Variable recommended tire pressure?

[jchadwell]

I had the first autocross on Saturday and took the opportunity to monitor tire pressures with both the car display and my gauge. Sometimes the two were right on while other times they weren't. Don't really car about that but I did notice the car's recommended inflation pressure changed throughout the day. At one point it was showing front recommended at 41 lbs and rear at 40. It previously said 39 lbs for both which I never really understood either since the official recommendation is 38.

Any thoughts/comments? Any one else have this happen?

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[XtremeMaC]

Perfectly normal. You'll see Supra adjusting recommended pressure, 39 psi, when it's cold as well.
TMPS and your gauge are not calibrated/adjusted and may even lose on significant digits...

 

[freeform911]

So is the recommended pressure we should be running? Or do we still have a target temp for the tire (oem super sport)?

I had to replace my front left after 1 track day ( roughly 4-5hr track time) do to outer shoulder wear...
My pressures were 38-40 a still had to much rollover...
Car kept recommending higher pressure?

TIA
Steve

 

[TimM.]

I’m commenting without researching this first but I’ve seen the different recommended tire pressures with each new engine start. Since we don’t have the typical Toyota tire pressure reset button that locks in a pre-set reference tire pressure, I believe the computer is using tire pressure at engine start to set the reference tire pressure. I think the algorithm is looking for an average tire pressure and also calculating if one or more tires has a pressure disparity of a certain percentage, let’s say 5 or 10 percent higher or lower than the others.

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