Machined Aluminium Pulley 6.5mm Shaft 3/32" (2.38mm) Gold

Machined precision so the belt never fails when it matters most

The SC-1703A from Scaleauto is a CNC machined aluminium pulley designed for tuners who do not accept compromises in transmission. With a 6.5 mm outer diameter and mounting on a standard 3/32" (2.38 mm) axle, it fits directly into the belt drive systems used by many 4WD slot chassis aimed at Rally and Raid categories.

Function and performance

In a four-wheel drive system, the front or rear pulley is the link that defines the gear ratio between the two axles. A piece with imperfect concentricity introduces vibrations that result in speed oscillations, premature belt wear, and loss of traction at the points of maximum demand on the track.

The CNC machining of the SC-1703A eliminates this problem at its root: the concentricity is virtually perfect, the belt operates consistently, and the motor's energy reaches the axle without losses due to play or rotational imbalances. The result is particularly noticeable in corner exit acceleration and braking consistency.

The anodised gold finish is not just an aesthetic nod, although the mechanics look spectacular from above. The anodised layer hardens the surface of the aluminium and protects it from continuous friction with the belt, extending the lifespan of the part even in intense running sessions.

Compatibility and mounting

The pulley is designed for 3/32" (2.38 mm) axles, the most common diameter in most competition chassis from brands like Scaleauto, Slot.it, or NSR. The fixing is done using an M2 grub screw (not included), which allows for a firm tightening and quick disassembly during configuration changes in the pits.

• Outer diameter: 6.5 mm
• Axle diameter: 3/32" (2.38 mm)
• Material: CNC machined aluminium
• Finish: gold anodised
• Fixing: M2 grub screw (not included)
• Reference: SC-1703A

Ideal for…

This pulley is particularly useful for those preparing slot cars with 4WD systems and needing to adjust the gear ratio between axles or replace plastic pulleys with more precise and durable parts. It is also a good choice when looking to reduce rotational mass without sacrificing mechanical strength, a factor that makes a difference in lap times on technical circuits with many chicanes and rhythm changes.

Mounting and preparation

Before installing the pulley, it is advisable to clean the axle with a lint-free cloth to remove any lubricant or dirt that could compromise the tightening of the M2 grub screw. Once mounted, visually check that it spins without eccentricity before closing the chassis: simply roll the axle slowly with your fingers. If the belt jumps or vibrates after installation, check the alignment between the front and rear pulleys; a few tenths of a millimetre of misalignment are enough to notice the difference on track.

Frequently asked questions

Is it compatible with toothed and smooth belts?

The SC-1703A can be used with both types of belts, as its outer profile is smooth. The choice between toothed or smooth belt will depend on the chassis and the transmission configuration you are using.

Does the M2 grub screw come included?

No. The M2 fixing grub screw is not included with the pulley and must be purchased separately. Scaleauto and other slot spare parts manufacturers sell it individually.

Can I use it on 2 mm axles?

No, not directly. This pulley is specifically designed for 3/32" (2.38 mm) axles. For 2 mm axles, there is a different reference within the Scaleauto catalogue.

In which slot categories is this type of pulley commonly used?

Belt drive systems with aluminium pulleys are common in Rally and Raid categories, where 4WD chassis require a distribution of traction between the front and rear axles. They are also used in club preparations that seek greater mechanical fidelity compared to standard mounts.

Is there a real performance difference compared to a plastic pulley?

Yes, and it is noticeable. Plastic pulleys can exhibit small eccentricities that generate vibrations at high revolutions. The CNC machining of aluminium offers much superior concentricity, resulting in smoother transmission and less belt wear over time.

Scaleauto SC-1703A aluminium CNC pulley, 6.5mm diameter, 3/32" axle, golden anodised finish for 4WD slot car belt drive systems. Precision-machined for rally and raid slot categories, compatible with standard 3/32" axles and M2 grub screw fixing. Ideal for club competitors and advanced hobbyists looking to reduce rotational mass and improve power transmission consistency.