Is the recommended 42 PSI working well?

[Gulfcoaster]

Hey guys,

Is the factory recommended 42 PSI for the M3P 20" Pirellis good?

I ask because sometimes slightly different settings are better.

Wondering if those of you who take tire pressure seriously found a better PSI for ride comfort and wear.

Thanks

 

[tm1v2]

For ride comfort downsize to 19" or 18". Tires will be cheaper too especially 18", basic 18" wheels can pay for themselves in just a few sets of tires.

I found 42psi cold okay, just slightly high feeling. Preferred 40-41psi cold on the stock 2021 M3P wheel+tire setup if I recall correctly. I don't think I tried anything lower on those wheels or tires.

Now on 245/45R18 on 18x8.5" wheels I've been liking 38-39 psi cold. Haven't tried anything lower yet. Tire shop overinflated to 45psi cold and that was predictably bad. 42psi cold was better but 38-39psi cold feels better still. Doesn't feel underinflated at all. Tire wear is fine so far though it is time I check my tread depth again.

I'll note that everything is better in this sizing. I even have more grip than stock thanks to better tires.

 

[Gulfcoaster]

Thanks. What I notice at 42 PSI on the stock 20" Pirellis is a grainey pebbely road feel if I described that right. Car has 47 miles on it Driving on glass smooth roads in Naples FL. I'm going to try 40 PSI tomorrow and see if that feels a little bit better.

If I understand correctly, 19" tires are hard to source and probably not much different feeling than the 20" tires.

I'll definitely consider 18" rims/tires when these are ready for replacement. However.....don't 18's look undersized in the wheelwells?

 

[tm1v2]

245/40R19 should be widely available and fit well on either 19x8.5" or 19x9" wheels. There are tire shortages these days like with so many things, but there are many options in that size.

Same with 245/45R18 for 18x8.5" wheels.

I do agree that 19" visually looks better on these cars than 18". I went with 18" for practicality (more sidewall) and price (wheels and tires both cheaper). 19" is a good size for this car too. Whereas 20" is really for looks above everything else.

 

[3Volts2aTes]

I'll definitely consider 18" rims/tires when these are ready for replacement. However.....don't 18's look undersized in the wheelwells?

I think so, but they do work better for range.

Personally, I think the 19 splits the difference nicely.

 

[Zcd1]

I run 38-40 PSI - seems a good compromise to the seat of my pants.

 

[Tdriver]

I run. 36-38 on 19 inch tires on a MYP. Good for comfort on non perfect roads. I was down to 35 recently without a warning recently.
32 is kinda normal on most cars so 35 is not an issue. Tesla likes 40-42 only to achieve max mileage ratings.

 

[jackmott]

Hey guys,

Is the factory recommended 42 PSI for the M3P 20" Pirellis good?

I ask because sometimes slightly different settings are better.

Wondering if those of you who take tire pressure seriously found a better PSI for ride comfort and wear.

Thanks

I wouldn't go any lower on the 20s", as your already high risk of wheel damage on potholes will get even higher. I have 18s on my M3P and it does get a bit more comfy if you drop it down to 38 instead of 42 with the downside of a loss in efficiency.

Also keep in mind if you go too low you risk tire damage/blowout. Biggest risk would be extended highway driving with extra mass in the car. 32 is normal on cars that tend to have bigger tire relative to their mass. I wouldn't go lower than 38 personally, but 35 may be fine, depending on the tire.

 

[dsgerbc]

Adjusting tire pressures down goes a long way toward greater comfort. I'm not gonna suggest any specific pressures, cause those will differ for different trims/typical loads.

If you're running your M3P with 5 adults fully loaded with luggage at its GVWR of 5100lbs, and your OEM tires are rated at 1389lbs @41psi, you don't have much room to lower tire pressures while still making sure your tires provide adequate load handling.

On the other hand, on OEM 235/45/18 tires, even if you go down to 35psi (SL rating point) you'd get 1477lbs per tire -- plenty to spare even on a fully loaded car. Tire's load is a linear function of its inflation pressure, so, knowing the rated load at 41 and 35 psi one can calculate what the tire should be able to handle safely at pressures below 35psi.

Now, driving at 35psi on an XL-rated tire will probably wear out tire shoulders faster, but if comfort is what you want....
And the point about wheel/tire damage from potholes at lower pressures is a valid one.

Personally, I daily 19" tires at 36ish psi cold.

 

[enemji]

What is with Tesla suggesting the same tire pressure of 42psi regardless of the 18” tire it comes with?

Michelin MXM4 is rated at 98w

• Max Load:
  1,653 lbs
• Max Inflation Pressure:
  50 psi

Hankook Kinergy GT is rated at 94v

• Max Load:
  1,477 lbs
• Max Inflation Pressure:
  51 psi

What is the actual tire pressure based upon the GVWR?

Front 2447 lbs
Rear 2771 lbs

 

[Perscitus]

Good info on why below the calculator found here... Tire Pressure Calculator

 

[gearchruncher]

The reason you would stay with a fixed pressure no matter what tire is because the size of the contact patch is defined by the pressure in the tire and nothing else.