TPMS Temperature Reading

[betoney]

For those that have a TPMS, is it normal to have a large difference between front and rear temperature?  Everything with the TPMS seems to be working fine, I set the cold pressure at 36F/38R and operating pressure raised about 10% as expected. 

Throughout the day the pressure and temp raised and lowered ever so slightly but the rear was always reading about 12 - 20 F warmer, regardless if I was charging through corners or cruising along @ 60mph with the cruise set, is this normal?

[SKYFLIX]

Looks fairly normal to me. There's more rubber back there, doing a lot more work. My FOBO TPMS usually indicates about 15-20 degrees warmer on the rear of the 'wing. Don't have one on the Tracer yet.

[Tango]

Good info... glad you guy's posted above. I received my SYKIK unit last week and and waiting on the steel T valves.

[Stew]

I don't have such things. But it is logical that the rear would be hotter than the front, it is doing more work, pushing you forward.

[Shizzle]

Lots of things can affect the tire temp. If the sun is on the back tire instead of the front the readings will be different also. Rear tire is more exposed to sunlight where the front is more shaded by the fender. I wouldn't be concerned about it. 

[betoney]

@SKYFLIX and @Stew - that makes sense but my thinking (logical or illogical?) was while holding steady with cruise on (not hard acceleration) that the F and R should be closer in temp. 🤷‍♀️  Glad to hear that it is reading normal. 👍

@Tango - I really like the Sykik unit though I have nothing else to compare it to, it tells me the exact basic info I need without tons of bells and whistles.  One thing to note for when you get yours installed, (this was my first TPMS so I didn't know this) it will hold the current pressure and temp when you stop until you move again, even overnight.  When I parked the bike for the night it read 100F and the next morning it was cool and raining yet it still read 100F, I thought it was malfunctioning... until I rode out of the driveway and it updated.  Silly me. 🙄

[Stew]

I'd crash from watching it all the time   If you are still unsure about it you could switch the 2 valve bits around of course, but I'd put money on it giving the same results. Of course, you could do a 100 yard stoppie and see if the front gets hotter while the rear cools down!

 

[SKYFLIX]

We're looking at Ideal Gas Law here. Which basically states P1*V1/T1 = P2*V2/T2 where P is pressure, V is volume, and T is temperature. Have you ever noticed that both tires basically increase the same amount of pressure on a long ride? If the tires temperatures both increased the *same*, then the overall pressure increase would be LESS on the rear tire than the front, owing to the fact that its VOLUME is greater. But that's not what we observe. The overall increase in pressure as we ride is usually the same, front and rear. The rear tire's temperature increases MORE than the front, compensating for the increased volume and therefore making the overall pressure increase the same.

Forgive me physicists if I oversimplified this. Been almost 3 decades since I was in school.

[betoney]

19 minutes ago, SKYFLIX said:

We're looking at Ideal Gas Law here. Which basically states P1*V1/T1 = P2*V2/T2 where P is pressure, V is volume, and T is temperature. Have you ever noticed that both tires basically increase the same amount of pressure on a long ride? If the tires temperatures both increased the *same*, then the overall pressure increase would be LESS on the rear tire than the front, owing to the fact that its VOLUME is greater. But that's not what we observe. The overall increase in pressure as we ride is usually the same, front and rear. The rear tire's temperature increases MORE than the front, compensating for the increased volume and therefore making the overall pressure increase the same.

Forgive me physicists if I oversimplified this. Been almost 3 decades since I was in school.

Thanks for the physics lesson 😄  I'm more of a caveman mentality, "constant pressure, good... dropping pressure, bad". 👍

Seriously, your explanation DOES make sense.

[Stew]

It's an education on here, right

Cheers @SKYFLIX

[Tango]

2 hours ago, Stew said:

..... Of course, you could do a 100 yard stoppie and see if the front gets hotter while the rear cools down!

 

🤣 🤣

[Tango]

1 hour ago, SKYFLIX said:

We're looking at Ideal Gas Law here. Which basically states P1*V1/T1 = P2*V2/T2 where P is pressure, V is volume, and T is temperature. Have you ever noticed that both tires basically increase the same amount of pressure on a long ride? If the tires temperatures both increased the *same*, then the overall pressure increase would be LESS on the rear tire than the front, owing to the fact that its VOLUME is greater. But that's not what we observe. The overall increase in pressure as we ride is usually the same, front and rear. The rear tire's temperature increases MORE than the front, compensating for the increased volume and therefore making the overall pressure increase the same.

Forgive me physicists if I oversimplified this. Been almost 3 decades since I was in school.

Wow 🤯... that's a lot of arithmetic there.

So doe's this mean I should or shouldn't have to change the air in my tires at every other oil change? 😉

[SKYFLIX]

With P being pressure, and t being the time between oil changes, then the equation is F=P/t*0.8

With F being the amount of ***** given.

[Stew]

Now I'll be worrying the next time I'm out on the bike if I've got enough f's in the tyres (tires)

[BBB]

2 hours ago, SKYFLIX said:

Forgive me physicists if I oversimplified this. Been almost 3 decades since I was in school.

You’re forgiven 😁. It’s a good enough explanation of volume/pressure/temperature relationships. Much easier than arguing frictional forces, tyre wall flex, contact patches, viscoelastic forces in tyre composition etc etc.