Tire Pressure for Rock Warriors with LT285/70/17, Load range Es?

[gaijin]

Does the load rating change the calculus? If I understand @gaijin post #7, the only thing that would change the PSI is P or LT, correct? 2015 LX570 with RW and LT285/70r17 BFG KO2 Load Range C (new takeoffs from a J**p Rubicon) should be inflated to 40PSI?

Load Range doesn't change your calculus, but vehicle choice does.

The RCTIP for LT285/70R17 tires on your LX570 is 35psi F/R.

HTH

 

[unclemat]

Load Range doesn't change your calculus, but vehicle choice does.

The RCTIP for LT285/70R17 tires on your LX570 is 35psi F/R.

HTH

Huge difference from 40psi on 200 LC...

 

[TeCKis300]

Huge difference from 40psi on 200 LC...

Unless you're towing or laden, there's not reason you can't use that same 35PSI.

 

[gaijin]

Huge difference from 40psi on 200 LC...

It's simply the way Toyota/Lexus have engineered the two different suspension systems. I'd be cautious of any advice from others who think they know more than Toyota/Lexus.

HTH

 

[silver tuna]

Load Range doesn't change your calculus, but vehicle choice does.

The RCTIP for LT285/70R17 tires on your LX570 is 35psi F/R.

HTH

Is the lower psi number for the lx570 because it has a lower GWVR than the land cruiser? Also, how low can air pressure be at normal highway speeds and still be safe on an empty LX 570? Is 32psi too low?? thanks!

 

[gaijin]

Is the lower psi number for the lx570 because it has a lower GWVR than the land cruiser? Also, how low can air pressure be at normal highway speeds and still be safe on an empty LX 570? Is 32psi too low?? thanks!

As far as the difference between LC200 and LX570 RCTIP (Recommended Cold Tire Inflation Pressure):

Toyota/Lexus engineered the suspensions on the two vehicles to provide optimum safe performance with different tire spring rates (i.e. tire pressures). Different vehicles, different suspensions, different engineering considerations from the manufacturer - simple as that.

The RCTIP for the LX570 is the lowest allowable cold tire pressure for all speeds and all vehicle loads up to the GVWR. If you are asking specifically about the LT285/70R17 tires on your LX570, then 35psi is the lowest allowable cold tire pressure. So, yes, 32psi is too low. Because tire pressures increase at a variable rate when warmed up, it is best if tire pressures are set/measured when the tires are cold. Toyota published an excellent TSB about what "cold" means:

This document also shows that "Hot" tires - which would fit your question about pressures during normal highway driving - would have a tire pressure of 4-5 psi higher than the "Cold" tire pressure. In the context of your question, this means that the minimum required tire pressure at highway speed with hot tires would be approximately 39-40psi.

Final note: do not trust your dash display TPMS for accurate tire pressures. Using a sophisticated dedicated tire pressure gauge (Maker info here: 99.99 PSI DIGITAL AIR PRESSURE GAUGE, Available for purchase on Amazon here: Intercomp Digital Pressure Guage), I have found the TPMS readout on my 2013 LC200 to be "off" as much as approximately 2-3psi.

HTH

 

[silver tuna]

As far as the difference between LC200 and LX570 RCTIP (Recommended Cold Tire Inflation Pressure):

Toyota/Lexus engineered the suspensions on the two vehicles to provide optimum safe performance with different tire spring rates (i.e. tire pressures). Different vehicles, different suspensions, different engineering considerations from the manufacturer - simple as that.

The RCTIP for the LX570 is the lowest allowable cold tire pressure for all speeds and all vehicle loads up to the GVWR. If you are asking specifically about the LT285/70R17 tires on your LX570, then 35psi is the lowest allowable cold tire pressure. So, yes, 32psi is too low. Because tire pressures increase at a variable rate when warmed up, it is best if tire pressures are set/measured when the tires are cold. Toyota published an excellent TSB about what "cold" means:

View attachment 2853860

This document also shows that "Hot" tires - which would fit your question about pressures during normal highway driving - would have a tire pressure of 4-5 psi higher than the "Cold" tire pressure. In the context of your question, this means that the minimum required tire pressure at highway speed with hot tires would be approximately 39-40psi.

Final note: do not trust your dash display TPMS for accurate tire pressures. Using a sophisticated dedicated tire pressure gauge (Maker info here: 99.99 PSI DIGITAL AIR PRESSURE GAUGE, Available for purchase on Amazon here: Intercomp Digital Pressure Guage), I have found the TPMS readout on my 2013 LC200 to be "off" as much as approximately 2-3psi.

HTH

Thank you, I appreciate it…I’ll run the correct 35PSI.

 

[AnyMal]

Unless you're towing or laden, there's not reason you can't use that same 35PSI.

Don't even bother brother.
For one, convincing others theyve been fooled, well, you know what they say.
Two, why ruin my entertainment?

 

[highfructose]

That's exactly what I've been saying.

The Toyota recommended pressure for the OEM P285/60-18 tires results in a load carrying capacity of 2,512 pounds which is 10% higher than it would be if it were mounted on a passenger car. So, at 33 psi 2,512 / 1.1 = 2,283 pounds which is the unadjusted load carrying requirement for the Land Cruiser.

Therefore ...

We do not have to increase the LT-Rated LT285/70-17 load carrying capacity because it is being installed on a truck. So, at 39.3 psi = 2,286 pounds which is the same as the unadjusted load carrying capacity of the P-Rated tire.

Here it is in a nutshell:

The load carrying capacity required for tires on the Land Cruiser is 2,283 pounds per tire.

Since the Land Cruiser is not a passenger car, if P-Rated tires are installed, this load carrying capacity must be increased by 10% (2,283 X 1.1 = 2,512 pounds. To meet that load limit for P285/60-18 tires, 33 psi is required.

But, if we install LT-Rated tires, which are designed to be installed on trucks, no adjustment to the load carrying capacity is required - it can stay at 2,283 pounds. To meet that load limit for LT285/70-17 tires, 39.3psi is required.

Clear as ... mud, right?

Does this mean that the wheels/rims we put on our truck only really need to be 2200 lb capacity?

Looking at published data on the wheels on f150’s shows that their wheels are rated at 1800-2400 lbs…with a lot of them in the 2000-2200 range.

 

[gaijin]

Does this mean that the wheels/rims we put on our truck only really need to be 2200 lb capacity?

Looking at published data on the wheels on f150’s shows that their wheels are rated at 1800-2400 lbs…with a lot of them in the 2000-2200 range.

No, it means they really need to be >2,512 lbs.

HTH

 

[highfructose]

No, it means they really need to be >2,512 lbs.

HTH

My apologies if it comes across as argumentative…it’s not intentional, I’m genuinely curious:

if the maximum load the rear axle of the truck is supposed to be 4,300 lbs, why wouldn’t wheels with a load limit of a total of 4,400 lbs (2200 a piece) suffice?

Wouldn’t this put the wheels as about as tough as the axles? Why would we need wheels capable of 5,200 lbs of load limit when the axle is only at 4300?

 

[lx200inAR]

My apologies if it comes across as argumentative…it’s not intentional, I’m genuinely curious:

if the maximum load the rear axle of the truck is supposed to be 4,300 lbs, why wouldn’t wheels with a load limit of a total of 4,400 lbs (2200 a piece) suffice?

Wouldn’t this put the wheels as about as tough as the axles? Why would we need wheels capable of 5,200 lbs of load limit when the axle is only at 4300?

I don't have a dog in this fight, or care much. But one reason a wheel could need to be rated higher than half the axle rating is because each wheel doesn't always see equal load that the axle is carrying. There can be dynamic situations where one wheel sees most of the load of that axle.

 

[gaijin]

My apologies if it comes across as argumentative…it’s not intentional, I’m genuinely curious:

if the maximum load the rear axle of the truck is supposed to be 4,300 lbs, why wouldn’t wheels with a load limit of a total of 4,400 lbs (2200 a piece) suffice?

Wouldn’t this put the wheels as about as tough as the axles? Why would we need wheels capable of 5,200 lbs of load limit when the axle is only at 4300?

No worries, understanding stuff better is always a good idea. Let's see if I can do a better job of explaining all this (or at least some of it...)

First of all, all these "pounds" referred to are not the same - and are not directly additive or subtractive, so must be addressed separately.

Let's start with the basis for all our discussions about "pounds" as they relate to a LC200 - the GVWR Plate attached to all our vehicles - mine looks like this:

The first kind of "pound" we encounter is the GVWR (Gross Vehicle Weight Rating) number = 7385 pounds.

The GVWR (gross vehicle weight rating) is a safety regulation used to prevent the overloading of vehicles. It's the maximum safe operating weight of a truck, including its net weight, plus driver, passengers, cargo, and fuel.

This is a STATIC weight. As such, you can measure it on a scale while the vehicle is not in motion. Load up your LC200, drive to a truck scale and weigh it. Compare that weight to the GVWR to assure you are not too heavy to be safe. Simple, right?

The next kind of "pound" we encounter is the GAWR (Gross Axle Weight Rating) number = 3595 pounds Front / 4300 pounds Rear.

Gross Axle Weight Rating (GAWR) is the most distributed weight an axle of a vehicle can support.

This is also a STATIC weight which we can measure on a scale while the vehicle is not in motion. But if the Front GAWR is 3595 pounds and the Rear GAWR is 4300 pounds, which totals 4300 + 3595 = 7895 pounds, 500 pounds more than the GVWR?

The GVWR takes precedence. For example, if you load your rear axle to the maximum 4300 pounds, then you can only load your front axle to a maximum 3085 pounds to remain within the GVWR.

So far, so good, right? All "pounds" so far are STATIC pounds and can be measured on a scale while not in motion. All measured static pounds are not directly additive, but are relational. All pretty straightforward.

Now we start getting into derivative load values that are indirectly specified by the information on the GVWR plate - specifically the tire size and inflation pressure required to provide the necessary tire Load Limit to safely support the GVWR / GAWR STATIC loads while the vehicle is in motion - these will be DYNAMIC loads which cannot be measured on a scale because they apply while the vehicle is in motion. These values must be tested by the tire manufacturers in accordance with established industry standards.

Going back to the GVWR plate we find the specified tire size and RCTIP (Recommended Cold Tire Inflation Pressure) - P285/60R18 @ 33psi.

At this point we must consult the Load/Inflation Tables published by the TRA (Tire & Rim Association) to determine the Load Limit. One can find these tables here: Guidelines for the Application of Load and Inflation Tables

The TRA Load/Inflation tables tell us that the Load Limit for P285/60R18 tires @ 33psi is 2512 pounds.

These are DYNAMIC pounds and are required to support LIVE Loading as opposed to STATIC Loading. As such, we find that the DYNAMIC Load Limit for two tires on a single axle totals 5024 pounds which is significantly higher than the STATIC load indicated by the GAWR of either 3595 pounds or 4300 pounds for the Front and Rear axles. A good way to think about DYNAMIC Load is to imagine the load on a tire while driving on a straight, smooth and level road at low speed (where Dynamic Load would be fairly close to STATIC Load), and then imagine the load on that tire hitting a pothole at high speed, or hitting a curb at speed, or during a high speed maneuver - under these conditions the DYNAMIC Load is much higher than the STATIC Load.

Since the wheels directly support the tires, the wheels should have a Load Rating > the Load Limit of the specified tire. A wheel's Load Rating is a STATIC amount which can be directly measured by the wheel manufacturer - the wheel Load Rating should be clearly available from the manufacturer. If it is not, I would not trust the wheel*.

It should be noted that several sources (most notably some wheel manufacturers) indicate that a wheel's Load Rating should be determined by dividing the higher GAWR by 2. In our case, this would mean dividing the Rear GAWR of 4300 pounds by 2 to determine a wheel Load Rating of 4300 / 2 = 2150 pounds. I strongly disagree with this as it does not take into consideration the DYNAMIC Loads presented to the tires. I am not alone in this disagreement. In fact, here is what the TRA (Tire & Rim Association) - the body that publishes the standards for these things - has to say:

This is contained in the 2020 TRA Yearbook - the latest edition I have. Sorry there is not a digital or online version I can link to.

I have underlined the most pertinent sentence directly related to our discussion here. Basically what it says is that if one has a tire that has a Load Limit of 2512 pounds @ 33psi, the wheel should have a specified Load Rating > 2512 pounds and a pressure rating > 33psi.

Lastly, if one wants to use a non-specified tire size/load/structure (e.g. using an LT-Metric tire on a LC200), the determination of the appropriate size/RCTIP is a separate exercise to wheel Load Rating requirements. The required wheel Load Rating is driven by the specified tire size/RCTIP found on the GVWR plate. Simply stated, whether one installs the stock P285/60R18 tires @33psi, or the optional LT285/70R17 tires @40psi, the required wheel Load Rating remains the same - i.e. >2512 pounds. Note that in this example the wheels pressure rating should be >40psi.

TL;DR:

Wheel Load Rating needs to be >2512 pounds to be safely used on a LC200.

HTH

* Note: this does not apply to Toyota stock or option wheels. Since I trust that Toyota would thoroughly test any wheel offering for performance and suitability, what I should have written is, "A wheel's Load Rating is a STATIC amount which can be directly measured by the wheel manufacturer - the wheel Load Rating should be clearly available from the manufacturer. If it is not, and the wheel did not come from Toyota as either stock or an option, I would not trust the wheel."

 

[highfructose]

No worries, understanding stuff better is always a good idea. Let's see if I can do a better job of explaining all this (or at least some of it...)

First of all, all these "pounds" referred to are not the same - and are not directly additive or subtractive, so must be addressed separately.

Let's start with the basis for all our discussions about "pounds" as they relate to a LC200 - the GVWR Plate attached to all our vehicles - mine looks like this:

View attachment 2962278

The first kind of "pound" we encounter is the GVWR (Gross Vehicle Weight Rating) number = 7385 pounds.

The GVWR (gross vehicle weight rating) is a safety regulation used to prevent the overloading of vehicles. It's the maximum safe operating weight of a truck, including its net weight, plus driver, passengers, cargo, and fuel.

This is a STATIC weight. As such, you can measure it on a scale while the vehicle is not in motion. Load up your LC200, drive to a truck scale and weigh it. Compare that weight to the GVWR to assure you are not too heavy to be safe. Simple, right?

The next kind of "pound" we encounter is the GAWR (Gross Axle Weight Rating) number = 3595 pounds Front / 4300 pounds Rear.

Gross Axle Weight Rating (GAWR) is the most distributed weight an axle of a vehicle can support.

This is also a STATIC weight which we can measure on a scale while the vehicle is not in motion. But if the Front GAWR is 3595 pounds and the Rear GAWR is 4300 pounds, which totals 4300 + 3595 = 7895 pounds, 500 pounds more than the GVWR?

The GVWR takes precedence. For example, if you load your rear axle to the maximum 4300 pounds, then you can only load your front axle to a maximum 3085 pounds to remain within the GVWR.

So far, so good, right? All "pounds" so far are STATIC pounds and can be measured on a scale while not in motion. All measured static pounds are not directly additive, but are relational. All pretty straightforward.

Now we start getting into derivative load values that are indirectly specified by the information on the GVWR plate - specifically the tire size and inflation pressure required to provide the necessary tire Load Limit to safely support the GVWR / GAWR STATIC loads while the vehicle is in motion - these will be DYNAMIC loads which cannot be measured on a scale because they apply while the vehicle is in motion. These values must be tested by the tire manufacturers in accordance with established industry standards.

Going back to the GVWR plate we find the specified tire size and RCTIP (Recommended Cold Tire Inflation Pressure) - P285/60R18 @ 33psi.

At this point we must consult the Load/Inflation Tables published by the TRA (Tire & Rim Association) to determine the Load Limit. One can find these tables here: Guidelines for the Application of Load and Inflation Tables

The TRA Load/Inflation tables tell us that the Load Limit for P285/60R18 tires @ 33psi is 2512 pounds.

These are DYNAMIC pounds and are required to support LIVE Loading as opposed to STATIC Loading. As such, we find that the DYNAMIC Load Limit for two tires on a single axle totals 5024 pounds which is significantly higher than the STATIC load indicated by the GAWR of either 3595 pounds or 4300 pounds for the Front and Rear axles. A good way to think about DYNAMIC Load is to imagine the load on a tire while driving on a straight, smooth and level road at low speed (where Dynamic Load would be fairly close to STATIC Load), and then imagine the load on that tire hitting a pothole at high speed, or hitting a curb at speed, or during a high speed maneuver - under these conditions the DYNAMIC Load is much higher than the STATIC Load.

Since the wheels directly support the tires, the wheels should have a Load Rating > the Load Limit of the specified tire. A wheel's Load Rating is a STATIC amount which can be directly measured by the wheel manufacturer - the wheel Load Rating should be clearly available from the manufacturer. If it is not, I would not trust the wheel.

It should be noted that several sources (most notably some wheel manufacturers) indicate that a wheel's Load Rating should be determined by dividing the higher GAWR by 2. In our case, this would mean dividing the Rear GAWR of 4300 pounds by 2 to determine a wheel Load Rating of 4300 / 2 = 2150 pounds. I strongly disagree with this as it does not take into consideration the DYNAMIC Loads presented to the tires. I am not alone in this disagreement. In fact, here is what the TRA (Tire & Rim Association) - the body that publishes the standards for these things - has to say:

View attachment 2962326

This is contained in the 2020 TRA Yearbook - the latest edition I have. Sorry there is not a digital or online version I can link to.

I have underlined the most pertinent sentence directly related to our discussion here. Basically what it says is that if one has a tire that has a Load Limit of 2512 pounds @ 33psi, the wheel should have a specified Load Rating > 2512 pounds and a pressure rating > 33psi.

Lastly, if one wants to use a non-specified tire size/load/structure (e.g. using an LT-Metric tire on a LC200), the determination of the appropriate size/RCTIP is a separate exercise to wheel Load Rating requirements. The required wheel Load Rating is driven by the specified tire size/RCTIP found on the GVWR plate. Simply stated, whether one installs the stock P285/60R18 tires @33psi, or the optional LT285/70R17 tires @40psi, the required wheel Load Rating remains the same - i.e. >2512 pounds. Note that in this example the wheels pressure rating should be >40psi.

TL;DR:

Wheel Load Rating needs to be >2512 pounds to be safely used on a LC200.

HTH

That was very clear, thank you.

I’ve seen a lot of rock warrior rims that are cracked for sale…what are the odds its load rating isn’t 2512 lbs or more? Does Toyota publish what their wheels are rated for?

 

[gaijin]

That was very clear, thank you.

I’ve seen a lot of rock warrior rims that are cracked for sale…what are the odds its load rating isn’t 2512 lbs or more? Does Toyota publish what their wheels are rated for?

You're welcome

I have never seen a Load Rating for the RW wheels published by Toyota.

 

[TeCKis300]

No worries, understanding stuff better is always a good idea. Let's see if I can do a better job of explaining all this (or at least some of it...)

First of all, all these "pounds" referred to are not the same - and are not directly additive or subtractive, so must be addressed separately.

Let's start with the basis for all our discussions about "pounds" as they relate to a LC200 - the GVWR Plate attached to all our vehicles - mine looks like this:

View attachment 2962278

The first kind of "pound" we encounter is the GVWR (Gross Vehicle Weight Rating) number = 7385 pounds.

The GVWR (gross vehicle weight rating) is a safety regulation used to prevent the overloading of vehicles. It's the maximum safe operating weight of a truck, including its net weight, plus driver, passengers, cargo, and fuel.

This is a STATIC weight. As such, you can measure it on a scale while the vehicle is not in motion. Load up your LC200, drive to a truck scale and weigh it. Compare that weight to the GVWR to assure you are not too heavy to be safe. Simple, right?

The next kind of "pound" we encounter is the GAWR (Gross Axle Weight Rating) number = 3595 pounds Front / 4300 pounds Rear.

Gross Axle Weight Rating (GAWR) is the most distributed weight an axle of a vehicle can support.

This is also a STATIC weight which we can measure on a scale while the vehicle is not in motion. But if the Front GAWR is 3595 pounds and the Rear GAWR is 4300 pounds, which totals 4300 + 3595 = 7895 pounds, 500 pounds more than the GVWR?

The GVWR takes precedence. For example, if you load your rear axle to the maximum 4300 pounds, then you can only load your front axle to a maximum 3085 pounds to remain within the GVWR.

So far, so good, right? All "pounds" so far are STATIC pounds and can be measured on a scale while not in motion. All measured static pounds are not directly additive, but are relational. All pretty straightforward.

Now we start getting into derivative load values that are indirectly specified by the information on the GVWR plate - specifically the tire size and inflation pressure required to provide the necessary tire Load Limit to safely support the GVWR / GAWR STATIC loads while the vehicle is in motion - these will be DYNAMIC loads which cannot be measured on a scale because they apply while the vehicle is in motion. These values must be tested by the tire manufacturers in accordance with established industry standards.

Going back to the GVWR plate we find the specified tire size and RCTIP (Recommended Cold Tire Inflation Pressure) - P285/60R18 @ 33psi.

At this point we must consult the Load/Inflation Tables published by the TRA (Tire & Rim Association) to determine the Load Limit. One can find these tables here: Guidelines for the Application of Load and Inflation Tables

The TRA Load/Inflation tables tell us that the Load Limit for P285/60R18 tires @ 33psi is 2512 pounds.

These are DYNAMIC pounds and are required to support LIVE Loading as opposed to STATIC Loading. As such, we find that the DYNAMIC Load Limit for two tires on a single axle totals 5024 pounds which is significantly higher than the STATIC load indicated by the GAWR of either 3595 pounds or 4300 pounds for the Front and Rear axles. A good way to think about DYNAMIC Load is to imagine the load on a tire while driving on a straight, smooth and level road at low speed (where Dynamic Load would be fairly close to STATIC Load), and then imagine the load on that tire hitting a pothole at high speed, or hitting a curb at speed, or during a high speed maneuver - under these conditions the DYNAMIC Load is much higher than the STATIC Load.

Since the wheels directly support the tires, the wheels should have a Load Rating > the Load Limit of the specified tire. A wheel's Load Rating is a STATIC amount which can be directly measured by the wheel manufacturer - the wheel Load Rating should be clearly available from the manufacturer. If it is not, I would not trust the wheel*.

It should be noted that several sources (most notably some wheel manufacturers) indicate that a wheel's Load Rating should be determined by dividing the higher GAWR by 2. In our case, this would mean dividing the Rear GAWR of 4300 pounds by 2 to determine a wheel Load Rating of 4300 / 2 = 2150 pounds. I strongly disagree with this as it does not take into consideration the DYNAMIC Loads presented to the tires. I am not alone in this disagreement. In fact, here is what the TRA (Tire & Rim Association) - the body that publishes the standards for these things - has to say:

View attachment 2962326

This is contained in the 2020 TRA Yearbook - the latest edition I have. Sorry there is not a digital or online version I can link to.

I have underlined the most pertinent sentence directly related to our discussion here. Basically what it says is that if one has a tire that has a Load Limit of 2512 pounds @ 33psi, the wheel should have a specified Load Rating > 2512 pounds and a pressure rating > 33psi.

Lastly, if one wants to use a non-specified tire size/load/structure (e.g. using an LT-Metric tire on a LC200), the determination of the appropriate size/RCTIP is a separate exercise to wheel Load Rating requirements. The required wheel Load Rating is driven by the specified tire size/RCTIP found on the GVWR plate. Simply stated, whether one installs the stock P285/60R18 tires @33psi, or the optional LT285/70R17 tires @40psi, the required wheel Load Rating remains the same - i.e. >2512 pounds. Note that in this example the wheels pressure rating should be >40psi.

TL;DR:

Wheel Load Rating needs to be >2512 pounds to be safely used on a LC200.

HTH

* Note: this does not apply to Toyota stock or option wheels. Since I trust that Toyota would thoroughly test any wheel offering for performance and suitability, what I should have written is, "A wheel's Load Rating is a STATIC amount which can be directly measured by the wheel manufacturer - the wheel Load Rating should be clearly available from the manufacturer. If it is not, and the wheel did not come from Toyota as either stock or an option, I would not trust the wheel."

While I agree with the overall sentiment.

Wheels are made to go round and round. The assumption that its rated for static use only is questionable in my mind.

 

[gaijin]

I’ve seen a lot of rock warrior rims that are cracked for sale…what are the odds its load rating isn’t 2512 lbs or more? Does Toyota publish what their wheels are rated for?

In all fairness, I should add to my post above that ANY wheel offered by Toyota as a stock or option wheel - even if not marked with Load/Pressure Ratings - should be trusted to have passed all Toyota rigorous testing for safety and suitability and, as such, can be trusted to have a "sufficient" Load Rating. I just don't know what Toyota's internal specs are for wheel Load Rating, and I have never seen a Load Rating on ANY Toyota factory/option wheel.

In my long post immediately above, I should have said, "A wheel's Load Rating is a STATIC amount which can be directly measured by the wheel manufacturer - the wheel Load Rating should be clearly available from the manufacturer. If it is not, and the wheel did not come from Toyota as either stock or an option, I would not trust the wheel."

HTH

 

[gaijin]

While I agree with the overall sentiment.

Wheels are made to go round and round. The assumption that its rated for static use only is questionable in my mind.

I certainly never said that. Are you making things up again? Or just unable to let even a single post of mine go by without some kind of inane criticism?

 

[USMCVader]

No worries, understanding stuff better is always a good idea. Let's see if I can do a better job of explaining all this (or at least some of it...)

First of all, all these "pounds" referred to are not the same - and are not directly additive or subtractive, so must be addressed separately.

Let's start with the basis for all our discussions about "pounds" as they relate to a LC200 - the GVWR Plate attached to all our vehicles - mine looks like this:

View attachment 2962278

The first kind of "pound" we encounter is the GVWR (Gross Vehicle Weight Rating) number = 7385 pounds.

The GVWR (gross vehicle weight rating) is a safety regulation used to prevent the overloading of vehicles. It's the maximum safe operating weight of a truck, including its net weight, plus driver, passengers, cargo, and fuel.

This is a STATIC weight. As such, you can measure it on a scale while the vehicle is not in motion. Load up your LC200, drive to a truck scale and weigh it. Compare that weight to the GVWR to assure you are not too heavy to be safe. Simple, right?

The next kind of "pound" we encounter is the GAWR (Gross Axle Weight Rating) number = 3595 pounds Front / 4300 pounds Rear.

Gross Axle Weight Rating (GAWR) is the most distributed weight an axle of a vehicle can support.

This is also a STATIC weight which we can measure on a scale while the vehicle is not in motion. But if the Front GAWR is 3595 pounds and the Rear GAWR is 4300 pounds, which totals 4300 + 3595 = 7895 pounds, 500 pounds more than the GVWR?

The GVWR takes precedence. For example, if you load your rear axle to the maximum 4300 pounds, then you can only load your front axle to a maximum 3085 pounds to remain within the GVWR.

So far, so good, right? All "pounds" so far are STATIC pounds and can be measured on a scale while not in motion. All measured static pounds are not directly additive, but are relational. All pretty straightforward.

Now we start getting into derivative load values that are indirectly specified by the information on the GVWR plate - specifically the tire size and inflation pressure required to provide the necessary tire Load Limit to safely support the GVWR / GAWR STATIC loads while the vehicle is in motion - these will be DYNAMIC loads which cannot be measured on a scale because they apply while the vehicle is in motion. These values must be tested by the tire manufacturers in accordance with established industry standards.

Going back to the GVWR plate we find the specified tire size and RCTIP (Recommended Cold Tire Inflation Pressure) - P285/60R18 @ 33psi.

At this point we must consult the Load/Inflation Tables published by the TRA (Tire & Rim Association) to determine the Load Limit. One can find these tables here: Guidelines for the Application of Load and Inflation Tables

The TRA Load/Inflation tables tell us that the Load Limit for P285/60R18 tires @ 33psi is 2512 pounds.

These are DYNAMIC pounds and are required to support LIVE Loading as opposed to STATIC Loading. As such, we find that the DYNAMIC Load Limit for two tires on a single axle totals 5024 pounds which is significantly higher than the STATIC load indicated by the GAWR of either 3595 pounds or 4300 pounds for the Front and Rear axles. A good way to think about DYNAMIC Load is to imagine the load on a tire while driving on a straight, smooth and level road at low speed (where Dynamic Load would be fairly close to STATIC Load), and then imagine the load on that tire hitting a pothole at high speed, or hitting a curb at speed, or during a high speed maneuver - under these conditions the DYNAMIC Load is much higher than the STATIC Load.

Since the wheels directly support the tires, the wheels should have a Load Rating > the Load Limit of the specified tire. A wheel's Load Rating is a STATIC amount which can be directly measured by the wheel manufacturer - the wheel Load Rating should be clearly available from the manufacturer. If it is not, I would not trust the wheel*.

It should be noted that several sources (most notably some wheel manufacturers) indicate that a wheel's Load Rating should be determined by dividing the higher GAWR by 2. In our case, this would mean dividing the Rear GAWR of 4300 pounds by 2 to determine a wheel Load Rating of 4300 / 2 = 2150 pounds. I strongly disagree with this as it does not take into consideration the DYNAMIC Loads presented to the tires. I am not alone in this disagreement. In fact, here is what the TRA (Tire & Rim Association) - the body that publishes the standards for these things - has to say:

View attachment 2962326

This is contained in the 2020 TRA Yearbook - the latest edition I have. Sorry there is not a digital or online version I can link to.

I have underlined the most pertinent sentence directly related to our discussion here. Basically what it says is that if one has a tire that has a Load Limit of 2512 pounds @ 33psi, the wheel should have a specified Load Rating > 2512 pounds and a pressure rating > 33psi.

Lastly, if one wants to use a non-specified tire size/load/structure (e.g. using an LT-Metric tire on a LC200), the determination of the appropriate size/RCTIP is a separate exercise to wheel Load Rating requirements. The required wheel Load Rating is driven by the specified tire size/RCTIP found on the GVWR plate. Simply stated, whether one installs the stock P285/60R18 tires @33psi, or the optional LT285/70R17 tires @40psi, the required wheel Load Rating remains the same - i.e. >2512 pounds. Note that in this example the wheels pressure rating should be >40psi.

TL;DR:

Wheel Load Rating needs to be >2512 pounds to be safely used on a LC200.

HTH

* Note: this does not apply to Toyota stock or option wheels. Since I trust that Toyota would thoroughly test any wheel offering for performance and suitability, what I should have written is, "A wheel's Load Rating is a STATIC amount which can be directly measured by the wheel manufacturer - the wheel Load Rating should be clearly available from the manufacturer. If it is not, and the wheel did not come from Toyota as either stock or an option, I would not trust the wheel."

This is an outstanding explanation of several issues I have wondered about for years…but not enough to spend the time researching it all. Thank you very much!

 

[gaijin]

This is an outstanding explanation of several issues I have wondered about for years…but not enough to spend the time researching it all. Thank you very much!

Thank you for the kind words. You are very welcome.

Semper Fi!