>recommendation is 18 front 19 rear.
>probably the rubber used "back in the day" was stiffer
It was the sidewalls were stiffer.
>tyres are Avon.
>25 front 28 rear
Roadrider or Slippery Mileage? Ime, Roadrider recommended pressures tend to be 29 psi (2 bar) front, 32 or 33 psi (2.2 or 2.3 bar) rear, irrespective of actual motorcycle. SM recommended pressures I don't know 'cos I haven't used SM's for decades, since one spat me off my 250 learner bike in the rain - 'phone Avon? 01225 703101.