I’ve been asked to do a thousand mile round trip to collect what looks like a rather large boat. The placard on the drivers side suggests 42 psi in the rear. I think this seems a bit high? What do people do for towing heavy loads? I’m running Grabbers AT 245/65/17 111H XL’s at 30psi all round.

It’ll be 42 PSI for the standard tyres, Grabbers probably not standard?

How heavy is the boat/trailer? Some ickle thing will make little difference, a half stocky cabin boat could be more than 3500kg and your truck probably doesn’t tow more than 3000kg.

If you want to get geeky you should be able to find a table of pressures for those tyres, with recommended pressure for the axle load.

A 3t trailer probably has around 200kg noseweight, then add a bit as it overhangs the rear axle, so work on 200-300kg additional weight on the rear axle?

Also, I’d take some spare bits and do some research before leaving, I was asked to collect a boat as a favour, the trailer was a cut and shut (extended) with very dodgy welding, the boat was balanced on wood blocks, brakes disconnected, tyres well under rated (and overinflated) and the electrics did not work. No joke. And when I had reversed to hookup, the front of the boat was a mere six inches from the back of my van…

42 is not high for the rears under heavy load. I run my 110 landrover with 32 front and 36 rear when empty. If towing that distance and weight I would bump the rears up to 45 psi for sure. My 3.5 tonne trailer needs 90 psi in the tyres. That is scarey. And you should see it bounce when empty 🙂

Remember to take into account the weight of the trailer. As said you will only probably be able to tow 3 tonnes.
If the combined weight of your truck, boat and trailer is more than 3.5t, you will need a tachograph.

Tachograph, if for commercial use, or financial gain. i.e. unless you can convince VOSA that you really are doing 1000 miles for free, no payment in kind, you should have a tacho.

If its your own boat and you are just moving it about, no tacho needed.

No tachometer, but the weight is certainly a big consideration. 45psi sounds perfectly reasonable too

What will your combined weight be?