It should have the rating on the tyre
I looked up triumph work shop manual
Bonnelville , Bonnelville T100 & Thruxton
Solo
Front 2.27 Bar (33 lb/in)
Rear 2.62 Bar (33 lb/in)
Fully laden
Front 2.27 Bar (33 lb/in)
Rear 2.62 Bar (33 lb/in)
I hope this helps