The braking system on the TD and TF is a Lockheed hydraulic system with 9-inch drums and 1½-inch wide linings at all four wheels. The front brakes use a twin leading shoe arrangement with two wheel cylinders per drum, and the rear brakes use a single floating wheel cylinder per drum that incorporates the handbrake lever mechanism. Operation is via a vertically mounted brake pedal acting on a combined supply tank and master cylinder, and the handbrake operates the rear shoes through a bell-crank arrangement at each rear cylinder. The system is fundamentally common between the TD and TF, with brake drums and shoes carrying through unchanged and the only chassis-number-dependent components being the wheel studs and nuts (BSF or Unified) and the rear hub and drum arrangement that follows the same thread split.
Section Layout
The Brakes section is divided into five sub-sections: Front Brakes covering the twin leading shoe assembly, wheel cylinders, brake shoes, drums, and front backplate hardware; Rear Brakes covering the single-cylinder rear assembly, shoes, drums, and rear backplate components; Handbrake covering the cable, lever, ratchet, and operating mechanism; Hydraulics covering the master cylinder, brake pipes, flexible hoses, fluid, and bleeding equipment; and Upgrades and Alternatives covering aftermarket upgrades to the standard system.
Brake Drum Construction
The brake drums on steel-wheeled cars are integral with the front and rear hub assemblies, a single casting carrying both the wheel mounting studs and the brake-friction surface. On wire-wheeled cars, the drums are non-integral: a separate drum bolts to the splined hub via twelve drum-retaining studs and lock tabs. The change from integral to non-integral was introduced when wire wheels became available, wire-wheeled cars were always supplied with the separate drum arrangement. Brake drums were factory-finished in black and remained that colour even where the rest of the chassis was being repainted.
The four steel-wheel front hub specifications described under Stub Axles & Hubs apply to the front brake drums; the BSF/Unified split at chassis 12285 applies to the rear hub and integral brake drum arrangement.
Production Changes
The brake system carried through the TD and TF production with relatively few changes. Brake shoe steady springs were not fitted to the very earliest TDs and were added during production to improve shoe stability. The wheel-stud thread change from BSF to Unified at chassis 12285 affected the wheel-stud arrangement on the integral steel-wheel brake drums and on the wire-wheel brake drum's wheel-stud equivalent. The brake pipe kit and the number of brake pipe clips required vary between TD, TF, TF LHD, and the TD Mark II, the Mark II requires the most clips, reflecting its slightly different routing.
Brake Fluid and Bleeding Equipment
Brake fluid is available in standard DOT 4 (Castrol Response), Super DOT 4 (covering DOT 4 and DOT 5.1 specifications, suited to high-performance use), and SRF competition fluid for extreme conditions. Silicone brake fluid is available as a non-hygroscopic alternative, it does not absorb moisture and does not strip paint, although it has different compressibility characteristics that some owners notice in pedal feel. A Gunson Eezibleed automatic bleeding kit simplifies the hydraulic bleeding process for one-person operation. Castrol brake cleaner aerosol is a fast-drying, low-odour solvent compatible with both metal and non-metallic brake parts, useful for cleaning components during overhaul.
Ordering Considerations
The chassis number determines the BSF or Unified thread for wheel studs and integral hub-and-drum specifications. The wheel type, steel or wire, determines whether the brake drum is integral with the hub (steel wheel) or a separate component (wire wheel). The brake pipe kit is specific to drive side (LHD or RHD) and to TD Mark II versus standard cars, with the corresponding pipe clip quantities varying accordingly. Master cylinder, wheel cylinders, brake shoes, hoses, and most other components are common between TD and TF.