tire pressure advice please.

[Deleted member 3011]

The correct tyre pressure is clearly stamped on the side wall of your tyre, you also have a production date code on the side wall too....jim

Not so!

Without knowing the wheel loadings it is not possible to determine the correct pressure. In most applications the advised pressures on placards and operator manuals are too high which results in harsh ride and uneven tyre wear.

BTW asking tyre fitters what the correct pressure is is the same as asking them what the correct wheel nut torque and fitting method is - they mostly don't have any understanding of the engineering and rarely have the slightest clue.

Our recommended tyre pressures are 79.5 PSI all round. However, the ride is rock hard and I often wonder if they have calculated it incorrectly.

For a start, giving pressure accurate to one decimal place is just crazy so that is a good indication "they" haven't done their homework properly. Then there is the very unlikely assertion that your axle loads are equal front to back. Not impossible of course but very unlikely. And then, "They" can't calculate any pressure unless you have weighed the MH in traveling trim and looked up the figures on the manufacturers web site. Check the tread depth across the tyre tread and see if it is even all the way. Quite likely that it is worn more in the middle on the front and maybe fairly even on the back depending on your weight distribution.

If the tyres are at the correct pressure for the load, they become part of the suspension and ride on rough surfaces and across road joints will be markedly smoother. Even as little as 10psi can make a big difference.

BTW, it is pleasing that we haven't had the claim that they rang michelin and michelin said pump them all up to maximum sidewall pressure because MH owners are too stupid to get it correct. Making progress.

 

[maingate]

Our recommended tyre pressures are 79.5 PSI all round. However, the ride is rock hard and I often wonder if they have calculated it incorrectly.

Who are 'they' who recommended an absurdly high pressure for such a small van? :scared:

At least you now know what do to rectify matters, thanks to this thread.

 

[Deleted member 8468]

They are Swift, the vehicle converters. It's on the tyre pressures sticker on the door post. Too early to look at wear as the vehicle has only done 2500 miles from new.

 

[maingate]

They are Swift, the vehicle converters. It's on the tyre pressures sticker on the door post. Too early to look at wear as the vehicle has only done 2500 miles from new.

Ignore it and follow the advice given on here, it is far too high. My small Autoquest (our first van) had the same sticker and the van was a death trap. As a newbie to motorhomes, it took a lot of searching to find the right pressures. I would estimate around 55 to 60 psi maximum for yours but use a weighbridge to get your axle weights.

Remember that if your pressures are far too high, your Insurance Company can refuse to pay out in the event of an accident, stating that you,as the driver, contributed to the cause by inflating your tyres far too much.

 

[jagmanx]

Renault Master

3.5 Ton
225/65 R16
Handbook says
Front 54
Rear 63

Tyres "bulge a touch at the bottom" so I dont think they are over-inflated.

The front/rear variation looks to be sensible

They are larger that most other tyres I see..
Given that there is more area on the road and thus pressures can be lower.
EG 10% more road contact = 10% LESS pressure

 

[Siimplyloco]

You mightl find the chart in this thread useful: it refers to my Merc 416i Sprinter but the tyre sizes are pretty common!
http://www.wildcamping.co.uk/forums...e-chart-ride-comfort.html?highlight=pressures

John

 

[maingate]

3.5 Ton
225/65 R16
Handbook says
Front 54
Rear 63

Tyres "bulge a touch at the bottom" so I dont think they are over-inflated.

The front/rear variation looks to be sensible

They are larger that most other tyres I see..
Given that there is more area on the road and thus pressures can be lower.
EG 10% more road contact = 10% LESS pressure

The tyres on the van of MollsPhot are liable to be 15" and his axle weights are probably lower than yours. His Swift model number is 320, which possibly refers to the MAM ...... 3200 Kg. That is why axle weights are important.

 

[Deleted member 8468]

Ours is the Rio 340 with 16 inch wheels and 225/75 R16 CP tyres. The recommended pressure also happens to be the maximum pressure as printed on the tyre. Thanks for the info, I shall certainly look at working out what they should be.

 

[justdoitviv]

When I got my van 8/9 years ago, I was told the tires should be at 40. And that's what I have always put in. Having a flat tire, the rac put on my spare. I asked him if its pumped to 40. He said 60 the min unloaded. When I went to get two new tires fitted the next day, I asked the tire fitters, about the air pressure..... and they said 55 to 60. So they had to pump up the other two tires to match. When I had a service done two days later, I asked the garage..... they looked at the metal plate on the drivers door and it said 43. I asked is that as a van or campervan. He said campervan.

tires are 15 inch commercial I think. Its a fiat ducato, mwb.
Many thanks

ok here is more info.
On the drivers door, on the metal plate it says............... bar 3.0 psi 43 195/70-R15
In the ducato handbook it says ............
version 10 195/70-R15 reinforced 3.0 front unladen and 3.0 fully laden rim rear 15"-6j-H2
version 14 195/70-r15c 4.1 front unladen and 4.5 fully laden rim rear as above

I believe my van is a ducato 10 so do I have the wrong tires on???? cause ive got the version 14 tires on.

 

[Deleted member 5816]

Viv both tyre sizes you quote are the same 195/70 R15

Alf

ok here is more info.
On the drivers door, on the metal plate it says............... bar 3.0 psi 43 195/70-R15
In the ducato handbook it says ............
version 10 195/70-R15 reinforced 3.0 front unladen and 3.0 fully laden rim rear 15"-6j-H2
version 14 195/70-r15c 4.1 front unladen and 4.5 fully laden rim rear as above

I believe my van is a ducato 10 so do I have the wrong tires on???? cause ive got the version 14 tires on.