Tire Pressures

[Markuson]

Sure! The good news is, it gets easier as we build our common knowledge base

If your truck were stock, the required Cold Tire Inflation Pressure for your 35x12.50R17LT tires would be 32.6psi

32.6psi = 2,285 lbs/tire -or- 9,140 lbs Total = Stock
35psi = 2405 lbs/tire -or- 9,620 lbs Total = 480 lbs over stock
40psi = 2625 lbs/tire -or- 10,500 lbs Total = 1,360 lbs over stock
45psi = 2840 lbs/tire -or- 11,360 lbs Total = 2,220 lbs over stock

Your additional 700 lbs over stock would put you between 35psi and 40psi.

In this pressure range, there is a Load Limit difference of approximately 176 lbs/psi.

700 lbs (your additional weight) - 480 lbs (additional Load Limit @ 35psi) = 220 lbs (required additional Load Limit above 35psi Load Limit)

220 lbs (required Load Limit increase) / 176 lbs/psi = 1.25psi additional required pressure above 35psi = 36.25psi

Round off and call it 36psi for your 35x12.50R17LT tires with 700 lbs additional weight over stock.

Looks like the 33psi you were running was perfect for a stock truck, but probably a little low for your current configuration. The 44psi you switched to was definitely too high.

HTH

This is incredibly helpful for some of us non-math-whizzes... Thanks!

 

[Willy beamin]

or a spread sheet with built in formulas

 

[gaijin]

Gaijin you are the Tire Whisperer
You should build up an app.

or a spread sheet with built in formulas

I'll look into it, but don't hold your breath - there are a lot of variables and an almost infinite number of tire/wheel/truck combinations.

Thanks for the kind words.

 

[CALandCruiser]

If you mean the LT285/60R18 118/115S D-Rated tires on a stock LC200, then you are close to correct. In order to achieve the requisite Load Limit of >2,286 lbs, you would need a Cold Tire Pressure of 46psi.

Inflating to only 40psi would yield a Load Limit of only 2,070 lbs - almost 10% less than required. This would be like running the stock P285/60-18 tires at 27psi when they should be at 33psi. Safe? I wouldn't do it.

HTH

Hi gaijin, thank you for all your help with cold tire pressure settings. I have one more question for you, which is similar to ones you've answered, but I just need a confirmation.

I just installed BFG All-Terain T/A KO2 LT285/60R18s on my 2011 Land Cruiser to replace the stock P285/60R18s. I called BFG and they recommended 50 psi front/rear. I noticed your recommendation is 46 psi for that tire size. Should I go with the 46 psi or the 50 psi that BFG recommended? I suspect BFG didn't take into account the 10% reduction in load limit when going from P to LT tires. Also, why is there a 10% reduction? Just curious.

Thanks again for all your help

 

[gaijin]

Hi gaijin, thank you for all your help with cold tire pressure settings. I have one more question for you, which is similar to ones you've answered, but I just need a confirmation.

I just installed BFG All-Terain T/A KO2 LT285/60R18s on my 2011 Land Cruiser to replace the stock P285/60R18s. I called BFG and they recommended 50 psi front/rear. I noticed your recommendation is 46 psi for that tire size. Should I go with the 46 psi or the 50 psi that BFG recommended? I suspect BFG didn't take into account the 10% reduction in load limit when going from P to LT tires. Also, why is there a 10% reduction? Just curious.

Thanks again for all your help

Published Load Limit tables only show Load Limits every 5psi - this means for your tire the tables show Load Limits at 45psi and 50psi, nothing in between. In your case, 45psi is too low and 50psi is higher than required. My guess is that BFG are reluctant to base a pressure recommendation on their own calculation of what the correct pressure should be and simply round up to the next higher published number. This means they round up from 46psi (the correctly calculated number) to 50psi (the next highest published number). It is strictly CYA for them. If they ever had to defend their recommendation, they could point to 50psi as a published number and use the fact that it is more than enough as a defense. If they were to recommend the correct 46psi, they would then have to defend their calculation/interpolation of the published data which could get sticky in a court of law.

All that boils down to ... yes, you should run 46psi. That Cold Tire Inflation Pressure will afford you slightly more than the Load Limit recommended by Toyota for the LC200.

The 10% reduction from P-Rated tires to LT-Rated tires is due to the difference in construction of the tires.

Glad you are finding the info useful.

HTH

 

[CALandCruiser]

Published Load Limit tables only show Load Limits every 5psi - this means for your tire the tables show Load Limits at 45psi and 50psi, nothing in between. In your case, 45psi is too low and 50psi is higher than required. My guess is that BFG are reluctant to base a pressure recommendation on their own calculation of what the correct pressure should be and simply round up to the next higher published number. This means they round up from 46psi (the correctly calculated number) to 50psi (the next highest published number). It is strictly CYA for them. If they ever had to defend their recommendation, they could point to 50psi as a published number and use the fact that it is more than enough as a defense. If they were to recommend the correct 46psi, they would then have to defend their calculation/interpolation of the published data which could get sticky in a court of law.

All that boils down to ... yes, you should run 46psi. That Cold Tire Inflation Pressure will afford you slightly more than the Load Limit recommended by Toyota for the LC200.

The 10% reduction from P-Rated tires to LT-Rated tires is due to the difference in construction of the tires.

Glad you are finding the info useful.

HTH

Thank you very much! I really appreciate it.

 

[Romer]

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

I have used this a few time so asked he moderator to add it to the FAQ

 

[Markuson]

For those of you with HEAVY 200's (arb bull bar, winch, skid plates, sliders, rear bumper, etc) with LT tires, what tire pressures are you running?

I know I should probably get the vehicle weighed and do the math, but just out of curiosity here. I currently run 50psi which I based on limiting the amount of bulging of the front tires. 45psi seems too low, but I think is more inline with the math.

My 35x27x22.5 Ridge Grapplers Street pressure is 33...but with my added weight...the PSI ninja reluctantly advised me to bump to 35 or 36..,

 

[gaijin]

My 35x27x22.5 Ridge Grapplers Street pressure is 33...but with my added weight...the PSI ninja reluctantly advised me to bump to 35 or 36..,

You might want to re-check that tire size, bro - I never recommended any pressures for that one!

 

[Markuson]

You might want to re-check that tire size, bro - I never recommended any pressures for that one!

Ha! Okok... they are wide...but not 22.5 inches wide.

In all honesty, I’m having a severe problem with my eyes. Triple vision in left eye...double vision in right eye...even when the other eye is closed. MRI yesterday trying to figure it out. So...I am often relying on auto-correct in these messages. Numbers no worky...

 

[gaijin]

Ha! Okok... they are wide...but not 22.5 inches wide.

Now I'm really confused, the size you posted was 27 inches wide on 22.5 inch rims ...

 

[Markuson]

Now I'm really confused, the size you posted was 27 inches wide on 22.5 inch rims ...

Oh. See? I couldn’t even see that.

My eyes are literally seeing three of everything. So the number 1...looks like a messy pile of 1’s.

Very frustrating, and pretty concerning, actually.

 

[SchobTime]

I usually run my MTs on 35/36 psi in the summer, but they are starting to wear and are becoming noisy as hell. I just cranked them up to 45/46 to shut down the noise some. My truck is heavy, full armor, front bumper with winch, sliders, rear bumper with spare and gerry can swing outs

 

[zeppelin23]

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

Sorry if someone already asked, but where do we find the respective load limit tables for different sizes? For instance, an LT285/65r18?

 

[gaijin]

Sorry if someone already asked, but where do we find the respective load limit tables for different sizes? For instance, an LT285/65r18?

All the info anyone needs to do all these tire pressure calcs for themselves: https://www.toyotires.com/media/2125/application_of_load_inflation_tables_20170203.pdf

Of course, always glad to help if anyone needs additional help or just a confirmation that their calcs are correct.

HTH

 

[zeppelin23]

All the info anyone needs to do all these tire pressure calcs for themselves: https://www.toyotires.com/media/2125/application_of_load_inflation_tables_20170203.pdf

Of course, always glad to help if anyone needs additional help or just a confirmation that their calcs are correct.

HTH

If I'm doing this right and interpolating correctly, I'm landing on 48PSI for my 285/65R18's. I believe my other numbers are identical to those in your example. I'm just using a different new tire.

If 48PSI is what I should be running, I need to inflate my tires immediately. I'm pretty sure Discount inflated them to around 37 or so.

 

[gaijin]

If I'm doing this right and interpolating correctly, I'm landing on 48PSI for my 285/65R18's. I believe my other numbers are identical to those in your example. I'm just using a different new tire.

If 48PSI is what I should be running, I need to inflate my tires immediately. I'm pretty sure Discount inflated them to around 37 or so.

Info I need to help you:

- Do you have a LC200 or LX570?
- Are the tires 285/65R18 (if so, what is the Load Index - 115, 116, 118, etc.?), P285/65R18 or LT285/65R18?
- Brand and model of tire would be a help, also.

Irrespective of the above, 48psi sounds high and 37psi sounds low, but I need the info to tell you exactly what you need.

To make it easier, let's assume the following for the sake of discussion:

LC200, LT285/65R18.

If that is the case, then the Recommended Cold Tire Inflation Pressure for the LT285/65R18 tires on a LC200 is 42psi F/R.

Please confirm the details of your installation just to make sure.

HTH

 

[zeppelin23]

Info I need to help you:

- Do you have a LC200 or LX570?
- Are the tires 285/65R18 (if so, what is the Load Index - 115, 116, 118, etc.?), P285/65R18 or LT285/65R18?
- Brand and model of tire would be a help, also.

Irrespective of the above, 48psi sounds high and 37psi sounds low, but I need the info to tell you exactly what you need.

To make it easier, let's assume the following for the sake of discussion:

LC200, LT285/65R18.

If that is the case, then the Recommended Cold Tire Inflation Pressure for the LT285/65R18 tires on a LC200 is 42psi F/R.

Please confirm the details of your installation just to make sure.

HTH

It's a 2019 LC200. They are 285/65r18 BFG AT KO2's. I'll look up the load index when I leave work. I know they're E-rated.

 

[gaijin]

It's a 2019 LC200. They are 285/65r18 BFG AT KO2's. I'll look up the load index when I leave work. I know they're E-rated.

If the tires are BFG All Terrain T/A KO2's, then they are NOT "285/65R18", they are LT285/65R18E 125/122R. If you look on the sidewall of the tire you will see LT in front of 285/65R18, followed by 125/122R and Load Range E.

Please check and confirm.

HTH

 

[zeppelin23]

Sorry, I left off the LT out of habit. I don't believe they make a P-rated tire in this size.

I'll get the exact specs here in a minute when I leave.