# Who is correct ?



## Webby1 (Mar 11, 2012)

Who is correct ?

Title is just to draw you in to the subject of tyre pressure...... again!!
I know............I've done a search...............BUT

The Ducato label clearly states pressure of 73 and 79 psi, but that was on their original Vancocamper 215 70 15 109r CP tyres, that has written on them that they are able to be inflated to that pressure.

I have just replaced 4 tyres with the Toyo H09 (well recommended on this site) but slightly larger at 225 70 15 112r. This extra load rating will enable Svtech to replate the rear axle loading to 2240 (but within 3850 in total)

The very helpful man at Toyo said pressure at that loading should be 62 and 65 psi (they're marked 65 psi) which is a lot lower than the Ducato plate states. We do have rear air assist suspension, but I don't know if that is relevant to tyre pressure

My inclination is to go with the tyre manufacturer advice rather than the van manufacturer and I wondered what others think..

Thanks


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## mack100 (Jul 18, 2013)

We went with info from the tyre manufacturer, in our case Continental.
Following advice on various forums we loaded the MH up to almost our normal touring capacity and took it to a local weighbridge.

I then emailed Continental with the axle weights and very quickly they replied with the correct pressures for our tyres.


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## WildThingsKev (Dec 29, 2009)

You definitely cannot go above the 65psi marked on the tyres.

Start with 60 front 65 rear and see how it handles.


Kev


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## grizzlyj (Oct 14, 2008)

Hiya

I would agree that you shouldn't go past the maximum indicated on the tyre.

I am no expert but I believe that its the air molecules in the tyre that carries the load, the tyre just contains it. So if you need a higher load you need more air. You can achieve that by a bigger volume or a higher pressure. 

In your instance you have the (theoretically) same load but a bigger volume, so a lower pressure would logically follow?

(Broadly speaking in my layman's view )


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## Webby1 (Mar 11, 2012)

*Tyre pressure*

That's a good point Jason and seems to make sense to me also ..............slightly larger tyres with more air can be run at a lower pressure????

But more to the point I guess is Kev's post that if it says 65psi on the actual tyre then that should be the limit.

It's great to have the M+S tyres and to know that they can handle the extra weight on the rear axle.


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## TheNomad (Aug 12, 2013)

Don't go over the max pressure stamped on the tyre wall. 
It's written there for a reason.
Lots of people over-inflate their MH tyres. The bottom of the tyre where it rests on the ground should have a slight bulge. Google for photos/diagrams of such correct inflation.
Experiment with 60, 62, 65psi to see which looks, feels and rides best for your taste.


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## Zebedee (Oct 3, 2007)

I run ours the same as Stanner - 60 front and 65 rear, and that seems about as good as it gets.

One question for Webby, and anyone else with air bags please. Do they make the rear end a bit less lively _(nay, positively explosive!!) _when you hit one of those little hemispherical sleeping policemen a tad too fast?

They are far worse than the wider tarmac burial mounds, and our van practically takes off at the rear at anything more than walking pace.

Thanks

Dave


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## Webby1 (Mar 11, 2012)

*Air assist*

Have never really run the van without....... so can only ASSUME(now there's a dangerous word) that is what they are there for and will absorb any bumps better than normal suspension.

Perhaps the proof is that you can get the rear axle loading increased slightly more with air assist fitted than without.


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## TheNomad (Aug 12, 2013)

*Re: Air assist*



Webby1 said:


> Have never really run the van without....... so can only ASSUME(now there's a dangerous word) that is what they are there for and will absorb any bumps better than normal suspension.
> 
> Perhaps the proof is that you can get the rear axle loading increased slightly more with air assist fitted than without.


No. I don't think they make your suspension softer (as in absorb sudden bumps more), in my experience, air-ride suspension assist makes your rear suspension stiffer, ie harder.

That's exactly what it is meant to do - so you can carry more weight on that axle, and get less side-to-side roll, and support the we're-loaded-to-our-max original equipment rear springs.

With air-ride assisters as well as the original leaf springs, the rear part of the body of the vehicle will bounce more over sudden bumps.


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## Webby1 (Mar 11, 2012)

*Assumptions*

So it just goes to show the danger of making assumptions............it

makes an ass of U and Me as David Brent used to say.


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## Mrplodd (Mar 4, 2008)

Regardless of whether you have Air-ride fitted or not the tyres are still going to be supporting the same load so surely the pressure needs to remain the same ???

I dont know, just asking the question


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## Zebedee (Oct 3, 2007)

Agreed Ploddy - sounds right to me.

I was talking to Steve of SvTech only yesterday about uprating our van from 3300kg to 3500kg.

I quizzed him about the rear axle rating, and he said he could increase it from 1900kg to 2000kg, but only if I had Air Rides fitted *and the tyres were suitably rated to carry the increased load*.

_(My main concern is about the MGV weight. I'm close on the rear axle, but just about within the limit when fully loaded, but last time I weighed I was 20kg over on the all up weight - and I've had a towbar fitted since then! 8O )_

IMHO the heavier you load up the van the higher should be the tyre pressure - within reason of course. Seems logical to me.

Dave


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## BrianJP (Sep 17, 2010)

Camper specific tyres eg Conti and Michelin always run at higher pressures than normal LT tyres at same loading however nowhere near the 5.5bar often stated by the vehicle maker .As already said consult with tyre manufacturer. There's lots of old threads and info on the subject on here.


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## Webby1 (Mar 11, 2012)

*Tyre loading*

Dave that's why we changed our tyres to the 225 70 15 with the 112r rating and therefore an increased rear axle load as agreed with Svtech.

I have indeed searched through all the posts on here but you know how they all stray off somewhere. What's David Brent got to do with tyres ??

Thanks to all replies and we will stick to 65 and 62 psi.............just still niggles me that there is this big sticker in the cab saying inflate to 72 and 79......................don't want to leave any wriggle room for insurance companies in the event of a claim.

Do you think just removing the sticker would help ?????? lol


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## TheNomad (Aug 12, 2013)

*Re: Tyre loading*



Webby1 said:


> Dave that's why we changed our tyres to the 225 70 15 with the 112r rating and therefore an increased rear axle load as agreed with Svtech.
> 
> I have indeed searched through all the posts on here but you know how they all stray off somewhere. What's David Brent got to do with tyres ??
> 
> ...


Yes. Just remove it. 
You'll be happier, and no one else will be tempted to over inflate your tyres to bursting point.


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## Wizzo (Dec 3, 2007)

> Regardless of whether you have Air-ride fitted or not the tyres are still going to be supporting the same load so surely the pressure needs to remain the same ???


The larger the tyre the lower the pressure required for the same axle weight.

For confirmation see the Tyre Safe pdf.

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

JohnW


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## cabby (May 14, 2005)

I was told that the sticker in question has nothing to do with campers. all the cabs have them no matter what their destination is. they are stuck on before they leave the Fiat factory. None of the converters take them off.
You have done the correct thing by approaching the tyre makers.

cabby


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