3.3TT Tire Pressures for non standard sized tire/rim combos

[Silverghost]

Hi Members
I am considering bigger tire/rim options and would like to find out how to determine the appropriate tire pressures that I would have to run.

Could you please give me some direction to websites, or apps or any organisation that would be able to provide me with the desirable pressures for a given set of larger sized tires and rims for the 3.3 Stinger?

Thanks in advance

 

[MerlintheMad]

The "wisdom" I have inculcated here says: go by the OE door sticker psi ratings. Manufacturers only show max ratings (there must be some exceptions).

Btw, when my new PS4S rear tires were put on a couple of weeks ago, the psi cold was set to c. 38 and the fronts are c. 36. This is backwards from the door sticker for 19s. I figured the reason (aside from just being casual about inflation, which I don't believe is the case with the Wheel Werks guys) for the reverse inflation settings (softer in front) is a gription balance thing: new treads in the rear and half worn down in the front require a softer rubber contact in front to equalize with new tires in the rear. But, I don't know. Somebody else can talk to us.

 

[Kamauxx]

Hi Members
I am considering bigger tire/rim options and would like to find out how to determine the appropriate tire pressures that I would have to run.

Could you please give me some direction to websites, or apps or any organisation that would be able to provide me with the desirable pressures for a given set of larger sized tires and rims for the 3.3 Stinger?

Thanks in advance

It'll depend on the tires and sizes you buy. Your best bet is to check the tire manufactures website.

 

[eflyguy]

Could you please give me some direction to websites, or apps or any organisation..

What you are looking for doesn't exist. Recommended pressures on the door jam sticker are for the provided tires on average roads with average driving styles. Any change in brand, model and size will be different for each vehicle and driving style. That said, those recommended pressures would likely be a safe starting point, and you should then monitor wear over time for your particular driving style.

If you find someone with the same tires, you can see what they are running.

 

[Silverghost]

Thanks to you long-time members.
I appreciate your feedback.
I am going to start out with doorjamb sticker - maybe down by 1 or 2 psi front and back from that sticker level and closely monitor tread wear.
Another very knowledgeable chap suggested I create a shallow puddle of water or a chalked area or even shallow mud might work and drive the car slowly through that (perhaps at an angle and in a large enough car park) and then carefully check the resultant imprint left on the dry tarmac looking at the shape of the imprint to discern whether they are over or under inflated.
A bit of an experiment I guess..
I am thinking this should be at running temperature as opposed to cold temps?

Thanks for your opinions. Much appreciated .

 

[MerlintheMad]

I think this would result in an exercise in frustration. "At an angle": what's that about? trying to see the tread pattern from the car window? I think you'd have to get out and peer very closely to see, what, exactly? And no, running hot would not make any difference vis-à-vis determining over/under inflation. The recommended psi is for cold; so all/any changes should be measured only when cold. Cold is a constant: running temperatures are all over the place.

 

[eflyguy]

I am thinking this should be at running temperature as opposed to cold temps?

That depends on how cold is "cold" when you check them, and how you plan to drive it.

For street use, it doesn't need to be that precise. Once you get them installed and are driving on them, see how it feels and make small adjustments to see how they change things.

 

[Kamauxx]

Thanks to you long-time members.
I appreciate your feedback.
I am going to start out with doorjamb sticker - maybe down by 1 or 2 psi front and back from that sticker level and closely monitor tread wear.
Another very knowledgeable chap suggested I create a shallow puddle of water or a chalked area or even shallow mud might work and drive the car slowly through that (perhaps at an angle and in a large enough car park) and then carefully check the resultant imprint left on the dry tarmac looking at the shape of the imprint to discern whether they are over or under inflated.
A bit of an experiment I guess..
I am thinking this should be at running temperature as opposed to cold temps?

Thanks for your opinions. Much appreciated .

I adjusted my tires with the chalk method when I first installed them. I think I settled on 33 psi or so.

 

[Silverghost]

I think this would result in an exercise in frustration. "At an angle": what's that about? trying to see the tread pattern from the car window?

I think this would result in an exercise in frustration. "At an angle": what's that about? trying to see the tread pattern from the car window? I think you'd have to get out and peer very closely to see, what, exactly? And no, running hot would not make any difference vis-à-vis determining over/under inflation. The recommended psi is for cold; so all/any changes should be measured only when cold. Cold is a constant: running temperatures are all over the place.

The thought was to drive in a bend/angle was probably the wrong term so as to avoid the larger imprint driving over and covering the barrier front imprint...
You know I am a total novice, don't you?

 

[Silverghost]

Reason for angle or rather a bend is to see 4 tracks instead of just 2 from driving in a straight line.

 

[Silverghost]

Reason for angle or rather a bend is to see 4 tracks instead of just 2 from driving in a straight line.

Upon further reflection:
Pressure is Pressure is Pressure.

Pressure of say 36 psi in a narrow tire is same pressure as in a wide tire.
So, I am thinking my question is irrelevant and I should just go with the doorjamb sticker - no matter that my tire and rims are wider than standard.
Is my logic faulty?

 

[Kamauxx]

Upon further reflection:
Pressure is Pressure is Pressure.

Pressure of say 36 psi in a narrow tire is same pressure as in a wide tire.
So, I am thinking my question is irrelevant and I should just go with the doorjamb sticker - no matter that my tire and rims are wider than standard.
Is my logic faulty?

What's printed in the doorsill is for stock or equivalent to stock tires not for tires of a different size/compound.

 

[Silverghost]

Th

What's printed in the doorsill is for stock or equivalent to stock tires not for tires of a different size/compound.

Thx
Back to experimenting and checking and fine tuning, like you and others have recommended.
Thx

 

[Ty Davis]

I can offer a bit of help here...

The Kia recommended tire pressure printed on the door jamb sticker is only a guideline.
Kia chose these pressures to reach specific targets for ride/handling/mpg/steering feel/grip/stability/tire wear/NVH/pothole resistance/and load capacity. You can adjust this pressure as you see fit, as long as you understand what changes and the consequences/benefits of those changes.

Kia seems to be a bit aggressive (high) on the Stingers tire pressure. This boosted fuel economy, steering response and reduced damage from potholes. The downside is that you may very well find the center of your tires contact patches wearing a bit prematurely and road texture and noise come through a bit more clearly than they would with a lower pressure.

That being said, for the purposes of answering the topic here, let’s assume we want to stay with the Kia specs and move to a different size or construction of tire. 36 psi in one tire does not behave the same as 36 psi in a dissimilar tire.

To get the new “KIA” recommended tire pressure for your new tire, you need to know several things.
You need to know the tires construction (standard load or xtra load).
You also need to know the stock Kia recommended psi setting.
Find too, the tires load index.

You need these 3 things from the stock tire. They will help you calculate the load capability of the stock tire.

I am going to attach a chart for you that will help you derive the new tires pressure from the stock tire.

Basically, you want the tires load handling to be the same, or close, between the new tire and old tire.

Be aware that some tires are standard load (SL) and others are extra load (XL).
XL tires require less psi for the same dynamics a SL tire.

My RWD GT2 stock rear tire is a 255/35/19 XL 96Y and Kia recommends 36psi for it.
Meaning Kia has specified 1379lbs of load capacity for that particular tire.

If I upgrade to a 265/30/20 XL 94Y tire, it will need to be set to around 38.4 PSI to have the same load carrying capability of 1379lbs. If I just aired this new size up to the Kia specified 36psi, I would be decreasing its load capacity to 1302lbs. This is quite a significant drop in terms of deviance from the characteristics Kia chose with the stock pressure in mind. 36psi on the new tire size would be equivalent to running the stock tire at about 33.8psi. Quite a drop.

Use the attached chart to make your conversions. If you want to keep the Kia specified trade offs and benefits mix, you will need to adjust your pressures to suit your new tire.

Also keep in mind that tires have a range they can operate in and you can tailor that to your specific use and demands too.

If you need more help with your specific tire, let me know what tire and size you have selected and I’ll help you calculate the new “Kia equivalent” psi for it.

 

[Silverghost]

I can offer a bit of help here...

The Kia recommended tire pressure printed on the door jamb sticker is only a guideline.
Kia chose these pressures to reach specific targets for ride/handling/mpg/steering feel/grip/stability/tire wear/NVH (Noise, Vibration, and Harshness)/pothole resistance/and load capacity. You can adjust this pressure as you see fit, as long as you understand what changes and the consequences/benefits of those changes.

Kia seems to be a bit aggressive (high) on the Stingers tire pressure. This boosted fuel economy, steering response and reduced damage from potholes. The downside is that you may very well find the center of your tires contact patches wearing a bit prematurely and road texture and noise come through a bit more clearly than they would with a lower pressure.

That being said, for the purposes of answering the topic here, let’s assume we want to stay with the Kia specs and move to a different size or construction of tire. 36 psi in one tire does not behave the same as 36 psi in a dissimilar tire.

To get the new “KIA” recommended tire pressure for your new tire, you need to know several things.
You need to know the tires construction (standard load or xtra load).
You also need to know the stock Kia recommended psi setting.
Find too, the tires load index.

You need these 3 things from the stock tire. They will help you calculate the load capability of the stock tire.

I am going to attach a chart for you that will help you derive the new tires pressure from the stock tire.

Basically, you want the tires load handling to be the same, or close, between the new tire and old tire.

Be aware that some tires are standard load (SL) and others are extra load (XL).
XL tires require less psi for the same dynamics a SL tire.

My RWD GT2 stock rear tire is a 255/35/19 XL 96Y and Kia recommends 36psi for it.
Meaning Kia has specified 1379lbs of load capacity for that particular tire.

If I upgrade to a 265/30/20 XL 94Y tire, it will need to be set to around 38.4 PSI to have the same load carrying capability of 1379lbs. If I just aired this new size up to the Kia specified 36psi, I would be decreasing its load capacity to 1302lbs. This is quite a significant drop in terms of deviance from the characteristics Kia chose with the stock pressure in mind. 36psi on the new tire size would be equivalent to running the stock tire at about 33.8psi. Quite a drop.

Use the attached chart to make your conversions. If you want to keep the Kia specified trade offs and benefits mix, you will need to adjust your pressures to suit your new tire.

Also keep in mind that tires have a range they can operate in and you can tailor that to your specific use and demands too.

If you need more help with your specific tire, let me know what tire and size you have selected and I’ll help you calculate the new “Kia equivalent” psi for it.

This is awesome information that I think a lot of people on this forum, and elsewhere, would find extremely useful.
May I suggest that an admin make this post from Ty Davis a sticky?

 

[MerlintheMad]

You know I am a total novice, don't you?

Who is the bigger novice here?

I can offer a bit of help here...

Thanks, Ty!

 

[Ty Davis]

Who is the bigger novice here?

Thanks, Ty!

Anytime Merlin!