Propper air pressure for the 911

For clarification, the book said 36 front 40 rear for the 18 inch. The gas lid says 36 for all size 18. The tire says 50 max. Wondering what you Porsche lovers run? Thanks.

The car's light and sidewalls are thin as is, I often run 30 F / 36 R on nothing-special Yokohama V601's. Different tires will want different settings, you just have to play with it. Up or down gives a different balance of steering response, handling bias, tire wear and fuel economy.

OK, i know less air pressure usually has a softer ride. I will try this and maybe lower the pressures and compare. I don't want to do harm to the tires etc. Thanks

I run 34F and 36R on my C4 . Works for me with 18 " wheels .

I run exactly what Porsche suggests.

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44 and 36 by my book. Also I see on my rear tires the manufacture date as, Rear has letters and #s ending in R3217;. I'm thinking that is the year 2017? The front is different, 4224, the year would be 2024?

The date stamp has a little raised oval border with just 4 numbers for week and year. So this one is week 27 2019. If you don�t see one, it may be on the inside sidewall. A marking with mixed letters and number is not it.

Yeah, the book says 36/44 for the 8/10 18s. Tire sidewalls and compounds have improved substantially over the last 25 years. It all depends on the tires you run, purpose and set-up. On the street, depending on the tire, I may run anywhere between 32-34F and 34-38R depending on wear and handling characteristics. But I like a stiff sidewall tire, so I have more sidewall support and feel of the road. If you run a soft sidewall tire, you may need a little more pressure. You can always start at 36-44 and then make adjustments down. Part of the fun is making the adjustments and setting up the feel and characteristics that you want. For sure, safety first. Make sure your tires aren't aged out. And get yourself a good tire pressure gauge and check the pressures. Especially on cold days when pressures can drop.

Needed tirepressure can be calculated if you know load on tire or axle 99% acurate, and have the tire-specifications. the most tricky part, and your responcibility Also need the max speed used, and wont go over for even a minute. If that is higher then allowed, natures law requires the higher pressure for that, you cant fool mother nature. Tire-specifications are given on sidewall , and responcibility of tire-makers. If you give those of your tires, this " pigheaded Dutch selfdeclared tirepressure specialist " can make a cold pressure axleload list with build in maximum reserve at wich comfort and gripp is still acceptable. For that I give 90% of calculated axleload for the cold pressure ( at 20 degrC/ 68 degr F ) , for max 160 kmph/ 99 mph, wich then is max speed to use. if you want for higher speed , write it, and I will make for that speed, but comfort and gripp gets lesser then. Need next from your tires, read from sidewall 1. Maximum load or loadindex 2. Kind of tire to determine the reference-pressure Porches most likely have XL tires, with referencepressure 42 psi. ​​​3.speedcode to determine the reference-speed. not that important here, above Q speedrated referencespeed is 160 kmph/ 99 mph. For reference-speed and -pressure the maxload is calculated, and given on sidewall. Porche and BMW give on tpms screen beside the pressure of all 4 tires, per axle recomended pressure for the setting, calculated from an index-temperature of 20 degrC/ 68 degrF ,to the temperature of gascompound in tire. so if cold measured at 100 degrF , gives higher recomended on screen . Then compare the pressures of each tire given, with that higher pressure, and dont need to do recalculations yourselves.

I'm running Michelin PS4S on heavy GT3 wheels. Pressures are at 34F & 42R. In theory, when I'm driving on the highway, the tires will heat up and the pressure will go up to 36/44. I don't know that this makes a difference as it is a detail beyond my driving skill. I certainly can feel when they get lowered to 30/38. i prefer the stiffer feel with the higher pressure.

Quotes source post: 20227954

Well, the 25 year old tire pressure recommendations don't really 100% apply to new 2025 tire construction and compounds. Also, the application usage is the determining factor for me on our 996 cars. Going autobahn speeds, pushing hard, needs the highest pressure. Tooling easy around town under 60mph, with no added load other than me and maybe a passenger, needs minimum pressure for comfort, handling, and tire wear longevity. My TPMS also registers tire heat. if your TP is not right, tire heat will rise substantially... Lower pressure like I run at slower speeds makes for incredible grip when pushing less than <10/10's... Always check/fill/adjust with cold tire, in morning before first drive. I run,,, around town easy top down cruising <66mph.... 28psi in front 225/40 18 tw200 _32 psi in rear 285/30 18 tw200 I run on highway cruising >66mph.... 32 front & 36 rear I find these pressures are comfortable and provide good even tire wear at OEM alignment specs, and a perfect tire balance job. If you look at this tire pressure/load calculator on a site I frequent, you can check your needed air pressure. on a early 996.1 C2 the tire front load is around 500-550lbs on rear its 1000-1100lbs. My tires are rated at full 50psi front 1402# rear1629# https://www.engineersedge.com/calcul...load_16251.htm

[QUOTE=jayzbird;20228559]The date stamp has a little raised oval border with just 4 numbers for week and year. So this one is week 27 2019. If you don�t see one, it may be on the inside sidewall. A marking with mixed letters and number is not it. [/QUOTE my rear must be on the inside. I�ll check, thanks!

Quotes source post: 20228446

Contrary to your 1st post, your manual and sticker do state the same pressures: 36 psi for 18" front and 40 psi for 18" rear. There's the answer to your question... BTW, change your Boxster size rear tyre to a 996 size tyre and put a cap on your tyre valve.

Quotes source post: 20229399

A little annoying when someone tries to tell a poster they are wrong when they are also. That fuel door sticker does not state 40 PSI. Boxsters never used a 255/30/18. 996s did come with a 255 when equipped with a 17" wheeel.

Quotes source posts: 20229473, 20229399

True but where's your contribution to answer OP's question?.. On a friendlier note: My bad, I missed the 44 on the sticker and couldn't be bothered to check 18" rear tyre spec on a Boxster (turns out it's not 255 either but always wider). Yes, 996 got 255 on a 17" but not on 18". Anyway, I found pointing out the 255 width to OP, worthwhile, since he is new to the 996, based on his questions in this and other threads he's started.

Sorry for any confusion, the car is not a Boxter, it is a 2004 911 Carrera. I did misplace the stem cap but found it...

After driving the past two days I am going to lower the standard pressure 3 lbs. I feel too much of the road. It will be interesting to see any difference.

Quotes source post: 20230611

No confusion. The previous poster was commenting on your rear tire size. It is not a standard size on 18" wheels for either a Carrera or Boxster. Stock sizes for a 2004 would be 285/30/18 R 225/40/18 F.

I do appreciate clarification! I don�t understand where this confusion came from? Those tires are stock size, stock & standard are the same?

Quotes source post: 20231077

Yes they absolutly are. The only thing @hardtailer mentioned that you are guilty of is not having your valve cap in place.

Guilty as charged, very observant!

I have the 18" Carrera wheels on my 2003 Targa and I run 44 psi rear, 40 psi front. Bumpy roads rattle the whole car but takeoffs and cornering are quick and nimble. Gas mileage averages around 18 mpg in mixed use.

Fwiw, running higher tire pressures than what is recomended reduces the contact patch. Be careful at highway speeds and corners with so much pressure in the fronts.

Quotes source posts: 20231111, 20231077, 20229399

It looked very much like 255, as you can see, zoomed in on your initial picture. That's what triggered my remark regarding wrong rear tyre width. This time I'll ask instead of assumming from what I think I see on your pictures: Is that an all-season front tyre (... 92W M followed by '+S') whilst at the rear it is not?

To add further confusion to this, check your pressure with 3 different gauges and I bet you will get 3 different readings. Which one is right??? Get a really good, quality tire pressure gauge, only use that one, and keep it in the car. Set the pressures to the door jam recommendations and go from there. If you start to see signs of premature wear in the middle, you have too much pressure. If you have premature wear on the outside, you haven't been running enough PSI. Also check this out www.tiresize.com Tons of info in there for all things related to tires, pressures, wheels, offsets, etc, etc...That has been one of my favorite websites over the years and always my go to when I'm looking for tires to compare specs. Most of my car life has been in the off-road world and it has a tire pressure calculator which when switching from one type of tire to another, IE, P tire to LT tire, is very helpful.

I reduced all the tires 3 lbs from what the car calls for. I really enjoy the ride better.

Quotes source post: 20233736

Nice. It's always amazed me how little it takes to change the feel of this car. I played around with pressures as well when I first bought the car. Then I changed from 17" to 18" GT3 wheels and started all over again. And then again when I put on coil-overs. These cars are infinitely adjustable!

Quotes source post: 20234432

For sure.

I started this season at the book pressures 36/44 (cold) on Continental ExtremeContact DWS 06 Plus tires. (Where do they come up with a tire name like "ExtremeContact"?). I experimented with lower pressures I think I found bottom for this tire at 29/33. When entering corners in spirited driving there is a decided sensation like the sidewalls rolled. Once that initial lateral slide transition is over, she's riding on rails. At higher pressures there is nothing but a hooked up feeling. I'm going up 3 lbs. I posted that I installed the Schrader TPMS a few months ago. I do the readout through CarPlay, but you can just use your phone. When you're wondering about tire pressure, I am happy to report that it is extremely reassuring to peek at the numbers. This is the first tpms system that tells you pressure and tire temp - in Montana at 90 mph and 90F it's just a good feeling to know that side slide thing is possibly all in my head. The group of guys I do drives with are an absolute blast. We had a 2014, 1973 1/2, my 996 and you can see the other brothers. At stops we had kids with their mom tell us we had the coolest cars, so one guy let the kids sit in his. Then a sheriff deputy pulled up and said he hopes to have a 911 someday. At the last place we stopped everyone was loving on our machines. All on a blue bird, glorious fall day. So fun!

I always ran what my car�s spec said (located on the driver side door), which is 36F/44R on my 99 Cab C2 and had good results. Glenn is right: if you overinflate, traction can drop off fast.