Tire Pressure recommendation (2 Viewers)

[Gamer]

@gaijin On a 2015 LX570, what would be the recommended cold tire pressure for these tires/wheels?
LT275/70R-18 BFGoodrich All-Terrain T/A KO3 E on Toyota 18" tundra rims (I don't think this information matters)

I used the calculator you posted and got this (which I hope is right, but should be good enough for gov't work):
New Size (LT275/70R18 E) Load Capacity: 2110 lbs. @ 36 psi.

 

[PDoyle]

Gaijin, my 2018 LX is riding on new GoodYear WeatherReady 2 ( 31.1 dia. ) 285/45R21's and having a tough time finding the correct tire pressure for these. Your insight would be great. Thanks much.

 

[gaijin]

Gaijin, my 2018 LX is riding on new GoodYear WeatherReady 2 ( 31.1 dia. ) 285/45R21's and having a tough time finding the correct tire pressure for these. Your insight would be great. Thanks much.

If those are the ISO-Metric 285/45R21 XL 113H tires, then the RCTIP is same as OEM 275/50R21 XL 113V: 33psi F/R.

HTH

 

[PDoyle]

Thank you sir.

 

[K9LTW]

@gaijin On a 2015 LX570, what would be the recommended cold tire pressure for these tires/wheels?
LT275/70R-18 BFGoodrich All-Terrain T/A KO3 E on Toyota 18" tundra rims (I don't think this information matters)

I used the calculator you posted and got this (which I hope is right, but should be good enough for gov't work):
New Size (LT275/70R18 E) Load Capacity: 2110 lbs. @ 36 psi.

I didn't see a reply to this, but...yes...that's correct.

 

[kcjaz]

I ran the calculator that @gaijin posted but wasn’t sure if my original OEM tire’s tire type. This is on my 2025 Tacoma, not my LC. The factory tires were BFG Trail-Terrain A/Ts. I don’t believe these are LT tires so I picked “Metric” as the tire type. Any thing else didn’t let me select OEM pressure below 35 and the door sticker says 30 psi.

Here is the data for the OEM tire(Load index of 115):

Here is my calc results for my new E rated K03s.

Discount Tire “calculated” 45 psi and filled them to that. Pretty sure that is too high. I ran the first ~4K miles at about 42 psi and then dropped to 30 psi to see how that felt. The ride is a lot more comfy at 30 but that is probably too low for the E rated K03s I’m running. Or is it? As I said, this is on my Tacoma and I don’t tow or carry heavy loads. Does an E rated tire really care if it is “under inflated” (within reason) if you are under the load capacity? It would be interesting of the calculator let you enter the load capacity in lbs to see the affect on recommended pressure. My curb weight is probably 5000 lbs or 1250 per corner. That is a lot less than the rated capacity of 2116. I’m just curious what the capacity would be at 30 psi. Or am I thinking about this wrong?

 

[gaijin]

I ran the calculator that @gaijin posted but wasn’t sure if my original OEM tire’s tire type. This is on my 2025 Tacoma, not my LC. The factory tires were BFG Trail-Terrain A/Ts. I don’t believe these are LT tires so I picked “Metric” as the tire type. Any thing else didn’t let me select OEM pressure below 35 and the door sticker says 30 psi.

Here is the data for the OEM tire(Load index of 115):

View attachment 3997409

Here is my calc results for my new E rated K03s.


View attachment 3997401

Discount Tire “calculated” 45 psi and filled them to that. Pretty sure that is too high. I ran the first ~4K miles at about 42 psi and then dropped to 30 psi to see how that felt. The ride is a lot more comfy at 30 but that is probably too low for the E rated K03s I’m running. Or is it? As I said, this is on my Tacoma and I don’t tow or carry heavy loads. Does an E rated tire really care if it is “under inflated” (within reason) if you are under the load capacity? It would be interesting of the calculator let you enter the load capacity in lbs to see the affect on recommended pressure. My curb weight is probably 5000 lbs or 1250 per corner. That is a lot less than the rated capacity of 2116. I’m just curious what the capacity would be at 30 psi. Or am I thinking about this wrong?

Skipping the "Easy Button" and actually doing the math using the industry standard Load/Inflation tables from the TRA (Tire and Rim Association) that I posted in the other link on calculating tire pressures (find it here: Guidelines for the Application of Load and Inflation Tables) we can better understand what you need.

Your OEM tires are ISO-Metric 265/70R17 SL 115S with a factory RCTIP of 30psi.

Looking at the tables on page 34 of the Guidelines for SL ISO-Metric tires, we find that the RCTIP of 30psi with your 115 Load Index gives you a Load Limit of 2,326 pounds. This is the Load Limit you have to meet with your new tires.

Since your new tires are LT-Metric LT265/70R18 Load Range E, the ISO-Metric Load Limit of 2,326 pounds must be adjusted to account foe the different construction of LT-Metric tires. This is done by dividing the ISO-Metric Load Limit of 2,326 pounds by 1.1: 2326/1.1 = 2114.5 pounds. Let's call it 2,115 pounds - This is the Load Limit you have to meet or exceed for your new tires.

Looking at the tables on page 27 of the Guidelines for LT-Metric tires, we find that the target Load Limit of 2,115 pounds falls between 35psi (1960 pounds) and 40psi (2155 pounds).

Some simple math shows that between 35psi and 40psi there is a 39 pound Load Limit change per psi. If we add 4 x 39 = 156 pounds to 1960 (1960+156 = 2116) we get the required pressure of 35 + 4 = 39psi.

So...

The RCTIP for LT265/70R18 Load Range E tires on your Tacoma is 39psi F/R.

Also note that the absolute minimum safe tire pressure for ANY LT-Metric tire on ANY vehicle is 35psi. Anything below 35psi allows too much flex in the heavy sidewall construction of the tire and allows heat build-up beyond the tires ability to dissipate it, resulting in an unsafe condition which could result in tire failure or at least overall weakening of the tire construction over time.

Further note:

I undertook this post as a one time only example so that others may be better able to do these calcs on their own.

HTH

 

[kcjaz]

Skipping the "Easy Button" and actually doing the math using the industry standard Load/Inflation tables from the TRA (Tire and Rim Association) that I posted in the other link on calculating tire pressures (find it here: Guidelines for the Application of Load and Inflation Tables) we can better understand what you need.

Your OEM tires are ISO-Metric 265/70R17 SL 115S with a factory RCTIP of 30psi.

Looking at the tables on page 34 of the Guidelines for SL ISO-Metric tires, we find that the RCTIP of 30psi with your 115 Load Index gives you a Load Limit of 2,326 pounds. This is the Load Limit you have to meet with your new tires.

Your new tires are LT-Metric LT265/70R18 Load Range E.

Looking at the tables on page 27 of the Guidelines for LT-Metric tires, we find that the target Load Limit of 2,326 pounds falls just below 45psi, so for safety we will round up to 45psi.

So...

The RCTIP for LT265/70R18 Load Range E tires on your Tacoma is 45psi F/R.

Also note that the absolute minimum safe tire pressure for ANY LT-Metric tire on ANY vehicle is 35psi. Anything below 35psi allows too much flex in the heavy sidewall construction of the tire and allows heat build-up beyond the tires ability to dissipate it, resulting in an unsafe condition which could result in tire failure or at least overall weakening of the tire construction over time.

Further note:

I undertook this post as a one time only example so that others may be better able to do these calcs on their own.

HTH

Thank you Sensei! I did go down the rabbit hole a bit and discovered the 35 psi minimum, but thanks for pointing that out as I have been driving with 30 psi. I’ll keep them at 45 psi for now but I’ll likely drop the pressure and maybe run at the minimum 35 psi. I like the feel of 30 psi but I also don’t want to blow a tire on the freeway. Maybe I’ll check the TPMS tire temp with OBD2 at 45 and again at 35 as see if there is a big difference. In the end I absolutely want “safe” but I’m OK with faster tire wear if I can feel a difference comfort.

 

[gaijin]

Thank you Sensei! I did go down the rabbit hole a bit and discovered the 35 psi minimum, but thanks for pointing that out as I have been driving with 30 psi. I’ll keep them at 45 psi for now but I’ll likely drop the pressure and maybe run at the minimum 35 psi. I like the feel of 30 psi but I also don’t want to blow a tire on the freeway. Maybe I’ll check the TPMS tire temp with OBD2 at 45 and again at 35 as see if there is a big difference. In the end I absolutely want “safe” but I’m OK with faster tire wear if I can feel a difference comfort.

Sounds like a plan

 

[gaijin]

Thank you Sensei! I did go down the rabbit hole a bit and discovered the 35 psi minimum, but thanks for pointing that out as I have been driving with 30 psi. I’ll keep them at 45 psi for now but I’ll likely drop the pressure and maybe run at the minimum 35 psi. I like the feel of 30 psi but I also don’t want to blow a tire on the freeway. Maybe I’ll check the TPMS tire temp with OBD2 at 45 and again at 35 as see if there is a big difference. In the end I absolutely want “safe” but I’m OK with faster tire wear if I can feel a difference comfort.

I screwed up! Sorry. I forgot to correct the LT-Metric Load Limit to account for the difference in construction between ISO-Metric tires and LT-Metric tires.

Please see my corrected post above.

To re-emphasize the key point: Your "safe" range is between 35psi and 39psi for the LT265/70R18 Load Range E tires on your Tacoma.

Again, sorry for the confusion.

HTH

 

[kcjaz]

I screwed up! Sorry. I forgot to correct the LT-Metric Load Limit to account for the difference in construction between ISO-Metric tires and LT-Metric tires.

Please see my corrected post above.

To re-emphasize the key point: Your "safe" range is between 35psi and 39psi for the LT265/70R18 Load Range E tires on your Tacoma.

Again, sorry for the confusion.

HTH

Thanks again. I read through the guideline this morning with my coffee. Looks like the error in the math Discount Tire made was the 10% ISO-metric “derate” for an ISO-metric tire run on a light truck. That accounts for the difference between 45 and 39 (with some rounding of decimal's). Easy to do, as the technician did not have the benefit of seeing the OEM tire and probably just assumed a Tacoma came with LT tires as the door sticker doesn’t say.

 

[hoser]

Also note that the absolute minimum safe tire pressure for ANY LT-Metric tire on ANY vehicle is 35psi. Anything below 35psi allows too much flex in the heavy sidewall construction of the tire and allows heat build-up beyond the tires ability to dissipate it, resulting in an unsafe condition which could result in tire failure or at least overall weakening of the tire construction over time.

I see the 35 psi minimum repeated but I don't see the reference. I've checked the TRA manual. Can you point me to it?

 

[gaijin]

I see the 35 psi minimum repeated but I don't see the reference. I've checked the TRA manual. Can you point me to it?

The clearest declarative statement can be found in the JATMA (Japan Automobile Tyre Manufacturers Association) Year Book:

Unfortunately, neither the TRA nor JATMA provide a declarative rationale for this requirement, but we are safe to infer that since there are no Load Limits provided for ANY LT tire below 35psi, there is no acceptable application for a lower pressure.

I can't remember whether it was a FMVSS or a tire manufacturer's tech paper, but I do remember reading a test procedure for low pressure testing that concluded that anything below 35psi was unacceptable. If I get a clearer idea of what that specific reference is, I'll post it up later.

HTH

 

[hoser]

Unfortunately, neither the TRA nor JATMA provide a declarative rationale for this requirement, but we are safe to infer that since there are no Load Limits provided for ANY LT tire below 35psi, there is no acceptable application for a lower pressure.

If you take a look at the pressure tables for the floatation sizes, they do indeed list 25 psi and 30 psi and their corresponding rated load. Floatation sized tires can be LT tires too. In fact, some of the Toyo/Nitto tires sold as LT-Metric come with the sticker on the tread that has the equivalent floatation size.

Added:

 

[gaijin]

If you take a look at the pressure tables for the floatation sizes, they do indeed list 25 psi and 30 psi and their corresponding rated load. Floatation sized tires can be LT tires too. In fact, some of the Toyo/Nitto tires sold as LT-Metric come with the sticker on the tread that has the equivalent floatation size.

View attachment 3998830

Added:

View attachment 3998869

My original statement, and your question regarding that statement, as well as my answer to your question... were all addressing LT-Metric tires - not LT Flotation tires which have their own (and different) Load Inflation table.

Any tire labeled as the one in your post should be considered a LT Flotation tire and use the LT Flotation Load Inflation table.

Just FYI, there are different Load Inflation tables for the following types of tires:

ETRTO (ISO-Metric) Standard Load (SL)
ETRTO (ISO-Metric) Reinforced Load (XL)
P-Metric
LT-Metric
LT Flotation

That is why, when discussing RCTIP, it is necessary to accurately identify the tire type.

HTH

 

[hoser]

@gaijin Okay, fine. New question, what is the minimum pressure for an LT-Flotation tire such as a 35x11.5R18?

 

[gaijin]

@gaijin Okay, fine. New question, what is the minimum pressure for an LT-Flotation tire such as a 35x11.5R18?

According to the TRA Load/Inflation tables, the minimum allowable pressure for continued use on improved roads is 25psi with a Load Limit of 1765 pounds.

Note that this is not an RCTIP for a LC200 - at 25psi on an LC200 these tires would be dangerously underinflated for use at speed. The RCTIP (minimum allowable pressure for use at speed) for an LC200 would be 37psi.

So... what's your point? Where are you going with this?

HTH

 

[hoser]

I'm just looking for facts. Thanks for trying. Report back if you come up with anything else. It is difficult to believe, 35 psi is the hard line lower threshold for an LT-Metric tire with ANY and all loads. Just because 35 psi is the lowest figure on the chart doesn't make it the minimum pressure without blowing a tire.

With regards to your statement about 25 psi / 1765 lbs being dangerously under inflated, I disagree. The RCTIP is acceptable up to and including the Gross Vehicle Weight Rating. The curb weight of a 2008 LC200 is only 5700 lbs. 1765 lbs x 4 = 7,060 lbs. Fuel mileage will suffer and tires will wear faster but it will not be dangerous.

 

[gaijin]

With regards to your statement about 25 psi / 1765 lbs being dangerously under inflated, I disagree. The RCTIP is acceptable up to and including the Gross Vehicle Weight Rating. The curb weight of a 2008 LC200 is only 5700 lbs. 1765 lbs x 4 = 7,060 lbs. Fuel mileage will suffer and tires will wear faster but it will not be dangerous.

I think you may be overlooking the fact that you are rationalizing a live load requirement (tire Load Limit) with a static load measurement (vehicle weight).

Toyota equips stock LC200's with tires that have a Load Limit of 2512 lbs x 4 = 10,048 lbs. That's for P-Metric/ISO-Metric tires, so keeping it all in the LT-Metric realm, for LT-Metric tires the factory tires would have a Load Limit of 2286 lbs x 4 = 9,144 lbs.

The TIP (Tire Information Placard) on the vehicle stipulates the GVWR (7385 lbs) and the tire size and inflation required to safely support that GVWR - that's 4 tires with a total Load Limit of 10,048 lbs.

If your statement were true, then why is Toyota requiring their tires to be so dramatically overinflated?

The key to that answer is the live loading a tire is subjected to while actually driving/maneuvering the vehicle. Every time a tire hits a bump, curb, pothole, make a sharp turn, brakes hard, etc. it is subject to a live loading which is greater than the load required to simply support the static weight of the vehicle, but also maintain integrity when subject to higher transient loads.

But this is all old stuff. I'm sure you have seen this from me many times. So if these facts don't float your boat - for whatever reason - then I hope you find the facts you are looking for.

HTH

 

[hoser]

There are A LOT of factors why Toyota or any manufacturer to stipulate a higher tire pressure than required including fuel mileage, tire wear, handling, emergency handling.... lawsuits.... a lot of people are past GVWR. The TPMS doesn't not alert unless a certain threshold below recommended tire pressure. That's probably a factor too.

There's a range of pressure that is considered safe, none exceeding maximum pressure listed on the sidewall. All choices have compromises. There's optimal and there is acceptable. I'd even say the manufacturer's pressure listed on the TIP is less than optimal when loaded to GVWR. Should probably be 5-10psi higher than stated

There's already a buffer built in to the tire's load rating with a static load. The difference between dynamic load and static load is even greater when going off road in the sand or desert. Members here, including myself are running ~20psi for hundreds (some thousands) of miles over washboard and bumpy terrain without issue.... and with more weight. This is not the same as driving on the road but it is a testament to the strength of these LT tires. Running 37 psi on washboard roads would be more dangerous than 20 psi. Don't believe me? Try it.