Tyre pressures

[in h]

ok, I get the maths bit, where I am still a bit lost is how it takes into account the actual tyre and the variables that come into play with different makes/models

The actual tyre has its individual load rating printed (in code) on the sidewall. It also has the pressure recommended for that load printed on the sidewall.

 

[molly 2]

Am I the only person who runs their tyres nitrogen filled? Does away with the temperature variances

Proberbly not ,I was told by a director of a major tyre company it is just a money maker driven by boy racers that like to think they racing drivers

 

[in h]

Well, I guess if you average out your rise in psi, your roughly at 4 psi, good enough to prove the rule.

Guess so, but the car has a plate giving the recommended pressures.
The recommended pressures for the tyres are in a complicated table showing load, speed and pressure. The recommended rear pressures vary (from memory) between 31psi and 47psi. The front pressures from 29psi to something in the mid 30s.
The table makes no mention of temperature differences.

 

[molly 2]

Yes, but in the view of someone who had the facts at their disposal, you would get a very different number.

If you bought a lambo would you use manufactures pressure or something from a web site ?

 

[in h]

If you bought a lambo would you use manufactures pressure or something from a web site ?

Of course not, my engineering team would work the correct pressure.

 

[Canalsman]

The point that we're all making is that to achieve the best comfort, and best tyre life, the pressures must be in accordance with the vehicle loading.

The correct pressures can be calculated yourself based on the weighbridge values or provided to the tyre manufacturer for advice.

Most cars, especially estates, have tyre pressures detailed in the handbook based on vehicle loading. Motorhome converters don't seem to provide this guidance.

 

[mark61]

Am I the only person who runs their tyres nitrogen filled? Does away with the temperature variances

Not for my van. On some trips I can be messing with pressures daily.
If I had built in inflation system it would be more, but I haven't.

 

[Nabsim]

Proberbly not ,I was told by a director of a major tyre company it is just a money maker driven by boy racers that like to think they racing drivers

On one of the coating plants we would get truck exploding due to the heat Baz. Michelin advised us to use nitrogen and the problem went away. If we had a power failure and the process stopped the drums would melt the tread on the tyres depending what we were mixing, much more heat than British weather that’s for sure.
When I had a new set of tyres fitted nitrogen fill was part of the service free. For anyone concerned about pressure changes with temperature I would say use nitrogen.
Now I have moved away I will gradually revert to good old air though, a little drift doesn’t bother me

 

[Nabsim]

Not for my van. On some trips I can be messing with pressures daily.
If I had built in inflation system it would be more, but I haven't.

I hadn’t had to touch mine for about 14 months so didn’t affect me. I wouldn’t go to onboard nitrogen tank unless I was drag racing lol

 

[molly 2]

Very true tp do increase with heat that is why tp should be checked when cold and not adjusted when hot

 

[molly 2]

On one of the coating plants we would get truck exploding due to the heat Baz. Michelin advised us to use nitrogen and the problem went away. If we had a power failure and the process stopped the drums would melt the tread on the tyres depending what we were mixing, much more heat than British weather that’s for sure.
When I had a new set of tyres fitted nitrogen fill was part of the service free. For anyone concerned about pressure changes with temperature I would say use nitrogen.
Now I have moved away I will gradually revert to good old air though, a little drift doesn’t bother me

Always had you down as a bit of a drifter Neil

 

[sydnsue]

The pressures plated in the cab are for the base chassis as a commercial vehicle. It is the manufacturers plate, not the motorhome plate. I'm on a Boxer chassis and like most others, 50 front 60 rear seems perfect. Vanco tyres. These are the pressures most users are receiving from the tyre manufacturer. The weights from one user to another don't vary that much from unladen to laden. We all have to stay within quite a small band.

 

[Sid]

Do VOSA actually check Tyre Pressures on a private vehicle? I can imagine they might be able to see an obviously underinflated tyre, but there is not a "one pressure fits all" tyre pressure to suit all circumstances - it depends very much on the loading of the vehicle and the type of driving.

Very true but there is the ability to check axle loads on moving vehicles, so it's quite straight forward to work out the appropriate pressures accordingly. I do however have no idea what the lea way is.

 

[wildebus]

Very true but there is the ability to check axle loads on moving vehicles, so it's quite straight forward to work out the appropriate pressures accordingly. I do however have no idea what the lea way is.

Not sure if that would tell you anything? Too many factors with tyre sizes as well.
Over thinking a non-issue

 

[Deleted member 80299]

Finally after 3 years of ownership I decided to drop the tyre pressures on the back axle from 70PSI to 65PSI and wow! what a difference to the internal travel noises, the bathroom door being the main one not rattling any more. I'll try dropping the fronts by 5PSI next.

What pressure do others run their tyres at.

What does your Motorhome maker say the pressures should be? mine(autotrail say 6 bar). If you run at less, does it invalidate your insurance?

 

[in h]

The correct tyre pressure depends on the load. The motorhome maker can only guess at the load you'll out on, so they estimate high. Very high. Too high, usually.
Read your insurance policy if you want to know what affects it: that defines the conditions, not something you read on the web.

 

[Tookey]

The correct tyre pressure depends on the load. The motorhome maker can only guess at the load you'll out on, so they estimate high. Very high. Too high, usually.
Read your insurance policy if you want to know what affects it: that defines the conditions, not something you read on the web.

In h,

You seem to be very knowledgeable and quite interested in this subject. Although it seems very straightforward to you, to others, myself included, it is a tad confusing. If you can be bothered to do a guide to tyre pressures, requirements and relevant calculations it would be an asset to the forum. ( vehicle manufacturer guidelines, tyre manufacturers guidelines, own weight calculations )

Just a thought as there is some good info in this thread but it's now all jumbled up and not very user friendly and I didn't find anything online that covered all aspects of such a crucial area. I do appreciate we are all busy people

 

[Okta]

The point that we're all making is that to achieve the best comfort, and best tyre life, the pressures must be in accordance with the vehicle loading.

The correct pressures can be calculated yourself based on the weighbridge values or provided to the tyre manufacturer for advice.

Most cars, especially estates, have tyre pressures detailed in the handbook based on vehicle loading. Motorhome converters don't seem to provide this guidance.

My Carthago hand book gives a full range of pressures for various axle weights and tyres.

 

[Deleted member 47296]

In the past when I looked into the question of which guidance is legal I have been told that in effect you are safe to follow the guidance of those who should know best. That means if you follow either the tyre manufacturers guidance, the vehicle manufacturers guidance or any other respected authority such as TyreSafe you cannot be seen to have been negligent. Basically if you can show that you didn’t make it up as you went along you are ok.

 

[Sid]

Am I the only person who runs their tyres nitrogen filled? Does away with the temperature variances

As far as I am aware Charles and Boyles law apply equally to nitrogen as to air, what using nitrogen does for you is reduce the water vapour so less corrosion.