Rolls Royce - Rolls Royce 20 HP
The Rolls-Royce 20 HP was an all new model produced for the post first world war economic climate. Prior to this Rolls-Royce only made one chassis model, their top of the range high priced 40/50 Ghost, and it was reasoned that a smaller lighter and altogether more affordable model was needed to keep the company in business. The 20 HP model was produced between 1922 and 1929 with a 6 cylinder engine of 3,128cc that had an overhead valve design. The power produced was 50 hp at 3,000 rpm. The 20 HP was arguably under powered for the overall weight of the chassis (fitted with bodywork), but since it was not built as a performance car, this smaller Rolls-Royce was a high quality machine perfect for the use to which it was intended. The Rolls-Royce 20hp power plant later became the basis for the range of 6 cylinder engined Rolls-Royce models using the same basic engine, but with the bore enlarged from 76 mm to 82 mm, and by 1936 stretched further to 89mm - a modified version of which was the basis for the Derby Bentley 3 1/2 and 4 1 /4 . . .
The Rolls-Royce 20 HP was fitted with the tyre size 32x 4 1/2 , fitted to 23" straight sided rims of the split rim type. Blockley produce this 32 x 4 1/2 tyre with the correct period tread pattern, as well as making a thicker correct inner tube to suit. Later models of the Rolls-Royce 20HP were fitted with 21" wheels in which case Blockley can also supply the 525x21 tyre. Quite a few of the earlier 20HP were fitted 21" wheels by their owners much later due to unavailability (or the huge expense at the time) of the 32x4 1/2 tyres, before Blockley made this size!
Blockley also produce the correct size high quality inner tubes for these tyres, made especially for these sizes.
See full details of Rolls-Royce 20 tyre sizes (32x4 1/2 for earlier 20HP and 525x21 for the later 20HP models) at the links below.
