High Tyre Pressures On New Boxster

[Guest]

Hi all,

I have been enjoying my first Porsche and Boxster for a couple of months now and over 2000 miles, after having the car from new. But I must confess and hang my head in shame as despite checking oil and water levels yesterday was the first time I checked my tyre pressures! [&o]

The car had been idle for about 24 hours in the garage when I checked the tyre pressures and I had a bit of a shock, the front tyres were ~37psi and the rears ~43psi. I immediately checked the owner's manual and it seems to say 29F/36R, regardless of wheel/tyre size (I have 18" wheels), confirming that indicated on the petrol filler cap.

I have had no ill effects (as far as I know) from running these "high" pressures, in fact the road holding has been phenomenal. I didn't want to lower the pressures too much in case they had been set to 37/43 for a reason so I lowered the pressures to a couple psi above the recommended pressures (31F/38R) and went out for a short drive around some "twisties". Far from scientific but the car seemed to handle the more or less the same, could have been my imagination but it felt a bit "softer" through some corners with more "roll".

I have had the car from new, any idea why the OPC would stray from the pressures in owner's manual? Or perhaps this is some "in transit" level and the OPC failed to lower the pressures prior to delivery?

Though I have searched a number of forums on the web, and discovered this on a US forum:

Factory recommends 29/36. Peter Smith on the PCA tech section indicates they set their customers with 18 in wheels at 36/44. Sez it handles better.

Has anyone heard of setting 18-inch tyres to 36psi front and 44psi rear?

Thanks,
Mark

 

[Mark_Bennett]

perhaps this is some "in transit" level

This seems to be the most likely scenario. Prevents the tyres from "flat-spotting" whilst the car awaits it's new owner.

The OPC should have re-set to factory settings - it is interesting that the Porsche Club America chap says different - those pressures look more like 911 pressures! The Boxster is better balanced than that - it does not have that huge lump of engine hanging out the back and therefore causing a need for higher pressures in the back tyres.

You will see here that a 2lb difference front to back is often advocated here by the Boxster Register long-termers (especailly for track work) I prefer a 3lb difference, slightly less tail happy. This would be 33F/36R.
However there is debate over whether an insurance company would have an issue with tyre pressures that are "not to manufacturers recommdations". That call is up to you.

Glad you like the car - It gets better and better!

 

[IainCameron]

Mark,

Do you have Michelin Pilot Sports fitted? [8|]

If you have Michelin Pilot Sports there is a warning printed into the side wall that stipulates that the tyre MUST NOT be inflated beyond 40 psi or damage will be done to the carcass. It also says that specialist tyre fitters (trained?) should be used to install the tyre to the wheel. I guess this is because the person fitting the tyre can easily over-inflate it while it is being installed (remember the loud POP you hear when in the kwikfit shop. See photo attached and open the pic to see detail of warning. [&o]

 

[Guest]

Checked the pressures on my brand new S after reading this - virtually the same issue - over 40psi both front and rear (tyres are P Zero Rosso's). Reduced them to c. 36 rear and 32 front (what I used on the previous 2.7) and it seems OK.

Regards

 

[Guest]

Thanks very much guys []