Tires: fitting passenger tire to 4wd, tire placard, t3 syncro

Question
QUESTION: G'day Barry. I've been all over the net trying to find out whether I'd be better off running a passenger tire on my t3 syncro 4x4 (vehicle weight is about 2 tonne loaded) or some sort of LT tire. Thing is I live in australia where the bulk of my driving is sand, street and more sand. I had this idea that a passenger tire sounds like it may offer a larger footprint when deflated giving better sand performance over a stiffer LT tire? Do you think a passenger tire would be a better choice for airing down than an LT or would i run into issues with side wall damage?  The p tire I had in mind are maxxis ma-1 in 235/75/15.. thanks a million!

ANSWER: Erik,

First, I am in the US and we don't get that vehicle over here, so I don't have my normal references.

I hope you are aware that every vehicle has a vehicle tire placard that lists the original tire size and the proper pressure for that size.  What does the placard on your vehicle say for both tire size and pressure?

---------- FOLLOW-UP ----------

QUESTION: Hi Barry, yeah sorry I should have mentioned this vehicle hasn't been produced since 1992. The tire placard gives a couple tire options
185R14C/6PR FRONT @43PSI
185R14C/8PR REAR @48PSI

205R14C/6PR FRONT @36PSI
205R14C/8PR REAR @43PSI

I've moved up to 15" rims since in order to fit larger than stock tires.
cheers

Answer
Erik,

Thanks for the info.  I was guessing it was the same as the EuroVan, but it's always best to be sure.

I am of the opinion that folks ought to stay in the same type of tire - but that applies to street usage and small changes in tire size.  You have neither.

I am also of the opinion that low pressures are better in sand and off road usage - but there is a danger.  First is that low pressure makes the tires more prone to damage from impacts (the tire bottoms out), and second is that the original set up of the vehicle was for a tire with a high spring rate (due to the inflation pressure), so changing to a low pressure tire will tend to make the tire do proportional more of the work - and that's not good.

Nevertheless, I think you ought to use passenger car type tires in an all terrain pattern.  If you want to use 235/75R15's, I would suggest 32 psi as a starting pressure.  See how that works. I would be very hesitant to use less than that, but if that doesn't appear to be working, you can always post a followup.