Tyre Pressures
- Thread starter machighlander
- Start date
Highlander - what for? Is it on a car, caravan etc? The manufacturer of your vehicle will state correct tyre pressures - it doesnt matter what the make of tyre is
Highlander
I suggest you have a look on here, you will be able to work out what load / pressure your tyres are
http://www.tyresafe.org/data/files/caravan 08.pdf
http://www.tyresafe.org/tyre-safety/
Sproket
I suggest you have a look on here, you will be able to work out what load / pressure your tyres are
http://www.tyresafe.org/data/files/caravan 08.pdf
http://www.tyresafe.org/tyre-safety/
Sproket
Hi guys, thanks for the replies, thought it would be obvious it was the caravan i meant. Most cars have 28psi all round. I couldnt make out the type because it was dark but i know they are Pirelli's. I only wanted a rough idea of what would be a sort of ok setting, something that wouldnt be too low or high.
I know there are recommended pressures from manufacturers but also lots of folk use a setting they feel comfy with.
Is there a sort of aversge between differnt types for pressures ?.
I know there are recommended pressures from manufacturers but also lots of folk use a setting they feel comfy with.
Is there a sort of aversge between differnt types for pressures ?.
- Jun 20, 2005
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Highlander
You are scaring me mate.
The caravan manufacturers together with the chassis manufacturer very caeful work out the axle loading and tyre loading for each application. They specify the type of tyre construction required and state the recommended tyre pressure.
Personally to ignore such a wealth of knowledge will be foolhardy and may result in a serious tragedy.
Also note carefully the tyre manufacturers specification printed on every tyre.
Take care mate .
Cheers
Dustydog
You are scaring me mate.
The caravan manufacturers together with the chassis manufacturer very caeful work out the axle loading and tyre loading for each application. They specify the type of tyre construction required and state the recommended tyre pressure.
Personally to ignore such a wealth of knowledge will be foolhardy and may result in a serious tragedy.
Also note carefully the tyre manufacturers specification printed on every tyre.
Take care mate .
Cheers
Dustydog
Parksy
Moderator
- Nov 12, 2009
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Highlander
It might be best if you write down what is marked on the tyrewall and post it on here where somebody will offer good advice.
I know that you are a new caravanner but there is no method of 'feeling' if the tyre pressure is ok because you are in a separate vehicle and the first sign when towing of guessing wrong might be when things go wrong and your caravan is turned into matchwood all over the road surface.
We don't want to hear about you from Sally Traffic!
It might be best if you write down what is marked on the tyrewall and post it on here where somebody will offer good advice.
I know that you are a new caravanner but there is no method of 'feeling' if the tyre pressure is ok because you are in a separate vehicle and the first sign when towing of guessing wrong might be when things go wrong and your caravan is turned into matchwood all over the road surface.
We don't want to hear about you from Sally Traffic!
Highlander
If you look at the links I posted for you & write down what is on your tyre's it's very easy to follow, if you can't make out what is on the side wall, have a look on the other side of the tyre
" Look after your tyres & they will look after you "
In my own view if it meant jacking the van up & removing the wheels to check the tyre coding, i would do it
Sproket.
If you look at the links I posted for you & write down what is on your tyre's it's very easy to follow, if you can't make out what is on the side wall, have a look on the other side of the tyre
" Look after your tyres & they will look after you "
In my own view if it meant jacking the van up & removing the wheels to check the tyre coding, i would do it
Sproket.
Hi again folks,
thanks for the quick replies and advice. I take on board everything you are saying, was only asking because i know there are some tolerances between manufacturers specified pressures and what is best for certain conditions. I am also a biker and my rear tyre has a manufacturers figure of 42psi, however, there are various circumstances that this can be altered to suit the use and environment, ie, when doing a track day the way to go is to lower the pressure way down to give more grip and dig in on powering out corners. Then again, if me and the wee wifey are going two up to tour the highlands i will set them slightly over.
No need to be scared or afraid for me as said in one of the posts, i understand the penaltys to be paid for wrongly inflated or maintained tyres, was only asking if there was a sort of bench mark that was used, as in a relatively safety zone.
As for going by the combination weights of the car and caravan, plus axle weights and payload, then surely that is a figure based on an idealistic match. There will be tolerances allowed in those figures because surely no two outfits are equal in weight once the owner packs their respective caravan with their own kit.
thanks for the quick replies and advice. I take on board everything you are saying, was only asking because i know there are some tolerances between manufacturers specified pressures and what is best for certain conditions. I am also a biker and my rear tyre has a manufacturers figure of 42psi, however, there are various circumstances that this can be altered to suit the use and environment, ie, when doing a track day the way to go is to lower the pressure way down to give more grip and dig in on powering out corners. Then again, if me and the wee wifey are going two up to tour the highlands i will set them slightly over.
No need to be scared or afraid for me as said in one of the posts, i understand the penaltys to be paid for wrongly inflated or maintained tyres, was only asking if there was a sort of bench mark that was used, as in a relatively safety zone.
As for going by the combination weights of the car and caravan, plus axle weights and payload, then surely that is a figure based on an idealistic match. There will be tolerances allowed in those figures because surely no two outfits are equal in weight once the owner packs their respective caravan with their own kit.
Highlander
I know were you are coming from regarding your motorbike i used to ride a trials bike & used to lower the rear tyre down to 3psi for grip in muddy conditions,
Just a bit more reading for you
http://www.caravanclub.co.uk/NR/rdonlyres/AA21C69D-ADCD-4264-9BE5-090BDEC6EF81/0/TyresandWheels.pdf
Sproket
I know were you are coming from regarding your motorbike i used to ride a trials bike & used to lower the rear tyre down to 3psi for grip in muddy conditions,
Just a bit more reading for you
http://www.caravanclub.co.uk/NR/rdonlyres/AA21C69D-ADCD-4264-9BE5-090BDEC6EF81/0/TyresandWheels.pdf
Sproket
One cannot reply repetively to ones post when one has already explained in earlier ones that one totally understands the workings of the said rubber. One should read back posts before one replies.
Highlander,
All Lutz is pointing out is the fact that you have still to mention the actual tyre size. We do not know if they are 13" or 14" tyres, or whether they are fitted to a Single Axle or a twin, as this will also determine the correct pressure required,
ATB, Martin
All Lutz is pointing out is the fact that you have still to mention the actual tyre size. We do not know if they are 13" or 14" tyres, or whether they are fitted to a Single Axle or a twin, as this will also determine the correct pressure required,
ATB, Martin
Referring to your point about pressure tolerance, Caravan manufactures quote a figure for the van being fully loaded, in this case a slightly lower pressure is ok infact preferably if the van is more lightly loaded.
For that you need a specific pressure chart for the tyre used, (as Tyresafe provide in the link), and the actual weight of the van.
In general;
Each type and size of tyre has to conform to a laid down international standard, by this and therefore regardless of actual manufacturer, that size/type tyre requires the same pressure for any given load.
Part of the standard requires the outside dimensions of a particular size tyre do not alter, regardless of type of construction, this means heavier built tyres with thicker walls have space taken from the inside volume of the tyre.
It's that fact that leads to different tyres of apparently the same size needing different pressure for the same weight.
The reason is, the volume of air required to support a given load is a constant, the volume then within the tyre dictates how much pressure is required to shove the correct volume of air into varying tyre volumes depending on category of tyre.
Therefore and as is popular, changing from a standard light car type tyre, often fitted from new to a caravan, to a heavier commercial tyre for safety reasons, means, the pressure for the new tyres will not be the same.
The correct volume of air in the light constructed car tyre will not all go into the heavier tyre at the same pressure, the pressure therefore needs increasing somewhat to shove it all in!
If you don't do that, the heavier tyre is being run 'under pressure' and libel to fail prematurely, that will negate any extra safety you think you may have added.
For that you need a specific pressure chart for the tyre used, (as Tyresafe provide in the link), and the actual weight of the van.
In general;
Each type and size of tyre has to conform to a laid down international standard, by this and therefore regardless of actual manufacturer, that size/type tyre requires the same pressure for any given load.
Part of the standard requires the outside dimensions of a particular size tyre do not alter, regardless of type of construction, this means heavier built tyres with thicker walls have space taken from the inside volume of the tyre.
It's that fact that leads to different tyres of apparently the same size needing different pressure for the same weight.
The reason is, the volume of air required to support a given load is a constant, the volume then within the tyre dictates how much pressure is required to shove the correct volume of air into varying tyre volumes depending on category of tyre.
Therefore and as is popular, changing from a standard light car type tyre, often fitted from new to a caravan, to a heavier commercial tyre for safety reasons, means, the pressure for the new tyres will not be the same.
The correct volume of air in the light constructed car tyre will not all go into the heavier tyre at the same pressure, the pressure therefore needs increasing somewhat to shove it all in!
If you don't do that, the heavier tyre is being run 'under pressure' and libel to fail prematurely, that will negate any extra safety you think you may have added.
- Mar 14, 2005
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The volume of air in a tyre is immaterial. Only the pressure is of any significance. The object of getting the pressure right is to ensure that the footprint between the tyre and the road surface, and hence also tread wear, is more or less uniform across the full width of the tread. Obviously the construction of the tyre will have some influence, too, as the construction will have some bearing on the stiffness and therefore, again, its footprint. A 'heavier', and hence stiffer, tyre that Gary has referred to may therefore, if anything, tend to have a lower recommended pressure than a 'lighter' one, assuming both carry the same load.
Lutz, "volume of air to support a given weight is a constant"
Required pressure then is directly related and a consequence of the available volume to contain it.
Looking at the same size tyre on tyresafes chart confirms that, the heavier constructed tyre requires more pressure to support the same weight as it's lighter constructed cousin.
- Mar 14, 2005
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I have had a look at the Tyresafe chart and, given a particular load, I cannot find any big difference between the recommended tyre pressures depending on whether they are of the standard, reinforced, or light commercial vehicle type.
Take a 195/70R14 carrying an axle load of 1110kg, for example. According to the Tyresafe chart, the recommended pressure would be 32psi both for a standard tyre and a reinforced one.
A 195/65R14 carrying an axle load of 1136kg has a recommended pressure of 36psi, regardless of whether it is a reinforced tyre or of the light commercial vehicle type.
...'the heavier constructed tyre'... requires more pressure to support the same weight as it's lighter constructed cousin.
You would do better to ignore the reinforced and go straight to Commercial as these are of the same but 'heavier construction' as standard tyres.
The reinforced tyre is of a significantly different construction to the others and are therefore not directly comparable. However and as convenient as it was, the internal dimensions of the pair you chose happen to remain the same as the standard tyres, that's all
Lutz's I think the main problem you have is not excepting the simple fact; 'a fixed volume of air is required to support a given load'
By that and therefore; a tyre with a smaller internal volume will require more pressure to maintain the same volume of air.
If that's the case, then perhaps this guys answer to the question will convince you?
It's dealing with different tyre sizes rather than wall thickness, nevertheless, it's still internal volume differential that is in question and it's effect on pressure
http://answers.google.com/answers/threadview/id/233041.html
- Mar 14, 2005
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I read the Google answers thread and nowhere is there any reference to a comparison between standard and commercial vehicle tyres of the same overall size. The difference in wall thickness between the two designs will undoubtedly be less than than a change from one size to the next size up (or down), so a change to a commercial vehicle tyre of the same size will not involve an increase in tyre pressure - as borne out by the Tyresafe chart.
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