# Working out tyre pressures



## pmcclure (Dec 6, 2011)

Its been suggested to me that it would be a good idea to get my motorhome weighed (fully laden) to allow me to have the correct pressures in the tyres.
(*) So I need to go to a weighbridge and be weighed three times.

Gross weight
Front axle weight
Rear axle wight

Tyres are Continental vancocamper 225/75 r16 cp
Motorhome has a vehicle identification sticker on the side with the following on
4000kg
5400kg
2100 kg (1)
2400 kg (2)
(Not to sure what it all means)

(**)Then I need to contact Continental (does anyone have the email address please) and they would tell me the recommended tyre pressures for the motorhome. 

Could anyone confirm that (*) & (**) are correct?

Thanks

Peter


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## Jean-Luc (Jul 21, 2005)

pmcclure said:


> ...........................So I need to go to a weighbridge and be weighed three times...........................................


Not quite, The easiest 'procedure' is to pretend you are truck making a delivery.

Park fully on the weighbridge and get the 'loaded' weight recorded drive off and back on with only the front axle on the weighbridge and get the 'unloaded' weight recorded. The operator will then print off the delivery docket to be read as follows.

Weight 1 (loaded) = total weight of motorhome.
Weight 2 (unloaded) = weight on front axle.
Weight 3 (load delivered (difference between 1 & 2)) = weight on rear axle.


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## wakk44 (Jun 15, 2006)

I got in touch with contintental to ask for recommended tyre pressures for my new set of Vanco 2 tyres.
The e mail address is [email protected]

I gave the details of just the front and rear axle loadings(which was on the MOT certificate)and they responded quickly with their recommendations.Very impressed with Continental customer service and I was surprised at how low the tyre pressures have to be on these particular tyres.

ps Don't forget to include the tyre details in your e mail.


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## pmcclure (Dec 6, 2011)

> Not quite, The easiest 'procedure' is to pretend you are truck making a delivery.


In a motorhome??????


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## drcotts (Feb 23, 2006)

pmcclure said:


> 4000kg
> 5400kg
> 2100 kg (1)
> 2400 kg (2)
> ...


5400 is the gross train weight. This is the maximum weigh that your fan and any trailer can be.

4000kg ios the gross weight of the van alone. This is the maximum weight that the whole van can be you the driver, a full tank of fuel and all your goods in

2100 is the max weigh that the front axle can be

2400 is the max weight the rear axle can be. This is the one most likely to be over.

Note you must be less than all of these weights to be legal ie if the front axle is ok and the rear axle is too heavy but the total weight is Ok then its still illegal.

Phill


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## TR5 (Jun 6, 2007)

As a guide to tyre pressures, if you have to hand the axle weight, the maximum weight printed on the tyre, and the maximum tyre pressure printed on the tyre;

If the maximum axle weight per wheel is for example 85% of the tyre's maximum weight, then it is pretty safe to assume the tyre pressure would be around 85% of the maximum pressure.
You can then vary the pressure accordingly, depending on the load carried. 
I.E. if running near or on the maximum axle load, then the pressure will be as above, if normally running lighter, then work out the % and adjust the pressures accordingly.

Too many dealers just put the maximum pressure in the tyres, regardless of the load they are taking, meaning many motorhomes could be running with 80 - 85psi in the tyres, when many should be around 50 - 60psi.


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## paulmold (Apr 2, 2009)

Use this guide (go to last page)

http://www.tyresafe.org/images/tyre-safety-guide/motorhome-leaflet.pdf


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## duxdeluxe (Sep 2, 2007)

I put mine across a weigh-bridge fully loaded up a few weeks ago and they got readings with front wheels on, then whole van then rear wheels on. It was explained that this was as a cross check. The F+R added up to about 10kg different so ok. The resulting email to Michelin gave 52 psi front and they said 80 rear as not sure of what weight would actually be in rear axle due to loads. I simply pro rated it based on the max pressure for the max axle load and it came out as about 63 psi. Much improved ride and no change to economy.


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## BrianJP (Sep 17, 2010)

paulmold said:


> Use this guide (go to last page)
> 
> http://www.tyresafe.org/images/tyre-safety-guide/motorhome-leaflet.pdf


Only problem here is that Continental will give you a different( higher) pressure for their tyres on the rear than stated on this chart .They say because of different load factors etc etc on motorhomes.
If you want the Conti tyre handbook (2010 version) which will if you wade through it give you a chart for pressures on motorhomes with their camper tyres Email me and I will send it to you as its a large PDF that connot be uploaded to here.


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## Jean-Luc (Jul 21, 2005)

pmcclure said:


> > Not quite, The easiest 'procedure' is to pretend you are truck making a delivery.
> 
> 
> In a motorhome??????


 :roll: :roll: :roll:


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## BrianJP (Sep 17, 2010)

pmcclure said:


> Its been suggested to me that it would be a good idea to get my motorhome weighed (fully laden) to allow me to have the correct pressures in the tyres.
> (*) So I need to go to a weighbridge and be weighed three times.
> 
> Gross weight
> ...


4000 kg max gross vehicle weight
5400 kg max train weight ( ie what you can add for towing in your case 1400kg)
2100 kg max front axle load
2400 kg max rear axle load

From the Conti tyre chart if you had max loading on both axles which of course is unlikely, this equates to front pressure of 4.0 Bar and rear of 5.25 Bar . It gives you a guide though as to what the max pressures you should be using are.


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## pmcclure (Dec 6, 2011)

Have had the motorhome weighed when fully laden, and have emailed Continental with the weights asking for the recommended tyre pressures.

They seem to be a long time in replying (wonder if there all on holiday?)

The weights are:

Full vehicle 3680kg
Front axle 1540kg
Rear axle 2060kg

Is there a means of calculating the pressures myself?

Thanks

Peter


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## BrianJP (Sep 17, 2010)

According to the Conti handbook your pressures should be 

Front 3.0 Bar 43.5 psi ( up to 1730 kg)
Rear 4.5 Bar 65.5 psi ( up to 2130 kg)

if you want a copy of the handbook PM your Email address and I will send it to you.


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## pmcclure (Dec 6, 2011)

Ooooop's

Have just checked tyre pressures and they were:

5.8 bar front and rear  

Have just had a reply back from Continental confirming Brians information.


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## EnGog (Sep 23, 2011)

Swift Sundance 580PR
1480kg front axle, 1820kg rear axle, 3260kg gross.

Used wakk44's link to e-mail yesterday and got reply back in no time.
Front 3.25 bar, rear 4.75 bar. Great service. (When new from dealer it had 4.35 all round).


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## Scattycat (Mar 29, 2011)

I know I'm still a novice at this MH game but I just use the figures that are in the AL-KO chassis book that came with the van. 
Their recommended pressures are 5 bar for the front and 5.5 for the rear.


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## ob1 (Sep 25, 2007)

Scattycat - Just ask yourself how any chassis manufacturer knows how much weight will be on their chassis considering the hundreds of different motorhomes made, some 3300GVW, some 3500/3850/4200... The only people who can tell you the correct pressure is the tyre manufacturer when given both axle weights when fully loaded for your intended use.

Even then several will state a rear axle tyre pressure of 80psi regardless of the actual weight as a precaution against overloading.

Ron


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## Scattycat (Mar 29, 2011)

ob1 said:


> Scattycat - Just ask yourself how any chassis manufacturer knows how much weight will be on their chassis considering the hundreds of different motorhomes made, some 3300GVW, some 3500/3850/4200... The only people who can tell you the correct pressure is the tyre manufacturer when given both axle weights when fully loaded for your intended use.
> 
> Even then several will state a rear axle tyre pressure of 80psi regardless of the actual weight as a precaution against overloading.
> 
> Ron


As I said, I'm a complete novice and always ready to learn from and be advised by those who've been around MH's for many more years than I.

But taking onboard what you say, I'm looking at the AL-KO booklet that came with my van and it states for the tyre sizes on my van, (215/70 R15CP), to have 5 bar in the front and 5.5 bar in the rear and those are the pressures that the dealer put in when it was taken for its CT, (MoT equivalent)

When we bought our first van I took advice from a number of long time motorhomers and put pressures in the tyres much higher and to be honest it gave a most uncomfortably hard ride so I reduced the pressures to those recommended in the AL-KO booklet that came with that van and the ride was much more comfortable.

Thanks for your comments Ron, but on this occasion I think I'll stick with what the AL-KO manual advises at least if I get stopped in a vehicle check I've got paperwork confirming what the pressures should be and also as I said I'll be getting a much more comfortable ride :roll:


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## Spiritofherald (May 18, 2012)

I've not been able to find a local weighbridge. I've checked Yell.com and come up with nothing locally. I do know a scrap yard with a weighbridge and I could possibly ask them to weigh it for a fee, but ideally a proper public weigjhbridge would be better. What does everyone else do?


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## wakk44 (Jun 15, 2006)

Spiritofherald said:


> ................but ideally a proper public weigjhbridge would be better. What does everyone else do?


Fortunately we have a local council run weighbridge that can be used,I was told they do charge a small fee(about a tenner),I don't know how much that is because the kind council chap didn't charge me.Perhaps if I had required a print out they would have charged me.


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## ob1 (Sep 25, 2007)

Scattycat said:


> Thanks for your comments Ron, but on this occasion I think I'll stick with what the AL-KO manual advises at least if I get stopped in a vehicle check I've got paperwork confirming what the pressures should be and also as I said I'll be getting a much more comfortable ride :roll:


Scattycat - I hear what you say but I feel that you are missing the points I am trying to make.

First, The tyre manufacturer is the only authority as to how much pressure should be in a tyre - once they know what your particular axle loading is.

Second, The chassis manufacturers recommended pressures can only be a general guide as they simply do not know what weight loading or weight distribution is applicable to your vehicle.

As an example, want to carry a scooter? Then fitting a tow-bar extension, scooter rack and the scooter itself, can easily add 200kg to your rear axle whilst at the same time levering some 70kg off the front axle. The chassis manufacturer cannot know this and therefore his recommended weights will be way out. This is an extreme example of course but it illustrates the point that the correct tyre pressures are those supplied by the tyre manufacturer, taking into account the caveat mentioned in my earlier post. This will give neither a bone shaking or over soft ride.

Nothing's simple is it?

Ron

Ron :? :evil: :evil:


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## Jean-Luc (Jul 21, 2005)

Spiritofherald said:


> I've not been able to find a local weighbridge. I've checked Yell.com and come up with nothing locally. I do know a scrap yard with a weighbridge and I could possibly ask them to weigh it for a fee, but ideally a proper public weigjhbridge would be better. What does everyone else do?


Any business which deals in bulk deliveries/receipts will have a weighbridge. 
Think of grain merchants - quarries - coal merchants etc. All these types of business check quantities delivered/received by weighing the vehicle loaded and empty.

By using their process, first weight = the whole vehicle, second weight = rear axle only on platform, the docket produced will show a third weight = delivery which will also equate to the front axle weight.


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## Scattycat (Mar 29, 2011)

ob1 said:


> Scattycat said:
> 
> 
> > Thanks for your comments Ron, but on this occasion I think I'll stick with what the AL-KO manual advises at least if I get stopped in a vehicle check I've got paperwork confirming what the pressures should be and also as I said I'll be getting a much more comfortable ride :roll:
> ...


Point taken  :idea:


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