Tyre pressures

[Mobilvetta]

I'm presently in Spain and my motorhome is on its weight limit, before setting of I checked my tyre pressures and put 80psi in the rear tyres and 75 in the front.

When I look at the Michelin camping tyres it says maximum pressure is 80 psi, with the weather been warmer in Spain than the UK and I have read that when the tyres are warm after a run the PSI could rise by as much as 6 PSI, so the rears could potentially be 86psi when I'm driving to a destination, is this dangerous as it's over the manufacturers max psi, so bearing this in mind, should I only have a max of 74psi in the rears to allow for the additional psi once they have got warm.

 

[SimonM]

I have Michelin’s like you and was advised to run 80psi rears and 65psi fronts. My Tyrepal pressure sensing kits regularly show the tyres reaching well in excess of 90 rears in the heat. I’m sure Michelin will have factored in the normal increase in tyre temperatures, so I don’t worry.

 

[TeamRienza]

I run on Michelin Aglis camping tyres. Rear axle max 2000kg actual weight 1940kg so I use 80psi as recommended by Michelin and tyresafe. I also use tyrepal monitors.

When in France or Spain the 80psi at rest rises to close on 90psi when running. I assume the manufactures take this into consideration when designing, manufacturing and advising on use.

At this time of the year my rear tyres are showing 75psi at rest. This is presumably down to ambient temperature. They lift to 79 or 80psi running.

I did try to find out what ambient temperature one should use as a benchmark for the default 80psi but info is very scarce. The best I can find is in this link to Wikipedia.

Cold inflation pressure - Wikipedia

en.m.wikipedia.org

Davy

 

[Fazerloz]

Check tyre pressures when they are cold.

 

[Deleted member 47296]

It may be that you are looking at something that is only applicable to the USA. See here https://www.tyresafe.org/wp-content/uploads/2015/12/motorhome-leaflet.pdf (page 3)

 

[trevskoda]

I run all mine at 60 psi as any harder and she bounces a lot as suspension is hard on my truck.

 

[Canalsman]

I run on Michelin Aglis camping tyres. Rear axle max 2000kg actual weight 1940kg so I use 80psi as recommended by Michelin and tyresafe. I also use tyrepal monitors.

When in France or Spain the 80psi at rest rises to close on 90psi when running. I assume the manufactures take this into consideration when designing, manufacturing and advising on use.

At this time of the year my rear tyres are showing 75psi at rest. This is presumably down to ambient temperature. They lift to 79 or 80psi running.

I did try to find out what ambient temperature one should use as a benchmark for the default 80psi but info is very scarce. The best I can find is in this link to Wikipedia.

Cold inflation pressure - Wikipedia

en.m.wikipedia.org

Davy

Ambient temperature is precisely what it says.

Tyre pressures must be set with the tyres cold. Ideally on a cloudy day so that the tyres have not been warmed by the sun. If the sun is shining the tyres at the front, or rear, or on one side will be warmer by some margin and this invalidates the process.

I know from my TyrePal system that when the weather is cold the pressures when cold are many PSI less than when the ambient temperature was greater.

Conversely when the weather is warmer than the ambient the pressures can be significantly higher.

So in summary the tyres should be inflated to the recommended pressure at the currently prevailing ambient temperature - when the tyres are cold and in the shade.

 

[Mobilvetta]

Check tyre pressures when they are cold.

That's what I normally do.

 

[Mobilvetta]

I run on Michelin Aglis camping tyres. Rear axle max 2000kg actual weight 1940kg so I use 80psi as recommended by Michelin and tyresafe. I also use tyrepal monitors.

When in France or Spain the 80psi at rest rises to close on 90psi when running. I assume the manufactures take this into consideration when designing, manufacturing and advising on use.

At this time of the year my rear tyres are showing 75psi at rest. This is presumably down to ambient temperature. They lift to 79 or 80psi running.

I did try to find out what ambient temperature one should use as a benchmark for the default 80psi but info is very scarce. The best I can find is in this link to Wikipedia.

Cold inflation pressure - Wikipedia

en.m.wikipedia.org

Davy

Hell I have drunk a bottle of wine, I'm going to have to wait until tomorrow to try and get my head around that explanation.

 

[Mobilvetta]

Ambient temperature is precisely what it says.

Tyre pressures must be set with the tyres cold. Ideally on a cloudy day so that the tyres have not been warmed by the sun. If the sun is shining the tyres at the front, or rear, or on one side will be warmer by some margin and this invalidates the process.

I know from my TyrePal system that when the weather is cold the pressures when cold are many PSI less than when the ambient temperature was greater.

Conversely when the weather is warmer than the ambient the pressures can be significantly higher.

So in summary the tyres should be inflated to the recommended pressure at the currently prevailing ambient temperature - when the tyres are cold and in the shade.

I'm going to have to get myself one of these when I get back to the UK, I usually check my tyres pressures once a week, this would save me having to do this.

 

[Mobilvetta]

I run all mine at 60 psi as any harder and she bounces a lot as suspension is hard on my truck.

I find the suspension is smoother when I load the van up as opposed to when it is empty, it's a lot finer ride when empty.

 

[Mobilvetta]

I run on Michelin Aglis camping tyres. Rear axle max 2000kg actual weight 1940kg so I use 80psi as recommended by Michelin and tyresafe. I also use tyrepal monitors.

When in France or Spain the 80psi at rest rises to close on 90psi when running. I assume the manufactures take this into consideration when designing, manufacturing and advising on use.

At this time of the year my rear tyres are showing 75psi at rest. This is presumably down to ambient temperature. They lift to 79 or 80psi running.

I did try to find out what ambient temperature one should use as a benchmark for the default 80psi but info is very scarce. The best I can find is in this link to Wikipedia.

Cold inflation pressure - Wikipedia

en.m.wikipedia.org

Davy

That's good to know, makes me feel more at ease, I've nether suffered a blow out and don't fancy it in a motorhome weighing over 4 ton.

 

[runnach]

I wouldn’t worry, other than agreeing with what has been said Michelin are french and it gets very warm in the south of France where a lot of product is used.

A lot of folk underinflate because it gives a softer ride

 

[barge1914]

Fiat recommendations for my Ducato on Michelin Agilis Campers are 5.5 bar all round. However the base vehicle although capable of 3650 kg is downplated to 3500 Kg by the converter. My actuals are 1800 kg front and 1600kg rear, not surprisingly it’s like driving over the potholes on concrete wheels. Has anybody got a load/ pressure chart for these tyres?

 

[SimonM]

Fiat recommendations for my Ducato on Michelin Agilis Campers are 5.5 bar all round. However the base vehicle although capable of 3650 kg is downplated to 3500 Kg by the converter. My actuals are 1800 kg front and 1600kg rear, not surprisingly it’s like driving over the potholes on concrete wheels. Has anybody got a load/ pressure chart for these tyres?

the safest way is to email Michelin and let them know your front and rear weights and tyres being used, they will let you know their recommendations- they also reply extremely quickly.

 

[Deleted member 47296]

Fiat recommendations for my Ducato on Michelin Agilis Campers are 5.5 bar all round. However the base vehicle although capable of 3650 kg is downplated to 3500 Kg by the converter. My actuals are 1800 kg front and 1600kg rear, not surprisingly it’s like driving over the potholes on concrete wheels. Has anybody got a load/ pressure chart for these tyres?

Michelin will always tell you to inflate your rear tyres to 79/80psi irrespective of the load. There is a chart in the link that I provided earlier that may be somewhere for you to start.

 

[barge1914]

Michelin will always tell you to inflate your rear tyres to 79/80psi irrespective of the load. There is a chart in the link that I provided earlier that may be somewhere for you to start.

Thanks, I’ve sent them an email, I’ll see what they come up with. My front axle is the heavy one 1800kg front, only 1650 kg rear.

 

[in h]

Fiat recommendations for my Ducato on Michelin Agilis Campers are 5.5 bar all round. However the base vehicle although capable of 3650 kg is downplated to 3500 Kg by the converter. My actuals are 1800 kg front and 1600kg rear, not surprisingly it’s like driving over the potholes on concrete wheels. Has anybody got a load/ pressure chart for these tyres?

The normal approach to calculate the correct pressure is to weigh the axle, fully loaded. Then look on the tyre to read the load rating and maximum pressure. The correct tyre pressure is simply calculated by dividing half* the actual axle load by the maximum load (look that up on the web), then multiplying the result by the maximum pressure.
*It's different for a twin-wheel axle, of course.
However, camper tyres have heavier sidewalls to protect from kerbing. That's actually the only significant difference, and it means they're more prone to overheating.
Ideally you'll replace them with proper commercial tyres, but failing that, keep the pressure at least 65psi.

 

[Canalsman]

Some commercial tyres have reinforced sidewalls too to protect against kerbing.

That's what I have on my Dakota.

 

[in h]

Yes, but not as heavily protected. And they don't recommend 80psi regardless of load.