Tyre pressures for van conversions.

Endless topic on here.
Not going to get into any argument, my 5 vans,  3PVC, 1 coachbuilt, current monocoque have all had 60psi all round.
No issues at all, a big variety of different tyres too

mikemelson wrote:Hi,
   I recently picked up a new Symbol from Marquis who said the recommended tyre pressures was 80psi.

Well, it seems like I'm driving around on solid tyres, especially on the potholed roads!

My previous Symbol was fine with 65psi, I'm sure 80 is far too much.

It will be interesting to note what you other campervanners use?

It depends what tyres you have and the maximum axle loads you are ever likely to have which can only be measured on a weigh bridge when you are fully loaded.  Put the figures into the TyreSafe on line calculator and it will give the ETRTO pressures for an axle mass that is 10% higher which is sensible.  Unfortunately, if you have CP tyres it will give 80 psi for the rear tyres regardless of the rear axle load.  This is because the ETRTO used to recommend this but no longer do.  Fortunately, Continental publish all the ETRTO pressures in their DataBook at intervals of 0.2 or 0.3 bar which can be accessed on line.  From this it is easy to work out the correct rear CP pressures to use for a rear axle mass that is 10% higher.

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Can I ask a question - do any of the Symbols have CP tyres?  If not and Marquis recommended 80 psi they should be shot as that exceeds the maximum permitted pressure of most C tyres.

mikemelson wrote:

My previous Symbol was exactly 20 years old & as I stated 65 was fine if a little firm but it seemed to be good for the tyre wear.

The Bridgestones on the back had done over 70,000 miles & still had plenty of even tread!

These were standard Commercial (C) van tyres that probably had a maximum permitted pressure of 65 psi.  If you ran them at 65 psi, they were probably overinflated hence the firm ride.  What we need to know is what size, load index and type (C or CP) of tyre your current 2024 Symbol has?  Based on Dbvwt's input, I doubt it is a CP tyre with a maximum permitted pressure of 80 psi.  The tyre pressure label on the passenger cab door C pillar should give a clue and show the recommended cold tyre pressures for when both axles are at their maximum permitted mass of 1800 kg front and 1900 kg rear.  As the Symbol's overall maximum permitted mass is only 3300 kg, and assuming it is not overloaded, both axles cannot be at their maximum permitted masses so in practice one or both will be less potentially allowing lower pressures to be used.

Using TyreSafe's on line calculator, if you have the same tyres as Dbvwt (215/70 R15 C 109/107), your fronts should be between 52 psi (for the minimum front axle mass of 1551 kg) and 62 psi (for the maximum permitted front axle mass of 1800 kg) and your rears should be between 46 psi (for the minimum rear axle mass of 1299 kg) and 65 psi (for the maximum permitted rear axle mass of 1900 kg. It all depends what your actual axle masses are when fully loaded on a trip.

If you have no idea what your actual axle masses are, I would stick to the pressures shown on the tyre pressure label.

Rocky wrote:Just a word of caution.  If your vehicle is fitted with TPMS - and I suspect it will be - then the TPMS sender units in each tyre will probably have been calibrated by Fiat or Peugeot (you don't say which) to a certain level.  Changing this level might set off warnings on your dash that your tyre pressures are too low, or that it senses a loss of pressure.

You can disable this, but you lose a valuable function.  It may be possible to adjust TPMS levels, but I don't believe this is easy.

This is just a further thought to consider before you make any major adjustments.

Yes - if the van has the TPMS as mine does, it will have been set in the factory around the cold tyre pressures shown on the tyre pressure label.  I found it was possible to run the tyres at slightly lower pressures without the TPMS being triggered.  However, I needed to drop my front tyres pressures more than this which a local Peugeot dealer eventually did for me.  

It's not possible to disable the TPMS.  If it's not functioning correctly because for example one of the TPMS sensors has stopped working, it will fail its MOT.

Tyre Pressure Monitoring System.  Peugeot describe it in their manual as Tyre under-inflation detection.  When you turn on the ignition all the warning lights on the dash will light up for a short while.  If one of these is the cross section of a tyre with an exclamation mark in it and is lit orange/amber, you have a TPMS.  It has been a legal requirement that all new passenger carrying vehicles since 2012 have it.  Not all campervans/motorhomes are classed as passenger carrying vehicles so not all have it.

mikemelson wrote:I've reduced the pressure from 80 to 70psi & noticed the difference, a better ride already.

I will reduce it further to 65psi like my old Symbol.

This TPMS thingy.....I can't see a tyre cross section among the warning lights so maybe I haven't got it, so that's a relief!

Out of interest, what does the tyre pressure label say on your passenger door pillar?

mikemelson wrote:

Just had a look at passenger door pillar, it states 79.5psi all round, but surely that’s for a load carrying commercial van.

Also had a look at the tyres, they are Continental Vancocamper with a maximum pressure of 79.5psi!

Well that's a surprise.  You have the same CP tyres as I do.  All that's different is that we have different axle masses.  79.5 psi equates to 5.5 bar which is the CP tyre's maximum permitted cold tyre pressure.  I am even more surprised that this pressure has been recommended for the front tyres.  In an earlier post I gave a link to Continental's data book which shows the pressures they recommend for each axle mass, which for the rear axle only are elevated pressures.  The pressures for the front tyres are lower and not dissimilar to an equivalent Commercial (C) van tyre of the type you used to have.  All I can advise is you load up your van - full fuel, LPG, AdBlue, windscreen washer, HW, fresh, grey and back water tanks (as you wild camp), passengers, food and everything else you take on a trip and record your highest axle masses on a weigh bridge.  Feed the figures into TyreSafe's on-line calculator which will give you a sensible pressure for your front tyres which will be nothing like 79.5 psi!  Unfortunately it will give you 80 psi or 5.5 bar for your rear tyres which is not helpful.  I suggest you add 10% to your rear axle mass and then see what rear pressure is recommended in Continental's data book for this mass.  Alternatively you could ask Continental as I have done.  By way of example only, my fully loaded axle masses are 1400 kg front and 1900 kg rear and for these masses +10% I run my front tyres at 3.3 bar (48 psi) and rear tyres at 5.5 bar (80 psi).  Your front axle mass will be higher than mine.  

Here is a photo of my tyre pressure label which is for the CP tyre:

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The front tyre pressure of 5 bar (72.3 psi) was ridiculously high for my front axle mass which was confirmed by Continental.

Their short answer is the important one - unlike Bailey they don't recommend any tyre pressure as they haven't tested their motorhomes with different tyre pressures and don't want to take any responsibility for them.  The problem is Peugeot haven't tested them either so all they do is give the maximum tyre pressures allowed assuming each axle is at its maximum permitted mass plus a bit more.  If these pressures are used but the actual axle masses are significantly less, the front and/or rear tyres will be overinflated.