Fig 10 shows a new lined shoe of the latest type. Although it is not shown on this image, the leading lining edge that is at the left top should be ground down fully across the lining for approx one inch from the edge. This provides a gently lead to the leading lining edge and can help prevent brake grabbing.

The actual lining thickness on both early and late type brake shoes, front or rear, is 0.322 inch + 0.015, most suppliers will provide 0.312 inch linings, which will suffice. The correct thickness is however listed for the record. Each lining covers 102 degrees of the drum surface at an inner lining radius of 5.800 inch and the width is 2.250 inch (+/- 0.015 inch). A number of different lining part numbers have been used, differing only in the material used, these part numbers include GB 3760, GB 4685, RG 3305 and RG 7146.

Fig 11 and Fig 12 show the hydraulic components of a cylinder; in this case both images show a left hand side cylinder, each side being handed. Fig 12 shows bronze inserts in this cylinder, these half inserts are fitted only half way down from each end of the cylinder so that any insert movement does not cut off the hydraulic fluid supply. Currently it is possible to source replacement cylinders of better quality material than the originals, so the viability of inserts might be questioned. The bronze inserts, or indeed stainless ones do prevent seizures especially if the cylinder is also fitted with stainless pistons as shown in these views. The red coloured material on the pistons and rubbers is special rubber grease.

The shortest hydraulic hose that can be fitted is 13.5 inches from end to end; a slightly longer hose of around 15.5 inch is also available. The former tends to keep pressure expansion to a minimum whilst the latter allows the brake assembly to be passed over the end of the stub axle without dismantling the brakes. This is handy during any suspension or kingpin work when any extra disassembly and brake bleeding may be avoided. Owners with cars having righthand side under wing fresh air intakes or Continental type under wing hot water demister matrix should be aware of the longer brake hoses fouling these parts when the suspension is on “bump”. Note that it is necessary to couple the hose, with interspaced copper washer, to the wheel cylinder before attaching the steel chassis pipe.

Fig 13 shows the special brake bleeder used on these late cylinders. This brake bleeder part no RG 5253 is 0.312 inch diameter and threaded 24 T.P.I to WHITWORTH form. This is not a normal TPI for 0.312 inch Whit, and the equivalent size in UNF will not do the job and is dangerous. Beware your local brake specialist is unlikely to stock this bleeder screw and because they are frequently seized it is advisable to purchase new genuine ones from a Crewe Parts source before undertaking the work.

For the record the brake bleeder fitted to the earlier Bentley MkVI, with the different brake cylinder, before June 1950, is a standard BSF thread and part no RG 7050.

Reverting back to Fig 7 note the position of the “sprag” and how it jacks, or mounts off, the cylinder. The positioning of this sprag is difficult to illustrate on a fully assembled brake. This illustration also shows the forks through which the clevis pin and off stop pin are fitted. Later heavy duty forks were standardised on R types after chassis B 60 XF, and were intended to be retrofitted to Bentley MKVI after chassis B1 GT, see Fig 14. Unfortunately it is not well known that these forks should be fitted, along with a different stop pin and clevis pins. One of these pins, the clevis, is not available but can be obtained commercially. Modified part numbers were, Fork RG 8490, Off stop pin RG 8489, and Clevis K 4561 / Z .

Fig 15 Shows the white guideline along the front brake hose, so placed to ensure the hose is not twisted during the tightening process. Note that hoses are now marked with their date of manufacture.