Tyre pressure

There is loads written on tyre pressures on this forum.  The best thing you can do is follow the advice given by TyreSafe and use their on-line calculator:

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For this you will need to know your tyres' size and type (C or CP) and your actual front and rear axle masses when your motorhome is fully loaded.  You will need to visit a weighbridge to measure your axle masses.  You will also need to ensure that your fully loaded axle masses and total mass of your motorhome do not exceed the plated levels.

dstoreuk wrote:Thanks for the info on the website Caraman.

Interesting that when I entered in the max Front/Rear axle weight and tyre size, the pressure stated was 57 front 40 Rear.

The Autosleeper manual says to refer to the Peugeot base manual for tyre pressures which are 44 front and 44 rear. Seems to be quite a discrepancy between Autosleeper/Peugeot figure and the Tyre safe website.

I'm sure the website is more accurate as you can just tell, the pressures seem low while driving.

Thanks again for the help.

If the calculator showed 57 psi front and 40 psi rear, the type of tyre you entered must have been a 'C' which maybe right and the front axle mass you entered must have been higher than the rear axle mass which is worth checking.

Auto-Sleepers in common with many other convertors take no responsibility for tyre pressures.  The Peugeot plated tyre pressures assume that each axle is loaded to its plated MTPLM.  If an actual axle mass when the motorhome is fully loaded is substantially less than its MTPLM, a lower tyre pressure should be used in accordance with the TyreSafe calculator or the tyre manufacturer's recommendations.

dstoreuk wrote:Autosleeper handbook for the 2.0 petrol says the following Vehicle weights.

Max Authorised mass of the front axle 1460Kg
Max Authorised mass of the rear axle 1460Kg

Tyres are 195/70R 15C 104/102 S max 65psi taken from the tyre rim.

So not sure why tyre safe gives such high pressure for front wheels.

If both axle masses are 1460 kg, the TyreSafe on-line calculator recommends the same pressure for both the front and rear tyres of 57 psi (3.9 bar) for the 195/70/R15 C tyre.

HairyFool wrote:You have to be careful referring to the Tyresafe website.

Most if not all insurance policies require that the vehicle is maintained according to the manufacturers service requirements. Using a different set of pressures means it is not.

This does not mean that in an accident you are automatically uninsured, they would still have to show that it was a contributing factor but you would then have to argue that the pressures you did use arise from an authoritative source. Tyresafe is itself a charity promoting tyre safety but is supported by the industry so does have SOME credence, is it enough?

The European Tyre & Rim Technical Organisation (ETRTO) are the regulatory body responsible among other things for the standardisation of tyre pressures across all tyre manufacturers for different tyre sizes, type and load indexes and for different axle masses.  Continental for example use these pressures in their data book for all of their tyres.  However, if an owner sets their tyre pressures to these ETRTO figures, one tyre on each axle will have insufficient air in it to support its load which is unsafe.  This is because in the real world loading across an axle is never even.  TyreSafe, who are sponsored by all the major tyre manufacturers including Continental, overcome this by using an ETRTO pressure for an axle mass that is 10% higher, it being safer for a tyre to have more air in it than it needs rather than less.  This 10% safety margin also takes into account variations in axle mass caused by moving a load around in the motorhome and adding to it after the axle masses have been measured on a weighbridge.  If a tyre manufacturer recommends lower tyre pressures than those recommended by TyreSafe for an axle mass, I would be suspicious of it.

PLOUGHLIN wrote:Not when I do it?

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You must be doing something wrong:

[size=30]Motorhome[/size]
Suggested cold tyre inflation pressure:

Front Axle : [size=50]57[/size] [size=40]psi /   [/size][size=50]3.9[/size] [size=40]bar[/size]

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Rear Axle : [size=50]57[/size] [size=40]psi /   [/size][size=50]3.9[/size] [size=40]bar[/size]

I've been playing with the TyreSafe on-line calculator.  I can get 58 psi front if I set the front axle mass at about 1480 kg and the 46 psi rear if I set the rear axle mass at about 1240 kg.

v8oholic wrote:I’ve just reduced mine from 64/66 front and 70/66 rear to 51 all round. According to that website, armed with my weighbridge results and even allowing for a small increase, it only needs to be 49 all round. I’m a bit sceptical but will try it. The danger is the sidewall overheating if it’s too low, and economy may suffer. However it is a long way under the maximum weight on both axles, so perhaps it’s ok. Hope so!

Don't you have CP tyres?  If so the TyreSafe on-line calculator, if that is what you are referring to, will give 80 psi for your rear tyres regardless of your rear axle mass.

v8oholic wrote:No, the OEM tyres are C (van) tyres. Probably last forever, but not very good.

Are Auto-Sleepers fitting C tyres to their new campervans/motorhomes?

v8oholic wrote:

FreelanderUK wrote:My 2016 WXL was fitted with Continental Vanco 100 tyres I took it to the weight bridge loaded for a trip and it weighed 1700kg front, 1800kg rear and total 3520kg, I am glad it was up plated  to 4500kg, I run my tyres at 50psi front and 60 psi rear according to the tyres safe website

These tyres were fitted as new from the build

No TPMS issues with the lower pressures then? The Peugeot sticker on mine says 59 front 65 rear, which is presumably based on maximum axle weights. But Tyresafe suggests 50 psi all round.

I think you will find that the front 59 psi is based on the front axle MPTLM of 1850 kg plus 7% and the rear 65 psi is based on the rear axle MPTLM of 2000 kg plus 3%.  If it were more than 3% it would exceed the C tyre's maximum permitted pressure of 65 psi which is why the rear tyres are 65 psi.  TyreSafe use 10% so their recommended pressures for the front and rear axle MPTLMs are 64 psi and 65 psi respectively.  If the actual axle masses of the fully loaded PVC are significantly less than the axle MPTLMs, TyreSafe will recommend lower pressures.  If TyreSafe are recommending 50 psi all around, it must be for front and rear axle masses around 1525 kg.