Tire Pressure for Rock Warriors with LT285/70/17, Load range Es? (1 Viewer)

[studawg]

Ok got it. It's fully rigged with drawers, fridge bumpers, Sliders, Rack- etc so looks like 45 it is. Have close to 500 pounds - even with rear seat delete.

This is another method I found here on mud....

Posted by LandcruiserPhil, that he pulled from somewhere else...

I worked for Michelin Tire Corporation for 7 years and Yokohama Tire Corporation for 11 years. I have given numerous tire seminars on tire maintenance and especially how to determine the correct tire pressures. So here goes.
The pressure on the sidewall of the tire is the maximum pressure at the published load at approximately 55 mph. (The speed can vary somewhat but it is not important for our discussion).
The air pressure is required to support the load that the tire must carry in such a manner that the tire flexes at the designed place on the sidewall of the tire.
If the load on the tire changes then the air pressure should change accordingly to keep the tire flexing at the proper place.
The reason for correct air pressure is to prevent the tire from overheating. It was put together with heat and it will come apart the same way. An under inflated tire will eventually self destruct due to excessive heat build up. An over inflated tire will ride harshly and be more likely to burst upon impact. Sorry for the long explanation but here is the bottom line.
To determine the correct air pressure, check the pressure when the tire is cold. Run the tire for several miles at highway speed. Stop and immediately check the air pressue in the tire. It should be higher than we cold but no more than 10% higher.
Now here is the hard to believe part. If the pressure is more than 10% higher you must ADD AIR and test again. For example if you start with 50 psi cold. If the pressure is 60 when hot, you have exceeded the (10%) in this case, 55 psi maximum safe heat build up pressure. You must ADD AIR. In this case I would add 5 psi which would take the tire to 65 psi when hot. After you run the tire again you will find the pressure to actually drop because the tire will run cooler. The heat build up causes the tire pressure to increase when under inflated.
On the other hand, if the 50 psi cold pressure does not change when hot. You have more air than needed. You can remove 5 psi or so and test again when they return to cold. Like the next trip you take.
So a fully loaded rig will require more air in the tires than one with empty tanks and a light load on board. Always error on the side of over inflation. Thus the maximum sidewall pressure indicated on the tire is usually used. It usually is more than needed. Each axle has its own requirement based upon the load on that axle.
So how do I get a 2 Rivet rating? Does this long explanation help or hurt?

Science.

 

[gaijin]

Thus the maximum sidewall pressure indicated on the tire is usually used.

Science.

Sure, junk science.

Like a lot of stuff on the internet, just a kernel of truth around which a misleading narrative is built.

I'm not getting dragged down that rat hole.

I would point anyone who's sincerely interested in how all this "stuff" really works to this site: Barry's Tire Tech

HTH

 

[studawg]

It seems thats more of a way to test your pressure to see if you are in the right range, Ive seen it mentioned elsewhere too...4wheelparts.com

 

[Obi Wong Kenobi]

Forgive me for asking @gaijin but what psi should I run for Toyo RT's in LT285/65R18's and Tundra 5 spoke steel wheels? I tried to follow the math but I got lost somewhere along the way.

 

[gaijin]

Forgive me for asking @gaijin but what psi should I run for Toyo RT's in LT285/65R18's and Tundra 5 spoke steel wheels? I tried to follow the math but I got lost somewhere along the way.

"The Book" says between 41psi and 42psi, so let's call it 42psi Front/Rear.

HTH

 

[Obi Wong Kenobi]

Thanks a bunch Gaijin!

 

[jetstream23]

Great thread. Thought I'd give it a bump.

I'm running at 42psi on the 285/70/17 KO2's and it feels right.

 

[gaijin]

Great thread. Thought I'd give it a bump.

I'm running at 42psi on the 285/70/17 KO2's and it feels right.

Even though it should be 40psi?

 

[jetstream23]

Even though it should be 40psi?

Yes. I'm a rebel.

I also ate some cereal 1 day after the "Best by" date this morning.

 

[linuxgod]

I ordered the tire inflation sticker this week for the Land Cruiser. It was $1. Plan to use my 15% off coupon. This should help when I go to any tire place from adjusting them down to 33 every time.

I'm going to set them to 44-46 since I have the Rock Warriors and LT 34x10.5x17 and ARB bumpers, winch, drawers, Fridge, roof rack, extra battery.

They seem to fluctuate with temperature here at sea level a couple of pounds when they get hot verses ambient.

It is odd that the spare is still shown lower at 33 on sticker. I throw that out there as the next topic to discuss/debate. Go.

Where did you order your sticker from? I can't seem to find this online

 

[ohsix]

Just had 285/70R17 BFG KOs mounted to Rock Warriors on my '17 LC. Drove away from Discount tire with 50-54 psi in each tire (I didn't specify pressure to them) and felt every imperfection in the road. I deflated to 40 all around and now rides much better. I've seen these tire pressure threads before, so figured I'd see if anyone else has already asked. I'm happy that I happened to guess correctly at 40 psi.

 

[gaijin]

Just had 285/70R17 BFG KOs mounted to Rock Warriors on my '17 LC. Drove away from Discount tire with 50-54 psi in each tire (I didn't specify pressure to them) and felt every imperfection in the road. I deflated to 40 all around and now rides much better. I've seen these tire pressure threads before, so figured I'd see if anyone else has already asked. I'm happy that I happened to guess correctly at 40 psi.

Excellent guess! 40psi is the correct recommended Cold Tire Inflation Pressure for the LT285/70R17's.

 

[dcs111]

You can search "Tire Pressure" for posts by me in this forum for all I've posted on the subject, but here is one of my posts that pretty much sums up the rationale for recommending 40psi F/R for LT285/70-17 tires on aa LC200:

**********************************************************

OK, but buckle up folks, it's going to be a bumpy ride ...

Without specific vehicle/tire info, all I can do is provide generalized info based on a stock 2013 LC200 running LT285/70-17 tires. It should be enough to get a feel for what may apply in your individual case.

As a base, we have the door sticker for the LC200:

The sticker gives us some important info:

- GVWR = 7,385 lbs
- GAWR Front = 3,595 lbs
- GAWR Rear = 4,300 lbs
- Tire size = P285/60R18
- Cold Tire Pressure = 33psi Front/Rear

From this info, using published Load Limit tables, we can calculate the Load Limit which results from the recommended tire size and pressure:

This calculation yields a Load Limit of 2,512 lbs (per P-Rated tire) @ 33psi.

Since we are talking about a LT-Rated tire replacing a P-Rated tire in our hypothetical, we need to calculate the required Load Limit for a LT-Rated tire. When replacing a P-Rated tire with a LT-Rated tire, the LT-Rated tire should have a Load Limit 10% less than the P-Rated tire. Therefore in our example, the LT-Rated Load Limit is calulated as follows:

P-Rated Load Limit / 1.1 (the 10% difference) = LT-Rated Load Limit
-or-
2,512 lbs per tire / 1.1 = 2,284 lbs per tire

Using this new LT-Rated Load Limit, again using published Load Limit tables, we can calculate the Cold Tire Pressure required to yield the required Load Limit. For the LT285/70-17 tires, it looks like this:

From the graph, we can see that approximately 39.3psi yields a Load Limit of 2,286 lbs which, when corrected for the P-Rated requirement = 2,515 lbs compared to the P-Rated requirement of 2,512 lbs. For simplicity, let's round up and call it 40psi.

It makes no difference whether the LT285/70-17 tire is D-Rated or E-Rated, the required pressure is the same.

**********
What we know now is:
For a stock LC200 running LT285/70-17 tires, the required Cold Tire Pressure is 40psi Front/Rear.
**********

Now, we can look at what might be appropriate for a LC200 which has additional weight added to it.

Relax, we've already slogged through the tough stuff - the rest is easy.

Examining the Load Limit graph for the LT-Rated tire above, we see the load Limits are approximately as follows at the indicated Cold Tire Pressures:

40psi = 2,315 lbs/tire -or- 9,260 lbs Total
45psi = 2,510 lbs/tire -or- 10,040 lbs Total -or- 780 lbs more than stock
50psi = 2,755 lbs/tire -or- 11,020 lbs Total -or- 1,760 lbs more than stock

So, roughly speaking:

- If you have added 780 lbs to your rig, you should be running 45psi instead of 40psi.
- If you have added 1,760 lbs to your rig, you should be running 50psi instead of 40psi.

But what if you have added a weight somewhere between the published 5psi increments?

It's not exact, but a simple calculation could be applied.

Let's say you've added 1,000 lbs to your rig.

Already you know you should be running somewhere between 45psi and 50psi. Between 45psi and 50psi, we see a difference of (11,020 lbs - 10,040 lbs = ) 980 lbs. 980 / 5 = 196 lbs per psi.

So, 1,000 lbs (desired increased capacity) - 780 lbs (added capacity @ 45psi) = 220 lbs / 196 (lbs/psi between 45psi and 50psi) = 1.12psi above 45psi = 46.12psi will yield a capacity 1,000 lbs above stock.

See? Easy, right?

*************************************************************

HTH

Such great knowledge in this Forum. @Giajin thanks for sharing. Sometime ago you recommended that I run 42PSI on my machine(stock 200 with 275/70/18E KO2s) and it works great. We are about to run the rig from Atlanta to Moab and back with an Rpod191 in tow and a bunch of stuff piled in back... if I am reading above correctly, (and likely not)for simplicity sake can I assume increase 1PSI for every 200lb added payload? E.g. trailer tongue weight is 400lb and so add 2psi to base pressure of 42psi?
Thanks again for sharing! DS

 

[gaijin]

Such great knowledge in this Forum. @Giajin thanks for sharing. Sometime ago you recommended that I run 42PSI on my machine(stock 200 with 275/70/18E KO2s) and it works great. We are about to run the rig from Atlanta to Moab and back with an Rpod191 in tow and a bunch of stuff piled in back... if I am reading above correctly, (and likely not)for simplicity sake can I assume increase 1PSI for every 200lb added payload? E.g. trailer tongue weight is 400lb and so add 2psi to base pressure of 42psi?
Thanks again for sharing! DS

That's a blast from the past - over 4 years ago. Since then, my approach to "added weight" and its effect on tire pressures has evolved - partly from newly acquired knowledge, and partly from an increased awareness of our responsibility to operate safely within manufacturer's limits.

Now, I'm sticking with Toyota's recommendations on pressure - i.e., The RCTIP is good for all weights up to and including GVWR. In your case, this means that 42psi is good for all weights within the GVWR, GAWR, GCWR, TWR/UTWR, and Tongue Weight recommended by Toyota. For the LC200, these break down as follows:

GVWR: 7385LB
GAWR: 3595LB Front / 4300LB Rear
GCWR: 14400LB
TWR: 8100LB Unbraked TWR: 1000LB
Tongue Weight: The gross trailer weight should be distributed so that the tongue weight is 9% to 11%. (Tongue weight /Gross trailer weight x 100 = 9% to 11%)

I would refer you to your Owner's Manual for more details on all of these requirements. The Owner's Manual section on trailer towing (Section 2.5 in my 2013 Manual) is very extensive and has a lot of excellent information. You can find the .pdf of the 2013 Manual here (start on page 306): 2013 LC200 Owner's Manual

All that said, the pressure you choose to run is your responsibility. I would suggest asking your question of others with a lot of trailer towing experience who can give you their recommendations. My personal experience has been that when towing, increased stability and lower tire temperatures may be achieved by increasing BOTH front and rear tire pressure by 2-3psi, but it's up to you. As long as you don't go below 42psi, and stay within all the weight requirements, you should be OK.

HTH

 

[bloc]

That's a blast from the past - over 4 years ago. Since then, my approach to "added weight" and its effect on tire pressures has evolved - partly from newly acquired knowledge, and partly from an increased awareness of our responsibility to operate safely within manufacturer's limits.

Now, I'm sticking with Toyota's recommendations on pressure - i.e., The RCTIP is good for all weights up to and including GVWR. In your case, this means that 42psi is good for all weights within the GVWR, GAWR, GCWR, TWR/UTWR, and Tongue Weight recommended by Toyota. For the LC200, these break down as follows:

GVWR: 7385LB
GAWR: 3595LB Front / 4300LB Rear
GCWR: 14400LB
TWR: 8100LB Unbraked TWR: 1000LB
Tongue Weight: The gross trailer weight should be distributed so that the tongue weight is 9% to 11%. (Tongue weight /Gross trailer weight x 100 = 9% to 11%)

I would refer you to your Owner's Manual for more details on all of these requirements. The Owner's Manual section on trailer towing (Section 2.5 in my 2013 Manual) is very extensive and has a lot of excellent information. You can find the .pdf of the 2013 Manual here (start on page 306): 2013 LC200 Owner's Manual

All that said, the pressure you choose to run is your responsibility. I would suggest asking your question of others with a lot of trailer towing experience who can give you their recommendations. My personal experience has been that when towing, increased stability and lower tire temperatures may be achieved by increasing BOTH front and rear tire pressure by 2-3psi, but it's up to you. As long as you don't go below 42psi, and stay within all the weight requirements, you should be OK.

HTH

The way I interpret it is gaijin’s recommendation should keep you from having physical problems with the tires, but there are times increased pressure may lead to more or even less stability. This is where people’s experience may lead you to increase pressures.

One example of this is the fire apparatus I drive frequently. If we run the manufacturer recommended pressure most of them are all over the road, wandering around, just a TON of work to keep within a lane that is only a foot wider than the truck, even though that gives the most load carrying capacity. Even though it’s counterintuitive per our shop’s recommendation for certain trucks we go about 10psi under that, and they are much easier to drive. Now we’re talking 110psi vs 120 here, not 32 vs 42, and not driven at the same speeds either (in fact our trucks are governed to much less than what a tractor trailer that typically use these tires may go).. but the point stands. As long as your pressure is “safe” to keep the tire falling apart (I consider gaijins numbers the minimum here), experience may lead you to tweak the pressures upward a bit.

 

[dcs111]

The way I interpret it is gaijin’s recommendation should keep you from having physical problems with the tires, but there are times increased pressure may lead to more or even less stability. This is where people’s experience may lead you to increase pressures.

One example of this is the fire apparatus I drive frequently. If we run the manufacturer recommended pressure most of them are all over the road, wandering around, just a TON of work to keep within a lane that is only a foot wider than the truck, even though that gives the most load carrying capacity. Even though it’s counterintuitive per our shop’s recommendation for certain trucks we go about 10psi under that, and they are much easier to drive. Now we’re talking 110psi vs 120 here, not 32 vs 42, and not driven at the same speeds either (in fact our trucks are governed to much less than what a tractor trailer that typically use these tires may go).. but the point stands. As long as your pressure is “safe” to keep the tire falling apart (I consider gaijins numbers the minimum here), experience may lead you to tweak the pressures upward a bit.

@bloc thanks. I will be bringing a compressor and tire kit - I may experiment a bit to see if we can find optimal pressure for towing.

 

[unclemat]

To bump this older thread re the 46 psi "mystery" for LT285/70/17E tires.

Clearly, by the book the psi front/rear should be 40 psi.

Toyota says 46 psi so TPMS lights up at 35 psi.

So the correct procedure should be like:

1. Inflate to 46 psi.
2. Reset TPMS so it remembers 46 psi.
3. Deflate to 40 psi.

Does that sound right?

 

[studawg]

Toyota says 46 psi so TPMS lights up at 35 psi.

No, that is not necessarily why Toyota says 46 psi. Resetting your TPMS by the button wont achieve what you are trying to achieve. The system has to be initialized, which is different, and, ultimately disproves the argument that 46 is the wrong pressure for the tires. Have fun! Im outta here!

 

[gaijin]

To bump this older thread re the 46 psi "mystery" for LT285/70/17E tires.

Clearly, by the book the psi front/rear should be 40 psi.

Toyota says 46 psi so TPMS lights up at 35 psi.

So the correct procedure should be like:

1. Inflate to 46 psi.
2. Reset TPMS so it remembers 46 psi.
3. Deflate to 40 psi.

Does that sound right?

For an LC200, you are correct - the RCTIP for LT285/70R17 tires is 40psi F/R.

The TPWS (Tire Pressure Warning System) will alarm when observed tire pressure reaches 25% below the pressure set when the system was initialized.

For the LT285/70R17 tires, no pressure below 35psi is recommended for normal use.

So... if your objective is to keep your tires at the RCTIP of 40psi and have your TPWS alarm at 35psi, then the procedure you outline (i.e. initializing the TPWS @46psi) will accomplish that goal.

HTH

 

[bhakjdlmn1]

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?