TPMS lessons in Thermodynamics
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Gives us a clue as to how much F1 Tyre pressures change over the course of a race weekend.
Now we can see why we were taught to check and adjust tyre pressures when cold back in the 70's!
PobodY
MB Enthusiast
It also shows why making a lot of fuss about the cold pressure is a waste of time. - Give it 30 minutes and they're nothing like where you set them.
Near enough is good enough.
Near enough is good enough.
Thanks. Very happy with the hardware - good, if not top, build quality and solid feel to every part. I did remove the frivolous top stickers, and painted the inside tops of valve caps in the same colour, as my wheels, but that's the only thing.
The app, on the other hand, is far from perfect - it takes a couple of minutes to get info from all the wheels, when it fired up for the first time (gets faster later, as I suspect it runs in the background for a certain period of time). I now open it up, leave it on, and go around the car for visual inspection, by the time I'm done, I have all four wheels "spinning", i.e. connected to BLE transmitters in the valves. I can live with that arrangement. The app was also greatly improved with the last update, so there's hope. There are some funny bugs, like the voltage checkup, for the batteries in the valves, comes up in Chinese, thankfully 2.9V is all I need to know
This is the same type as I bought (select Internal Sensors) - the actual kit doesn't show up anymore (bought mine in Nov 2017):
Newest Universal TPMS Bluetooth Android/iOS Phone Auto Tire Pressure Monitor 4 Sensors IN/EX Bluetooth Low Energy Alarm Care-in Tire Pressure Alarm from Automobiles & Motorcycles on Aliexpress.com | Alibaba Group
It's simple gas laws. Pressure is proportional to temperature but you have to use absolute temperature.
This formula calculates the temperature increase required to increase tyre pressure from 2.0 bar to 2.1 bar
(-1+273)*(2.1+1)/(2+1)-273 = 8 Deg C.
This formula calculates the temperature increase required to increase tyre pressure from 2.0 bar to 2.1 bar
(-1+273)*(2.1+1)/(2+1)-273 = 8 Deg C.
Stratman
MB Enthusiast
I suspect the front temperature being higher after a drive is more to do with the front brakes doing about eighty percent of the braking. My car is rear wheel drive yet the fronts are much hotter than the rears after a drive too.
Gbrowncls55
MB Enthusiast
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Mine adds about .2 to .3 bar cold to hot. which is a little more than yours. 19 inch rims.
The % temperature increase in a tyre is a useful measure of whether the cold pressures were correct in the first place. Without knowing the exact figure there will be rule of thumb e.g. any increase of more than 15% tells you the cold pressure was too low. That's what the racers do except they are targeting a specific tyre temperature.
Steve84N
MB Enthusiast
I've noticed this over the years and purposefully adjust them if it's been a few weeks and the weather is notably warmer or cooler.
stephenmercedes
Active Member
I've used TPMS on my GT4 for about 10 years, and have been obsessed in the past monitoring temp/pressure. Especially fun when car parked with one side in sun, and the other in shade! Just fitted a dedicated TPMS on my 17 year old and I still get obsessed! Attached is after I just drove home after a 15 mile motorway run. Started cold at 33 front/37 rear.
