What tire pressures are you running?

[urbo73]

The recommended tire pressures for this car on the OEM 265/30R19 tires are 35F/33R. I see many running 18" wheels with 265/35R18 tires. What pressures are you running there?

If I use the caculator here:

https://tiresize.com/pressure-calculator/

I get the below for 35 fronts. It recommended 31 for fronts, 4 psi lower. Same for 33 rears - it will recommend 29psi, 4 lower. Is this the thing to then follow and do?

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[chopsuey34]

Good question. Following because I would like to know as well.

 

[CTRifecta]

I'm running 35psi all around on my 265/35/18s, feels fine

 

[urbo73]

I'm running 35psi all around on my 265/35/18s, feels fine

Why so high?

 

[TypeRD]

@urbo73 4 PSI lower than stock seems like a lot. That’s 11% less in front and 14% less in rear…but I guess it makes sense. It’s only a slightly smaller wheel and slightly larger tire. I’d probably start with what the calculator says (as it seems logical to me) and see how it rides, handles, and also check tire wear. From there I’d adjust by maybe +\- 2 PSI to get it dialed-in how you like it. Note, I’m not a tire expert.

This is a helpful thread, tho. I plan on getting a set of 18’s, same setup as you, at some point.

 

[urbo73]

I actually have the OEM 19”s, but with 265/35 tires instead of the 265/30. So same sidewall as 265/35R18s, but on OEM 19” wheels. Speedo is off a bit, but it’s worth it for me. For me, the calculator recommends 5 lower F/R, so 30/28, but I’m now driving with 33/31 and seems more than enough. I’ll go with 32/30 for a bit more compliance and still be within the recommended range.

 

[ayau]

there's isn't perfect tire pressure. it depends on what your goals are. the stock pressures are optimized for street driving/MPG, so i would stick to that unless you have some other use case e.g., track, autox.

 

[TypeRD]

@ayau You’re correct. But, I believe he’s trying to translate the stock pressures to a different wheel/tire setup to establish a logical, safe, baseline for every day driving (on said alternate setup). Of course, from there he can add more or less air depending on wear, comfort, stability, etc. as necessary.

 

[ayau]

changing tire pressures more or less only affects the stiffness of the tire's sidewall. you'll need to do testing to see what the 'correct' pressures are, which is why i'd just use the door jam pressures. an online calculator will just get you the ballpark pressures.

for example, if you run too low of pressure, you'll roll the sidewall too much. too high and you sacrifice grip. furthermore, all of this depends on the tire's characteristics, alignment, temps, etc.

 

[urbo73]

Yeah, but one thing is true: 35/33 is not the correct pressure for anything but the stock tires, and even that's a bit high as it's for max load (4 passengers + luggage). The calculator correctly, I believe, translates that to other size tires based on load. Whether one chooses to follow that or not, that's another question. But that was not my question.

 

[TimeRacer]

Yeah, but one thing is true: 35/33 is not the correct pressure for anything but the stock tires, and even that's a bit high as it's for max load (4 passengers + luggage). The calculator correctly, I believe, translates that to other size tires based on load. Whether one chooses to follow that or not, that's another question. But that was not my question.

As others have said, there's no perfect tire pressure. There's always tradeoffs and static load is only one of the considerations. Without testing on specific tires in specific sizes the construction can be entirely different with different characteristics. Plugging everything into an online calculator is simply a starting point, just like the Honda factory recommendations. Sidewall stiffness, contact patch resistance to balooning and stiffness across the tread, ride quality consideration, desired handling characteristics are just part of the tire pressure consideration, all vary across tires of the same size. What a PS4s likes is going to be different than say the Ventus S1 Evo 3 which will be different than a Advan V107, etc. Then you need to account the tire is just one piece of the suspension of the car and you can tune the tire pressures along with your preferred shock setting and other than factory tire sizing. What pressure I use for autocross is different than the track which is different than daily use which is different than the weekend canyon run in part because half of those consider traction control being completely off seeking rear rotation vs daily & canyon seeking the most grip.

TL : DR - there is no perfect tire pressure for everything. Adjust to your own personal goals and desired handling characteristics for your driving style.

 

[ayau]

The best way to determine optimal pressure is to get an IR thermometer gun and measure the cross section of the tire surface right after some spirited driving. Your goal is to get the temps as even as possible across the surface of the tire.

if outer edge is hotter, bump up 2psi and retest.
If inner edge is too hot, decrease 2 psi.

if you don’t want to test, then run door jam pressure when it’s cold.

 

[Splice247]

You should use the stock pressures unless tracking. Wheel and tire size do not matter. The Oem pressure is setup for the weight distribution of the car, handling, and mpg. Just bec you change the brand or size of tire does not mean you change the pressure. The weight stays the same.

 

[hwessin]

You should use the stock pressures unless tracking. Wheel and tire size do not matter. The Oem pressure is setup for the weight distribution of the car, handling, and mpg. Just bec you change the brand or size of tire does not mean you change the pressure. The weight stays the same.

Tire load ratings depend on pressure, and that load rating/tire pressure relationship does change depending on the tire size/brand/pr. The tire data sheet should be able to tell you what psi is required to support a particular load. The OEM pressure is setup to support a particular axle load rating that should not change, but the new tires should try to match that rating regardless of the pressure needed to do so. I’m speaking mostly from my commercial vehicle design knowledge, but cars share a similar philosophy.

 

[TypeRD]

You should use the stock pressures unless tracking. Wheel and tire size do not matter. The Oem pressure is setup for the weight distribution of the car, handling, and mpg. Just bec you change the brand or size of tire does not mean you change the pressure. The weight stays the same.

I fully understand the logic, but you’re incorrect. Even though the load remains constant, a larger tire (because it holds more air volume) does not need to be inflated to as high of PSI as a smaller tire in order to handle said load and perform as intended. I did some digging and here’s some good info I found.
https://vehq.com/do-bigger-tires-need-more-psi/

It seems to me that the calculator is indeed correct…at least as a safe starting point for normal street driving.

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