987 Boxster 18" Wheel Questions

[vincesf]

Originally Posted by Quickurt

my 06 Boxster S says 30 psi front/37 psi rear for the 18's.
I also run them at 28/36 for better wear pattern. They were wearing in the middle from over inflation.

I called my Porsche Dealer and they also stated that proper inflation on a 2008 Boxster S with 18" wheels is 30 psi front / 37 psi rear. I am going to look in my 2008 manual again. In regards to your '06, I also have a Boxster, Boxster S manual for 2006 and the recommended tire pressure for cold tires is 29 psi front / 36 psi rear. Looks like I should put more air in my tires as 26 psi front and 33 psi rear may be a bit too low, and am a bit puzzled as to why someone stated that 26/33 was the correct number as per the TPMS.
The differences between the sticker and the manual are rather trivial, but why can't Porsche at least be a bit more consistent? Different tire brands specify different psi's?
vincesf

[vincesf]

I went back to my 2008 owner's manual and found that the recommended cold tire pressure for 18" tires is 29 psi front and 36 psi rear. Those owners that have a sticker that references 18" tires and loading information on the inside of the driver's door jam tell me that the recommended cold tire pressure is 30 psi front and 37 psi rear, no problem as 1 psi is not a big deal, and there is also a reference to: "See Owner's Manual For Additional Information". What is confusing to me is that when my car was cold (not driven overnight), I manually checked the tire pressure with a tire pressure gauge, the tire pressure is 29 front 36 rear, and the Tire Pressure Monitor System read 26 front 33 rear or an alternative reading of -0- on each wheel, indicating perfect pressure. Driving the car about 5 minutes, the TPMS read 29 front 36 rear and again indicating perfect pressure -0- to be added at each wheel. Makes me believe that the TPMS is not completely accurate when the car has been sitting and cold, that the truer reading can be obtained after driving the car for 5 minutes to provide a "cold-operating" psi of 29 and 36.
vincesf

[renzop]

Remember TPMS did not come with early 987s. So depending where you got your 18" wheels they may not have the indents designed to hold the TPMS sensors. In that case fitting the 19" wheel sensors will be a pain.

[vincesf]

Originally Posted by renzop

Remember TPMS did not come with early 987s. So depending where you got your 18" wheels they may not have the indents designed to hold the TPMS sensors. In that case fitting the 19" wheel sensors will be a pain.

I imagine that could be an issue. Fortunately, these 18" wheels/tires came off a new '08 987S, and the TPM's are the same for 18" and 19" wheels/tires. The TPMS allows for a set up programming for both 18" and 19" wheels/tires. It's actually quite a nice system. Someday I need change my avatar, as my car is pictured with the 19" wheels/tires.
vincesf