From RROCA-info

20/25 H.P. ROLLS-ROYCE

(From a contemporary Road Test report, 1926)

Specification

Number of cylinders, 6; size, 3� in. by 4½ in.; capacity, 3,670c.c.; nominal h.p., 25.3; number of main bearings, 7; top gear ratio, 4.55; petrol capacity, 18 gallons, tires, 6 by l9in.; turning circle, left 43ft. 1 in., right 48ft. 6in.; wheelbase, 11 ft.; tracks, 4ft. 8in.; ground clearance, 8in.; weight of car, 34cwt. Price, £1,625. The above are all the data given by the makers.

The 20/25 h.p. Rolls-Royce touring saloon responds at once to sympathy and a fine sense of touch. It has great refinement of power, and a gentleness and quietness in doing its work, which make results deceptive. It is an up-to-date looking car, and the Hooper body gives great comfort.

There are four doors and four side windows, and the fittings include inside adjustable visors, a sliding roof, scoop ventilators in the front floor, flush-fitting electrically lighted signalling arms in the rear quarters with a time switch, wells in the back floor, three armrests behind and two in front, sunk ashtrays, and window louvres, while in the sloping back there is a luggage boot, which can be got at from inside or outside. The small tools are kept here in a fitted tray, and the petrol filler can be got at through its own door. Permanent jacks are a useful provision. The wipers are concealed below the screen when not in use, and the screen and windows give a wide and safe view. Entrance is only fair in front, especially by the driver's doorway.

The six-cylinder engine has the valves overhead, worked by push-rods at the bottom of which are easy means of adjustment, the forced lubrication is taken out to the ball and cup connections of the push rods and rockers, and the cover over the valve mechanism can be detached by hand, as can the cover plates in front of the tappets. The shutters in front of the radiator work thermostatically, and the fan belt is not difficult to tighten.

On the offside there are the vertically driven make-and-break and distributor, and just aft the water pump. Water drainage is more convenient than running the oil out of the sump. The sparking plugs are accessible and are set at an angle in the head, while the coil is in a cool place forward. In the ordinary way ignition is by battery and coil, but by simple means the shaft connecting the magneto, and which is normally free, can be connected, thus giving an alternative ignition. The carburettor is on the offside, and there is a metal bowl for the filter. Steering is by worm and nut. Timing is by gear, and the generator and magneto are driven in tandem on the near-side. Both ignitions use a common distributor. The four-branch inlet manifold is of circular section and has a hot-spot centrally. The exhaust manifold has three branches and the pipe is connected to the middle of it. The oil switch for the engine starter is under the bonnet and the starter itself is below the magneto. There is a float level indicator for the oil and this is near the filler, which is merely a tube. On the dash there are the oil tank and pump for the centralised chassis lubrication - which includes such points as the pivot pins and the brake control bearings, and the vacuum petrol tank.

The engine, single-plate clutch, and four-speed "easy change" gearbox are supported together in front by a rectangular horizontal cradle, with a grease valve for the swivel bearing, and a point either side of the flywheel. There is a torque reaction damper in front on each side. The speed lever works in a visible gate on the offside and changes from second to third, third to top, and top to third are rendered simple and noiseless by braking cones or synchromesh. The box has a level filler on the nearside, and here also is the mechanical servo for the four-wheel brakes. The propeller shaft is open, and the fully-floating back axle has spiral bevel drive. The offside hand brake lever works additional side-by-side shoes in the back drums. Partly rods and partly cables are used for the brake application, and the pairs are compensated by enclosed differentials. The brakes can still be used should the servo fail, and the latter is arranged to be useful in reverse as well as in a forward direction. With the four-wheel brakes a lead is given to the back brakes. The front brake operating spindles are neatly carried in the axle ends, and pull rods behind the axle expand the cams. The half elliptical springs work with Rolls-Royce hydraulic shock absorbers and are shackled forwards in front, while the back springs are underhung.

ON THE ROAD

This model gives an exceptionally good driving position, and one feels the highest degree of control, which, coupled with the responsiveness of the car, makes it very pleasing and untiring to drive. The saloon had done 11,000 odd miles, and felt to me to be in its best form. The engine, being a Rolls-Royce, is naturally quiet at all times, and its power is swiftly and smoothly given off even under heavy load at low speed. The clutch took its loads firmly yet with proper graduation, and showed improvement on the last one I tried. The change-speed is simple enough for a novice, yet can be enjoyed by the experienced driver. The steering, owing to its self-centring action, could be lighter on the turn, but it has a safe enough feel and no undue reversibility. The brakes were efficient, and the suspension, though a little hard in effect at the back, allowed the car to hold the road properly. The touring saloon will run up to about 40, 60 and 75 miles an hour on second, third and top, and at 65 there is good reserve. There were two persons in the car, the roads were dry, and the breeze was mostly adverse to the tests. The 15 at the beginning of the upgraded stretch rose to 61, the rates on the new hill were 30 and 59, and with good standing starts on the old Dashwood hill on third and top the crest was passed at a slightly accelerating 38 and 22 miles an hour respectively.

NOTE: - There is a quiet second as well as third, the carburettor has an air silencer, and in addition to several minor alterations the braking has been improved.