Recommended Tire Pressure

[rhregis]

In the owner's manual Porsche recommends rear and front tire pressures, do these tire pressures apply for all tire sizes? I am confused since inside the gas tank cover the tire pressure recommended is aligned with a particular tire size. Any input will be appreciated Thanks.

[Q-Ship986]

In the owner's manual Porsche recommends rear and front tire pressures, do these tire pressures apply for all tire sizes? I am confused since inside the gas tank cover the tire pressure recommended is aligned with a particular tire size. Any input will be appreciated Thanks.

Porsche has numerous tire/wheel fitments for the Boxster. The owner's manual may cover many/all of these (for your model year), since the manual is inserted into a given Boxster with any one of these combinations.

My manual, for 2003 models, says to use Porsche-approved tire sizes (consult dealer) and use 29 psi front and 36 psi rear, regardless of size.

The sticker on the fuel door may be more specific to your vehicle. It may have just your size, or it could include others.

Check your tires to determine if the proper sizes are fitted front and rear. Follow the pressures recommended on the fuel door for that size (which should also correspond to same recommendations listed in the owner's manual). Let us know if there is a conflict or if you have a question about the proper fitments.

--Brian

[rhregis]

Thanks for the response Brian. That is where the confusion originated, I checked the owner's manual and it recommended the tire pressure you listed, but when I checked the fuel door it had a column for rear tire sizes and one for front tire sizes and the only tire size that had the 29/36 psi pressures were 205/50 r17 and 225/45 r17 respectively. I guess the question is do the pressures listed apply to all the tires listed on the fuel door? Thanks, Raul

[Q-Ship986]

Thanks for the response Brian. That is where the confusion originated, I checked the owner's manual and it recommended the tire pressure you listed, but when I checked the fuel door it had a column for rear tire sizes and one for front tire sizes and the only tire size that had the 29/36 psi pressures were 205/50 r17 and 225/45 r17 respectively. I guess the question is do the pressures listed apply to all the tires listed on the fuel door? Thanks, Raul

Well, I guess I'd like to see your sticker to fully understand where the confusion originates.

This is mine (2003 986S):

This sticker lists numerous tire sizes/types, depending on what came as standard equipment (the ZR17 tires), optional equipment (the ZR18 tires, standard on my S), or special equipment (i.e. the 17" and 18" M+S tires). Your sticker may vary, depending on model year among other things.

All the road tires listed on that sticker above are to be set to 29 psi (front) and 36 psi (rear) respectively. (The temporary spare is an exception, which is to be set to 60 psi.) This also corresponds to the information provided in my owner's manual.

If your sticker looks like mine, is it possible that you are interpreting the table to mean that 29/36 applies only to that very row of tires? In other words, are you looking at it like this?:

(Red box added for emphasis.)

If that's how you are reading it, I see your confusion. The table above is correctly interpreted by applying the pressures to the other rows of tires as well. Hope that helps.

--Brian

[rhregis]

Brian, thanks for going through the trouble of taking pictures and providing an in-depth explanation. I also have an MY 03 just like yours and yes I interpreted the sticker to apply to that particular row. Don't you agree (at least a little bit) that it could easily be interpreted to apply just to that tire size?

Once again thanks for the troubles.

Raul :clapping:

[jmatta]

Interestingly, there is a post on the PCA Tech forum regarding Boxster tire pressures. It states Boxsters running 18" wheels may follow the recommended pressures for the 996, which would be 36/44. Any comments out there? I am going to adjust mine to see what difference it makes.

http://www.pca.org/tech/tech_qa_question.a...B-14C71E506D95}

Edited July 26, 2006 by jmatta

[mickf]

Interestingly, there is a post on the PCA Tech forum regarding Boxster tire pressures. It states Boxsters running 18" wheels may follow the recommended pressures for the 996, which would be 36/44. Any comments out there? I am going to adjust mine to see what difference it makes.

http://www.pca.org/tech/tech_qa_question.a...B-14C71E506D95}

The higher pressure will make the handling feel more crisp and the ride more firm, both due to less sidewall flex. It may also decrease grip though. IMHO, for best handling try rear in mid-30s and front a couple psi higher than the rear. I believe the 29 psi front specification is designed to ensure understeer, which is easier to recover from than oversteer should you get out of shape.