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Touring Van Tyre Pressures & TyrePal


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I recently fitted Tyrepal TPMS valves to my tourer. I inflated tyres to recommended PSI and set low and high pressure alerts on the sensors. After setting off and into my journey I noticed the tyres heated up considerably and hence the tyre pressures increased dangerously close to the high pressure alert on my Tyrepal sensors. I was amazed at how hot the tyres got and the increase in tyre pressure. So much so, I stopped and deflated the tyres back to manufacturers recommended pressures and set off again. For the remainder of my journey the tyre pressures stayed at the recommended pressure. Was this the correct thing to do as the pressure was obviously correct for the temperature of the tyres but I guess would have been significantly lower if the tyres has been cold. One thing I learnt from this was the effect on caravan tyres in relation to the increase in heat and pressures during the journey and I would not have been aware of this if Tyrepal sensors had not been fitted. Can anyone provide advice on whether I did the right thing reducing the tyre pressures mid journey, thank you. Robbie

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The temp of the tyre can go up by quite a large amount. I had them fitted to my old van on a journey from Birmingham to Portsmouth the temp went up by   10 degrees the pressure went up by 15 psi . a ferry trip of 8 hours and a 5 mile journey to the campsite. Three weeks later when I was about to return BOTH valve stems had developed a leak. The fitter that came to my rescue thought that the stems were to long so fitted shorter ones These were still on when I sold the van

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Recommended tyre pressures are based on cold tyres, accepting that they will heat up during a long run. Adjusting them hot will result in them being too low when cold. This will, in fact, result in more heat build up.

You should however get your brakes checked to ensure that the heating is not due to them binding.

Edited by Stevan
typo
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The classic test for correct pressures (after over night rest is best) is to set them cold then check them again after at least 20 miles (when fully heated up). If the pressures rise by less than 4 psi the pressures should be reduced sightly, if they rise by more than 4psi they should be increased.

This negates any errors due to the gauge used or ambient temperature. This has almost always confirmed that the recommended pressures is correct on both my cars &  caravans.

It does require some effort but it only has to be done once to get the best pressures. Make sure you use the same gauge every time!

It's very noticeable that uneven side-to-side loading, on such as my 'van approx 50Kg+ heavy on NS),  raises the pressure more (by 1-2psi) on the heavy side.  I load the 'van with awning & spare wheel on OS to compensate.

 

3L auto Nissan Terrano, 2004 & Swift Elegance 530, 2018. As Leonardo da Vinci once said: 'If you find from your own experience that something is a fact & it contradicts what some authority has written down, then you must abandon the authority & base your reasoning on your own findings' ie: use your common sense!

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How hot were the tyres?

If tyre pressures should be set when the tyre is cold, why is anyone changing them when warm?

I suggest the op was wrong to reduce tyre pressure when they were hot.

 

Is there too much reliance on technology without understanding?

 

When ever I stop for a break or fuel having been towing, I check wheel and tyre temperature of car and trailer wheels. If any are hot, I have a problem. Excess heat could be a wheel bearing or brake binding.

 

I also let the engine idle if I have been towing as it is good practice for the turbo.

 

macafee2

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It may be worth checking the actual weight of your van.

I had just this scenario with my van, which I thought was lightly loaded.

After putting the van on a weighbridge and discovering I was well over the MTPLM, I now run the van almost empty, which brings me just below the MTPLM.

I now notice that the pressure increase and temperatures are much lower than previously.

My tyres specs are well within the weight of the van - even overloaded 😊😊

 

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1 hour ago, Stevan said:

Recommended tyre pressures are based on cold tyres, accepting that they will heat up during a long run. Adjusting them hot will result in them being too low when cold. This will, in fact, result in more heat build up.

You should however get your brakes checked to ensure that the heating is not due to them binding.

Thank you Stevan, I inflated to recommended pressure when cold and was worried when they went up to almost 70 psi when hot, hence why I reduced the psi but I’m also conscious of correct psi when setting off with cold tyres.  I’ll take on your advice regarding getting my brakes checked. Thank you. 

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To confirm other posts:

Tyre pressures should be set when cold.

Flexing and friction will cause the tyres to heat up and the air in the tyres to heat up and and because pressure, temperature and volume of gasses are related (Boyle's law from memory) the pressure will rise. 70psi doesn't seem excessive for a warm tyre.

 

Using Tyrepal I even notice that the side of the van in the sun on a long journey in the same direction has higher pressure/temperature than the side in shade (black tyres are excellent at absorbing radiated heat from the sun).

All quite normal. 

However, as has been mentioned it is a good idea to check wheel temperature from time to time. Depending on the amount of braking the wheel can get quite warm but if it is very hot after normal towing I would suspect a problem.

Most likely brake bind, but can be wheel bearings if they are totally shot.

 

Under inflation is usually much more dangerous than a similar amount of over inflation. Many blowouts occur because of underinflation and excessive flexing and heat due to a relatively slow puncture rather than as a direct result of the puncture itself.

 

Hmmmm - I wonder if Tyron bands have ever been discussed on this forum?................;)

 

Edited by Ukzero
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27 minutes ago, macafee2 said:

How hot were the tyres?

If tyre pressures should be set when the tyre is cold, why is anyone changing them when warm?

I suggest the op was wrong to reduce tyre pressure when they were hot.

 

Is there too much reliance on technology without understanding?

 

When ever I stop for a break or fuel having been towing, I check wheel and tyre temperature of car and trailer wheels. If any are hot, I have a problem. Excess heat could be a wheel bearing or brake binding.

 

I also let the engine idle if I have been towing as it is good practice for the turbo.

 

macafee2

 

27 minutes ago, macafee2 said:

How hot were the tyres?

If tyre pressures should be set when the tyre is cold, why is anyone changing them when warm?

I suggest the op was wrong to reduce tyre pressure when they were hot.

 

Is there too much reliance on technology without understanding?

 

When ever I stop for a break or fuel having been towing, I check wheel and tyre temperature of car and trailer wheels. If any are hot, I have a problem. Excess heat could be a wheel bearing or brake binding.

 

I also let the engine idle if I have been towing as it is good practice for the turbo.

 

macafee2

I can’t remember the temperature (it was a while back) but the pressure rose from 55 to 69. If my memory serves me right, I wasn’t  too  concerned about the temperature (I think that was fine) it was the psi rise that concerned me. You’re right about adjusting the psi when wheels are hot, that’s why I felt uncomfortable about doing it but the significant rise in psi meant I felt I had to do it. I truck for a living so it’s common nature for me to check tyre heat whenever I stop. I do remember touching the tyres and they felt fine and they was no smell of burning or binding brakes that is associated with overheating brakes, but the Tyrepal reading of 69psi was what worried me. I am also confident the running gear was fine, as I know through experience when brakes are binding etc, however, you’re right and I will get them checked just to be sure they’re alright. Thanks for your comments, much appreciated.

33 minutes ago, AlwynMike said:

It may be worth checking the actual weight of your van.

I had just this scenario with my van, which I thought was lightly loaded.

After putting the van on a weighbridge and discovering I was well over the MTPLM, I now run the van almost empty, which brings me just below the MTPLM.

I now notice that the pressure increase and temperatures are much lower than previously.

My tyres specs are well within the weight of the van - even overloaded 😊😊

 

Hello Alwynmike, thanks for your response. My van was under the MTPLM as I weight it each time I go out with my portable scales but I might go to a weighbridge to confirm my scales are accurate, thank you👍

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7 minutes ago, Robbie McCabe said:

 

I can’t remember the temperature (it was a while back) but the pressure rose from 55 to 69. If my memory serves me right, I wasn’t  too  concerned about the temperature (I think that was fine) it was the psi rise that concerned me. You’re right about adjusting the psi when wheels are hot, that’s why I felt uncomfortable about doing it but the significant rise in psi meant I felt I had to do it. I truck for a living so it’s common nature for me to check tyre heat whenever I stop. I do remember touching the tyres and they felt fine and they was no smell of burning or binding brakes that is associated with overheating brakes, but the Tyrepal reading of 69psi was what worried me. I am also confident the running gear was fine, as I know through experience when brakes are binding etc, however, you’re right and I will get them checked just to be sure they’re alright. Thanks for your comments, much appreciated.

Hello Alwynmike, thanks for your response. My van was under the MTPLM as I weight it each time I go out with my portable scales but I might go to a weighbridge to confirm my scales are accurate, thank you👍

 I was only suggesting more why I check my wheels and tyres for heat, not that this is the reason for you rise

 

macafee2

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Found this on the internet, says pressure should rise up to 5psi more than cold reading...we used to own a high performance Corvette, and we never saw more that 5psi increase in pressure in normal road driving, but slightly more when we took it on a track...which is expected due to higher speeds...

 

Change in tyre pressure while driving

As the tyres deform on the road as they turn, it creates resistance and some of this is turned into heat. This causes the air in the tyres to expand and it increases the pressure by about 1 PSI for every five minutes up to a maximum of between 4-5 PSI.

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3 hours ago, Robbie McCabe said:

That’s exactly about the same that mine went up by, almost 70psi 🥴

So, if your tyre was say 45psig cold, and they rose by 70psig, that means they were 115psig (45+70). At that pressure they would have exploded off the rim.

Do you mean they rose to 70psig?

You have not said what the starting pressure was.

The above posts that mention a pressure rise of c 4psig are correct. If they are a lot more than this, there is something wrong.

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Our Mini has tpms and you can watch the pressure on the go. Hard driving gives max 3-4psi rise no more.

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My tyres cold are 44psi, most tows throughout the summer saw them rise to 49/50psi.

 

I just set the parameters and forget it, if there is a problem it will let me know as it did once, mines a TyrePal TC215B.

Stay safe - Griff.  :ph34r:

Wheels at the front - Discovery 4. Wheels at the back - Bessacarr 845.

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As well as seeing what the pressures are with Tyrepal, check it with a pressure gauge, it is possible the Tyrepal is not accurate in your case and might have a fault. To go from 55 psi to 69 psi the temperature rise would need to be around 60°C  so possibly going to 75° if the cold temperature was 15°C (calcs have to be done using absolute values if anyone is checking).

 

Is it possible you misread one of the values and the pressure rose from 55 to 59 psi or from 65 to 69 psi which would seem normal going by comments from others ?

Edited by Paul1957
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I set mine on my Pegasus at what it says in the book cold and never check them again until the next trip ! Never had a tyre problem yet ?  Some years ago i was a mechanic on a car racing team, the cars were standard production models , so we had to use the original size and type as the cars came out on. The book pressure was 30lbs, to soft for racing.

We used 60 and 65 lbs (cold ) in a 500 mile race . Never did check them hot, but man they got hot. Only had to replace the LF in the race as most of the corners were RH. Never blew a tyre in 6 or 7 years of racing, did replace some because of wear of course. I do feel some people worry needlessly about some aspects of caravaning ? Not trying to be rude please !

 

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23 hours ago, daveat92 said:

So, if your tyre was say 45psig cold, and they rose by 70psig, that means they were 115psig (45+70). At that pressure they would have exploded off the rim.

Do you mean they rose to 70psig?

You have not said what the starting pressure was.

The above posts that mention a pressure rise of c 4psig are correct. If they are a lot more than this, there is something wrong.

Hello daveat92, yeah they rose to 70psi. Starting pressure was 55 and went up to 69.  All these comments etc are great and gives me options now, particularly if I’m doing something wrong, misreading things or have faulty Tyrepal sensors. Once lock form has lifted I’ll be out checking . Thanks Pal

19 hours ago, James Donald said:

I set mine on my Pegasus at what it says in the book cold and never check them again until the next trip ! Never had a tyre problem yet ?  Some years ago i was a mechanic on a car racing team, the cars were standard production models , so we had to use the original size and type as the cars came out on. The book pressure was 30lbs, to soft for racing.

We used 60 and 65 lbs (cold ) in a 500 mile race . Never did check them hot, but man they got hot. Only had to replace the LF in the race as most of the corners were RH. Never blew a tyre in 6 or 7 years of racing, did replace some because of wear of course. I do feel some people worry needlessly about some aspects of caravaning ? Not trying to be rude please !

 

You’re not being rude James and you’re right. I never once worried about my tyres before fitting the sensors. I’d inflate whilst cold before setting off, check torque settings and set off. 20-30 miles into journey I’d check again and then check each time I stopped for a rest break. Now all I see is a reading rising steadily which gets me worrying. I’m gonna get you the bottom of this though. Many Thanks Pal.

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My tyres on my current 1500Kg  Swift set at 64psi and  rise to 70psi with a temperature increase of around 6*C. As per previous posts the temperature can vary quite a bit between the two sides especially when combined with the effect of the sun. The Swift stays fairly steady between the sides but a previous Lunar was always around 3*C higher on the offside even though the layouts are similar i.e.offside kitchen, rear bathroom. I like tyrepal and find it an excellent piece of kit especially on long continental trips, our current batteries have lasted over 7000` since purchase three years ago and so far the system has performed without fault.

 

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My tyres are 65psi cold, I've seen a rise of 10psi on hot days but in the wet sometimes no rise at all.

I was quite surprised to see how much the pressures and temperatures can change, even during the same journey.

 

I wouldn't worry about pressure increases, your tyres should be checked cold and are designed to heat up. For me the tyrepal's real value is warning of a puncture.

 

 

 

 

 

 

 

 

Hymer 545 Luxusline hauled by Audi SQ5 plus.

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My caravan 65psi (specified pressure at mtplm) tyres regularly exceed 70psi, even approached 80psi towing in 35deg in Southern France. That sort of pressure increase is within their specification. The key is to have the correct cold pressure at the outset.....and not exceed the mtplm.

 

In contrast, my BIL had two blowouts en route to Spain.... because he ‘didn’t know his tyres should be 64psi’ (despite having a plate on the side of his caravan). He put 45psi in them as he thought 10psi more than his car was enough.

Edited by ericfield
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On 29/11/2020 at 15:49, Robbie McCabe said:

I recently fitted Tyrepal TPMS valves to my tourer. I inflated tyres to recommended PSI and set low and high pressure alerts on the sensors. After setting off and into my journey I noticed the tyres heated up considerably and hence the tyre pressures increased dangerously close to the high pressure alert on my Tyrepal sensors. I was amazed at how hot the tyres got and the increase in tyre pressure. So much so, I stopped and deflated the tyres back to manufacturers recommended pressures and set off again. For the remainder of my journey the tyre pressures stayed at the recommended pressure. Was this the correct thing to do as the pressure was obviously correct for the temperature of the tyres but I guess would have been significantly lower if the tyres has been cold. One thing I learnt from this was the effect on caravan tyres in relation to the increase in heat and pressures during the journey and I would not have been aware of this if Tyrepal sensors had not been fitted. Can anyone provide advice on whether I did the right thing reducing the tyre pressures mid journey, thank you. Robbie

No you certainly didn’t. Adjusting tyres when hot is totally wrong. You have effectively reduced the pressure below the recommended pressures (always specified and set when cold). Reducing the tyre pressures below the recommended level increases side wall flexing, thus increasing tyre temperature and escalating the process risking a blowout. Caravan tyre pressures can easily increase 10+psi without risk provided you haven’t overloaded the caravan beyond its MTPLM.   Just set your Tyrepal limits higher

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