Tyre pressures and temps.

[Hutch]

Got away from RMK, (Rural Milton Keynes) on route to Gwithian, Cornwall, With a stop at Peak view cl site Rooksbridge, BS26 2UA. FSP, £18 . Just south of Sedgemoor services. Lovely little local pub 10 minutes walk from the site.

Left RMK and watching the Tyre pal, left home both tyres at 64 psi and 17 ⁰c( doesn't happen often) once out of RMK and on straight road I noticed the tyre pressures were matched at 71 psi but the left tyre was showing 22⁰c and the right 24⁰c .

As we went through rain the tyre pressures matched, also the tyre temps matched with the 2 ⁰c difference. ie 69 psi, and 20 ⁰c /22⁰c.
Checked the next day,,and the reading matched the day before, the tyre pressures matched The right hand Tyre was 2⁰c above the left.

All I can think of is my cars exhaust is on the right hand side of the car. Giving the rise in temperature.

Anyone else noticed this.

 

[RogerL]

It may be a minor difference in brake shoe clearance - or minor differences in the TPMS battery state of charge.

 

[toad a caravan]

Hutch,are you stopping in Cornwall?

 

[Buckman]

Could be a variation in the compounds in the tyre as have noticed this on many occasions even with the tyres on the car?

 

[Beardy]

Could be a variation in the compounds in the tyre as have noticed this on many occasions even with the tyres on the car?

Is it easier to spot with the tyres off the car?

 

[Beardy]

All I can think of is my cars exhaust is on the right hand side of the car. Giving the rise in temperature.

Anyone else noticed this.

I doubt that its relevant in your case, but I've noticed a slight difference in pressure when the car has been parked with the sun on one side for a couple of hours. (I don't have temperature monitoring).

You do have quite a significant change in pressure though, 10 degrees C is supposed to change the pressure by 1 to 2 PSI, you're seeing much more than that.

 

[Hutch]

I doubt that its relevant in your case, but I've noticed a slight difference in pressure when the car has been parked with the sun on one side for a couple of hours. (I don't have temperature monitoring).

You do have quite a significant change in pressure though, 10 degrees C is supposed to change the pressure by 1 to 2 PSI, you're seeing much more than that.

I have always noticed a change in pressure of 5 to 7 psi cold to running, but never noticed a difference in temps. Except if the sun is on one side, it's just that every thing was identical before setting off.

 

[Hutch]

Hutch,are you stopping in Cornwall?

Yes, we are at Gwithian Farm caravan site, 3 miles from Hale , until 29th.

 

[Dustydog]

Yes, we are at Gwithian Farm caravan site, 3 miles from Hale , until 29th.

You devil! Only a spit from the Red River🍺🍺🍷🍷

 

[Hutch]

You devil! Only a spit from the Red River🍺🍺🍷🍷

Pitch 3, less than 100 yards.

 

[Sam Vimes]

Never ceases to amaze me that for years we managed without such devices and now we have them we get worried over the small variations that have probably always occured.

 

[ProfJohnL]

We seem to lulled iso easily into a false sense of security when anything is "digitally controlled"

The differences reported in this thread might all be within the equipment's specified limits of accuracy.

 

[RogerL]

We seem to lulled iso easily into a false sense of security when anything is "digitally controlled"

The differences reported in this thread might all be within the equipment's specified limits of accuracy.

I recall doing some consultancy work in the '80s for Otter Controls, who made fixed temperature thermostatic switches for the car industry - the switches couldn't be made with any level of consistency so every single one was tested and calibrated with wealthier car makers paying a higher price for a smaller range variation and the mass manufacturers paying a lower price for a much wider temperation variation.

Whilst I imagine the equivalent modern product has smaller numeric variations I'd expect the principle to be the same.

 

[ProfJohnL]

I recall doing some consultancy work in the '80s for Otter Controls, who made fixed temperature thermostatic switches for the car industry - the switches couldn't be made with any level of consistency so every single one was tested and calibrated with wealthier car makers paying a higher price for a smaller range variation and the mass manufacturers paying a lower price for a much wider temperation variation.

Whilst I imagine the equivalent modern product has smaller numeric variations I'd expect the principle to be the same.

We were a customer of otter, and visited their buxton premises many times during 80's and 90's on product development. A great company to work with.

Even so ,if the sensors are selected, there will be a range conformance which some may be at the top and others at the bottom, and in the instances reported it's been a combination of temp and pressure which means each senor has to produce two different values, So pressure reading could be bottom range, and tem could be top range in one sensor and reversed in another, yet all fall within the designed range for the product.

Couple manufacturing tolerances, and the other variables such as solar heating, generally rougher roads near the kerbside, water, etc, etc ,etc and it is far from rare to find different wheels on a car produce un equal self heating and pressurisation after driving.

 

[Sam Vimes]

I've noticed that if my car is on a slope, side to side, then despite the air pump reaching the same pressure, when I drive off there's a difference.

 

[AndrewAventura]

With TyrePal, pressure is sensed quite directly by the device and should be quite a good indication of the 'real' pressure. They state an accuracy of +/- 1.5 psi, which seems pretty good to me. And means that you should try to be entirely relaxed about indicated pressures within 3 psi of each other.....
But I've always doubted whether the temp measurement is particularly relevant. Different parts of the wheel, tyre and air inside it will be at different temperatures, and the tyrepal sensor is in fresh air, just connected by the valve stem to the wheel. So its probably measuring the temperature of itself, and probably quite a bit cooler than the tyre once you're underway. Since generally I find the pressure increasing by about 6 psi after a while towing, that implies that the air inside the tyre has heated up by about 20 deg C, whilst in the same condition the tyrepal device might show an increased temp of about 10 deg C. So I'd say - don't pay any attention to the tyrepal temperature reading (unless it goes completely mad).