Porsche_nuts

Everytime I check my tire pressure display while driving, the left rear tire lags. My tires are set cool at 32F 36R. As the tires heat up, they move to around 38F and 41R, however what usually happens is the two fronts usually show 38 around the same time, but the backs show 41 left and 39 right. Eventually, the rear right reaches 41, but wondering why it lags behind so much. Does this happen to everyone?

ieatfishburritos

Curious what the time differential is between the two rear tires reaching temps? Is it a 1-3 minutes?

Are you driving a specific route each time which may have more turns in one direction etc?

Both tires have similar age?

I'd imagine there is a scientific reason.

Al.Fresco

My guess is its a "partial lb" and also a bars to psi conversion issue. If you watch the tire pressures increase on the multi function display, there are certain psi numbers that never appear because the conversion from bars to psi eliminates a psi number here or there. As an example, you will not see a 40. So if your RR starts close to a half lb lower when cold (effectively showing the same on the MFD as the LR because of conversion rounding), I can see your situation happening as the tires heat up to "tweener" pressures like between 39 and 41. I would pump a half lb into your RR and see if it closes the gap in time that both rears jump to 41.

LexVan

I suspect the left rear tire has "wetter" air in it. Has that tire even been plugged or patched? Or re-filled or topped off with an air hose?

bkrantz

Or maybe a slightly tired battery in the RR pressure sender?

Jabs1542

This ^^^^

Someone wrote about this in detail in an older thread, and the conversion is bars to psi. He went through all of the math (the issue is the rounding on the initial pressure data in bars). In psi it ends up skipping numbers like 37, 41, 45, etc.

Al.Fresco

Not sure what I was thinking.... C to F...of course its bars to psi...thanks for the correction. My only defense is I just came back from a week in London, so the C to F conversion must have been on my mind when typing. I edited my original post so as not to confuse others who initially read it.

asia

TPMS accuracy +/- 1 psi typical according to manufacturer. If you see a 2 psi left to right difference, check again a few minutes later. On my car such differences so far have been short lived.