Master Brake Cylinder Dual-Circuit A-Quality

Master brake cylinder for dual-circuit brake system, A-quality.
Diameter: 19.05 mm.
2 brake light switches.
VW Beetle 1302 | 1303 left-hand drive (LHD).

All Volkswagens had a single-circuit brake system up to 1966, except the Beetle, which continued to use this system in Europe on the cheaper versions up to 1969. The dual-circuit brake system was introduced in 1967; the brake lines front and rear were separated. If, for example, the pressure on the front brakes drops, you still have the brakes at the rear. With the single-circuit system you lose all your braking power in such a case. The dual-circuit brake system can be recognised by the two supply points between the brake fluid reservoir and the master brake cylinder.

These master brake cylinders are all of very high quality and most are from the same manufacturer as the original Volkswagen supplier. These are not cheap, but if you want to reduce your costs, the most common master cylinders are also available in B-quality. A good alternative, but do not expect a miracle from them. The stated diameter is the piston size. If in doubt, open the old master cylinder and measure the piston before ordering. The dual-circuit master cylinders for the Beetle (except 1302-1303), Karmann Ghia and VW Thing have two versions, with one or two brake light switches. If your master cylinder is fitted with two brake light switches, it is for the warning light on the dashboard that indicates a pressure difference between the front and rear brake system, i.e. a problem with the braking function. Often this warning light is not present, but the master cylinder is fitted for it.
It is not as the original should be, but this does not affect its function. If your car is fitted with disc brakes at the rear and this is also the case at the front, the following master cylinders are not suitable. For more information on this application, see the larger master cylinders developed specifically for this purpose.

Larger master brake cylinder:
When fitting front and rear disc brakes, the standard master cylinder is no longer sufficient. The efficiency is too low and the pressure in the brake system cannot be high enough. The standard diameter of the master cylinder is 17.46 mm or 19.05 mm depending on the year for a single-circuit brake system and 19.05 mm for a dual-circuit brake system. These larger master cylinders have a cylinder of 22.2 mm for the single-circuit brake system and 20.6 mm for the dual-circuit brake system, resulting in a higher pressure required for all 4 calipers. Applies only to Beetle, Karmann Ghia and VW Thing.

Single-circuit brake system 4003301.
Dual-circuit brake system 4003298 (except Beetle 1302 and 1303).
Dual-circuit brake system 4003243 only for Beetle 1302 and 1303.