Brass removable pinion z12 7.5mm M2.5

Transmission Precision: Removable Brass Pinion z12 for 2 mm Shafts

The pinion is one of the elements that most influences the behaviour of a slot car: its size, material, and fit largely determine the gear ratio and, therefore, the response in acceleration and top speed. This removable brass pinion z12 from Sloting Plus (reference SP085812) is designed to work with 2 mm motor shafts and is secured using an M2.5 x 2.5 mm allen set screw, ensuring a firm grip and easy disassembly when it's time to change the gear ratio.

Main Features

• Material: brass, compatible with steel and duralumin crown gears.
• Number of teeth: 12 (z12).
• Pitch: 7.5 mm.
• Shaft diameter: 2 mm (standard motor shaft).
• Fixing: M2.5 x 2.5 mm allen set screw.
• Bag contents: 1 pinion + 2 allen set screws.

Function and Performance

Brass is one of the most commonly used materials in slot car pinions because it combines precise machining with adequate hardness to work alongside steel or duralumin crown gears without causing excessive wear on either piece. A z12 with a 7.5 mm pitch offers a relatively short gear ratio, favouring lively and direct acceleration, particularly useful on tracks with many slow corners or moderately long straights.

The fixing system using an M2.5 allen set screw allows for precise adjustment of the pinion on the shaft without the need for special tools: a corresponding size allen screwdriver is sufficient. Additionally, the inclusion of two extra set screws in the bag is a very practical detail: set screws are small parts that can be lost or worn out with use, and having spares from the outset prevents unnecessary downtime at the workbench.

Compatibility and Installation

This pinion is designed for 2 mm motor shafts, a standard size in the vast majority of motors used in competitive and prepared slot racing. Before installation, it is advisable to verify that the crown gear it will work with has the same pitch (7.5 mm) to ensure correct meshing without play. A poor pairing of pitches is one of the most common causes of noise, vibration, and premature wear in the transmission.

For installation, it is recommended to clean the shaft and check for any burrs or marks from previous pinions that could prevent a perfect fit. Once in place, tighten the allen set screw firmly but not excessively to avoid damaging the shaft.

Common Mistakes

• Combining this pinion with crown gears of different pitches: meshing will be incorrect and wear will be accelerated.
• Not cleaning the shaft before installation, which can cause eccentricities and vibration during operation.
• Over-tightening the set screw, which can mark or deform the motor shaft.
• Forgetting to keep the spare set screws: they are small parts and easy to misplace.

Frequently Asked Questions

What crown materials is this brass pinion compatible with?

It is compatible with steel and duralumin crown gears. Brass works well with both materials without causing aggressive wear on either.

What gear ratio does a z12 provide when combined with different crown gears?

The gear ratio is calculated by dividing the number of teeth on the crown by that of the pinion. With a z27 crown, for example, the ratio would be 2.25:1; with a z30, it would be 2.5:1. A higher ratio provides more top speed but less acceleration, and vice versa.

Why is it important for the pitch of the pinion and crown to match?

The pitch determines the spacing and geometry of the teeth. If the pinion and crown have different pitches, the teeth will not mesh correctly: vibrations, noise, and premature wear will occur, shortening the lifespan of both pieces.

Can I use this pinion with any motor that has a 2 mm shaft?

Yes, as long as the motor shaft measures 2 mm in diameter, this pinion is compatible regardless of the manufacturer or type of motor (sidewinder, inline, or anglewinder).

What allen key do I need to tighten the M2.5 set screw?

You will need a 1.5 mm allen key, which is the standard size for M2.5 set screws in slot and precision modelling applications.

The Sloting Plus SP085812 is a 12-tooth brass pinion gear for 2 mm motor shafts, with a 7.5 mm pitch and M2.5 allen set screw. Designed for slot car racing preparation, it pairs with steel or duralumin crown gears and delivers precise, low-backlash power transmission. Compatible with sidewinder, inline, and anglewinder motor configurations. Each pack includes one pinion and two spare set screws. A reliable choice for club racers and slot car hobbyists seeking consistent performance and easy gear ratio adjustment.