip is not important for the performance of the model car, but it is important to absorb the roughness of the terrain in order to have the straightest possible motion. The steering is less responsive to controls and it is easy to maintain a straight line.

Let us analyse the behaviour of the left front wheel (highlighted with the circle and the line in red); the right wheel has the same behaviour as the left wheel, but mirrored in relation to the central axis of the car (highlighted in blue).

When the car steers to the right, the left wheel is outside the turning radius. The centre plane of the left wheel tilts towards the car: there is a difference between the perpendicular axis of the wheel (highlighted in blue in the picture) and the centre plane of the wheel (highlighted in red in the picture) forming an angle of a few degrees (highlighted in black in the picture).

Under these conditions, the left front wheel touches the road surface on the inside of the wheel on the foam side, completely raising the outer and middle parts which no longer touch the road surface. By touching the foam side, the wheel offers more grip, improving handling when cornering.

When the car steers to the left, the left wheel is within the radius of curvature. The centre plane of the left wheel tilts towards the outside of the car: there is a difference between the perpendicular axis of the wheel (highlighted in blue in the picture) and the centre plane of the wheel (highlighted in red in the picture) forming an angle of a few degrees (highlighted in black in the picture).

Under these conditions, the left front wheel touches the road surface on the outside of the wheel on the foam side, completely raising the inside and middle parts, which no longer touch the road surface. By touching the foam side, the wheel offers more grip, improving handling when cornering.

For these reasons, the Diplo wheel provides better control than a normal sponge or rubber wheel both in curves and straight ahead.
This set can be installed as an accessory on the following models:

– Porsche 934 Turbo RSR model number 58001,
– Porsche 935 Turbo model number 58002,
– Lamborghini Countach LP500S model number 58005,
– Martini Porsche 936 Turbo model number 58006,
– Ligier JS9 Matra model number 58010,
– Ferrari 312T3 model number 58011,
– March 782 BMW model number 58013,
– Martini Mk.22 Renault model number 58014,
– B2B Racing Sidecar model number 58017,
– Ralt RT2 Hart 420R model number 58018,
– Can-Am Lola model number 58021,
– Datsun 280ZX model number 58022,
– Tornado model number 58032 and
– Ford C100 model number 58033.

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