Technical Motorhome-Van tyre pressures

[gm6vxb]

Starting to get confused about 'recommended' tyre pressures for my van
Last week had new tyres fitted to my motorhome. Now I have always run the old Michelin tyres
at 55PSI front, and 66PSI rear. Even tyre wear, reasonable (for weight) handling, and did not get too hot on long motorway drives.
Have now changed to Continental Vanco Camper tyres. Garage recommended 65PSI front, 75PSI rear. This to me seemed a little high but ran it for a few days at these pressures but noticed more 'squirrely' on cornering and definately harder ride.

Looking on the sidewall of the new tyres near the tyre size is '69PSI'. Is this Maximum, or Minimum pressure !!!.
Have sent an Email to Continental but no reply yet.

A quick look around some websites (caravan club, Motorhomefacts and others) showed yet more different tyre pressures so getting more confused.

So after a bit more earching found this website for Continental tyres, old, but probably still relevent: https://blobs.continental-tires.com...3fdecf55055ed13a723d5eff564/databook-data.pdf

After some confusion it looks like my tyre pressures for 'known' axle weight should be somewhere between 47-54PSI front, and 50-65PSI rear.
To me, both lower pressures seem too low, but the higher pressures are very close to what I used to run.

So has anyone got a clue what the correct pressures are for the below:

Tyres are Continental Vanco Camper 215/70X15 CP 109R 8 ply
Van front axle weight 1560Kg (These weights measured on local weighbridge)
Van rear axle weight 1720KG

Martin, GM6VXB

 

[cris1117]

Your overthinking this a few pounds either way wont make any difference, the between pressures probably refers to loaded or empty most campers would be loaded when in use go for what feels comfortable 50/65 sounds about right to me I am pretty sure that's what I used to run at when I had my camper of similar weight and tyre size.

 

[HughJampton]

AIUI, the 69psi figure is a maximum required by the USA (DOT) authorities for some reason, and doesn't apply outside that market. See this snip from a rather dated article on motorhome tyres.

The current Conti tech book is here:

https://blobs.continental-tires.com/www8/servlet/blob/85806/71c96d7b7f5265e7fdacae088b19f8e6/download-technical-databook-data.pdf

...and for your tyres doesn't appear to differ materially from the copy you're using.

FWIW, ever since my first 'van with Camper-specific tyres I've run at significantly reduced pressures from the very high ones generally quoted on the door aperture or elsewhere.

For some time, Michelin would quote pressures specific to measured axle-loadings (I have some old email exchanges from years ago), but over time they simply resorted to quoting maximum pressures, particularly for the rears. My own theory on this is that a large number of motorhomes (particularly on the continent) are significantly overloaded on the rear axle, and they don't want any reputational damage.

Anyway, I have always weighed my 'vans in full holiday mode, ensured that actual front and back axle weights are well below the vehicle's maxima, and then generally run at the Continental (tech book) pressures relevant to those plated maxima (not the lower actual pressures). This still results in pressures lower than most quoted with the vehicle, avoids the filling-removing ride, and has had no deleterious effects over many years. You may choose to do the same, but it's patently your decision.

(My current 'van, on different tyres to yours, is generally considered to require 69F/80R. I run at 55F/65R, which is still more than quoted by Conti for my maximum axle loadings, both of which I am well under).

 

[theoneandonly]

1 there is a sticker on the door pilar
2 Michelin reccomend much higher pressures dont worry about going lower
3 side marking on max pressure relate to USA only
4 you've done the right thing contacting Continental
5 previous advice here spot on
6 My van @3500kg was supplied (same contis) @80,80 I now run much lower 65,70 @ 3850kg

 

[gm6vxb]

Definately not over thinking this issue, just totally confused !!.
Found a short sentance on a law website saying ' All tyres should be inflated to their recommended pressure'. I presume this would be shown in the handbook or door sticker.

No sticker on the door pillar, so refering to the handbook (page 222 and last page in 2007 handbook) is says 4.1Bar (72PSI) front, and 5.5Bar (79PSI) rear for camper type tyres.
I presume this would be what VOSA or police would be looking at if I were stopped.

Knowing that with the old Michelin tyres, 55/66PSI seemed about the right pressure with our motorhome in 'holiday' mode, I will go back to these pressures for now and maybe try going up in 2PSI steps for the next journey.

 

[theoneandonly]

I presume this would be what VOSA or police would be looking at if I were stopped.

I suspect they would only be interested if obviously underinflated eg 30ps and running almost flat, or too inflated and running very hot. The use of a quality TPMS or Tyepal would indicate your concern or interest as opposed to disinterest in safety of tyres. 5psi here or there won't interest them

 

[Reg 65]

Thing about recommended tyre pressures is its a compromise.
For minimum friction, maximum fuel economy you increase pressure
But if you take that to its logical conclsion we would have tyres as hard as steel which would shake us and our vans to bits.
You have to have some cushioning,
So you have to reduce the pressure at the expense of fuel economy etc
Where you draw the line is to some extent a matter of opinion - how much weight do you give to each competing factor
So recommended pressures vary a bit
The O/E Continental 215/75 R16C 116/114R tyres on my Ducato say 86psi for 1250kg max
But the same size Hankook LT I have replaced them with recommend 80psi for the same weight.
To add to the complications, it seems some tyre manufacturers don't trust us not to overload the back axles of our motorhomes.
And I can see their point as we weigh our vans and then gradually accumulate more clutter in them adding to the weight.
Michelin used to recommend 80 psi for the rear axle irrespective of weight.
Tyresafe calculator https://www.tyresafe.org/motorhome-tyre-pressure/ still gives higher pressures for the back axle than the front with the same weight.

I can see no other reason why they recommend more pressure for the same weight when its the back axle?
Please let me know if I am missing something here?

So maybe if you are sure you are not going to go over the weight you are quoting I suppose you could put the same pressure in the back that you would in the front for the same weight?

As recommendations vary, I suppose it is possible to 'overthink' this by worrying too much about which of the slightly different recommendations you follow. If slightly different pressure is better for one thing, it will be worse for another.

 

[Communicator]

Definately not over thinking this issue, just totally confused !!.
Found a short sentance on a law website saying ' All tyres should be inflated to their recommended pressure'. I presume this would be shown in the handbook or door sticker.

No sticker on the door pillar, so refering to the handbook (page 222 and last page in 2007 handbook) is says 4.1Bar (72PSI) front, and 5.5Bar (79PSI) rear for camper type tyres.
I presume this would be what VOSA or police would be looking at if I were stopped.

Knowing that with the old Michelin tyres, 55/66PSI seemed about the right pressure with our motorhome in 'holiday' mode, I will go back to these pressures for now and maybe try going up in 2PSI steps for the next journey.

??????? 4.1Bar~59.5psi, 60psi would be close enough.

On our PVC with 3300GVM, I have always followed the sticker values of 4.1Bar (Front), and 4.5Bar (Rear), with discretionary rounding to 60psi & 66psi respectively. The ride quality has never been a problem for either me or my wife.

 

[Keith Spencer]

Starting to get confused about 'recommended' tyre pressures for my van
Last week had new tyres fitted to my motorhome. Now I have always run the old Michelin tyres
at 55PSI front, and 66PSI rear. Even tyre wear, reasonable (for weight) handling, and did not get too hot on long motorway drives.
Have now changed to Continental Vanco Camper tyres. Garage recommended 65PSI front, 75PSI rear. This to me seemed a little high but ran it for a few days at these pressures but noticed more 'squirrely' on cornering and definately harder ride.

Looking on the sidewall of the new tyres near the tyre size is '69PSI'. Is this Maximum, or Minimum pressure !!!.
Have sent an Email to Continental but no reply yet.

A quick look around some websites (caravan club, Motorhomefacts and others) showed yet more different tyre pressures so getting more confused.

So after a bit more earching found this website for Continental tyres, old, but probably still relevent: https://blobs.continental-tires.com...3fdecf55055ed13a723d5eff564/databook-data.pdf

After some confusion it looks like my tyre pressures for 'known' axle weight should be somewhere between 47-54PSI front, and 50-65PSI rear.
To me, both lower pressures seem too low, but the higher pressures are very close to what I used to run.

So has anyone got a clue what the correct pressures are for the below:

Tyres are Continental Vanco Camper 215/70X15 CP 109R 8 ply
Van front axle weight 1560Kg (These weights measured on local weighbridge)
Van rear axle weight 1720KG

Martin, GM6VXB

Hi gm6,
Remember that the pressure in your tyres will vary due to the heating of the air in the tyre, this then expands and the moisture contained within the air also rapidly increases it's volume. All of which makes your tyre pressure increase. So when you check your tyres on a hot day they could be 3 psi higher. In formula 1 they inflate tyres with dry nitrogen to minimise this problem.
An under inflated tyre will deform more the lower the pressure is. You will see the bulge in the side walls and when rotating this continual movement of the tyre wall generates heat, this heat has a detrimental affect on the tyre construction, which can lead to catastrophic failure.
A good check to assess if your pressure settings are good, is to go around all tyres immediately after a journey and feel the tyre temperatures. They should all feel equally warm but not hot. If 1 tyre is hotter then feel the rim, excess rim temperature would indicate a binding brake. Remember to adjust your assessment according to ambient conditions, rain, sunny, cold day and snow. You will often see lorry drivers in service areas going around feeling their tyres.
The more you do it the more proficient you will become, then you can try adjusting the pressure slightly and seeing the affect.

 

[gm6vxb]

All noted. I have been driving for over 50 years now, Bikes, cars, vans, and smaller lorries and when pumping up tyres always refered to the handbook for recommended pressures.
So, looking at my 2006 Ducato handbook, for my size tyres (as stated above) is 72 front, 79 rear.
Now for the interesting bit.
If I then look near the top of the page I see for a 3500Kg van (same max weight as motorhome) with same size tyres the pressures are 59 front, and 65 rear.
The only difference is my motorhome has camping tyres, wheras the van has standard tyres. Presumably difference is ply rating ? but could be wrong.

Got a nice 250 mile drive on Monday on all types of roads (no motorways this far North), so will see how the van handles and report back next weekend.

 

[Keith Spencer]

All noted. I have been driving for over 50 years now, Bikes, cars, vans, and smaller lorries and when pumping up tyres always refered to the handbook for recommended pressures.
So, looking at my 2006 Ducato handbook, for my size tyres (as stated above) is 72 front, 79 rear.
Now for the interesting bit.
If I then look near the top of the page I see for a 3500Kg van (same max weight as motorhome) with same size tyres the pressures are 59 front, and 65 rear.
The only difference is my motorhome has camping tyres, wheras the van has standard tyres. Presumably difference is ply rating ? but could be wrong.

Got a nice 250 mile drive on Monday on all types of roads (no motorways this far North), so will see how the van handles and report back next weekend.

Hi gm6,
Interesting I wouldn't have discovered that myself.
My 2009 fiat ducato motorhome is the same at 72 F 79 R. Or 5.5 bar and the previous idiot had inflated my tyres to 50 and 55 psi because it says 5.0 and 5.5 bar, 1 bar = 14.5 psi (atmospheric pressure).
My understanding of the camper spec tyres is that their load ratings are much higher to accommodate the higher continuous loads sustained from a motorhome. Normal van tyres will very rarely be loaded to the max.
I'm sure the Camping and Motorhome Club website has articles written over this issue. So don't try to reinvent the wheel lol
Safe journey.

 

[Ednic]

Here's my thoughts.

Sticker on the cab states 5.5 bar, this is the original Fiat sticker.

Tyres are Maxmiler EX 215/75/R16C
Quoted as max pressure of 75psi at 1250 kg (5.17 Bar)

1250kg per tyre is 2450 per axle

Axle max weights are 1620 front and 1880 rear _810kg per tyre front & 940kg rear

810 is 65% of 1250 and 940 is 75% of 1250

65% of 75psi is 48.75 (3.36 Bar)
75% of 75psi is 56,25 (3.88 Bar)

Tyresafe quote 50 psi 3.45 Bar front and 60 psi 4.16 Bar rear

1 Bar is 14.5 psi

Others, no doubt, will think differently.

 

[Keith Spencer]

Here's my thoughts.

Sticker on the cab states 5.5 bar, this is the original Fiat sticker.

Tyres are Maxmiler EX 215/75/R16C
Quoted as max pressure of 75psi at 1250 kg (5.17 Bar)

1250kg per tyre is 2450 per axle

Axle max weights are 1620 front and 1880 rear _810kg per tyre front & 940kg rear

810 is 65% of 1250 and 940 is 75% of 1250

65% of 75psi is 48.75 (3.36 Bar)
75% of 75psi is 56,25 (3.88 Bar)

Tyresafe quote 50 psi 3.45 Bar front and 60 psi 4.16 Bar rear

1 Bar is 14.5 psi

Others, no doubt, will think differently.

Hi ednic,
Are you sure you have camper rated tyres, I don't think you have?
The reason for saying that is when you corner very hard, all the vehicle weight transfers onto 1 side and in the event of you going over onto 2 wheels god forbid, you will severely overload your tyres and more than likely they will de-rim or totally fail making your vehicle uncontrollable,under that situation.
It is common practice on caravans that each tyre is rated at a higher loading than the total weight of the whole caravan.
So I think you have standard van tyres fitted hence the pressures being much lower on the tyre and you would be seriously over pressurising them if you go to the vehicle pressures 5.5 bar.
I use continental camper tyres and the rated max pressure is 90 psi if my memory serves me right.
So get 4 new tyres of the correct type, urgently.

 

[Keith Spencer]

Here's my thoughts.

Sticker on the cab states 5.5 bar, this is the original Fiat sticker.

Tyres are Maxmiler EX 215/75/R16C
Quoted as max pressure of 75psi at 1250 kg (5.17 Bar)

1250kg per tyre is 2450 per axle

Axle max weights are 1620 front and 1880 rear _810kg per tyre front & 940kg rear

810 is 65% of 1250 and 940 is 75% of 1250

65% of 75psi is 48.75 (3.36 Bar)
75% of 75psi is 56,25 (3.88 Bar)

Tyresafe quote 50 psi 3.45 Bar front and 60 psi 4.16 Bar rear

1 Bar is 14.5 psi

Others, no doubt, will think differently.

Ps ednic,
Just physically checked my continental tyres and it says Max load 1030kg, Max pressure cold 150 psi.
So check your maxmilers sidewalls and see what it says?.

 

[Ednic]

Hello Keith
Thanks for your thoughts.

The markings on the sidewalls are as I've quoted them.
As you'll see from my calculations, I'm well inside the maximum.

As regards to whether they are van tyres or specific CP tyres, I don't know. There's nothing on the tyres to indicate one way or another.

 

[Ednic]

Sorry if I'm being obtuse, but I don't understand your point regarding weight transfer when cornering. Is that not the same for any vehicle?

 

[Reg 65]

Just physically checked my continental tyres and it says Max load 1030kg, Max pressure cold 150 psi.

Thats incredible - are you sure?
I've never heard anything like it - Even the 44 ton Lorries I had only went up to 120psi
The O/E continental tyres (215/75 R16C 116/114R) fitted to my Ducato say max 1250kg max pressure 86psi
.. and I thought that was a bit high as Hankook advise 80psi for the same weight
Mind you, I don't go round corners on 2 wheels LOL

 

[Keith Spencer]

Thats incredible - are you sure?
I've never heard anything like it - Even the 44 ton Lorries I had only went up to 120psi
The O/E continental tyres (215/75 R16C 116/114R) fitted to my Ducato say max 1250kg max pressure 86psi
.. and I thought that was a bit high as Hankook advise 80psi for the same weight
Mind you, I don't go round corners on 2 wheels LOL

My eyes are failing me it says 69psi lol, see photos

 

[jadatis]

This " pigheaded Dutch selfdeclared tyrepressure specialist" found this topic with google, and registered to give you advice.

Made a pressure/axleloadcapacity list for your tyre, but can be used for every tire with loadindex 109/ maxload 1030kg AT 69 psi upto 160kmph/99mph.

Gives 90% of loadcapacity calculated for the pressure with tighter formula then the official european. And for max 99mph. I determined this to give maximum reserve, but still acceptable comfort and grip, and no nervous steering.
So now you ONLY have to determine the real axleloads in your use 99% accurate, thats your responcibility, and look them back in my list, for the needed cold filled pressure at about 21 degr C. / 70 degr F.
So dont do pre- or after-calculations yourselfe, like adding reserve or pressure, I did all the rocket science.
Did you weigh fully loaded, so also persons and water?

Axleload/ cold psi
736 kg/ 25 psi
762 kg/ 26 psi
788 kg/ 27 psi
814 kg/ 28 psi
840 kg/ 29 psi
866 kg/ 30 psi
892 kg/ 31 psi
918 kg/ 32 psi
944 kg/ 33 psi
970 kg/ 34 psi
995 kg/ 35 psi
1021 kg/ 36 psi
1047 kg/ 37 psi
1072 kg/ 38 psi
1098 kg/ 39 psi
1124 kg/ 40 psi
1149 kg/ 41 psi
1175 kg/ 42 psi
1200 kg/ 43 psi
1225 kg/ 44 psi
1251 kg/ 45 psi
1276 kg/ 46 psi
1302 kg/ 47 psi
1327 kg/ 48 psi
1352 kg/ 49 psi
1378 kg/ 50 psi
1403 kg/ 51 psi
1428 kg/ 52 psi
1453 kg/ 53 psi
1478 kg/ 54 psi
1504 kg/ 55 psi
1529 kg/ 56 psi
1554 kg/ 57 psi
1579 kg/ 58 psi/ front 1560kg
1604 kg/ 59 psi
1629 kg/ 60 psi
1654 kg/ 61 psi
1679 kg/ 62 psi
1704 kg/ 63 psi
1729 kg/ 64 psi/ rear 1720 kg
1754 kg/ 65 psi
1779 kg/ 66 psi
1804 kg/ 67 psi
1829 kg/ 68 psi
1854 kg/ 69 psi/ maxloadpressure
1878 kg/ 70 psi
1903 kg/ 71 psi
1928 kg/ 72 psi
1953 kg/ 73 psi
1978 kg/ 74 psi
2002 kg/ 75 psi
2027 kg/ 76 psi
2052 kg/ 77 psi
2077 kg/ 78 psi
2101 kg/ 79 psi/ maximum inflation pressure often also given in sidewall of C-tyres in the Continental groop.

 

[VinceS]

I have the Continental Vanco Camper tyres on my motrohome (3500kg) max and initially ran them at 70 psi - at which they give a pretty harsh ride. After much checking I now run them at 50 front and 60 rear. When the time comes I will change to an all weather tyre as the grip in the wet is poor and non existent on wet grass!
As I understand it CP (Camping Tyres) have stiffer side walls to better cope with a lot of time spent not moving and the generally higher basic weight of MHs