Hi Dan,
The standard Avons are 4.0 x 19" as are the Blockley replacements.
The switch to an 18" rim allows a wider choice of tyres but as far as I know only a few racers are using these.
Chris, thanks.
As I read one of the replied I thought all Avons were 18", obviously my mistake.
I agree that with 18" wheels you get a wider range of choices for front tires. But even then, very few are designed for side loading and steering pressures.
