Loss of tyre pressure

[redfox1]

Redfox, clean the white residue off & make up thick washing up liquid/water mix & apply with a paintbrush between tyre/rim,look for bubbles,also check tyre valves for cracks or leaks from the base where it goes through the wheel.

Good idea-it's the fact that both tyres are both leaking at once which makes me doubt corrosion-they're year-old BT 23's which I've always had a problem with retaining pressure-will check the rims with the washing-up water to see if I can see anything