Tyre pressures... - Page 1 - 911/Carrera GT - PistonHeads UK

Can someone help me to decipher the tyre pressure plate on my 992.1 T wearing PS4Ss. Should I be looking at 34 & 38 psi for normal two person driving? But what on earth does the 0-165MPH mean? I guess that is the lower pressure values? What pressures do you run given the time of year and weather in the UK and the fact that I'm probably not going to be doing 165mph anytime soon.

My 911 handbook refers to 'comfort' tyre pressures - which are the low end of the door card pressures. That's what I run at as I rarely drive over 150mph. The car feels much less skittish at the comfort settings. But everyone has different thoughts!

Normal 2 person driving in the UK would be 30/32 psi. If you are intending to exceed 165mph then you should inflate to the 34/38 psi. I think the higher pressures are required at very high speed to avoid damaging the tyre & rim if you hit a bump or road imperfection - this could cause the sidewall to completely collapse

Decoding the Pressure Chart Two People (Light Load, Normal Driving): Front: 2.3 bar / 34 psi Rear: 2.6 bar / 38 psi This is your standard everyday setup — good for daily driving, normal speeds, and a light load. Two People + Luggage (Heavy Load): Front: 2.5 bar / 37 psi Rear: 3.1 bar / 45 psi This is for when the car is heavily loaded, like long trips with bags, or more weight in general. It keeps the tyres firmer for stability and safety. High-Speed Driving (up to 270 km/h or ~165 mph): Front: 2.0 bar / 30 psi Rear: 2.2 bar / 32 psi These lower pressures are for track or very high-speed driving, likely to increase grip as the tyres heat up and pressure rises. Not suitable for daily driving. That's what the "0–270 km/h" (0–165 mph) section means. So yes — you’re right in thinking this is a "track-focused" setting. UK Road Use & Weather Advice (PS4S, Autumn/Winter) Since you’re in the UK and unlikely to be pushing 165 mph, stick to: Front: 2.3 bar / 34 psi Rear: 2.6 bar / 38 psi Perfect for normal temperatures (10–20°C) and daily use. Tip: Tyre pressures should be measured cold (car not driven for ~3 hours or less than 2 miles at low speed). Personal Recommendations for UK (PS4S) Daily driving / dry conditions: 34 / 38 psi Cold weather (below 7°C), keep an eye on cold inflation: Consider bumping pressures up by ~1–2 psi if cold ambient temps cause your TPMS to alert. Spirited driving (road, not track): You can stick to 34 / 38 — PS4S warm up fast and work well. Tyres Listed on Sticker Your car supports: Front: 245/35 ZR20 Rear: 305/30 ZR21 You're on Michelin PS4S, which are excellent for mixed UK use (wet/dry performance).

I think the last post is unfortunately incorrect - I blame the confusing sticker rather than the poster. The pressures on the top half of the sticker are for all speeds including high speeds (I.e. all the way around the Speedo). The bottom half of the sticker is for speeds up to 165mph. For normal driving, I d recommend using the bottom left setting, I.e. 30/32 psi. I ve had my 992 for two years and found it very sensitive to tyre pressures, it can quite easily feel skittish and lose traction and grip if the pressures are any higher than the comfort setting.

Recomended tyrepressures are determined for load on tyre and max speed used. All to give tyre a deflection that wont overheat any part of tyre-material when driving the speed constantly for wich its determined. Thats main goal of tyremakers, but comfort and gripp are also important. The here 270 kmph is already high, mostly "normal use " pressures are for upto 160 kmph/ 99 mph, and axleloads determined by carmaker for 3 persons and a little load. Heavy use recomended is determined for Max Permissable Axle Weights ( on VIN-plate given) and max technical carspeed. Tyres with speedcode Q to V , maxload is calculated and given on sidewall for 160 kmph/ 99 mph, W 190 kmph, Y and (Y) for 220 kmph ( converse to mph yourselfes) And there is an official system for highening up the reference-pressure ( standard load 2,5 bar/ 36 psi, XL 2.9 bar/ 42 psi for higher max speed then that 99 mph. On that plate they assume people in Porches drive faster then 99 mph often, so dont bother to give that advice and give directly for 270 kmph. So if you are able to determine the axleloads in your use 99% acurate, you can calculate a pressure for that. Succes with that, the most tricky part in this all, and your responcibility. Also then give your maximum speed used, and wont go over for even a minute, not even once. This " pigheaded Dutch selfdeclared tyrepressure specialist " can make a cold pressure/ Axleloadcapacity- list for your tyres and max speed. For higher speed I have my own system of lowering maxload , looked off from C- tyres and Trucktyres. Then I also use 160 kmph/ 99 mph reference-speed for W and Y speedrated , wich Porches have. Above 270 kmph / 165 mph Y speedrated tyres , also maxload us lowered in the official system , 15% for 300 kmph. Need next of tyres, to be read from sidewall, to make a list for your tyres ( front and rear different) . 1. Maxload or loadindex 2.XL/ reinforced/extraload or if not given its Standard load 3. Speedcode less important , to determine the reference-speed, I explained about. But I use 160 kmph for all speedcodes. Then give if wanted in bar or PSI , kg or lbs, and give that max speed you use, and wont go over for even a minute. Be hounest about it ,I am no policeman. So higher pressure is not to prevent snakebites, as someone wrote, but only because at higher speed, more heat is produced by more cycles a minute, wich has to be compensated by lesser deflection, so lesser heat produced per cycle.

G-996 said: I think the last post is unfortunately incorrect - I blame the confusing sticker rather than the poster. The pressures on the top half of the sticker are for all speeds including high speeds (I.e. all the way around the Speedo). The bottom half of the sticker is for speeds up to 165mph. For normal driving, I d recommend using the bottom left setting, I.e. 30/32 psi. I ve had my 992 for two years and found it very sensitive to tyre pressures, it can quite easily feel skittish and lose traction and grip if the pressures are any higher than the comfort setting. I agree. Top pressures are if you are driving at very high speeds eg in Germany Lower figures are up to 165 mph so the ones you should use for normal use. Track pressures are a whole different thing but, as poster above mentions, are generally much lower than normal road ones for either speed. This is because they heat up in the corners and under braking and acceleration rather than just speed per se.

Agreed, I keep mine at 30/32 for normal UK use.

If it helps I drive my 991.2 at roughly 30F33R after they warm up which is the comfort setting. From cold they're around 2PSI down while the car and rubber warms up and can creep to 32F35R on longer runs under normal driving. I tried the standard pressures when I got it and it was awful. Way too harsh.

Thanks everyone. I won't be going on track so the comfort settings sounds about right.

jdubs76 said: Thanks everyone. I won't be going on track so the comfort settings sounds about right. My 911 is my first Porsche and it feels the most sensitive to tyre pressures out of all the cars that I've owned. When I first had it the tyres were pumped up to max (not by me) and it felt a bit weird and unsafe at motorway speeds.... even giving that little and unsettling wobble over bumps. However, normal service was resumed by letting them down to 'comfort'. This included 2,000 + miles across France this summer two up and full of luggage.

The figures on the door sticker are for tyre pressures being set when the whole system is in equilibrium at 20° C A rare event. Tyres generally change temperature when the car is driven and the pressures shown in TPM will reflect this. In summer conditions the tyre temperature will generally rise. . According to the Gas Laws (°K) and assuming the tyre volume stays constant, then 2.1 bar at 20°C will rise to 2.2 bar at an internal tyre air temp of 30°C and 2.3 bar at 45°C. It has never been clear to me whether Porsche have allowed for this temperature change in setting the 20° C pressure as shown on the door sticker.

Porche and BMW give on tpms screen besides the pressure as it is at that moment, the recomended pressure per axle for the setting, calculated from 20 degrC to the temperature of gascompound in tyre , also sended by the sensors. Some motorcycle tpms systems do it the other way around. They give on screen the pressure calculated back from temperature in tyre , to 20 degrC . This gives no confusion for the average user, but for users who think further questions of why pressure dont rise warm. Rimex, a mining tyre company , has a calculator, and calls this 20 degr C the Index temperature. But generaly is written, that recomended cold pressure, should be filled at any ambiënt temperature, be it minus 10 degr C or 40 degrC. Best definition of cold pressure, is when temperature of gascompound in tyre is practically the same as outside the tyre, so ambiënt temperature. That is when not driven long enaugh, and no external factors. This has become the definition in time, but does not indicate why . So there are 2 camps in this , I am in the index temperature camp,together with Porche and BMW ( and Rimex) who's ingenieurs shall not be dumb to. Edited by Jadatis on Wednesday 17th September 12:05 Edited by Jadatis on Wednesday 17th September 12:08 Edited by Jadatis on Wednesday 17th September 13:11

For what it’s worth, I run 32 front and 36 rear on my 991.2 with P-Zeros. I had to play around a bit. Comfort figures actually made the car feel sluggish and less responsive, whereas it was skittish at the higher end. Play around and see what suits your tastes.

Jadatis said: Porche and BMW give on tpms screen besides the pressure as it is at that moment, the recomended pressure per axle for the setting, calculated from 20 degrC to the temperature of gascompound in tyre , also sended by the sensors. Some motorcycle tpms systems do it the other way around. They give on screen the pressure calculated back from temperature in tyre , to 20 degrC . This gives no confusion for the average user, but for users who think further questions of why pressure dont rise warm. Rimex, a mining tyre company , has a calculator, and calls this 20 degr C the Index temperature. But generaly is written, that recomended cold pressure, should be filled at any ambiënt temperature, be it minus 10 degr C or 40 degrC. Best definition of cold pressure, is when temperature of gascompound in tyre is practically the same as outside the tyre, so ambiënt temperature. That is when not driven long enaugh, and no external factors. This has become the definition in time, but does not indicate why . So there are 2 camps in this , I am in the index temperature camp,together with Porche and BMW ( and Rimex) who's ingenieurs shall not be dumb to. Edited by Jadatis on Wednesday 17th September 12:05 Edited by Jadatis on Wednesday 17th September 12:08 Edited by Jadatis on Wednesday 17th September 13:11 Is your first language Google Translate?

Maxym said: Jadatis said: Porche and BMW give on tpms screen besides the pressure as it is at that moment, the recomended pressure per axle for the setting, calculated from 20 degrC to the temperature of gascompound in tyre , also sended by the sensors. Some motorcycle tpms systems do it the other way around. They give on screen the pressure calculated back from temperature in tyre , to 20 degrC . This gives no confusion for the average user, but for users who think further questions of why pressure dont rise warm. Rimex, a mining tyre company , has a calculator, and calls this 20 degr C the Index temperature. But generaly is written, that recomended cold pressure, should be filled at any ambiënt temperature, be it minus 10 degr C or 40 degrC. Best definition of cold pressure, is when temperature of gascompound in tyre is practically the same as outside the tyre, so ambiënt temperature. That is when not driven long enaugh, and no external factors. This has become the definition in time, but does not indicate why . So there are 2 camps in this , I am in the index temperature camp,together with Porche and BMW ( and Rimex) who's ingenieurs shall not be dumb to. Is your first language Google Translate? How's your Dutch?

Mayby som mis-spellings ( if I use the right word) , but I directly write in English , and dont go searching every word first , when I dont know it, but sometimes write around it. My Dutch is " voortreffelijk"

Jadatis said: My Dutch is " voortreffelijk" I am sure it is - I was asking Maxym who was criticising your English.

NDA said: How's your Dutch? Pretty poor. Thing is, I don't mind crappy English if I can gain some benefit from what I read. You wouldn't catch me posting in Dutch on a Dutch website. (The great majority of Dutch people, in my experience, speak great English anyway.)

991.2 T or P zeros - 34F 38R feels good, stable, compliant but not squishy. B roads, A roads and tracked it - perfect for all situations - for me...