Tyre pressures

the rocket · Guru

Tyre pressures

rockylizard · Guru

Gday...

Personally, I run 50PSI in the LT 195x14 LT tyres on my 23ft 2,600Kg (weighed) van when on sealed roads. I arrived at that pressure from experimentation of advice given by the van's compliance plate, tyre shops and experience with the tyre gauge ... when I first headed off, I began with 55PSI in the tyres but over time found that 50PSI seems to give the best wear.

This article quite likely will tell you 'how to suck eggs' a bit .. but might be worth the read -

http://www.withoutahitch.com.au/caravan/correct-caravan-tyre-pressures/

This one may assist ... populate the fields with info for your van -

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

Hope that helps.

Cheers - John

the rocket · Guru

rockylizard wrote:
Gday...
Personally, I run 50PSI in the LT 195x14 LT tyres on my 23ft 2,600Kg (weighed) van when on sealed roads. I arrived at that pressure from experimentation of advice given by the van's compliance plate, tyre shops and experience with the tyre gauge ... when I first headed off, I began with 55PSI in the tyres but over time found that 50PSI seems to give the best wear.
This article quite likely will tell you 'how to suck eggs' a bit .. but might be worth the read -
http://www.withoutahitch.com.au/caravan/correct-caravan-tyre-pressures/
This one may assist ... populate the fields with info for your van -
https://www.tyresafe.org/check-your-pressures/caravan-pressure-calculator/
Hope that helps.
Cheers - John

Hi john, does that pressure give a smooth ride or does your van bounce around a bit. Appreciate your input.

rockylizard · Guru

Gday...

The van tows very smoothly. However, it also towed smoothly when the pressures were 55PSI as well. hmm I only dropped the pressures from 55PSI because of the wear occurring in the centre of the tread pattern ... indicating over-inflation.

It is rare for anything to be dislodged, come open, or move off a bed etc. That is the only indication of 'smooth' ... I don't notice any 'bouncing', 'swaying' or anything untoward when on the road. The van sits and tows without any drama ... the old saying "I don't know it is there" smile

I renew my tyres each three years, irrespective of how much tread left and they have not even been half-worn when replaced. Just safer to not leave them on for too long.

Cheers - John

the rocket · Guru

rockylizard wrote:
Gday...
The van tows very smoothly. However, it also towed smoothly when the pressures were 55PSI as well. I only dropped the pressures from 55PSI because of the wear occurring in the centre of the tread pattern ... indicating over-inflation.
It is rare for anything to be dislodged, come open, or move off a bed etc. That is the only indication of 'smooth' ... I don't notice any 'bouncing', 'swaying' or anything untoward when on the road. The van sits and tows without any drama ... the old saying "I don't know it is there"
I renew my tyres each three years, irrespective of how much tread left and they have not even been half-worn when replaced. Just safer to not leave them on for too long.
Cheers - John

Thanks for that. Will pass on to strop.

darjak · Senior Member

Run our van tyres ( Bridgestone dueller A/T 10ply 275/75/16 LT) on bitumen at 38>40psi weight 3100>3200kg and never had any adverse wear problems in the past 11+yrs on the road fulltime. Life of a tyre is 5yrs according to manufacturers.
Off-road is a total different senerio.

Darrell

Tony Bev · Guru

John above has given good advice, rocket

Different manufactures of the same size tyre, sometimes give different pressures, which may not always be the same as the compliance plate

As a rule of thumb, all manufactures will have the maximum pressure stamped on the sidewall of the tyre
It is important that this is the maximum pressure you should put into that tyre

Higher than the maximum pressure may result in the tyre casing failing
Failure of the tyre casing sometimes results in an egg, which makes the tyre bounce, as you drive up the road

Hope that this info is useful to someone in the future

Opps, edit to say that Darrell had posted while I was dithering

-- Edited by Tony Bev on Sunday 19th of November 2017 01:26:34 PM

RustyD · Guru

My van tyres (single axle 1600kg gross) 50psi. That's the van manufacturers recommendation. Next size up van with dual axle suggests about 40psi. Too soft and the tyre / tube will get hot and the tubes will melt & burst. Too high and the van will bounce. I'm happy with my 50psi and it's within the range recommended by the tyre manufacturer.

Hetho · Senior Member

Hello The Rocket.

I have Bridgestone RD613 Steel, 205 75R14 109/106S on my 21Ft 6in tandem van which weights 2200 empty.

I run them at 45 PSI, have done 45000 Km`s so far and the van/tyres have a good feel. I started at 50 PSI, but found 45 better.

As fellow members have already suggested; its a matter of finding the best "fit" for your tyres and van/tug.

I also run 45 on the 200 series and it all have a good positive road feel (Tug/Van combo)

Hope this helps.

Regards.

Hetho

SouthernComfort · Guru

I've always assumed recommended pressures are a calculation based on a combo of van weight, wheel size & tyre type. When I picked up my van the manufacturer made triple sure I understood the required pressures are 48psi (i.e. he told me twice then asked me to repeat it as I left!) which is very specific and presumably based on my van's specs (single axle, 15in light truck tyres, 2123 ATM). It's no different to a car manufacturer specifying pressures for particular models, I imagine based on similar criteria.

Your best bet could be to check with the manufacturer.

RustyD · Guru

As someone noted above: too high and you will get premature wear in the centre, too low and you will not get any wear in the centre. Also too high and bouncing may show uneven wear across the tyre and not around it.

45 psi on a tandem with 45,000 kms sounds good. My single with 50 psi and 28,000 kms and even wear looks like I may be OK too.

I run 36-38 on my Ranger. The highest comfortable pressures usually equate to good fuel economy. Been thinking of 40-42 on the rear when towing.

the rocket · Guru

thanks everyone. Strop has read everyones reply n is onto it. Gotta love this forum. Thanks everyone.

Lancelot Link · Senior Member

Just a quick comment, pressure and temperature are related, so if pressure is set in Victoria at 15C and left at that when hitting higher temperatures up North we can have a blowout situation.

Kebbin · Guru

I suggest you do more research not just on this forum, I see you have a tandem and with them the rear is usually heavier depending on weight distribution, as such the rear set should be 10/15% higher inflation then the front, also tug tyre pressures are often to high when towing and should also be looked at with the front tyre usually being to high. I would if I had a tandem search the other forum looking for Collyn's posts in particular, he stresses the importance of proper pressures with tandems.

-- Edited by Kebbin on Monday 20th of November 2017 08:05:14 AM

Hewy54 · Senior Member

A good way to get your exact pressure needs is by using the 4 psi rule.
Check your tyre pressure in the morning to get the cold pressure.
Check again after a couple of hours of highway driving.
If the pressure has gone up by 4 psi you have the correct pressure.
If they have gone up by more, your initial pressure was too low.
If they have gone up by less your initial pressure was too high.

I have a TPMS on the tug and run at 40 psi cold. This seems to work well for the 4 psi rule.
I used to run the trailer (single axle, 1700 kg) at 38, but had shocking wear out of a set of Coopers. A mate in the tyre industry suggests that I should be running 50 psi on the Mickey Thompson Deegans I have now put on.

Hylda&Jon · Guru

The normal advice I give is....take no notice of what other people put in their caravan tyres as every setup is different so will require different pressures.

I have been using the calculator on site to work mine out for years and it has worked well. https://caravanchronicles.com/guides/calculate-the-correct-tyre-pressure-for-your-caravan/

Safe travels

SouthernComfort · Guru

Hylda&Jon wrote:
The normal advice I give is....take no notice of what other people put in their caravan tyres as every setup is different so will require different pressures.
I have been using the calculator on site to work mine out for years and it has worked well. https://caravanchronicles.com/guides/calculate-the-correct-tyre-pressure-for-your-caravan/
Safe travels

Makes sense.

I imagine this would be the formula, if not one similar, used by manufacturers to determine optimum pressures. Either way, what goes for one van doesn't necessarily follow for another, manufacturer specs are very specific as you suggest. Incidentally, the max. cold pressures for my van are stamped on the compliance plate.

Hylife · Guru

the rocket wrote:
hello everyone. Strop n i got new tyres for the caravan. They r bridgestone dewellers 15 inch rims. the caravan is 25 foot. Are there any tyre experts on here that know the correct size to pump them to. We r about to drive a long distance on tar. Thanks everyone. Kind regards rocket

Dear oh dear. So much nonsense advice.
Excuse the pun Rocket, but it is not rocket science (LOL), just look on the side wall of your tyre.
Every tyre for decades has had the maximum pressure for a given weight stamped in the manufacturing mould .

The first step is to know the weight of your caravan and divide it by how many wheels you have. EG, your van is 2500kg with four wheels, this is 625kg per wheel

Lets say your tyre sidewall states 60PSI at 900KG, now simple maths will tell you your recommended tyre pressures.

625kg is 69.4% of 900kg (625/900=0.694).

69.4% of 60PSI is 41.6PSI

rockylizard · Guru

Hylife wrote:
Dear oh dear. So much nonsense advice.

Gday...

Yep ... what we all look forward to ... unbiased critique of everyone's advice from one who knows it all.

GEEZ ... confuse confuse makes wonder why anyone offers advice on this forum to any question ... 'nonsense advice' - yep - wish we'd realised first, must remember to just send Hylife a PM in future.

Cheers - John

SouthernComfort · Guru

Hylife wrote:
the rocket wrote:
hello everyone. Strop n i got new tyres for the caravan. They r bridgestone dewellers 15 inch rims. the caravan is 25 foot. Are there any tyre experts on here that know the correct size to pump them to. We r about to drive a long distance on tar. Thanks everyone. Kind regards rocket

Dear oh dear. So much nonsense advice.

Just the sort of "put down" comment that creates angst on the forum, unnecessary and unwelcome. Everyone has tried to be genuinely helpful in this thread and if you must come along as the expert, do it with respect.

rockylizard · Guru

Hylife wrote:
Dear oh dear. So much nonsense advice.

Gday...

Talking from experience ... that "formula" you provide arrives at a tyre pressure for my tyres/van at 46PSI ... tested evaluation over time, I have had my tyres down at that and they show excessive wear beginning on the outer edges - ie under-inflated.

By observing tyre wear over time (each time I have renewed tyres) I have adjusted between 55PSI and 40PSI, usually at 5PSI increments, over 100>200Km each setting, and my tyres wear, on this set, correctly when at 50PSI. Of course, this pressure is the pressure to set the tyre at when COLD.

I have also found that the 4%-6% rule is also only a good guide rather than a firm rule as there are far too many temperature variables every day to make it a possible to be a 'firm' rule.

Your "formula", like any of the other "advice", is an excellent starting point. However, one needs to carefully observe the wear pattern on a particular tyre in its particular application and determine the pressure that provides the best handling/ride (very difficult to assess in a van) and the optimum wear pattern.

Yeah NOT rocket science - just observation, experimentation and common sense.

Cheers - John

-- Edited by rockylizard on Tuesday 21st of November 2017 08:10:48 AM

Hewy54 · Senior Member

Hylife wrote:

Dear oh dear. So much nonsense advice.

Excuse the pun Rocket, but it is not rocket science (LOL), just look on the side wall of your tyre.
Every tyre for decades has had the maximum pressure for a given weight stamped in the manufacturing mould .
The first step is to know the weight of your caravan and divide it by how many wheels you have. EG, your van is 2500kg with four wheels, this is 625kg per wheel
Lets say your tyre sidewall states 60PSI at 900KG, now simple maths will tell you your recommended tyre pressures.
625kg is 69.4% of 900kg (625/900=0.694).
69.4% of 60PSI is 41.6PSI

So good that we have an expert on here.

Sorry rocket for giving nonsense advice.

In future I need not respond to any questions as we have someone here who can give all the expert advice we need.

We could shortcut the whole forum and just pm the expert.

Aus-Kiwi · Guru

Pressures go up a little with use and heat . Best be if anything over inflated than under . Most blow outs are from under inflating, tyre damage..

rockylizard · Guru

Aus-Kiwi wrote:
Pressures go up a little with use and heat . Best be if anything over inflated than under . Most blow outs are from under inflating, tyre damage..

Gday...

Apologies up front ... do not mean to make this a tit for tat wasted effort in advice. (Hylife will correct us if we are wrong anyway)

BUT ... under-inflation will certainly make a tyre more prone to blow-out because of excessive heat build-up due to tyre wall flexing excessively.

However, over-inflation has the potential to make a tyre more prone to puncture - as the entire tyre is 'tight' and in some ways, under stress and not as flexible over terrain - or obstacles.

So there just needs to be a balance between over and under inflation ... my suggestion is that each person's advice on here, including Hylife, should be taken aboard and applied to one's own circumstances and van ... and just keep a watchful eye on tyres not just for pressure, but for indicators for wear, cuts. abrasions etc etc.

Cheers - this has sort of become an 'overblown' thread - John

Aus-Kiwi · Guru

Yes . Keep in mind these tyres are only holding weight. Not driving and note too much breaking ! So wear to a point is not a problem . Just today a car trailer with duel axles went past . The rear assembly was bouncing badly . Can only assume bad tyres or real bad balanced wheel !! Some tyres have had issues with yard delamination . Passed on and used on trailers or vans ? You still need quality wheels !! In general the age of tyres would be up before they wear out !! New rules I have heard depending on weight ? Light truck tyres are required now on heavier van etc .

Hylife · Guru

Really guys and Gals? You think I was just putting everyone else's advice down? I was actually calling your advice downright dangerous unsound and unsafe nonsense.

Just what the h3ll do you think the tyre manufacturers do by testing their tyres and then putting the correct pressure settings on the side wall for?

Wake up, please! If your car manufacturer states to a maximum weight of 2.5 ton do you just ignore that and try towing 3 ton? Do you use the 91 RON fuel the manufacturer suggests or do you go ignoring their advice and plonk 95RON in the tank?

What I was trying to do was educate you all.

The formula is right there on your tyres and has been an industry standard for decades.

Who you gunna trust? Some totally anonymous strangers (me included) on a forum or the folks that made your d@mn tyres?

Rocket, you don't have to believe me, go talk to a reputable tyre outlet such Bob Janes, or Beaurepaires, or TyrePower, or whatever you have in your neck of the woods and ask them about how the sidewall tyre pressure formula works.

And Rocky Lizard, if your pressures are NOT following the manufacturers recommendations then you are overinflating your tyres. I would suggest your tyres are wearing excessively because they are unsuitable for the rig/weight you are carrying. If you don't or can't get to a tyre dealer, the manufacturers web site will have all their specs listed.

Hewy54 · Senior Member

Thanks Hylife for educating us all.
I should have said that the 4 psi rule comes from the Coopers website and that the 50 psi recommendation came from the largest Khumo dealer in SA.
I am also wary of tyre dealers unless I know their backround and level of experience.

rockylizard · Guru

Hylife wrote:
Really guys and Gals? You think I was just putting everyone else's advice down? I was actually calling your advice downright dangerous unsound and unsafe nonsense.
And Rocky Lizard, if your pressures are NOT following the manufacturers recommendations then you are overinflating your tyres. I would suggest your tyres are wearing excessively because they are unsuitable for the rig/weight you are carrying. If you don't or can't get to a tyre dealer, the manufacturers web site will have all their specs listed.

Gday...

Hylife, many responses have flooded through my mind after reading that post.

However, I think I have successfully tempered my thought processes and will offer the following instead.

Might I simply suggest you re-read any of my posts and I think if you do that carefully, and diligently, you will find I have NEVER had tyres on any of the vehicles I have owned for the past 52 years wear excessively ... I have owned caravans and camper trailers for the past 35 years - I have NEVER had any tyres on any of them wear excessively. I cannot see how you have arrived at your misplaced statement that "your tyres are wearing excessively because they were unsuitable for the rig/weight you are carrying."

For all my life, I have taken into consideration, with every tyre for every application, the advice from ALL sources, the tyre dealer, tyre fitter, manufacturer of the vehicle, manufacturer of the tyre, construction of the tyre, application I will subject the tyre to, and apply all that to a series of observations. I begin firstly with the advice provided by the manufacturer of the vehicle and the tyre and use that as my beginning position.

From that point onwards, I observe the outcome. If that beginning point creates no adverse situation over a period of some kilometres ... eg 150>200Km - whether it be poor handling/ride or poor wear - then I accept the advice from those sources. However, if there are any 'adverse' outcomes, then I move the pressures up and/or down and observe the outcome - again over 150>200Km. Ultimately, I arrive at the optimum pressure for the tyre, vehicle/van, and the application ALWAYS within the specified limitations dictated by the manufacturers.

[edit: just remembered - current van manufacturer says 55PSI ... current tyre manufacturer states max for 950Kg 65PSI .. so I don't think you understand anything I have said given your strange, but interesting statement, "if your pressures are NOT following the manufacturers recommendations then you are over-inflating your tyre". How does my application of 50PSI contribute to "over-inflating" ??]

I am sorry you feel that all the advice provided by the good folk on this forum prior to your intervention was "downright dangerous unsound and unsafe nonsense".

I feel differently - I believe the advice provided, taken in its entirety and given consideration, is definitely not as you insist.

cheers - John

-- Edited by rockylizard on Tuesday 21st of November 2017 10:26:24 PM

Hylife · Guru

rockylizard wrote:
Talking from experience ... that "formula" you provide arrives at a tyre pressure for my tyres/van at 46PSI ... tested evaluation over time, I have had my tyres down at that and they show excessive wear beginning on the outer edges - ie under-inflated.
By observing tyre wear over time (each time I have renewed tyres) I have adjusted between 55PSI and 40PSI, usually at 5PSI increments, over 100>200Km each setting, and my tyres wear, on this set, correctly when at 50PSI. Of course, this pressure is the pressure to set the tyre at when COLD.

Hi RockyLizard, it was this post that YOU made about excessive tyre wear that I was referring to.

I was assuming that you actually calculated the pressures based on what was on YOUR tyres, but upon re-reading your post it could be interpreted that you were doing your calculations on MY hypothetical sidewall reading, in which case it may very well be completely bonkers to have your tyre at 46PSI.

To know for sure I would need to know what brand and model and size of YOUR tyres, what does the sidewall of YOUR tyres state. eg, what PSI at what weight, and also I would need to know how many tyres are carrying what laden weight of YOUR van.

Manufacturers test their tyres for all sorts of uses and also for shape deformation at various weights and pressures to arrive at the best practice PSI/KG rating on the sidewall. Unfortunately, just because they matched the size or type of some previous set or have the same dimensions as stated on the compliance plate does not mean they are the appropriate tyres to fit to a particular van.

rockylizard · Guru

Hylife wrote:
rockylizard wrote:
Talking from experience ... that "formula" you provide arrives at a tyre pressure for my tyres/van at 46PSI ... tested evaluation over time, I have had my tyres down at that and they show excessive wear beginning on the outer edges - ie under-inflated.
By observing tyre wear over time (each time I have renewed tyres) I have adjusted between 55PSI and 40PSI, usually at 5PSI increments, over 100>200Km each setting, and my tyres wear, on this set, correctly when at 50PSI. Of course, this pressure is the pressure to set the tyre at when COLD.
Hi RockyLizard, it was this post that YOU made about excessive tyre wear that I was referring to.
I was assuming that you actually calculated the pressures based on what was on YOUR tyres, You assume correctly - I used the data/info from MY tyres but upon re-reading your post it could be interpreted that you were doing your calculations on MY hypothetical sidewall reading, in which case it may very well be completely bonkers to have your tyre at 46PSI. Now ya getting the drift
To know for sure I would need to know what brand and model and size of YOUR tyres, what does the sidewall of YOUR tyres state. eg, what PSI at what weight, and also I would need to know how many tyres are carrying what laden weight of YOUR van.
If you read my last post you would have seen these comments -
"current van manufacturer says 55PSI ... current tyre manufacturer states max for 950Kg 65PSI .. so I don't think you understand anything I have said given your strange, but interesting statement, "if your pressures are NOT following the manufacturers recommendations then you are over-inflating your tyre". How does my application of 50PSI contribute to "over-inflating" ??"
Manufacturers test their tyres for all sorts of uses and also for shape deformation at various weights and pressures to arrive at the best practice PSI/KG rating on the sidewall. Unfortunately, just because they matched the size or type of some previous set or have the same dimensions as stated on the compliance plate does not mean they are the appropriate tyres to fit to a particular van.

Gday...

Hylife, I am unable to fathom your thought processes. You seem to fail to grasp what is written.

I guess, given the futility of this discussion, you may be right ...... myself, like all the other good folk on the forum who foolishly saw fit to proffer opinions that you consider "downright dangerous unsound and unsafe nonsense" are indeed dangerous fools.

Cheers - sorry to have wasted your time and advice - John