Tyre pressure

Ron-D · Guru

Tyre pressure

Sparkster · Senior Member

If I were you I would either email or 'phone the tyre manufacturer/distributor with the details you have posted here. I've always had good results in contacting them and if you use email you get it in print for future reference.

The 'vans I've had/have, the tyre pressures are listed on the nameplate.

I know what I would start with but I'm an electrician not a tyre expert.

Keith.

EJP · Senior Member

As Sparkster said, contact the manufacturer/distributor, 60 psi sounds about right but do not exceed the max pressure stated on the tyre, ie 550 Kpa or 80 psi. I run 40 psi on my van but it is lighter than yours, approximately 1600 kg loaded.
Regards EJP

nswoutback · Member

A few questions'-

** How many axles does the caravan have?
** Are the tyres P, C or LT construction?
** What is the tyre load index / maximum tyre load in kg?

Radar · Guru

Ron-D wrote:
can anyone help me work out the exact tyre pressure for my failey new van ,I have spoken to others with the same van ,and they run 60 psi ..
tare 1862 kg
Gtm 2008 kg
ATM 2162 kg
load 300 kg
axel load 2200 kg
tyre 235/75/15
cold 550 kpa max load...

-- Edited by Ron-D on Tuesday 15th of May 2018 04:58:18 PM

-- Edited by Ron-D on Tuesday 15th of May 2018 05:01:33 PM

Hi Ron D

First off I don't have any trade or science degrees, just plain ordinary experience in life with one good rule, "I take with little notice of saleman" and that what tyre people are.

Caravan vin plates are written by caravan builders with no knowledge on tyres. They would be better leaving a few blank spacers on the vin plate.

My thoughts only, look at your tow vehicle recommended "loaded" tyre pressures, in my case when I owned a single axle caravan I started at similar pressures of 42psi and then I applied the 4psi rule that is if after a couple of hours running I checked the pressures if they over 4psi more then when I started I would add 4 pounds more until I found the right balance. 44psi where I left them, very satisfied I was around the right mark, car and caravan traveled well.

Even now owning a dual axle caravan gross around 2500kgs on 4 tyres I have found 42psi enough to keep the pressures right by the 4psi rule which has been around more then 50 years that I know of.

Car and tyre manufacturers spend big money putting recommended tyre pressures on their vehicles before selling which is worth noting, the caravan manufacturers are only using the maximum cold pressure of the grade of tyre they are suppling with the caravan they are selling eg in my case "speed rating S and 550kpa tyre pressure" way over my findings.

Have fun trying to work it out, give the 4psi rule a thought.

rockylizard · Guru

Gday...

Perhaps you could use this site Ron.

https://www.tyresafe.org/check-your-pressures/caravan-pressure-calculator/

Cheers - John

Radar · Guru

rockylizard wrote:
Gday...
Perhaps you could use this site Ron.
https://www.tyresafe.org/check-your-pressures/caravan-pressure-calculator/
Cheers - John

Hi John

Interesting link, the problem is it relates to UK. The first thing I noticed is it don't have common Australian tyre sizes, ie ours are light truck 235r15, 4 caravan friends run this size, 1 friend runs 14 inch his size is not there.

The 14 inch size caravaner was told by the tyre retailer maximum cold tyre pressure of 65psi. The tyre guy didn't say run them at 65psi, he did say "maximum cold tyre pressure of 65psi".

-- Edited by Radar on Tuesday 15th of May 2018 09:06:25 PM

Ron-D · Guru

Thanks John 65psi on that site

Radar those are all the tire details supplied

Single axel van.

I dont think I will bother chasing tyre manufacturers the things are probably made in China

The vans a single axel nova compliance details above are all thats on the plate, I wont contact the suppliers thats been a complete waste of time in the past,Iam out of warranty and glad biggrin looks like 60 kpa might be close 20 kpa under max tire pressure seems safe enough hopefully,

next time out I will see what the pressure is when hot on the road

-- Edited by Ron-D on Tuesday 15th of May 2018 10:26:26 PM

Roy E · Senior Member

Ron,
I have a van with similar weights to yours and the same sized tyres on single axle.
I run the tyres at 46 psi (3.2 bar) and used the "4 psi rule" (as suggested by Radar) to establish the right pressure which wasn't too far from maker's recommendation.
At the end of a run, if the tyres haven't been exposed "full-on' to the sun, I hand check tyre temperature. Should be nicely warm. Hot equals pressure too low. Cold equals pressure too high. Tug and van tyres should feel the same temp after a run.
Cheers,
Roy.

Radar · Guru

Roy E wrote:
Ron,
I have a van with similar weights to yours and the same sized tyres on single axle.
I run the tyres at 46 psi (3.2 bar) and used the "4 psi rule" (as suggested by Radar) to establish the right pressure which wasn't too far from maker's recommendation.
At the end of a run, if the tyres haven't been exposed "full-on' to the sun, I hand check tyre temperature. Should be nicely warm. Hot equals pressure too low. Cold equals pressure too high. Tug and van tyres should feel the same temp after a run.
Cheers,
Roy.

Thats a big yes from me. I do a walk around the car and caravan to check everytime we stop while doing that I a have a stretch also.

Ron-D · Guru

Roy that sounds pretty low to me but you have checked it out with 4psi rule I will do the same,I have just over two ton of van with reasonably big tyres sitting on a single axel ,just curious anyone else here running a single axel van with similar specks ?and what your tyre pressures might be ....

P/s the tyres are rated to take 80 psi max so 60 psi is still well under max...

-- Edited by Ron-D on Wednesday 16th of May 2018 08:36:30 AM

WAssa41 · Senior Member

The tyre has max kg load at max pressure marked on it. Add the 4 tyre load kg then work out the van load as a % of the combined tyre load. Apply this % to the max tyre pressure which will give you the manufactures recommend tyre pressure for the weight of your van. I would then use the 5psi rule. The difference between cold tyre pressure and the pressure after running for say 30minutes should be around 5psi higher, if it is lower then the tyre is over inflated and higher under inflated. Over inflated tyres can cause blow outs as the tyre has very little give/flex when running over a sharp object and a under inflated tyre overheats.

Just my way of doing it.

Wassa

Possum3 · Guru

Ron-D, Check out the Australian Standard in Technical Notes from Caravan Council of Australia www.caravancouncil.com.au/technical-articles Check the PDF listed at "Tyres"

nswoutback · Member

Load inflation tables are published for most tyre sizes.

There are just two factors required to use the tables;-

1) Tyre load
2) Tyre size.

1) Tyre load. It is better if you know you actual tyre load but very few people do.

A good estimate of tyre load is ATM times 0.91 divided by the number of tyres on the caravan.

Example 2162 kg times 0.91 divided by 2 equals 984kg

2) Tyre size. Read all the data on the tyre wall.

Examples of tyre sizes include;-

a) P235/60R17XL load index 102, maximum load 850kg at 270kpa, (39psi )
b) 235/75R15LT load index 110, maximum load 1060kg at 450kPa (65psi)
c) 235/75R15LT load index 116, maximum load 1250kg at 550kPa (80psi)

There are other 235/75R15 tyres that I have not listed.

Then look at the Load Inflation Tables.

It does not matter who manufactured the tyre.

So, assuming;-

1) Tyre load is 984kg
2) Tyre size is 235/75R15LT load index 116, maximum load 1250kg at 550kPa (80psi)

The appropriate inflation pressure from the Load Inflation Tables is 390kPa or 57psi.

Aus-Kiwi · Guru

Trouble is different tyres can be fitted . I see thereâs a ruling soon that trailers over a certain weight should have light truck tyres . Where car tyres were . Often cheap too . Just looking at tyre . With experience I find gets me through . Just looking at the contact area . How much the tyre deflects ., Comparing to other tyres .. Too much deflection creates heat ., Too high . Makes a hell ride . Yes if your not sure ? 42 lb is a good average pressure . What happens is tyre pressure can drop over time if not checked .

Radar · Guru

Possum3 wrote:
Ron-D, Check out the Australian Standard in Technical Notes from Caravan Council of Australia www.caravancouncil.com.au/technical-articles Check the PDF listed at "Tyres"

You have done it again, nothing about tyres, just wheels.

Possum3 · Guru

Radar 5th item down on technical articles heading Tyres - is ONLY about tyres

Radar · Guru

Possum3 wrote:
Radar 5th item down on technical articles heading Tyres - is ONLY about tyres

Not about tyre pressures.

Lots of other good stuff wheels, alignment, good stuff.

Radar · Guru

Possum3 wrote:
Radar 5th item down on technical articles heading Tyres - is ONLY about tyres

After several attemps at downloading a pdf about tyres come up which had some interesting information but really little about tyre pressures,, once again they cover themselfs by telling us to contact the experts. Hey where are they?

ruffnut09 · Veteran Member

Both van and tug have 16" BFG LT A/T's. Put the outfit over the weighbridge to ascertain individual axle weights (single axle off road van) and calculated from the Maximum Load stamped on tyre at 80 psi, the tyre pressures for each axle.

Worked out to be: tyres on steer axle 36 psi, drive axle 52 psi and van axle 72 psi.

All tyres, after an hours drive, increased pressure by 4 psi.

What is interesting is the "footprint" of all the tyres are pretty much identical.

Ruff.

Bukhouse · Veteran Member

Hi,

Try this link

https://www.tyresafe.org/check-your-pressures/caravan-pressure-calculator/

Ron-D · Guru

nswoutback wrote:
Load inflation tables are published for most tyre sizes.

There are just two factors required to use the tables;-

1) Tyre load
2) Tyre size.

1) Tyre load. It is better if you know you actual tyre load but very few people do.

A good estimate of tyre load is ATM times 0.91 divided by the number of tyres on the caravan.

Example 2162 kg times 0.91 divided by 2 equals 984kg

2) Tyre size. Read all the data on the tyre wall.

Examples of tyre sizes include;-

a) P235/60R17XL load index 102, maximum load 850kg at 270kpa, (39psi )
b) 235/75R15LT load index 110, maximum load 1060kg at 450kPa (65psi)
c) 235/75R15LT load index 116, maximum load 1250kg at 550kPa (80psi)

There are other 235/75R15 tyres that I have not listed.

Then look at the Load Inflation Tables.

It does not matter who manufactured the tyre.

So, assuming;-

1) Tyre load is 984kg
2) Tyre size is 235/75R15LT load index 116, maximum load 1250kg at 550kPa (80psi)

The appropriate inflation pressure from the Load Inflation Tables is 390kPa or 57psi.

To much information to reply to everyone but this is the perfect starting position thanks outback for your informat..

Hylife · Guru

I agree with WAssa41.
The industry standard for decades has been provided by the manufacturer.
Because every tyre is different, the maximum load in KG (maybe just a letter rating) and max PSI is on the tyre.

The recommended pressure is simply calculated by finding what % is your load compared to the maximum load that is allowed for the tyres.
Look up the load rating on the internet if it is marked by a letter and is not specified in KG on the tyre.

Divide the loaded weight of your van by the max load of all the tyres combined. Less load, less PSI. More load, more PSI.

EG.
If the tyres have a 800kg load rating at 65PSI, and you have 4 tyres then the max load a spread across all the tyres cannot exceed 3200kg (assuming the axels can also carry that much), and, if the load was 3200kg you should have 65PSI in the tyres.

So, if your van was maxed out to the ATM of 2162kg you would calculate as follows:

2162 divided by 3200 equals 67% of the maximum tyre load rating.
67% of 65PSI equals 43PSI.

If your van was empty and at the tare of 1862kg you would calculate as follows:
1862 divided by 3200 equals 58%
58% of 65PSI equals 38PSI.

This is for blacktop driving at less than the maximum speed rating which should also be found on the tyre.
Dirt road or corrugations or gibber requires more or less PSI

grahamg · Senior Member

what about dropping the pressures down when on rougher/dirt roads?

Peter_n_Margaret · Guru

grahamg wrote:
what about dropping the pressures down when on rougher/dirt roads?

Absolutely, but when you do that, the speed that is safe for the tyre must be reduced dramatically.

Reduced pressure will increase the flex of both the sidewalls and the tread belt. That increase in flexing increases the heat developed in the tyre. Slowing down will reduce the rate of flexing and the rate of heat build up. If the heat builds up faster than it dissipates, the tyre will overheat and will be rapidly destroyed. This is often the result from a slow leak that goes in noticed.

Cheers,

Peter

nswoutback · Member

The steps for highway travel;-

1) Establish tyre load
2) Establish tyre size / full specification (read all the critical numbers and words stamped on the tyre).
3) Establish optimum tyre inflation pressure from the best reference - the load inflation charts.

If you propose to reduce tyre inflation pressure for slower travel speeds, the steps are;-

4) Determine the proposed maximum speed and adhere to this maximum speed.
5) Apply the tyre inflation pressure factor based on the chosen speed multiplied by the optimum tyre inflation pressure.

-- Edited by nswoutback on Friday 25th of May 2018 08:11:07 AM

Hylife · Guru

grahamg wrote:
what about dropping the pressures down when on rougher/dirt roads?

No problems except that less wear and tear on your vehicles suspension is offset by increased wear on your tyre when they are underinflated.

You only drop your pressures for corrugations, not just because the road is dirt. In fact for gibber roads such as the Birdsville track you might even increase the pressures to help resist punctures.

IAN zzz · Veteran Member

I have been using the 4 psi method for many, many years ... IT WORKS WELL for me

I drop pressures on both tow vehicle and van by 33% on dirt.

And out of curiosity, I use a hand held infra red thermometer ... very quick and easy to check bearing temps as well, as I do a walk around each time I stop :)