Wheel diameter

[Ian Williams]

It is well known that lowering the final drive ratio on some sevens will actually increase the top speed, this is particularly true of 4.9 rear axle ratios, most post war specials ran on 15" wheels although this size is less acceptable in some quarters today. Several publications cover gearing well, as does Dave Armstrong's Speedex site.

Edit, Although close in size a 400 x 17" is marginally smaller than a 350 x 19" it all depends on the tyres used