Tire PSI

Hey, what PSI do you guys run your tires at? I have michelin ps4s with stock 18 inch tires and my door sticker says to run at 30psi f and 37 psi r. I was going through some of the older posts on the forum and I see a lot of confusion about the psi, and how .2 models have a recommended pressure closer to 32 psi for front and rear. Should I just stick to what the door jams say or is there an optimal pressure you guys have found?

I have 987.2 and door has 30 and 31 psi.

did your car come with 18 inch wheels or 19 inch wheels?

18, but now I have 19 and running 30 and 31

My 987.1 w/19” wheels says 30-37 on the door sticker.

I'm on 18s and start out at 32. On a hot day, after the tires warm up, they get up to 36/37. On rainy days, they tend to settle at 34. I'm in the tropics and avg temperature is 33* C. High humidity and sea level. This is higher than what the door sticker prescribes but I find my pressures better for my day to day use and it helps lift the car that little bit more to help with the front lip which has already seen too many scrapes.

987.2 Base 2.9 L here in the tropics of Malaysia … On my door sticker, I think for 19s, its labelled as 34/32 (Front/Rear). But I usually top-up with 35/33 as I like my PS4s a wee bit firmer!

its weird that the .1 and .2 caymans seem to have different recommended psi's even if by only a little bit, considering they don't have any drastic changes in suspension. Is this a sign of maybe porsche learning through the years of development and revising their numbers?

almost didn't recognize your account there with a new profile picture lol

I think you've got that flipped: 987.2 with 19s is 32 front 34 rear cold. With the roads around here I don't go higher as I'd probably chip a tooth.

There's a difference in pressures for 987.1 and the later cars. Never heard anything but that it's a bad idea to mix them up. I don't know what Porsche changed in the suspension. Follow the door sticker though you might find the car more neutral with an extra psi or two in the front. Plenty of old threads about this for both street and track from when the 987.1 was new.

Thanks for the tip @Greywolf ! You mean follow the door sticker PSI recommendation for the rear, but add an extra psi or two for the front? What does "neutral" mean on our 987.2 Caymans? I love the steering feel as it is!

Having a 987.1 myself I've never looked into optimizing the 987.2 . I'd suggest trying the threads from when the 987.2 was new. The cars typically have a slight bias toward understeer. A little extra pressure in the front tends to balance it. It was suggested back when I went looking back in 2008 and I liked it a bit better. Not that the car was bad to start with. Tire choice may effect this too.

Have to admit I do not have the driving expertise to tell the difference between neutral and under-steer on my 987.2 … But I will try 1 PSI more in the front this weekend, and keep it to the label on the rear! Feedback to follow ….

I've heard and now starting to see for myself that my (recent new) PS4s get greasy and don't like too high psi when hot. Probably 36f/42r max hot. My PS4s will increase about 6 psi during aggressive driving in the summer when it's hot. and it's true that to balance out the inherit understeer, you should increase the front psi and/or decrease the rear. I run 33/35 cold on normal days and bring down it to 31/33 cold in summer when it's a hot day. Invest in a good gauge so you can trust your pressure numbers.

Thanks for tip … Yes, will try 33 or 34 / 35 this weekend! Hmmm, never thought of buying a good gauge to check for tyre pressures … My wife already thinks I am spending too much time (and cash!) with my "other wife" so this may be tricky!

Bad Bay? The MG is 50 yr old engineering at best. We had a new MGB in 64. It was fun but now they are better enjoyed at car shows. 30/31 is working well for my 19" Bridgestone 's

That's a Fiat 124 spider with a Lampredi twin overhead cam, dual brake reservoirs, discs on all four corners and OEM Michelin or Pirelli . I used to prey upon every MG I could find when I was a younger testosterone lad. The Fiat was faster period but I tuned mine up every few weeks as practice for all the other ones I did to help keep food on our family table. When it was points , condenser , plugs and timing that was a considerable edge. We had a Champion spark plug cleaner, it was used a lot! My best memory was crushing this rich big mouth from high school, not only was his car slower but his shifting was atrocious. He later keyed my car like the little ___tch he was, my first lesson about winning the battle but losing the war. Here's the history for those interested. From the article: the Fiat twin-cam was on a par with a Porsche 911T in terms of its power-to-litre ratio. Not bad for a humble little four-pot that also powered more pedestrian family fare such as the Fiat 125. https://tinyurl.com/yytnytba My favorite MG was the TD

I realized I hadn’t checked my pressures in a while, and the weather’s gotten a lot cooler, so I checked it yesterday and I was at 27 front, 31 rear. I inflated to 31 front, 34 rear.

Oh forgot to add I am on 18” Conti DSW’s

The owner's manual for my 987.1 indicates that the recommended tire pressure for cold tires for 19" wheels is 32psi front and 36psi rear.

Something to consider is that it’s easier for a manufacturer to update a sticker on the chassis than it is to reprint a 500 page owners manual. Does your manual differ from your door sticker?

The door jamb sticker only indicates the recommended cold tire pressure for 18" wheels (30psi front and 37psi rear) and to see the owner's manual for additional information. It is in the owner's manual that I found the recommended cold tire pressure for 19" wheels (32psi front and 36psi rear).

I also have 18” rims and MPSS and occasionally track car. I saw on Robert Mitchell Apex channel on YouTube goes through tyres they use including MPs4s. He explains these Mitchelins have soft sidewalls hence they run higher pressure. For my car I ran at pressure where could no longer feel any sidewall deflection through steering on turn in. I usually use around 34 to 35 psi cold and it will heat up to about 38/39 and my lap times were good.

'09 987.2 base with 18" PS4S for street is 30F/32R cold. Wonderful tires . AutoX 19" RE1R at 30F/35R. Sticky but SO noisy. YMMV

My 2006 Cayman S calls for 32 front/37 rear, but as has been mentioned, that's because the factory wanted the car to have more understeer. My 2015 Boxster S calls for even pressures all around, and I run 33 psi, which seems fine on the 20" PS4's I'm running. In the Cayman , I typically reduce the rears to 35 psi with the fronts at 33 psi.

With a few days under my belt now, just daily-driving 987.2 Base PDK … 34/35 (F/R) seems to feel really good on my 19" PS4's. Have a safe day, forum-buddies!

987.2 have different DFI engines to the 987.1 . Perhaps they are lighter hence lower rear pressures.

It’s taken me 5 years to conclude that…