Checking Motorhome tyre pressure

[Nickorchard]

Hello
We recently bought an Auto-trail EK 590
I wanted to check the tyre pressures which need to be 75 PSI

Took it to local garage and the supermarket garage however the compressor max pressure was 60 PSI

Where do people take Moto homes to check tyre pressures or do I need to get my own compressor?

Cheers

Nick

 

[gwyntaxi]

Hello
We recently bought an Auto-trail EK 590
I wanted to check the tyre pressures which need to be 75 PSI

Took it to local garage and the supermarket garage however the compressor max pressure was 60 PSI

Where do people take Moto homes to check tyre pressures or do I need to get my own compressor?

Cheers

Nick

Go to a local tyre depot, they will usually let you use their airline some will even check them all for you, mine does so I always give them 3or4quid...Just sayin....

 

[gwyntaxi]

Being a cheapskate I have a Lidl pump a bit like the Ring version but much cheaper . It works fine but I do double check the pressures with a separate gauge.

I have also got the Lidl pump which I use to top up my rear air bags, but there’s no way it will get my rear tyres up to 70psi even from 60psi.

 

[Richard J]

You're right. We shouldn't be using ambient here.
Tyre pressures are specified for an 18Deg C temp.
If you want to check & adjust tyre pressures at when a tyre is at other temps, use the chart

I am pretty sure tyre pressures are not specified for a reference temperature, they are specified for rested ‘cold’ tyres. It doesn’t matter if it is -2c or 35c, it’s the pressure in the tyre that matters. So they need adjustment if the ambient temperature changes significantly. Using the chart to adjust from the recommended pressure could put them dangerously underinflated in the cold or overinflated in the heat.

 

[Gaston aires]

Question. If you deflate a bit for a softer ride, how do you stop the warning light on a Fiat dashboard? we have sensors fitted.
Phil

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[peterc10]

Question. If you deflate a bit for a softer ride, how do you stop the warning light on a Fiat dashboard? we have sensors fitted.
Phil

Phil,

I wondered that too. It turns out you need some clever software on a pc which plugs into the OBD port. Our son had it all and he changed the settings. Trouble is he has got a new job in Australia now so I am stuffed if I want them changed again

 

[Gaston aires]

Phil,

I wondered that too. It turns out you need some clever software on a pc which plugs into the OBD port. Our son had it all and he changed the settings. Trouble is he has got a new job in Australia now so I am stuffed if I want them changed again

Can’t you pay for his flights home ? Then he can fix yours followed by mine
Phil

 

[kevenh]

I am pretty sure tyre pressures are not specified for a reference temperature, they are specified for rested ‘cold’ tyres. It doesn’t matter if it is -2c or 35c, it’s the pressure in the tyre that matters. So they need adjustment if the ambient temperature changes significantly. Using the chart to adjust from the recommended pressure could put them dangerously underinflated in the cold or overinflated in the heat.

Ambient temperature affects the cold tire pressure. Cold tire absolute pressure (gauge pressure plus atmospheric pressure) varies directly with the absolute temperature, measured in kelvin.

I don’t find pressure and temperature and tyre physics simple so go by this assumption: -
Temperature of the environment AND how recently the car was driven does matter when you check tyre pressure.

So, If I adjusted my tyres’ pressures on the last warm October day when the vehicle was unused and parked in shade, I’d have an ambient temperature of 15deg C and a tyre temp of 12DC
Going out now, with the vehicle at the same spot but with -1 deg c temps I find the tyre pressure are lower but I’m not putting in more pressure.
Minutes after starting a journey and the tyre is “working”, the tyre temperature and pressures are back at expected parameters.

Edit: also, it wasn’t me that greyed the 18deg c column and row. I’ve seen the same indicator on other tyre pressure v temperature charts.
But This one jumps in 5deg C steps and has 20deg C as it’s T Nominal

The tyre pressure marked on tyres is the “Cold inflation pressure”. Which sounds a vague term for our ever changing outside temps

 

[Dorset Diver]

I have also got the Lidl pump which I use to top up my rear air bags, but there’s no way it will get my rear tyres up to 70psi even from 60psi.

Mine works just fine. Maybe there are different models, although I don't think it would get to the 150psi they say.

 

[Hugoman]

I don’t find pressure and temperature and tyre physics simple so go by this assumption: -
Temperature of the environment AND how recently the car was driven does matter when you check tyre pressure.

So, If I adjusted my tyres’ pressures on the last warm October day when the vehicle was unused and parked in shade, I’d have an ambient temperature of 15deg C and a tyre temp of 12DC
Going out now, with the vehicle at the same spot but with -1 deg c temps I find the tyre pressure are lower but I’m not putting in more pressure.
Minutes after starting a journey and the tyre is “working”, the tyre temperature and pressures are back at expected parameters.

Edit: also, it wasn’t me that greyed the 18deg c column and row. I’ve seen the same indicator on other tyre pressure v temperature charts.
But This one jumps in 5deg C steps and has 20deg C as it’s T Nominal
View attachment 696716
The tyre pressure marked on tyres is the “Cold inflation pressure”. Which sounds a vague term for our ever changing outside temps

So is this saying that if you put 80psi in they would be fine if the temperature was 20°C but 3psi over inflated if the temperate went up to 30°C. So you should put 77psi in if you are going to be mainly travelling in places that are 30°C

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[Lenny HB]

So is this saying that if you put 80psi in they would be fine if the temperature was 20°C but 3psi over inflated if the temperate went up to 30°C. So you should put 77psi in if you are going to be mainly travelling in places that are 30°C

Adjust mine as and when needed often adjust them on route if starting off in the UK at 5° and then arriving in Spain at 25°. Having a Tyrepal means you can keep an eye on them.

 

[Reallyretired]

On my car the built in tpms puts up a low pressure warning if its really cold even though the pressures are correct. It disappears after a little driving as the tyres warm up.

 

[Peregrinator]

I use tyre pressure sensors, some times while driving on very hot days it can go up ten PSI, so I always stop and let air out.

 

[Hugoman]

Adjust mine as and when needed often adjust them on route if starting off in the UK at 5° and then arriving in Spain at 25°. Having a Tyrepal means you can keep an eye on them.

Hmmm….so what psi do you reduce them by for the 20°C difference….presumably 7psi

 

[Lenny HB]

I set them for my normal cold pressure where I am. e.g. If i start off in the UK at 5° and the tyres are at say 70psi and I arrive in Spain in at 25° and the tyres are now at say 75 psi when cold I reduce them to 70 psi. I'm not that pedantic would probably only do it if they were a bit more out than that.

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[Richard J]

So is this saying that if you put 80psi in they would be fine if the temperature was 20°C but 3psi over inflated if the temperate went up to 30°C. So you should put 77psi in if you are going to be mainly travelling in places that are 30°C

That's one way of doing it but it would be better to set to 80psi at 20deg rested tyres, then recheck and adjust to 80psi when the (resting) temperature is higher (30deg in your example) That saves you doing calculations and you know you are correct. Basically what Lenny says.

 

[BobilG600]

I carry a foot pump. Having had two 12v pumps go pop and fed up trailing a cable around through the doors or windows to access all the tyres, not to mention the need to have a suitably rated cigarette lighter socket, I went back to basics. It works, just takes a bit of excercise.

 

[Hugoman]

That's one way of doing it but it would be better to set to 80psi at 20deg rested tyres, then recheck and adjust to 80psi when the (resting) temperature is higher (30deg in your example) That saves you doing calculations and you know you are correct. Basically what Lenny says.

Yes but on the tyre it says 113 (which is 2300kg across the axle) at 80psi (Michelin Agilis Camping that is). It doesn’t give a temperature. People say when cold but what’s cold 20°C or 5°C.

Also are we saying that rested tyre pressures go up on their own when the temperature changes. In Lenny HB ’s case he is saying he puts in 70psi when the temperature is 5°C and when he arrives in Spain where the temperature is 30°C his resting tyres are suddenly 75°C so he lets them down. Is that correct ?

I think “when cold” is the confusing thing. It’s not really when cold its 80psi at the rested temperature of the temperature you happen to be in which now I’ve written it is the same thing.

Lenny HB so what axle weight at the rear do you run on. I know I am sounding a bit obsessed but I nearly died this year going over a viaduct when the tyre blew . Their was lots of screaming from er indoors as well….which was more frightening than the tyre blowout.

 

[Richard J]

Yes but on the tyre it says 113 (which is 2300kg across the axle) at 80psi (Michelin Agilis Camping that is). It doesn’t give a temperature. People say when cold but what’s cold 20°C or 5°C.

Also are we saying that rested tyre pressures go up on their own when the temperature changes. In Lenny HB ’s case he is saying he puts in 70psi when the temperature is 5°C and when he arrives in Spain where the temperature is 30°C his resting tyres are suddenly 75°C so he lets them down. Is that correct ?

I think “when cold” is the confusing thing. It’s not really when cold its 80psi at the rested temperature of the temperature you happen to be in which now I’ve written it is the same thing.

Lenny HB so what axle weight at the rear do you run on. I know I am sounding a bit obsessed but I nearly died this year going over a viaduct when the tyre blew . Their was lots of screaming from er indoors as well….which was more frightening than the tyre blowout.

"Cold" tyres are when they have been stationary for a couple of hours or more. When the vehicle is driven the tyres heat up and so the tyre pressure increases ( See here ). But all the pressure recommendations are for "cold" tyres so don't bother measuring the tyre pressures when they are "warm".
If you live more than a mile or two from where you need to top up the air the tyres will have warmed up so then you have a problem! To get around that I suggest checking the pressures at home, then if when you get to the garage if the pressures are higher adjust your target pressure accordingly (ie 70psi at home, 74 at the garage, target 80, inflate to 84psi). That's just my application of logic as no-one ever really addresses this little problem!

 

[kevenh]

Yes but on the tyre it says 113 (which is 2300kg across the axle) at 80psi (Michelin Agilis Camping that is). It doesn’t give a temperature. People say when cold but what’s cold 20°C or 5°C.

Also are we saying that rested tyre pressures go up on their own when the temperature changes. In Lenny HB ’s case he is saying he puts in 70psi when the temperature is 5°C and when he arrives in Spain where the temperature is 30°C his resting tyres are suddenly 75°C so he lets them down. Is that correct ?

I think “when cold” is the confusing thing. It’s not really when cold its 80psi at the rested temperature of the temperature you happen to be in which now I’ve written it is the same thing.

Lenny HB so what axle weight at the rear do you run on. I know I am sounding a bit obsessed but I nearly died this year going over a viaduct when the tyre blew . Their was lots of screaming from er indoors as well….which was more frightening than the tyre blowout.

the chart has nominal, ambient air temperature at 20°C
If you're in the UK and 80psi pressure at 20°C is spec'd but it's only 10°C where your vehicle is, then 77psi is the adjusted tyre pressure yy

edit: i picked the UK for the location as 20°C is rare for us ain't it

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[Richard J]

the chart has nominal, ambient air temperature at 20°C
If you're in the UK and 80psi pressure at 20°C is spec'd but it's only 10°C where your vehicle is, then 77psi is the adjusted tyre pressure

edit: i picked the UK for the location as 20°C is rare for us ain't it

The charts are interesting as they illustrate how much your tyre pressures can be off target when the temperature changes. But in practical terms they are not relevant; it is the pressure in the tyre that needs to be kept to target and that is achieved by increasing or decreasing the amount of air in the wheel following changes in the ambient temperature to achieve the target pressure.

 

[BouncyBoatFolk]

I use tyre pressure sensors, some times while driving on very hot days it can go up ten PSI, so I always stop and let air out.

I would have assumed that the tyre manufactures took into account that the pressure would de/- increase in normal usage, and have built the tyre to accommodate for those variations. By the time you have stopped and done a lap of the van adjusting the pressures they will have fallen back to near the setting you run at .
Mike.

 

[Lenny HB]

Also are we saying that rested tyre pressures go up on their own when the temperature changes. In @Lenny HB ’s case he is saying he puts in 70psi when the temperature is 5°C and when he arrives in Spain where the temperature is 30°C his resting tyres are suddenly 75°C so he lets them down. Is that correct ?

Basically yes they will be much higher when driving, I always let them rest for at least an hour after driving.

@Lenny HB so what axle weight at the rear do you run on. I know I am sounding a bit obsessed but I nearly died this year going over a viaduct when the tyre blew . Their was lots of screaming from er indoors as well….which was more frightening than the tyre blowout.

Front axle 1930kg, Rear axle 2300kg, tyre pressures Front 56 PSI, Rear 69 PSI, got the pressures from the tyre manufacturer, I have Toyo Observer Van fitted a winter tyre I run all year round.

 

[Nirvanauk]

Does anyone actually put 80psi in their tyres.

 

[Hugoman]

Does anyone actually put 80psi in their tyres.

Well I didn’t used to but following a blowout I looked into it a bit. A Michelin Agilis Camping states 113 at 80psi. 113 equates to 1150 kg on each tyre so 2300kg across axle. My rear axle runs at 2200 (went to a weigh station yesterday). Each .5 bar or 7psi takes 100 kg off each tyre so 200 kg across axle. So the minimum I should run at is .25 bar or 3.5psi under maximum….so 4.75 bar or 76.5psi. Seems high to me but don’t want another blowout. Only alternative is to run at a lower rate on rear axle (difficult as have a scooter in rear garage) or buy something like Michelin Cross climates which somehow run 113 at 65psi. Will do that when my existing ones wear out.

The blowout by the way caused tread to completely come away from the tyre and rip through my garage floor causing £4,300 worth of damage !

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[Hugoman]

Basically yes they will be much higher when driving, I always let them rest for at least an hour after driving.

Front axle 1930kg, Rear axle 2300kg, tyre pressures Front 56 PSI, Rear 69 PSI, got the pressures from the tyre manufacturer, I have Toyo Observer Van fitted a winter tyre I run all year round.

My blowout was on a Toyo

 

[vkr15s]

Well, its just arrived courtesy of Prime and it had better be right as its the wife Christmas present.

Bought the wife a bike one Xmas,she asked what do I need that for. Christmas was not the same after I told her I was selling her car

 

[Paulypaul]

I must admit, I'm a bit over cautious with tyre pressures but that's probably due to operating a truck.

I've been doing some different work these last few weeks running loads weighing 28 ton, so grossing 44t. The first load I did made one of my outer drive axle tyres look like it was flat and the truck handled like it was on jelly. After checking the tyre, it was 10 psi down from its normal 100psi. With lighter loads (boats) I wouldn't have noticed, but with a heavy load it looked well dodgy!

It just shows how critical correct pressure is, regardless of ride comfort, which is predominantly down to the suspension set up.

 

[BouncyBoatFolk]

Well I didn’t used to but following a blowout I looked into it a bit. A Michelin Agilis Camping states 113 at 80psi. 113 equates to 1150 kg on each tyre so 2300kg across axle. My rear axle runs at 2200 (went to a weigh station yesterday). Each .5 bar or 7psi takes 100 kg off each tyre so 200 kg across axle. So the minimum I should run at is .25 bar or 3.5psi under maximum….so 4.75 bar or 76.5psi. Seems high to me but don’t want another blowout. Only alternative is to run at a lower rate on rear axle (difficult as have a scooter in rear garage) or buy something like Michelin Cross climates which somehow run 113 at 65psi. Will do that when my existing ones wear out.

The blowout by the way caused tread to completely come away from the tyre and rip through my garage floor causing £4,300 worth of damage !

Ouch . I tend run 75 in the rears, as we have the scooter with us as well
Axle 2240. Probably using about 2100 of that. The fronts get 65. Michelin camping tyres.
Mike

 

[Hugoman]

Ouch . I tend run 75 in the rears, as we have the scooter with us as well
Axle 2240. Probably using about 2100 of that. The fronts get 65. Michelin camping tyres.
Mike

Yep that’s what I’m going to go with. I’m running 2180 of 2200 and that’s with six bottles of wine and a crate of beer in the garage. Obviously can’t throw those out.

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[Peregrinator]

Yes but on the tyre it says 113 (which is 2300kg across the axle) at 80psi (Michelin Agilis Camping that is). It doesn’t give a temperature. People say when cold but what’s cold 20°C or 5°C.

Also are we saying that rested tyre pressures go up on their own when the temperature changes. In Lenny HB ’s case he is saying he puts in 70psi when the temperature is 5°C and when he arrives in Spain where the temperature is 30°C his resting tyres are suddenly 75°C so he lets them down. Is that correct ?

I think “when cold” is the confusing thing. It’s not really when cold its 80psi at the rested temperature of the temperature you happen to be in which now I’ve written it is the same thing.

Lenny HB so what axle weight at the rear do you run on. I know I am sounding a bit obsessed but I nearly died this year going over a viaduct when the tyre blew . Their was lots of screaming from er indoors as well….which was more frightening than the tyre blowout.

Just think 80psi, forget temperatures, just 80psi will do. you can get Solar Wireless Tyre Pressure Monitoring System Sensors for around £18.00 on ebay, with these readings you know if you need to pump or release air when needed, it's what I have, and it's one of the best items I have bought, just put's my mind at ease.