EVERY Subaru I’ve owned since 2002 has had this 2lb difference between front and rear. It’s for safety according to subaru reps and engineers. It adds additional understeer. In my autox days i’d run 5lbs over front in the rears and you can really feel the handling difference. For rallyx I’d run equal pressures. For everyday driving I follow that placard with an extra pound. So if it says 35f 33r I’d fill them to 36f 34r. With a proper alignment, rotations with balance the tires seem tol last for ever following the posted pressures.Subaru has reason to specify 35 front, 33 rear.
Is not just "comfort".
Running them high like that long term will only cause uneven tread wear to the center of the tires. Otherwise you won't feel any ride or handling difference.Took delivery of our '18 last week and noticed the tires were reading 42psi on the display. Gauge checked them cold and indeed they were about that. The placard shows 35 for both front and rear. It wasn't riding rough or anything but I lowered them to 38psi for now. Might take them down to 35 after reading this thread.
I see a 2 - 3 pound increase in the pressure readout after driving for 20 min. So far (on city streets and highways) it hasn't gone above that even after several hours of highway driving.I've always wondered what the difference is in operating temperature when a tire is warmed up on the highway. Setting "cold" pressure at a fixed value means a big difference in the amount of air in the tire depending on the ambient "cold" temperature. Those of you who live in northern climes know what I mean: tires set at the recommended cold inflation in the summer will give you a TPMS warning when the temperature goes sub-freezing in winter. A warm-day setting of 32psi can drop to the mid-20s psi when it gets cold outside!
The pressure in a tire is going to rise linearly according to the actual (absolute!) temperature (Boyle's Law and all that), which means that if the difference between the cold and warmed-up temperature is greater in the winter than in the summer, the tire will actually be running on the highway at a higher pressure. Maybe I'm OCD about this and the difference isn't of any concern, but I think about it every time I adjust my tire pressures seasonally.
(I don't currently have a car with a numeric TPMS readout, which would help solve this issue for me.)
When you do the math, the temperature rise is very close to 1 psi per 10 degrees F. The placarded (cold) tire pressures take this variation into account. I just set the tire pressures seasonally, adjusted to the typical expected morning-start temperature. If you're really OCD, you can consult National weather Service/NOAA climatological data for your area.The pressure in a tire is going to rise linearly according to the actual (absolute!) temperature ...