Tyre Pressue

[sean_374452308]

Grreting to you all, just a quick question that I am struggling to come to terms with.......

My caravan is challenger 450/5 1992 model, the hand book states that the PSI should be 42, on the tyre it states 51psi.

Which figure should I be following ???? currently they are inflated to 42psi but look a little flat, I have checked the pressure daily and it is maintaining 42 so there is no small puncture, I expect this is obvious to some but its really foxing me as Im new to caravaning and would dread a "flat" on route to a site........

Many Thanks

 

[Parksy]

Hi Sean

I'm not a tyre expert but as I understand it the figure on the sidewall of the tyre is the maximum pressure for that tyre.

I'd follow the figure quoted in the caravan handbook provided that the tyres fitted to your caravan are the same size as the ones in the handbook instructions.

The tyre pressures are given on the metal identification plate on our caravan.

 

[Lutz]

What it says on the tyre is the maximum pressure that applies to the tyre when at its full load carrying capacity. The lower pressure given in the handbook suggests that the tyre is not carrying the maximum load and is a compromise in the interest of uniform wear across the tread, thus optimising the lifespan, and a slightly better ride (doesn't shake the crockery about as much). However, few caravan tyres ever need to be replaced because of wear, usually because of old age. Therefore, increasing the pressure, although it will increase wear in the middle of the tread, is quite in order and can benefit stability. In other words, increasing the pressure will do no harm.

 

[sean_374452308]

Gents, I thankyou.

If i were to slightly increase the pressure to around 45psi it shouldnt do any harm and hopefully it will take away the look of being "flat",

Without this forum and all the answers I received from fellow caravaners I would be at a total loss and would not have purchased a caravan, so once again many thanks

 

[Dustydog]

Hi Lutz

Surely increasing above the manufacturers recommendation will cause more bouncyness and maybe less stability?

There will be less tyre tread in direct contact with the road and also more wear on the caravan running gear as I thought the tyres were an integral part of the suspension design.

As the tyres heat up pressure increases and thus the volume does . Thus is it possible in the given circumstances that the tyre could theoretically become overinflated when under stress?

I ask purely out of idle curiosity, remembering my old pysics days and Charles Law.

Cheers

Dustydog

 

[xtrailman]

My bailey has 42psi, however at the start of the season i usually put 44psi in, then just check the pressure before every outing.

A higher pressure is better than a low.

But the tyres will still look under inflated, as do the tyres on my xtrail. Its just the tyre construction.

 

[sean_374452308]

My bailey has 42psi, however at the start of the season i usually put 44psi in, then just check the pressure before every outing.

A higher pressure is better than a low.

But the tyres will still look under inflated, as do the tyres on my xtrail. Its just the tyre construction.

Thanks Ray, I thought it was just mine that were looking flat but it obviously how they are supposed to look, but i will check on every outing,

 

[Lutz]

Hi Lutz

Surely increasing above the manufacturers recommendation will cause more bouncyness and maybe less stability?

There will be less tyre tread in direct contact with the road and also more wear on the caravan running gear as I thought the tyres were an integral part of the suspension design.

As the tyres heat up pressure increases and thus the volume does . Thus is it possible in the given circumstances that the tyre could theoretically become overinflated when under stress?

I ask purely out of idle curiosity, remembering my old pysics days and Charles Law.

Cheers

Dustydog

Lateral compliance of the tyres (and of the suspension system, although there's not much one can do to influence that) is an important factor which contributes to stability and this sidewall stiffness is improved by raising the tyre pressure.

 

[Gafferbill]

Sean ...... look at this earlier discussion.

http://www.practicalcaravan.com/newforums/fm_messages.asp?fo=1&fm=450120
Sean..Your original caravan tyres were of a type that required 42psi

What happens is that they get replaced by commercial van tyres probably 175 x R13C.

These should be inflated to 50psi if you have them.

 

[smiley]

Can't look at our tyres but, we have a sticker on the side of the van above the wheel arch saying 42 psi.

Weve always done this, and always wondered was the level for a full or empty van. Never found out.

Always flat looking and worse when we put stuff in van....

 

[EmmanuelMuldoon]

When I was investigating this area a couple of years ago the only reasonably comprehensive info. I could find was in the booklet "Tyre tips for caravans & Trailer tents" which I obtained from the "British Tyre & Rubber manufucturers Ass'n" on 020 7457 5040. This has a table showing pressures versus loading for a range of sizes.

 

[ProfJohnL]

Hello Smiley,

Logically, the caravan manufacture will publish a tyre pressure figure that represents the correct value for the fully load (maximum weight) of caravan. So provided the sticker was applied by the manufacture you should be able to assume that to be correct.

As for the different pressures required for different loads, then technically yes you should reduce the pressure accordingly, but in reality most caravans are rarely towed completely empty for any great distance, so for a short distance the greater pressure should not be a major issue, and not illegal either.

In practice most caravans will have at least half of their pay load at all times, for the major distances of going on holiday and returning they will be close to their maximum so the full pressure is required and appropriate.

Provided the correct good tyres are fitted and they are inflated to the recommended pressure, then their appearance will be as the manufactures expect. Modern radial ply tyres do look "softer" than crossply tyres due to the compliance of the side walls.

Don't inflate them to 'look right' your perception of what looks right may be quite wrong. Always inflate them to the correct pressure and check them with a reliable pressure gauge.

 

[smiley]

Thanks John L

Were always full coming back from france, depends on the region were in to how heavy.

But we store our van 85 miles away empty. tyres still look very low.

Can't remember what we have on, they were changed last year.

Which are the best tyres to put on the van?