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Discussion Starter · #1 ·
Hi everyone. I'm looking for advice on tire pressure for city driving. With stock tires Subaru recommends 33 psi front / 32 psi rear.
I switched to Toyo AT2 215/75R15 and 33psi looks pretty flat. It looks more round at 42 in the front and 36 in the rear so that's what I'm running for now. Is there any more scientific way to determine proper pressure?

P.S. I'm talking about city driving here. Off-road I vary between 18-30 depending on the terrain.
 

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Tire pressure is entirely objective but as long as you do not go over the maximum PSI on the side of the tire. If you go offroading then maybe you'll want maximum traction thus lower the PSI to 20 or better gas mileage on a road trip but also firm (teeth rattling) go to 45 PSI. I like a firmer tire, my '18 Crosstrek I have the OEM Falkens at 36 but the Falkens WP AT3W on my 4Runner I have a 34, anything over that then the ride is too harsh.

Are your Toyos LT or P? Where did you buy them from?
 

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Discussion Starter · #3 ·
I'm using the P type, I bought them from a local shop. I'm happy with it so far, but this if my first AT tire. I suppose a taller sidewall generally requires higher pressure to stay round.
 

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The toyo has 100 load index so by right does not need much different tire pressure. If you are ok with rear at 36 then you can try 37 at front. Certain AT tire will not be round due to focus to be used on low speed. Of course if sidewall is too soft you can increase a few psi as long not to exceed the maximum pressure stated at the tire
 

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Based on TRA inflation charts my P-rated 225/55-18 OEM Falkens (2019 Limited) have a load rating of 1609# at 35 Psi; the LT 215/75-15 BFG AT KO2 is rated 1605# at 45 Psi (within 1% , 1609/1605=1.002)

So doing the math, the OEM 33 Psi front/ 32 Psi rear works out to be 42.43 Psi front/ 41.14 rear. I’ve only been running the new setup couple days so I will monitor performance.

P charts start on p.13 and LT charts on p. 20, see link below

https://www.toyotires.com/media/2125/application_of_load_inflation_tables_20170203.pdf



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Discussion Starter · #6 ·
Thanks for the link, that's exactly what I was looking for! But these numbers don't make sense or I'm reading it wrong.
OEM tires are P225/55R17 at 32psi in the rear, so according to this table the load rating is 1477 lbs.
I look up my replacement P215/75R15 and it says 1510 lbs at 26 psi. At 26 psi these tires look very flat and and are well suited for rock crawling or sand, but there's no way I would drive on the highway like that.
 

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Thanks for the link, that's exactly what I was looking for! But these numbers don't make sense or I'm reading it wrong.
OEM tires are P225/55R17 at 32psi in the rear, so according to this table the load rating is 1477 lbs.
I look up my replacement P215/75R15 and it says 1510 lbs at 26 psi. At 26 psi these tires look very flat and and are well suited for rock crawling or sand, but there's no way I would drive on the highway like that.
Based on the tables your stock 225/60-17 (assuming you meant that size not 225/55-17) and the P rated 215/75-15 AT tire can both handle 1587# load at 32 Psi and 29 Psi respectively (slightly stiffer sidewall of the AT tire can handle same load with slightly lower pressure)
You could try 30 front and 29 rear and go from there


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Discussion Starter · #8 ·
I meant what I said, my stock Geolandar tires were P225/55R17. Anyway, I've been running the Toyos at 44 psi front and 38 rear because it looks right visually and handles well on the highway.
 

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You could use Water and a Paint brush to set the tire pressure. Start with the max air pressure recommended for your tires and plan on letting air out of the tires. On your driveway or in a parking lot use the brush to paint a 4 inch wide strip on the driveway surface. Then drive over it, the tire will pick up the water then with 1 rotation the tire will make it's pattern back on the driveway. Adjust the air pressure in the tire down till you see full contact of the tire tread pattern on the ground. Once you determine full contact of the tread pattern that should be the correct pressure for those tires and the weight of your car. How I always set the air pressure on my oversized Jeep tires.
 

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Based on TRA inflation charts my P-rated 225/55-18 OEM Falkens (2019 Limited) have a load rating of 1609# at 35 Psi; the LT 215/75-15 BFG AT KO2 is rated 1605# at 45 Psi (within 1% , 1609/1605=1.002)

So doing the math, the OEM 33 Psi front/ 32 Psi rear works out to be 42.43 Psi front/ 41.14 rear. I’ve only been running the new setup couple days so I will monitor performance.

P charts start on p.13 and LT charts on p. 20, see link below

https://www.toyotires.com/media/2125/application_of_load_inflation_tables_20170203.pdf



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Just realized the OEM tires are not P- rated but are SL standard load rated (98H) so using the SL tables the numbers will very slightly. (no more than 1-1.5 psi)
 

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The table is just guideline for minimum pressure for load safety, actual pressure need to be tuned for handling and comfort. My experience often even for going with tire with higher load index but it has softer sidewall, i end up inflate additional 2 psi.
 

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Reached out to BFG regarding my AT KO2 LT215/75R15’s and got this reply





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Interesting....it seems you were really close using the chart to what BFG sent you. Based on this about 42 PSI would be good.
I run mine at 40 PSI (per standard tire gauge) and the dash readout says about 38 Front and 37 Rear when cold. What does yours say?
 

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Interesting....it seems you were really close using the chart to what BFG sent you. Based on this about 42 PSI would be good.
I run mine at 40 PSI (per standard tire gauge) and the dash readout says about 38 Front and 37 Rear when cold. What does yours say?
I use my Autel TS508 TPMS tool to set pressures when cold, along with an external digital gauge (Green Slime), both can display tenths of a Psi, and the TPMS display in DIC matches the external gauge pretty close (within +/-0.5 Psi) You have to drive the vehicle, maybe a half a block or so down the road for the display to update since it always shows the last reading when the vehicle was turned off, and tires were running at higher pressures since they were warmed up. I'm currently running 40 front 38 rear cold psi, since I'm never at max GVWR of 4343#, until i can get to a scale to weigh front and rear axles separate and combined to get a better idea of actual weight and then fine tune pressures accordingly.

Interestingly the inflation tables for LT215/75R15 (C load/100H) tires do not even list pressures below 35 Psi (1345# load), so if you are running OEM pressure of 33/32 for daily driving you are probably causing premature wear from increased heating of sidewalls. Best to weigh vehicle and do a chalk test to find the sweet spot for your specific vehicle with accessories/mods, etc.
 

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FYI, if this info helps anyone else...


Hello Robert,

Thank you for contacting Toyo Tires U.S.A.

Based on your original vehicle's fitment, we recommend for the Open Country A/T III P225/75R15 102T tire pressure to be ran at 26 PSI cold for both front and rear tires.

Thank you,
Toyo Tires

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A consumer recently filled out the Contact Us web form. This is what they posted on the web:

Reason for Contacting Us - Tire Fitment

2021 Subaru Crosstrek Limited / 225.75 R15

Question / Comment Regarding -

Comments - Hello Toyo Support! I just replaced the OEM 225/55R18 Falken Ziex ZE001 A/S tires with 225/75 R15 Open Country A/T III tires. What PSI would you recommend I run in these tires with this car?
 

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FYI, if this info helps anyone else...


Hello Robert,

Thank you for contacting Toyo Tires U.S.A.

Based on your original vehicle's fitment, we recommend for the Open Country A/T III P225/75R15 102T tire pressure to be ran at 26 PSI cold for both front and rear tires.

Thank you,
Toyo Tires

------------------------------------------------------------------------------------
A consumer recently filled out the Contact Us web form. This is what they posted on the web:

Reason for Contacting Us - Tire Fitment

2021 Subaru Crosstrek Limited / 225.75 R15

Question / Comment Regarding -

Comments - Hello Toyo Support! I just replaced the OEM 225/55R18 Falken Ziex ZE001 A/S tires with 225/75 R15 Open Country A/T III tires. What PSI would you recommend I run in these tires with this car?
Interesting. I have these tires. I know I would get a low tire pressure warning if I went to 26 psi cold
 

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I'll play along. I contacted Yokohama since they don't have tire pressure load charts published. Here is their response for Geolandar G015 LT215/75/15:
Organism Font Darkness Event
 
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