Tyre pressures for road use

[bobrabagliati]

I recently had a new set of 4 x 18” Goodyear Eagle F1s put on my 13 plate Boxster 981. Once home I checked the pressures and found 32psi on the front and 37psi at the rear. I rang my Porsche specialist, who had fitted them, to ask if there was a good reason for inflating the tyres to these levels when the handbook states 29psi all round. He stated it was personal preference. The former set of tyres on my car were inflated to 29psi as detailed in the handbook. I don’t go on track days and use the car for normal Boxster touring. Is there any practical reason for running the car on tyres which are inflated higher than the recommended handbook levels? I would be interested to hear other views on this topic.

 

[Chappelle]

Personally I wouldn't deviate from the manufacturers recommended pressures, unless there was some issue with how the car drives. Over and under inflation will just cause more wear.

I have F1s on my 987. Liked them on other cars but less impressed on the Boxster. Steering feel and turn-in doesn't seem as good as when it had Bridgestones

 

[bobrabagliati]

I tend to agree that the manufacturer’s recommendations should be the default setting and I will stick to that unless something (like inferior handling) determines that I do something different. On my previous Boxster I replaced old and crusty Dunlops with Goodyear Eagle F1s and the contrast was very apparent in a positive way instantly. On that basis on my current Boxster I replaced old and crusty Goodyears with this new set of the same. The same result, instant improvement all round on handling, steering and ride. Thanks for your helpful comments.

 

[Motorhead]

Bob,

I’d agree that sticking with the Porsche recommended pressures is the best approach, although you may wish to change them slightly by experimenting to suit your driving preferences. If they’re Porsche N-rated tyres in particular, the development engineers will have chosen the pressures based upon the best compromise for steering feel, ride and handling, refinement (noise and harshness) and optimum tyre wear.

Jeff

 

[bobrabagliati]

Hey Bob

I would be interested in what you think of your Eagle F1,s compared to others you have tried

i had the same experience with my OPC, tyres were lower pressure compared to what I prefer, but really I find my pressures fluctuate depending on outside temperature +- a few psi

i check them before every journey bearing in mind my Boxster is not my day to day car, still under restoration in fact



Please see my comments in response to Richard Chappell. I inherited both my Boxsters from reputable sports car dealers with original old tyres on them. My understanding is that tyres degrade and become hardened and less pliable with age and should be changed, regardless of wear, at about 6 years. On the latest Boxster I tried to encourage the dealer to put new tyres on. He wouldn’t because they had a good level of tread left and he could not say if they were the original tyres. The cracking on the tread and the hardness of the ride indicated that in all likelihood they were over 8 years old and original. I can’t comment on other makes other than to say that the relatively new Dunlops I tested on a friend’s Boxster seem very much on a par with my new Goodyear Eagle F1s. You are right too that pressures do alter with use and temperature fluctuations. One other feature of the Goodyear tyres is their quietness on the road, which is a plus point. Thanks for your comments. Bob

 

[bobrabagliati]

Thanks Jeff. I agree with your comments and advice. Very helpful. Bob

 

[911hillclimber]

987.2, 2.9 used for touring, don't blast along UK roads.

Have Bridgestone Potenza RE 050 19" on my Boxster.

Drives great, though have no other experience of other Boxsters and tyres, it just works well.

Handbook pressures, Factory geo settings, all good.

IMHO you can mess about too much with these factors. Porsche spent a lot of time getting a set of pressures that give all you need as said above, so who am I to deviate from theses thinking I can do better?

The only factor I might question in the UK is the top speeds you may use.

I'm sure Porsche had a good eye to those who may well run max velocity where they can but also bounce around/over UK potholes, and run 70/80 mph max.(me)

I feel factory is best.

 

[malarcy]

Remember that the handbooks often mention pressure at a given ambient temperature and that a tyre warm from being driven will have a higher pressure than a “cold” one. Can make a few psi difference.

i Tend to use handbook figures which on my car are different front and rear and then Tweak slightly if needed Because if the above variance its a non exact science.

 

[bobrabagliati]

Thanks Paul. Very helpful. Bob

 

[Motorhead]

Bob,

Just to add to Paul’s comments, you could always consider a nitrogen fill which will help to stabilise tyre pressures under different ambient temperatures and driving conditions. [I’ll leave it to you to find out what people say about it!]

Jeff

 

[MrDemon]

you will get more MPG

but I run 29/33

 

[bobrabagliati]

I thought better mpg would be a bonus. What made you put 23psi in your rear tyres? Trial and error or something more scientific? Thanks. Bob