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What PSI Should You Run in Upsized Tires? (GX470, GX460, GX550)

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Updated October 10, 2026

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Your door jamb says 32 PSI. That number was calculated for the stock tire. Once you bolt on 285s, the right pressure comes from the tire load tables, not the door jamb. Here is the method, a worked GX470 example, and the chalk test that confirms it.

Who This Guide Is For

This guide is for the GX owner who just upsized tires and is staring at the new rubber wondering what pressure to run. The door jamb still says 32 PSI. The tire shop set them to 40. A forum thread says 28. All three can be wrong. This guide gives you the method tire engineers actually use: match the load capacity of the stock tire at its placard pressure, then confirm with the chalk test.

Why the Door Jamb Number Stops Being the Answer

The pressure on your door jamb is not a magic number. It is the pressure at which the stock tire supports the stock truck’s weight with the safety margin Lexus designed in. Change the tire and the math changes.

A GX470 left the factory on P265/65R17 tires at 32 PSI front and rear 1. A GX460 left the factory on P265/60R18 tires at 32 PSI front and rear 2. Those pressures are correct for those exact tires. A 285/70R17 has a different carcass, a different load curve, and often a different construction (P metric versus LT metric, covered below). The pressure that supports your truck on the new tire is almost never the same number.

Running the door jamb pressure in an LT tire usually means underinflation. The LT load tables do not even list pressures below 35 PSI for most sizes. Running the tire shop’s 40 PSI in everything usually means overinflation on a light truck: harsh ride, a skittish feel on grooved pavement, and the centers wearing out first.

P Metric vs LT Metric

The letter before the size tells you which load table the tire follows.

P metric tires are passenger car tires. They have flexible sidewalls, a comfortable ride, and lower maximum pressures (usually 35 or 44 PSI). Your GX came with P metric tires from the factory.

LT metric tires are light truck tires. They have stiffer, thicker sidewalls, higher maximum pressures, and load ranges instead of a single max: Load Range C (50 PSI max), D (65 PSI max), and E (80 PSI max). Most all terrain tires GX owners buy in 285/70R17 are LT metric.

The stiffer LT carcass needs more air to do the same work. That is the whole reason the door jamb number stops working. A P265/65R17 at 32 PSI and an LT285/70R17 at 32 PSI are not carrying the same load, and the LT tire at that pressure is running soft.

Three panel diagram showing how the tire contact patch gets longer at low pressure and shorter at high pressure

The 1.10 Rule

Here is the step everyone skips. When a P metric tire is used on a light truck or SUV, the tire industry derates its published load capacity. You divide the P metric load by 1.10 3.

Why this matters: your stock GX tire is a P metric tire on a truck. Its real working capacity is the table value divided by 1.10, about 9 percent less than the printed number. If you skip this step, your replacement tire target is 10 percent too high and you will end up running more pressure than you need.

LT metric tires are not derated. Their table values are used as printed.

The Load and Inflation Table Method

Tire makers publish load and inflation tables: for each size, how many pounds the tire supports at each pressure. The method is five steps.

  1. Look up your stock tire size in the P metric table. Find the load at your door placard pressure.
  2. Divide that load by 1.10. This is the minimum load each new tire must support.
  3. Look up your new tire size in the correct table (P metric or LT metric). Find the lowest pressure that supports at least that load.
  4. That pressure is your starting point, set cold (before driving, in the morning).
  5. Confirm with the chalk test below and adjust 1 to 2 PSI at a time.

Two rules that come with the method. Never run below the table’s minimum listed pressure for your size. And the maximum pressure on the sidewall is a structural limit, not a target. Nobody’s daily driving pressure should be near it.

Worked Example: GX470 from P265/65R17 to LT285/70R17

Stock: P265/65R17. The P metric table gives 2,260 lb per tire at the 32 PSI placard pressure 4.

Derate for truck use: 2,260 divided by 1.10 equals 2,055 lb. Each new tire must support at least 2,055 lb.

New tire: LT285/70R17, Load Range C. The LT table for this size reads 5:

Pressure Load per tire
35 PSI 2,105 lb
40 PSI 2,315 lb
45 PSI 2,510 lb
50 PSI 2,755 lb (Load Range C maximum)

35 PSI supports 2,105 lb, which clears the 2,055 lb requirement. So 35 PSI cold is the starting point. Notice the table has no entry below 35 PSI. Running the old 32 PSI placard number in this LT tire would be off the chart and underinflated.

From there, the chalk test usually lands GX470 owners on LT285/70R17 somewhere between 35 and 38 PSI unloaded. Load Range E versions of the same size follow the same table at these pressures (the size determines the low pressure values; the load range determines the maximum). The E tire just rides stiffer getting there.

GX460 Note

Same method, different starting number. Stock is P265/60R18. The P metric table gives 2,183 lb per tire at the 32 PSI placard 6. Derated: 2,183 divided by 1.10 equals 1,985 lb. An LT285/70R17 at 35 PSI supports 2,105 lb, which clears it. Same answer: start at 35 PSI cold, then chalk test.

GX550 Note

GX550 placard pressures vary by trim, verified from the 2024 owner’s manual: 33 PSI front and rear on the 265/55R20 and 265/50R22 setups, 35 PSI front and rear on the 265/70R18 Overtrail setup 9. Run the same five steps above with your stock size and you will get your answer. The method does not care what year your truck is.

Recommended Starting PSI for Common Upsized Sizes

Each number below comes from the same five steps: stock tire load at placard pressure, derated by 1.10, matched to the LT table. They are starting points. Chalk test to confirm.

Generation Stock tire (placard) Common upsized tire Start here, cold
GX470 P265/65R17 (32 PSI) LT265/70R17 (31.6 in) 40 PSI
GX470 P265/65R17 (32 PSI) LT285/70R17 (32.7 in) 35 PSI
GX470 P265/65R17 (32 PSI) LT255/80R17 (33.1 in) 40 PSI
GX470 P265/65R17 (32 PSI) LT285/75R17 (33.8 in) 35 PSI
GX460 P265/60R18 (32 PSI) LT265/65R18 (31.6 in) 40 PSI
GX460 P265/60R18 (32 PSI) LT285/65R18 (32.6 in) 35 PSI
GX460 P265/60R18 (32 PSI) LT275/70R18 (33.2 in) 35 PSI
GX460 P265/60R18 (32 PSI) LT285/70R17 (32.7 in) 35 PSI
GX550 (Overtrail, 18 in) 265/70R18 (35 PSI) LT275/70R18 (33.2 in) 50 PSI
GX550 (Overtrail, 18 in) 265/70R18 (35 PSI) LT285/70R18 (33.7 in) 45 PSI
GX550 (Overtrail, 18 in) 265/70R18 (35 PSI) LT315/70R17 (34.4 in) 35 PSI
GX550 (20 in trims) 265/55R20 (33 PSI) LT275/70R18 (33.2 in) 40 PSI
GX550 (20 in trims) 265/55R20 (33 PSI) LT285/70R18 (33.7 in) 35 PSI
GX550 (20 in trims) 265/55R20 (33 PSI) LT315/70R17 (34.4 in) 35 PSI
GX550 (22 in trims) 265/50R22 (33 PSI) LT275/70R18 (33.2 in) 35 PSI
GX550 (22 in trims) 265/50R22 (33 PSI) LT285/70R18 (33.7 in) 35 PSI
GX550 (22 in trims) 265/50R22 (33 PSI) LT315/70R17 (34.4 in) 35 PSI

Notice the GX550 Overtrail needs 50 PSI in an LT275/70R18. The truck is heavier and its stock tire carries more, so the replacement has to work harder to match it. This is exactly why you run the math instead of copying a forum number. A 35 PSI guess that works fine on a GX470 would leave a GX550 Overtrail underinflated in that size.

Load Range C vs D vs E

The letter is a strength rating, expressed as a ply rating. C is 6 ply rated, D is 8, E is 10. Modern radials do not literally have that many plies. It is shorthand for how much pressure the tire is built to hold: C tops out at 50 PSI, D at 65, E at 80.

Moving up a range buys a stiffer, heavier, more puncture resistant tire and costs ride comfort, unsprung weight, and fuel economy. An E range 33 on a stock weight GX470 rides harsh because the sidewall barely flexes at the 35 PSI the truck actually needs.

Buy the lightest range that covers your computed pressure. For a GX470 or GX460 on 33s, Load Range C usually covers it with margin. An LT285/70R17 in C carries up to 2,755 lb at 50 PSI, and you only need 35. Load Range D is the common middle ground in 33 and 34 inch sizes and suits armored trucks and most GX550s, which need 45 to 50 PSI in common 33s. Load Range E makes sense when the truck is genuinely heavy (steel bumpers both ends, winch, roof tent, full armor, towing) or when the size you want only comes in E, which is true of many 35s. Never inflate past the max pressure stamped on the sidewall, and never assume an E tire needs E pressures. The load table sets the pressure, not the sidewall.

Parts and tools

You need very little for this job:

  • A quality tire pressure gauge. Dial type gauges are easier to read precisely than pencil gauges. Shadetree alternative: the pencil gauge in your glove box. It works, just check it against a known good gauge once.
  • Sidewalk chalk, the fat sticks kids use on driveways. Shadetree alternative: white shoe polish or a paint marker. Chalk washes off; paint does not.
  • A portable 12 volt tire inflator. You will be bleeding pressure down and adding it back during the test, and you need one on the trail anyway for airing back up. Two proven options. The VIAIR EVC88P clips directly to the battery terminals, has a digital gauge with preset auto shutoff, and runs to 120 PSI max. It is the trail standard for airing up 33s. It cannot run from the cigarette socket. It draws too much current, which is the point. The AstroAI S1 plugs into the cigarette lighter, has a digital display with preset auto shutoff, and runs to 150 PSI max. It lives in the glovebox for occasional use. It is slower on big tires and can pop the socket fuse on some trucks, so carry spare fuses and run the engine while it works. VIAIR EVC88P. AstroAI S1.
  • A flat, level paved surface about 50 feet long. An empty parking lot is ideal.

If you pull wheels for any reason during the process, torque the nuts to spec:

Model Wheel nut torque
GX470 (2003 through 2009) 83 ft lb (112 N·m) 7
GX460 (2010 through 2012) 83 ft lb (112 N·m) 8
GX460 (2016 through 2023) 76 ft lb (103 N·m) 8
GX550 (2024 and newer) 97 ft lb (131 N·m) 9

The GX460 changeover year between 2012 and 2016 is unverified. If yours is a 2013 through 2015, check your owner’s manual.

The Chalk Test, Step by Step

The tables get you the starting pressure. The chalk test confirms the contact patch is actually even on your truck, with your alignment and your load.

  1. Set all four tires to your calculated starting pressure, cold.
  2. Draw a thick chalk stripe straight across the tread of each tire, edge to edge.
  3. Drive straight forward about 50 feet on flat pavement. No turning. Turning scrubs the chalk sideways and ruins the reading.
  4. Look at each stripe.

Three panel diagram showing chalk wear patterns for overinflated, underinflated, and correctly inflated tires

  • Chalk scrubbed off in the center but still on the edges: too much air. The tire is riding on the middle of the tread. Bleed 2 PSI and repeat.
  • Chalk scrubbed off on the edges but still in the center: too little air. The tire is riding on its shoulders. Add 2 PSI and repeat.
  • Chalk scrubbed evenly all the way across: this is the target. Write the number down.

Test front and rear separately. The GX is nose heavy, so the fronts often want a touch more air than the rears. Repeat the test with your normal load in the truck. A pressure that chalks perfectly empty can chalk edge heavy with a full cargo area.

Front vs Rear

The door placard gives one pressure for front and rear because it has to cover the worst case simply. In practice, the V8 sits over the front axle and the front tires carry more. Many GX owners end up running the front about 2 PSI higher than the rear when unloaded. This is owner reported practice, not a factory spec, so treat it as a starting experiment and let the chalk test decide. Never run the rear lower than the table minimum for your load.

Armor changes the math. The placard assumed stock weight. A steel front bumper and winch add roughly 150 to 250 lb over the front axle. A rear swing out tire carrier with a full size spare, jerry cans, and a steel rear bumper can add a similar amount behind the rear axle. After armor, both ends want more air. The honest way to set it is a trip across a CAT scale to get real axle weights, then re run the five steps above against those numbers instead of the stock baseline. Chalk test with the armor on before calling it done.

Loaded, Unloaded, and Towing

Pick two pressures, not one. Your daily unloaded pressure comes from the method above. Your loaded pressure comes from running the same method against the heavier axle weights, or simply from adding 3 to 5 PSI to the rear when the truck is fully loaded or hitched to a trailer, then confirming with the chalk test under that load. Towing on soft tires is where blowouts come from: heat builds in the flexing sidewall, and a loaded trailer adds both weight and sway leverage. Air up before the trip, not after the first rest stop.

Check pressures cold, in the morning, before driving. Pressure climbs 3 to 5 PSI as the tire warms up. Never bleed a hot tire down to your cold target; you will end up underinflated. Keep the spare at placard pressure or a few PSI above. Spares lose air sitting in the carrier for months, and a flat spare is discovered at the worst possible moment.

Airing Down for Trails and Sand

Off pavement, the rules change temporarily. Dropping pressure lengthens the contact patch, which is traction on sand and a smoother ride on rocky trails. Start at roughly 50 percent of your street PSI. If you run 35 on the street, air down to about 17 or 18 for sand and slow trails. You can go lower for very slow speeds and short distances. Drive gently with no sharp turns, and air back up before touching pavement. Below about 15 PSI you risk debeading a tire off the wheel without beadlock wheels. This is trail practice from the owner community, not a factory spec. The load tables do not cover it because the tables assume highway speeds and loads.

TPMS After a Tire Swap

All three GX generations have a tire pressure monitoring system, and it still works after upsizing. It reads pressure, not tire size, so nothing needs recalibrating for the larger diameter. Three things to know. The warning light comes on around 24 to 26 PSI, roughly 25 percent below placard, so if you now run 35 PSI on a 32 PSI placard, the light still comes on around the same low pressure as before. If your new baseline is much higher than stock, use the TPMS reset button (in the multi-information display or under the lower dash) to store the new pressure as the baseline. Then the light trips at 25 percent below your new number instead of the old one. When you air down for a trail, the light comes on. That is normal. Air back up and it goes off. Disabling the TPMS is possible with aftermarket tools, but it is not advised and not necessary. And if you got new wheels or new sensors, the sensors must be registered to the truck or the light stays on no matter what the gauge says. Any tire shop does this in a few minutes, or do it yourself with a TPMS relearn tool like the Autel TS508. If four new sensors will not register, try syncing all five including the spare. Photograph each sensor’s label with your phone before the tires are mounted. Having the sensor IDs on hand makes registration much simpler.

OEM sensors are Toyota 42607-33021 (2003 to 2017 GX470 and GX460) and 42607-06030 (2021 and newer GX460, all GX550). If you have a 2018 to 2020 GX460, check the part number on your old sensor before ordering. Denso makes Toyota’s factory sensors, so the Denso 550-0103 and 550-0105 are the same hardware in a Denso box. The programmable Autel MX-Sensor is the budget route if you already own the TS508.

Sources

Footnotes

  1. 2005 GX470 factory repair manual, tire size and pressure spec table: P265/65R17 110S front and rear at 220 kPa (32 PSI). Confirmed across 2003 through 2008 owner’s manuals.
  2. 2010 and 2012 GX460 owner’s manuals, maintenance data: P265/60R18 109H at 32 PSI front, rear, and spare.
  3. Toyo Tires RV load and inflation tables, application notes: when P metric tires are used on light trucks or SUVs, divide the published load by 1.10.
  4. Nitto load and inflation tables, P metric section: P265/65R17 110 SL carries 2,260 lb at 32 PSI and 2,337 lb at 35 PSI.
  5. Toyo Tires commercial load and inflation tables, LT metric section: LT285/70R17 carries 2,105 lb at 35 PSI, 2,315 lb at 40 PSI, 2,510 lb at 45 PSI, and 2,755 lb at 50 PSI (Load Range C maximum).
  6. Nitto load and inflation tables, P metric section: P265/60R18 109 SL carries 2,183 lb at 32 PSI.
  7. GX470 owner’s manuals and 2005 factory repair manual torque table: wheel nuts 112 N·m, listed as 83 ft lb in the owner’s manuals (82 ft lb in the repair manual table).
  8. 2010 and 2012 GX460 owner’s manuals list 83 ft lb (112 N·m); the 2016 GX460 owner’s manual lists 76 ft lb (103 N·m). The changeover year is unverified.
  9. 2024 GX550 owner’s manual, Specifications section: 265/50R22 112V at 33 PSI front, rear, and spare; 265/55R20 113V at 33 PSI front, rear, and spare; 265/70R18 116H at 35 PSI front, rear, and spare; wheel nut torque 97 ft lb (131 N·m) all trims.

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