Axle load/<span class="highlight">tyre</span> <span class="highlight">pressures</span>

Would be having a look at the load ratings and pressure stamped on the tyre. Most 235/65R16 have a load rating of around 900-1000kg at around 44 psi. Based on that you may be a bit overloaded.

wombat100

When I read the loading and thn the tyre size my immediate thought was, tyres far too small.
I had a 60 series LC and when was loaded it never got anywhere near that weight on 265/75/16.

What vehicle are you referring to? I can't think of a vehicle with that size tyre would operate at that weight. I don't think it a matter of tyre pressure selection at all.

Ross M

Hi Wombat

Tyre load limits and the pressure that it is set at can be found in the Tyre & Rim Manual put out by Standards Australia.
Your local tyre service should (but probably hasn't) have a copy.

The manual will tell you what the load rating is from the code on the tyre and also what the minimum pressure is to carry that load.
It also has tables that let you work out how much you can lower the pressures for low speed continuous operation.

The load rating takes into account ply rating and tyre construction. One size tyre might come in many different load ratings depending on its intended use, so you need both to do your calculations.
Regards
A

Wombat,
here is a link to a tyre pressure/axle load calculator.

TYRE LINK

What you are looking for is a load V pressure table for the tyre in question.

Now the tyres are 235/65R16.....just checking are they a passenger or light truck rated tyre...it makes a difference.

Unfortunately my copy of the wheel & tyre manual is a couple of years old & I cant find that particular tyre in it

The load v pressure characteristic should be pretty much the same from brand to brand......but note the maximum load capacity of the particular tyre

A toyo document written for the american market lists the following

235/65R16 pasenger radial
PSI...load in pounds
26....1598
29.....1675
32.....1764
35.....1819
remember to half loads for KG

Some one with a current coppy of the manual may be more help...every tyre shop should have a current coppy.

or check the manufacturer.

cheers

I was given this formulae some years ago by a tyre techno, works well for me.

Actual tyre load (kg) divided by the tyre load rating on side wall (kg), multiplied by the max psi shown on the side wall. Less 20% on rough roads @ 80 km/h.

Hi Jerry,

1. the formula uses tyre load, not axle load, so axle load/2. Using that formula I find that tyre psi increases about 6-8 psi which is OK for LT tyres going from cold to midday ambient temp. at highway running. The so-called 4psi rule is OK for Highway tyres not carrying much load but I find too low for my rig.

2. not sure where the 20% originated from but seems to be the number used by off-road drivers (20-30%). The late Adam Platt also suggested that figure, so good enough for me.

3. for soft sand driving, most say another 20% reduction is OK. I have done the Simpson a few times and found that 20psi worked for me, with 16-18 psi on a few tough dunes.

See if this helps
http://www.peakhillcaravanpark.com.au/Tyre%20Pressuresa.htm