Dalema

Glad I checked this thread. My tire pressure hasn't changed since delivery (I look at the TPM each morning) - but looks like they were set way too low!!

My fact pattern: 20 inch wheels, in the US - so comfort would be appropriate (165mph is just a dream) I guess

Questions:
1. What would full load vs partial be?
2. Does TPM read lower than a tire gauge - ie I should not rely on the TPM?

naaranha

You should use Partial load unless you usually keep your frunk full and usually have 2 or more passengers. I use comfort and the recommended pressure per the manual is 31F and 34R. Keep in mind this is measured at 68F. So if you are at a lower temp then you should have less air in your tire. There is a formula. But the following link will help you: http://www.tirerack.com/tires/tirete....jsp?techid=73

Dalema

Regarding the TPM vs manual gauge - I have found the exact same thing with the rears matching but lower per TPM on the front. Should you just rely on the TPM?

chuckbdc

I think that if you check the settings for tpm- you can adjust for adjust for the tire and the season.

chuck911

This is why I tell people to check with a gauge. Obviously in this case there's 3psi variance on the fronts. This is enough to throw off the whole f/r balance. And who knows if on some cars the readings could be off side to side? TPM is a handy guide but a quality gauge is more reliable.

The manual numbers are fine for general guidance or baseline, which is all they can be as they're pretty broad. Several guys here have the right idea, which is that within the recommended range you simply set whatever pressure works and feels best for the driving you're doing. Which can change- with ambient temp, your driving, elevation (yes, elevation), etc. - constantly.

The most important thing to remember is that the only thing that matters is working pressure. The psi of a cold parked tire means nothing. Second most important is knowing that while an under inflated tire will grip great but respond slow, an overinflated tire will lose grip but respond fast. That's all you really need to know to figure out what works best for you.

Key Left

Do older tires make more noise than newer versions with less miles?

LexVan

Yes. Older tires tend to get noisy and lose grip and performance.

walterwu

So I got a tire pressure warning this morning, in my four and a half month old 2014 C2S, with 1971 miles (getting close!). It triggered about 3 minutes after starting the car. My cold tire pressure has not changed since I received it from the dealer, 28/29 L/R front and 33/34 L/R rear when cold, and 30/30 and 35/35 after they warm up.

After the warning light came on, I checked the multi-function display "fill up" screen, which read -4/-3 and -3/-3' with the -4 in red. After warming up and reaching the next intersection, the screen read -3/-3 and -3/-3, but the left front -3 was still red. I went ahead and went to work, and on my way home in the evening, the same warnings occurred. When I got home, I let the car cool down for a few hours, then went and pumped the fronts so they were both 30 and topped off the left rear to get it to 34. I then restarted the car, but the warning still came on, and even though the tires now were 30/30 and 34/34' the fill up screen still read -3/-3 and -3/-3. Per the manual, I thought the warning would automatically cancel upon increasing the pressure, but it didn't seem to do that. Do I need to reset the TPMS after the warning, or is there something else wrong? (TPMS failure?) do I need to pump the fill in screen until all the tires are at zero fill in?

Also, I have the tires set for 20" summer, partial load, comfort setting, so I thought the fill up screen would target the tires for 31 front axle and 34 rear axle, per the manual, but it seems to want to get to 33/37 based on the differences on the fill in screen vs. the tire pressure screen. Does the tire pressure targets on the multi-function display match the car manual, or are they off?

Samp4

Mine have sometimes changed as soon as I aired them up and other times it has taken a drive around the block. I would go ahead and pump up the fronts to the recommended 31.

walterwu

Thanks, I'll give that a try first. If that doesn't work, I'm think I'll try resetting TPMS next, and if that doesn't work, I'll try pumping it up to the fill in screen's target pressure.

Porsche 25th

I settled on 31F 37R verified by two different handheld gauges. TPM reads 32/38. I think the handling is great and would not want a harsher ride around town.

trysixty

i've used 33 front/38 rear cold.........reach 36-38 front/ 40-42 rear once warmed up in air temps of 45-80F

changed at 10k miles, fronts good, rears shot

walterwu

After topping off some of the tires to 30/30 and 33/33 cold pressure, the warning still didn't clear even after driving 7 miles, so I reset TPMS and the warning went away. I definitely notice that the tire noise is greater with the fronts at 30/30 instead of 28/29 as the originally were, so I might back it down a bit.

addysdaddy

My SA (whose also a racer) recommended 35f/39r and like the OP, I've found this to be as good balance between comfort and performance. FWIW, the readings on my digital tire gauge & the TPMS match exactly.

Hothonda

36-44 perfect for me....