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45 psi in tires on Forester from factory?

My Forester is 3 months old and going in for free first oil change Wed. In checking wife's tires today I checked mine and found the G900 Yokohoma Geolanders to all be at 45 psi. Thought gauge was defective and checked with 2 others and got same reading - wife's tires were 32 lb as expected on her Nissan. Dealer says maybe all three of my guages defective! No harm anyway since only result would be higher mileage. I'm not letting air out until I see him Wed. and have a little tete-a-tete ;) Frank

Reply to
Frank Logullo
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Reply to
Edward Hayes

I used to work at a Subaru dealership a couple years ago. It was very common for the cars coming from the factory to have 45+ PSI. Part of the "pre-delivery inspection" is checking/setting tire pressure. Don't know if they still do or not, but when I was working in the dealership, the tires even have BRIGHT green stickers on them stating something to the effect of "Dealer set tire pressure" Sounds like whoever did the PDI on your vehicle didn't do a very good job of it.

Reply to
someone

Thanks for the comments. Don't know who I spoke to at the dealership but it was not the service manager. I'll set them straight tomorrow and have them reset pressures. Car has been fine. It replaced '98 Forester that was totaled in an accident, but ride not any smoother than '98. Maybe this will improve it. Frank

Reply to
Frank Logullo

Checked my '03 Forester after the first week at home and all four tires were at 38psi, which is about 10psi higher than they should be. (Yes, I checked the tires cold.) I don't think changes in ambient temperature could account for this much difference in tire pressuer. I suppose they could have filled it to 29psi when it's way below freezing.

-R.

Reply to
Richard Chang

oh yeah, it will be smoother, no doubt, but expect to wallow around a bit more too as you get reintroduced to sidewall flex!

i run 42 psi (cold) in all 4 corners of my wrx. treadwear is BETTER than at stock suggested numbers, which are ridiculously low imho.

jm2c ken

Reply to
Ken Gilbert

Reply to
Edward Hayes

P1/T1 = P2/T2 is more like it. Your formula would have the pressure

*decreasing* as the temperature increases.

If you assume a pressure of 29.3 lb/in^2 at a temperature of +20 C (+68 F), his calculation of 1 lb/in^2 increase for every 10 degrees C increase is right on. And it agrees very nicely with my experience in checking tire pressures at various temperatures (front tire pressure for my 1997 Legacy Outback is 29 lb/in^2).

David

Reply to
David or Jo Anne Ryeburn

No, I start with gas law which is PV=nRT. I never remeber the differences between Boyles and Charles law (which is which). T of course is in degrees Kelvin (-273 deg. C). Since the volume of the tire is essentially constant, and n and R are constants for the same gas the ratios of temperature and pressure reduce to: P1/T1=P2/T2 Frank

Reply to
Frank Logullo

Reply to
Edward Hayes

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