Recommended tire PSI for MTs on street?

[JustSomeName]

I just picked up some 33" MTs and was wondering what PSI do you guys run on the street for a good balance of MPG & ride comfort? I know that the recommended range is 32-35psi for stock tires, but how about for 33" MTs? Should it be increased?

 

[H20skier70]

I'd use the recommended psi from the tire manufacturer. I'd be more concerned with proper wear.

 

[Ol'Baditude]

I just picked up some 33" MTs and was wondering what PSI do you guys run on the street for a good balance of MPG & ride comfort? I know that the recommended range is 32-35psi for stock tires, but how about for 33" MTs? Should it be increased?

My 33's are LT, so they do get run at a higher PSI that the stock P rated tires in order to safely carry the same load. Personally I run them at 38psi in the summer for normal driving and will increase to 40-42psi depending on load after that. In winter they get run at 35psi max, otherwise the ride is way too sketchy and rough.

It's a combination of proper wear, load carrying capability, safety and ride comfort. Therefore it normally requires a bit of trial and error to get to your final ride pressures. I used a chalk test then tweaked a bit for as much ride comfort as could be allowed without going too low. In the end I ended up running what most guys around here run in their 33" LT tires, which is ~38psi. The 4psi rule also applies if you happen to be going for a drive on the highway any time soon.

I'd use the recommended psi from the tire manufacturer. I'd be more concerned with proper wear.

Forgive me if I'm missing something, but I've never seen a tire manufacturer provide a recommended tire pressure. I'm not sure how they could do that, as they don't know what type of vehicle the tire is going to be installed on and what kinds of loads are going to be carried. They'll provide maximum inflation pressures so you don't overfill and potentially explode the tire or cause an unsafe driving experience, but as far as recommended inflation pressures, the only place I've ever found that is on the vehicle door frame and that's only for the stock P-Rated tire where they know the tire and vehicle combination.
As far as proper wear, the only way you can ensure that is to make sure you have a proper alignment and proper inflation pressure for your vehicle and load. A chalk test should confirm this for you. I've found that the 4psi rule works pretty well too.

 

[JustSomeName]

I'd use the recommended psi from the tire manufacturer. I'd be more concerned with proper wear.

tire manufacturer only tells you max PSI to the tire. I'm under the impression that the PSI is dependent on the curb weight of the entire vehicle, so my question is what PSI everyone else on the forum runs, since all our vehicles are the same, the weight would all be pretty similar (dependent on mods), so a general range from people here would give me a good starting point on what PSI to run

 

[ddnww]

My 33's are LT, so they do get run at a higher PSI that the stock P rated tires in order to safely carry the same load. Personally I run them at 38psi in the summer for normal driving and will increase to 40-42psi depending on load after that. In winter they get run at 35psi max, otherwise the ride is way too sketchy and rough.

It's a combination of proper wear, load carrying capability, safety and ride comfort. Therefore it normally requires a bit of trial and error to get to your final ride pressures. I used a chalk test then tweaked a bit for as much ride comfort as could be allowed without going too low. In the end I ended up running what most guys around here run in their 33" LT tires, which is ~38psi. The 4psi rule also applies if you happen to be going for a drive on the highway any time soon.


Forgive me if I'm missing something, but I've never seen a tire manufacturer provide a recommended tire pressure. I'm not sure how they could do that, as they don't know what type of vehicle the tire is going to be installed on and what kinds of loads are going to be carried. They'll provide maximum inflation pressures so you don't overfill and potentially explode the tire or cause an unsafe driving experience, but as far as recommended inflation pressures, the only place I've ever found that is on the vehicle door frame and that's only for the stock P-Rated tire where they know the tire and vehicle combination.
As far as proper wear, the only way you can ensure that is to make sure you have a proper alignment and proper inflation pressure for your vehicle and load. A chalk test should confirm this for you. I've found that the 4psi rule works pretty well too.

have you ever looked on the side of a tire, it tells you the recommended psi.

 

[eddiebx]

have you ever looked on the side of a tire, it tells you the recommended psi.

recommended MAX psi...I really hope no one runs them at that, must feel like you're driving on solid core tires, lol.
[MENTION=84223]JustSomeName[/MENTION] here's a handy thread by [MENTION=2798]JB.[/MENTION] to figure out the proper pressure if those tires you picked up are LT tires: http://www.toyota-4runner.org/engin...s/110299-lt-tires-need-more-air-pressure.html

 

[Ol'Baditude]

have you ever looked on the side of a tire, it tells you the recommended psi.

As I mentioned in my last post, there is a tire pressure marked on the sidewall of the tire, but this is the Maximum Allowable pressure and the tire manufacturer is required by law to have it there. This is not a recommended running pressure unless you like driving around at 60-80psi in a 4th Gen 4Runner, but even then it would be a terrible idea. If there are tires out there with a recommended running PSI, I've never seen one.

recommended MAX psi...I really hope no one runs them at that, must feel like you're driving on solid core tires, lol.

[MENTION=84223]JustSomeName[/MENTION] here's a handy thread by [MENTION=2798]JB.[/MENTION] to figure out the proper pressure if those tires you picked up are LT tires: http://www.toyota-4runner.org/engin...s/110299-lt-tires-need-more-air-pressure.html

Thx Eddie, I posted the link to JB's thread in my first post, but I can see now that it's not too visible.

 

[ddnww]

As I mentioned in my last post, there is a tire pressure marked on the sidewall of the tire, but this is the Maximum Allowable pressure and the tire manufacturer is required by law to have it there. This is not a recommended running pressure unless you like driving around at 60-80psi in a 4th Gen 4Runner, but even then it would be a terrible idea. If there are tires out there with a recommended running PSI, I've never seen one.



Thx Eddie, I posted the link to JB's thread in my first post, but I can see now that it's not too visible.

ah, i missed that in your post.. carry on.:moping:

 

[JustSomeName]

recommended MAX psi...I really hope no one runs them at that, must feel like you're driving on solid core tires, lol.

[MENTION=84223]JustSomeName[/MENTION] here's a handy thread by [MENTION=2798]JB.[/MENTION] to figure out the proper pressure if those tires you picked up are LT tires: http://www.toyota-4runner.org/engin...s/110299-lt-tires-need-more-air-pressure.html

Thanks, but that thread got me even more confused.

I found two things online a tire pressure calculator equation and the chalk test.

But after the calculation, it said I should run at around 25psi, that seems a bit low, so I'll just try the chalk test this weekend to see what results I get.

And for the record, here's the equation I found, not really sure if it's accurate or not, but I kind of understand the reasoning behind it. If anyone care's to chime in, please do!

Got it from some heep forum

1. Take the max load of the tire and multiply by 4.
2. Divide the curb weight of the vehicle by the number you found from step one. To get a percentage #.
3. Multiply the max PSI of the tire by % # you got from step two.

The curb weight of an 08 SR5 4x4 v6 is 4300lbs+500lbs (random arbitrary weight I added to account for car mods heavier than OEM, random stuff in the car, weight of driver, and an additional passenger), total weight of 4800lbs.

The tire I got has a max PSI of 65 @ 3195 lbs.

So the calculations would be:

1: 3195*4=12780lbs

2: 4800lbs/12780lbs=~38%, rounding up to 40%

3: 65PSI*40%=26psi?

So according to this "calculation" it says to run 26psi, that does not sound right at all. maybe I did something wrong there? anyone care to chime in?

At this point, I'm more confused than I was before, so I'll be doing the chalk test to see what that gets me. Ironically, the YouTube video describing the chalk test is from another Heep driver

 

[ebg18t]

I ended up using a digital pyrometer. Measure the temp of the tread at center and each edge, adjust as needed.

On the track we use these temp reading to readjust psi and alignment.

 

[BlackWorksInc]

I think Toyota says to run about 46-ish PSI on their LT tire equipped FJ Cruisers, so I run that on my 4Runner with no issues (I have LT285/70R17 Nitto Terra Grapplers on my vehicle. I haven't done the Chalk Test on my 4Runner, but typically when I dry on dirt and then on the road it looks pretty even; the tires also seem to be wearing pretty evenly for me (outside edge is getting a bit chewed up, but I drive the 4Runner hard so that's expected.)

 

[eddiebx]

Thanks, but that thread got me even more confused.

I found two things online a tire pressure calculator equation and the chalk test.

But after the calculation, it said I should run at around 25psi, that seems a bit low, so I'll just try the chalk test this weekend to see what results I get.

And for the record, here's the equation I found, not really sure if it's accurate or not, but I kind of understand the reasoning behind it. If anyone care's to chime in, please do!

Got it from some heep forum



The curb weight of an 08 SR5 4x4 v6 is 4300lbs+500lbs (random arbitrary weight I added to account for car mods heavier than OEM, random stuff in the car, weight of driver, and an additional passenger), total weight of 4800lbs.

The tire I got has a max PSI of 65 @ 3195 lbs.

So the calculations would be:

1: 3195*4=12780lbs

2: 4800lbs/12780lbs=~38%, rounding up to 40%

3: 65PSI*40%=26psi?

So according to this "calculation" it says to run 26psi, that does not sound right at all. maybe I did something wrong there? anyone care to chime in?

At this point, I'm more confused than I was before, so I'll be doing the chalk test to see what that gets me. Ironically, the YouTube video describing the chalk test is from another Heep driver

youtube]ojGsavK0Uwc[/youtube]

Here's another way that I used originally to settle on an optimum pressure when I switched to LT tires. First download this chart: http://cache.toyotires.com/sites/default/files/imce/LoadInflation_Table_P-LT_102913.pdf

Now go to the P-metric section and find your OEM tire size and recommended cold pressure (found on your door jamb). Let's use mine for example: 265/70R17 @ 32psi. Now look on that chart and you see it correlates to 2425 lbs load limit.

Now scroll down the chart and find your new tire size in the LT inflation table. For me I stayed the same size so I dropped down to the 265/70R17 row again (single tire) and found that at 45 psi the load limit is: 2255 lbs; and at 50 psi it is: 2470 lbs. This means I need somewhere around 45-50 psi to achieve the same load limit as intended by Toyota.

I would skip the chalk test and just pick a number and test it out for about 5000 miles. Once that many miles are up, measure your tread wear and adjust accordingly. The chalk test is not useful unless you plan to drive in a straight line only.

Hopefully this way makes a bit more sense and you can figure it out from here

 

[JustSomeName]

Here's another way that I used originally to settle on an optimum pressure when I switched to LT tires. First download this chart: http://cache.toyotires.com/sites/default/files/imce/LoadInflation_Table_P-LT_102913.pdf

Now go to the P-metric section and find your OEM tire size and recommended cold pressure (found on your door jamb). Let's use mine for example: 265/70R17 @ 32psi. Now look on that chart and you see it correlates to 2425 lbs load limit.

Now scroll down the chart and find your new tire size in the LT inflation table. For me I stayed the same size so I dropped down to the 265/70R17 row again (single tire) and found that at 45 psi the load limit is: 2255 lbs; and at 50 psi it is: 2470 lbs. This means I need somewhere around 45-50 psi to achieve the same load limit as intended by Toyota.

I would skip the chalk test and just pick a number and test it out for about 5000 miles. Once that many miles are up, measure your tread wear and adjust accordingly. The chalk test is not useful unless you plan to drive in a straight line only.

Hopefully this way makes a bit more sense and you can figure it out from here

how is load range calculated? is that total curb weight of the vehicle or how much weight can be stored in the car? it doesnt seem it should be curb weight of car, since then, we'd be in the 4000lb+ range

 

[eddiebx]

how is load range calculated? is that total curb weight of the vehicle or how much weight can be stored in the car? it doesnt seem it should be curb weight of car, since then, we'd be in the 4000lb+ range

Not exactly sure how that all works out but, I think the load rating you see on the chart is per tire? or maybe per axle? I actually noticed that on page 92 of that chart I linked you to above provides an example of how to determine your air pressure when going from P-metric to LT-metric.

 

[nevada]

the size of the tire has a lot to do with it.

I would assume they are 33x12.50s. you'll be able to run a much lower pressure than say a stock size tire. the more volume you have, the less pressure you need.

id try 30psi and see how it works.

 

[nevada]

Here's another way that I used originally to settle on an optimum pressure when I switched to LT tires. First download this chart: http://cache.toyotires.com/sites/default/files/imce/LoadInflation_Table_P-LT_102913.pdf

Now go to the P-metric section and find your OEM tire size and recommended cold pressure (found on your door jamb). Let's use mine for example: 265/70R17 @ 32psi. Now look on that chart and you see it correlates to 2425 lbs load limit.

Now scroll down the chart and find your new tire size in the LT inflation table. For me I stayed the same size so I dropped down to the 265/70R17 row again (single tire) and found that at 45 psi the load limit is: 2255 lbs; and at 50 psi it is: 2470 lbs. This means I need somewhere around 45-50 psi to achieve the same load limit as intended by Toyota.

I would skip the chalk test and just pick a number and test it out for about 5000 miles. Once that many miles are up, measure your tread wear and adjust accordingly. The chalk test is not useful unless you plan to drive in a straight line only.

Hopefully this way makes a bit more sense and you can figure it out from here

somehow that's not right.
that means you need to run something like 25psi for the 4runner?

you don't need 9k+ load capacity.

 

[nevada]

oh, even 25 would be too much. it would be more like 15.
yeh, that's not right.

don't trust that chart. im not sure where that info comes from, but that's no good.

 

[JustSomeName]

somehow that's not right.
that means you need to run something like 25psi for the 4runner?

you don't need 9k+ load capacity.

I think the poster's idea was to look at the stock tire's load capacity, then use that chart to see what # that would be with the bigger tires. It somewhat makes sense, I ended up with somewhere around 42psi for my new tires compared to the stock size ones

 

[nevada]

I think the poster's idea was to look at the stock tire's load capacity, then use that chart to see what # that would be with the bigger tires. It somewhat makes sense, I ended up with somewhere around 42psi for my new tires compared to the stock size ones

that's WAY too much.
it will be stiff as shit.

but, your tires, and your truck, do as you wish.

 

[BlackWorksInc]

that's WAY too much.
it will be stiff as shit.

but, your tires, and your truck, do as you wish.

But Toyota has a Campaign for Tacoma, Tundra, and FJ Cruiser for TRD Wheel Equipped Vehicles with LT Tires to update the tire placards with new PSI ratings and they are 46 PS.

(Found the new spec, it IS 46psi)