Yo,

So I normally run my 145s 28psi front and 30psi rear. There's a noticeable difference in speed and economy if the rears drop to 20 (there's a slow leak).

So, next week I'm driving up to see Jojo with a fairly large number of panels in the back of the van, along with camping gear and everything else you need for a weekend away.

Would it hurt to whack the rear tyres up to 40psi?

Sam

Probably not... We have the racers pressure quite high and they take much more of a beating then road cars

You will wear the tires in the middle, not across the whole face. Look for max PSI stamped on the tires, usually around 36 PSI. In hot condition and loaded, they may explode.
Stick to max 30 PSI

Sam,
why don't you just be done with it and fit solid rubber tyres, if you're running them at such high pressures?
After all, it is only 119 years since Andre and Edouard Michelin first fitted pneumatic tyres on an automobile to provide improved levels of both roadholding and comfort...

Fwiw, I've been using 145 tyres on two of our Dyanes for many years, both run at 22 psi front and 28 psi rear, even when the one with Acadiane chassis and running gear is freighted up with 'about' 400kg of laser cut metal...

I've previously run my road car at cold pressures of 32 PSI on 135s, and I know we use higher than that on the racers, as Patch said.

I've previously run my road car at cold pressures of 32 PSI on 135s, and I know we use higher than that on the racers, as Patch said.

There's no reason bigger tyres need more psi. Irrespective of size, I'd stay close to what citroen recommend for a loaded 350, then personally maybe add a couple more psi all round because I like economy.

I sometimes have 50psi in the rears of my car but that's so it does better skids, I doubt more than 30 in your van is necessary.

i had 50 psi all round - it made the windows rattle, however they didn't actually explode either.

it was an error from seating the tyres on the rim but not adjusting the running pressure. I havent a clue what pressure is in any tyre on any vehicle, if they wallow in corners i give them a bit more if the windows rattle then i just relax knowing that im saving petrol or diesel

This tire exploded at 80 kmph pumped to 40 PSI on my overloaded raid Viking van on very hot sealed road in northern Australia