Is it safe to run a caravan using maxium Tyre pressures as printed on the tyre wall

[silverfozz]

I have a Lunar Delta Ti twin axle 2011MY.
My Lunar hand book tells me to run my tyres at 42psi. The maximum tyre pressure printed on the tyre wall shows 36psi. I called Lunar who told me it is ok to run at 36psi as there was a tyre change for a short period between 2011-2012 manufactured vans. I questioned the saftey of running tyres at maximum allowed pressures. I often go from the midlands to cornwall, st ives area, a considerable distance on motorway / dual carrigeway at maximum permissible speeds. I asked the dealer who sold me the van, and he repeated what Lunar said after an excahneg of emails.
Should I be concerned about running at maximum pressure or are caravan tyres built for such extremes?

Would anybody who has knowledge please help.

 

[colin-yorkshire1]

hi silverfozz,
no it should be fine there is a margin built into the max psi, as well as the load index, if the maximum says 36psi then thats the accepted maximum for those tyres,as Lunar has said, now if the pressure was 36psi and you wanted them higher then there would be a problem.

 

[RogerL]

The maximum (cold) pressure on the tyre wall is a maximum you must never exceed in any circumstances - the optimum is usually below that so running at maximum may make it a bit bouncy, at worst.
Lunar aren't very good, in my experience, at giving sensible information on tyre pressures - the maximum load rating of my tyres is considerably in excess of the caravan's uprated MTPLM but Lunar simply quote 65 psi, the maximum, as recommended - but have conceded privately that I can run at 54 psi which is more suitable for the MTPLM.
Unlike car manufacturers who give a big margin on load rating of tyres AND spend development time/money road testing to establish optimum tyre pressures - caravan makers just use the lowest rating that gives 10% above the MTPLM and either quote maximum possible pressure or do the simple calculation.

 

[silverfozz]

thanks for the information. i will try it and see how the caravan tows.

 

[silverfozz]

Ok, many thanks. How do I read the load rating of my tyres and then calculate the ideal pressure?
Since the van is twin axle, I am guessing the load is distributed across all four and therefore the pressure would be lower than a normal single axle van, or am I being too simplistic?
Also how can two different tyres with the same profile have different pressure one recommended 42psi and teh other running at maximum 36psi?

 

[Surfer]

Ok, many thanks. How do I read the load rating of my tyres and then calculate the ideal pressure?
Since the van is twin axle, I am guessing the load is distributed across all four and therefore the pressure would be lower than a normal single axle van, or am I being too simplistic?
Also how can two different tyres with the same profile have different pressure one recommended 42psi and teh other running at maximum 36psi?

If I recall correctly the Lunar twin axle has normal car tyres and not commercial tyres. Which brand of tyres do you have on your caravan? Are you saying that one of the tyres on the caravan is rated at 36psi while the others are rated at 42psi.
With the exception of one of my tyres, the other three are inside out and I cannot read the Date of Manufactrue on them. By the same token, I have not checked by tyres since the caravan was serviced last year except to do a visual check. I have no idea if they should be 42psi or 36psi.

 

[otherclive]

My S5 Bordeaux came with Trailermaxx which had a max pressure of 42psi and that was the pressure recommended by Bailey. I had the tyres for 5 yrs with no problems and as said above there is a margin built in and despite you running at max legal speeds that too will be below the tyres rated maximum continuos speed. I had the van load upgraded such that the vans MTPLM was only 20 kg less than the tyres combined load index. Whilst legal I decided to upgrade to higher LI tyres which also had a higher speed rating. Van bounces a bit more but still tows well. The updated tyres were commercial van tyres so are designed to work hard with White Van Man and also as they are a well known brand they were only 3 months from date of manufacture when purchased.

 

[Surfer]

We have just found out from the mobile tech today that we are in the same predicament with the book stating 42psi but the tyres have a maximum rating of 36psi on them. Why couldn't Lunar print an amendment and post it out to dealers or customers?

 

[RogerL]

The moulded panel on the side of tyres specifying maximum load and maximum pressure also has the wording "Only applicable to USA and Canada" - it's there to comply with their legislation but has no legal status here.

 

[Surfer]

The moulded panel on the side of tyres specifying maximum load and maximum pressure also has the wording "Only applicable to USA and Canada" - it's there to comply with their legislation but has no legal status here.

If stopped by VOSA for suspected overloading, they will probably check the load index on the tyres and weigh the caravan and if the weight of the caravan exceeds the total load index, I doubt very much if they will allow you to proceed as they may be condoning an offence.

 

[otherclive]

The moulded panel on the side of tyres specifying maximum load and maximum pressure also has the wording "Only applicable to USA and Canada" - it's there to comply with their legislation but has no legal status here.

Have a spare caravan tyre in the hall, as one does, but there is no wording to match yours. It just gives maximum load at maximum operating pressure, and a warning not to fit the tyre at a pressure exceeding 40psi. The tyre came from the Netherlands but its a make available here, Kargomaxx St6000.

 

[Lutz]

Have a spare caravan tyre in the hall, as one does, but there is no wording to match yours. It just gives maximum load at maximum operating pressure, and a warning not to fit the tyre at a pressure exceeding 40psi. The tyre came from the Netherlands but its a make available here, Kargomaxx St6000.

The tyre may have been supplied out of the Netherlands, but Kargomax tyres are manufactured by GT Radial (Gajah Tunggal), Indonesia.

 

[otherclive]

Have a spare caravan tyre in the hall, as one does, but there is no wording to match yours. It just gives maximum load at maximum operating pressure, and a warning not to fit the tyre at a pressure exceeding 40psi. The tyre came from the Netherlands but its a make available here, Kargomaxx St6000.

The tyre may have been supplied out of the Netherlands, but Kargomax tyres are manufactured by GT Radial (Gajah Tunggal), Indonesia.

Lutz,
I know they are not Dutch, but my point was that nowhere on the tyre does it say anything about the max inflation pressure being US and Canada regulations. Looking at Tyresafe Orgs website they do make the point that max infaltion pressure is not relevant to the EU, but that seems to confuse, as surely any article has limitations on its maximum design/working limits, and why would the EU not require max inflation pressure to be shown? No wonder some owners find tyres a bit of a maze!!

 

[JonnyG]

Bit of a mixing up of things here, i thing roger was speaking about a specific batch that some tyres have on them that quotes max weight in pounds [ not the load index number] and max tyre pressure. they are normal in an encircled box and do not apply to the EU. those instructions are in another area on the tyres....

 

[Brum1]

Raised a similar question a few years back when concerned about flexing sidewalls on tow car tyres.
I rang the technical department of a very large well known tyre manuracturer and was told that "the pressure quoted on the sidewall of the tyre is the MINIMUM that must be used when the trye is loaded to its MAXIMUM load".

The gentlman went went on to advise that it would be OK to go above the quoted sidewall figure if I wanted to stiffen up the sidewall to overcome flexing.

Hope this helps.

 

[JonnyG]

Raised a similar question a few years back when concerned about flexing sidewalls on tow car tyres.
I rang the technical department of a very large well known tyre manuracturer and was told that "the pressure quoted on the sidewall of the tyre is the MINIMUM that must be used when the trye is loaded to its MAXIMUM load".

The gentlman went went on to advise that it would be OK to go above the quoted sidewall figure if I wanted to stiffen up the sidewall to overcome flexing.

Hope this helps.

umm did you get that in writing? as it states the psi on the sidewall is the Max, unless you have writing proof from Mr dunlop or Mr goodyear i'd say your on very dangerous ground to be over inflating the tyre... there is a proper way to calculate what a tyre can carry and at any given psi, at the max psi quoted it normally already exceeds the qouted load index printed on the sidewall,so if you still felt the sidewalls were flexing too much you clearly had faulty tyres or the wrong indexed tyres fitted and to be pumping them up even further! ummm i'll say it again get it in writing because MAX means MAX and not minimum!