Correct Tire Pressure - very confused

[agaisin]

My quick question is "What is the correct tire pressure for my front/rear tires?"

Yes, I know the question has been asked numerous times. However, I can't seem to find a definitive or even clear answer.

I have an '05 LX470 and just got Michelin Latitude Tour HP Tires 275/60R18 (OEM).

Here are the facts I have:
1) Manufacturer (posted on door jamb and all other documentation from Lexus) recommends cold tire pressure of 29 psi on the front, 32 psi on the rear. If towing, they bump it up to 32 on the front and 35 on the rear.

2) Apparently, if using LT (light truck) size tires instead of P metric, then the tire pressure needs to be upped (have seen different numbers for how much additional pressure). Problem is, I can't find anyone that says whether Michelin Latitude Tour HP are LT or P Metric (not on Michelin site or other sites either). They don't have the P in front of them (so they're not P-metric), but they also don't have the LT in front of them. Which are they? http://www.tirerack.com/tires/michelin/michelin-tires.jsp puts them in the Light Truck category but I don't think that is to be taken literally (i.e. they are for cars that are light trucks not that the tire is LT size). But again, I can't find any definitive info one way or the other.

3) The Lexus dealership set all 4 to ~35psi and they aligned all 4 wheels at that pressure.

4) I see some people referring to the Latitude Tour HP as LT tires that require higher pressure. I also see some people saying Latitude Tour HP should be set to manufacturer recommendations. As a matter of fact, Michelin says to follow the manufacturer's recommendations for the vehicle, which tell me they should be set to 29 at the front and 32 at the rear.

Now - I have an additional question: I set my colt tire pressure (not driven and not in ambient heat) front to 29 and rear to 32 and it doesn't feel quite right (turning steering wheel feels like the tires are under inflated). My follow on question is if they aligned the tires all at 35, and I reset the front to 29 and rear to 32, then do i need a new alignment at the correct tire pressures? Most important, WHAT THE HECK is the correct tire pressure?


A little history: I recently bought an '05 lx470 with 70k miles. Didn't realize at the time but front right tire was significantly more worn than the other tires (believe it was > 2/32). I also had been bugged by pulling to the left. I brought it to the Lexus dealership and they told me one of the tires was more worn but they didn't tell me about the possibility of damage to the drivetrain. I took it to an indepent shop for a different issue and asked them about the pulling and tire problem. They at least pointed out that my front right tire was more worn, but the pulling was to the left - doesn't add up. Well, after 5k miles and doing my own service, I looked more into it and learned that my front right tire, although more worn than the rest, also had waaaaay higher tire pressure than the rest leading me to believe that's why it was wearing so unevenly and that's why it was pulling to the left. Can't believe 2 different technicians didn't catch the tire pressure issue and didn't warn me about the damage to drivetrain.

So, that's why I got new tires, and that's why I want to get the tire pressure right I appreciate much more than ever before how much of a difference the tire pressure/alignment can effect the driving experience as well as the safety...

Any insight and information would be much appreciated!

 

[Jim_Chow]

The latitude HP's are street tires...pretty sure they are not LT's. I used to set my Dueler HT's (OEM size) to 32-33 psi fr/rr. By the time I replaced them, the tread wear indicated that they were under-inflated. I replaced them w/ 275/65R18 Michelin LTX2's. Dealer inflated them to 38psi. So far, I keep them around 38psi. Ride quality at that pressure is about the same as the Dueler's at 32psi. As far as fuel economy is concerned, 38psi should give better economy, but the LX is the wife's DD now, and her heavy foot is more of a factor than tire pressure...

Once I contacted Michelin regarding tire pressure, and their response was to use the pressure recommended on the door jamb. What else are they going to say? That is the legally "correct" answer. If they tell you to run a different pressure and the tire explodes, causing injuries, they'd be liable.

 

[Greg E]

I just changed my Mich Lat Tour HP's after only 28000 miles - i got about 43,000 out of the Pilot LTX's that came on it. Do not worry about it to much because you will only have them for a couple of years or so. I ran them at 32 in the front and 34 in the rear. The Toyota recomended tire pressure was a little low for my taste.

 

[Skidoo]

Look at the fine print on tire for max pressure and max load. Then compare to other tires same size that you know are P and LT, that may give you a clue on what you have.

 

[hoser]

Your tires are metric or Euro-metric. They offer your Latitude Tour HP in some sizes in an XL or extra load version but yours isn't one of those.

For your Colt, I wouldn't worry too much about the alignment. Your tire pressures weren't much different. Had you said 15psi vs 35psi, then yes.

 

[LandCruiserPhil]

I'm not the author -


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.

 

[agaisin]

I'm not the author -


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.

LCPhil - thanks for posting that. I appreciate the original author's intent - there's no one number for everyone, you can't blindly follow the door jamb numbers, it depends on load per axle, under-inflation causes tire to overheat, overinflation can cause tire to blow etc.
The cynic I am, though, I have a hard time taking his pseudoscientific formula literally - no one else that I've seen (formal documentation or otherwise) provides this "formula" so how is he the only one talking about it? Is it his own home grown formula, or is it accepted by tire manufacturers and experts around the globe?

Just makes me even more eager to find a definitive and scientific method to determine the proper tire pressure

 

[Tinkerer]

The purported ex-Michelin employee writeup may be correct, but: When is the last time you saw a tire fail because of underinflation or overinflation?

The concept of [under = excessive sidewall flex & heat, over = increased risk of impact damage/blowout from inadequate flex] is sound. But the reality is that modern radials are incredibly tough and robust.

It would take more than a few miles at high ambient/road temperature and VERY underinflated condition to cause a tire to actually fail due to underinflation.

For typical (i.e. moderately) underinflated condition, the only significant affect to tire life is excessive treadwear at outer tread. While the sidewalls do endure higher temperature extremes due to increased flex, the probability of sidewall failure is still negligible within the expected wear life. (Assuming a tire of adequate quality. Tires like those involved in the Ford Explorer tire fiasco some years ago are defective anyway.)

Same idea for overinflation, except that excessive treadwear is concentrated in center tread area. Sidewall not likely to fail for moderate overinflation.

So, for e.g. 32psi door jam recommendation, 36psi max inflation marked on tire, setting cold pressure anywhere between, say, 30 to 38 psi, will not pose any danger. (Just ride quality and treadwear effect.)

Keep in mind also that accuracy of tire pressure gages varies widely; one gage may read 30 psi but another 32 psi, for same pressure. Tire manufactures and OEMs know this, too. It is not a razor-precise/accurate thing, and tires are very rugged and accomodating of this.

I worked as tire mounter for a few years when I was a pup. Very rarely saw any significant sidewall damage from heat/flexing, and for the few I did, they had been run nearly flat (or flat) for miles. Ruptured sidewalls were also very rare, and were associated with severe impacts such as hitting a curb at high speed.

 

[EdsCruisin]

When is the last time you saw a tire fail because of underinflation or overinflation?

The concept of [under = excessive sidewall flex & heat, over = increased risk of impact damage/blowout from inadequate flex] is sound. But the reality is that modern radials are incredibly tough and robust.

It would take more than a few miles at high ambient/road temperature and VERY underinflated condition to cause a tire to actually fail due to underinflation.

However, don't forget that the Ford Explorer rollover issue was mostly attributed to underinflated tires. Some of the tires did not specifically fail, so much as the handling of the vehicle was severely compromised by tires that were too soft. Then of course there was a series of failures resulting in death and destruction.

 

[Brock]

For passenger tires I keep it to the manufacturers rating on door or maybe 2-3 psi more at most....for LT tires or E rated tires I tend to go up a lot. For my Nitto Trail Grapplers, Nitto Terra Grapplers and BFG KM2 I ran 42psi on highway and then aired down to 18-20psi for normal trails.

If your tires are not rated for the higher weight loads....then stick with what is in your door jam unless you have done something to change weight of vehicle permanently....as mentioned already above.

 

[agaisin]

Thanks everyone for posting lots of good info.

For interest's sake (and more data points) what tires and psi do members here ride at? Would love to see what works for others.

I'll start off: Michelin Latitude Tour HP Tires 275/60R18, 34psi front, 35 psi rear
(no I can't tell a difference b/w 34 and 35 but the front happened to be at 34 when I stopped the compressor and I figured I'd leave it just so the front was a tad less than the rear).

Feels better for me at ~35 than the 29/32 settings according to the manufacturer. Also, for fun I tested out the method from LCPhil's and it appeared to work for me in the sense that when I was at 29psi and then rode at speed for a few miles the tire pressure went up more than 10%. When I brought it back up to 34/35 the pressure went up 2 psi after driving around (less than the 10% threshold). So I'm a believer.

 

[Skidoo]

A couple of links for future reference:
Technical Information: Wheels and Tires

Tire Pressures for 4-Wheeling

 

[Tinkerer]

However, don't forget that the Ford Explorer rollover issue was mostly attributed to underinflated tires. Some of the tires did not specifically fail, so much as the handling of the vehicle was severely compromised by tires that were too soft. Then of course there was a series of failures resulting in death and destruction.

Part of the problem with the Exploder (pun intended) fiasco was that Ford, attempting to compensate for pathetically crude vehicle engineering and poor build quality of their vehicle, specified a very low tire pressure of 26 psi to soften the ride. Mind you, these tires were nominally similar to tires that usually are specified to run 32 psi.

Then, Explorer owners probably did what many drivers do - they neglected to keep their tires inflated to mfg specs, so many Explorers were likely rolling on tires closer to 20 psi or less.

So, sure, when you run that low, on a vehicle that beats the crap out of the tires due to crude hard-riding suspension and chassis, you're gonna have problems from heat and mechanical impact over the long run.

 

[wareagle]

Guys,
There is a big difference in LT and Passenger rated tires. P is usually C rated. LT is usually D for land cruiser type tire. The Max tire ratings are tied to Max load. You should not run anywhere near max lload on the 100 series. I'd guess a land cruiser would run 35 PSI for C rated Passenger tires or 28-32 LT rated tires. A chalk test can be used to determine proper inflation.

 

[Sandroad]

Tire categories now are more sophisticated than simply P or LT. There is a set of excellent explanations for many of the questions on this thread, including adjustments to pressure based on vehicle speeds, loads, and tire tire type at:

Tire Tech at Tire Rack

It is fair to say that there is no one pressure that is "the answer" for any one tire. There are both subjective and objective variables to account for. For me, for on-road conditions with Michelin LTX AT/2 (275/65-18), I started with the pressure on the door jamb (29F 32R) and went up from there to achieve the best handling and lowest noise. That varies with the load and whether or not I'm towing, but never get close to the maximum on the sidewall (44). Off road is even more subjective, but the benefits of lower pressure in sand really start to kick in well below 20 psi.

 

[Topoguide]

Then, Explorer owners probably did what many drivers do - they neglected to keep their tires inflated to mfg specs, so many Explorers were likely rolling on tires closer to 20 psi or less.

So, sure, when you run that low, on a vehicle that beats the **** out of the tires due to crude hard-riding suspension and chassis, you're gonna have problems from heat and mechanical impact over the long run.

Then add to that doing 90+ mph in 100+ deg heat (where road temps far exceed the ambient) and you have a recipe for disaster.

But I digress... The formula given for measuring the tire pressure and staying within 10% sounds plausible, although the formula would have to be adjusted if your tires are inflated with nitrogen.

I've had tire guys say all sorts of weird things, some correct some not. But truly the best way I've found for any vehicle (carrying a load or not) to find proper inflation for that vehicle for that tire is by the wear pattern. If the tires wear properly they are inflated to an appropriate pressure, if not then it needs to be changed. As mentioned above the first thing you can do is to use the chalk test to get an idea if it is correct, after that watch your wear. If you pay close enough attention in the first few thousand miles you should know if it's right or not, adjust accordingly, then just check the wear pattern when you check your tire pressure.

As for your drive-train, I wouldn't worry about it. These trucks are way over built for what you're probably doing with those tires, plus with the open diffs on the LC you have very little to worry about.

 

[NMuzj100]

Once I contacted Michelin regarding tire pressure, and their response was to use the pressure recommended on the door jamb. What else are they going to say? That is the legally "correct" answer. If they tell you to run a different pressure and the tire explodes, causing injuries, they'd be liable.

A real professional would get the tire load table grab the vehicle specific axle weights from a reference source and do a calculation. That's what the Bridgestone "Tire Doctor" did for me and produced the perfect pressure of 38 PSI for LT285/75R16 on the 100.

The Michelin guys pressure/heat/pressure/add is a common technique.

The OPs tire is a standard passenger tire and should use the door jamb guides. Then run the chalk, shoeshine, business card and puddle tests to fine tune.

 

[cruiser100]

FWIW, I run 38psi in MT/AT type tires (33x10) and 34psi in passenger (stock) tires - both front and back. I haven't used stock tires since I added the ARB and Slee rear bumpers 50k miles ago; my wear patterns have been pretty even with regular rotation and pressure checks.

 

[staggrlee]

A couple of links for future reference:
Technical Information: Wheels and Tires

Tire Pressures for 4-Wheeling

Sorry to bite on this and take the OP's thread even more in an offroad direction...

This guy's post is pure BS as far as Landcruisers is concerned. Take it with a grain of sand and don't drink the Kool-Aid. An LC/LX is not a sandrail and a fully loaded/armored LC is never going to find a "floatation" tire suitable to the weight that will make an iota of difference. They'd have to be f'in huge!

Keep in mind what Camel Trophy Rovers ran for decades for all-around conditions in Siberia/Africa/S. America: Skinny tires!

His arguments about airing down are valid but overly wide tires on a heavy vehicle aired down to <15psi bag out and push a bigger "wave" of sand in front of you and this actually reduces forward traction and steering responsiveness.

Here's a good series on sand driving from ExpeditionOz:
YouTube - ExpeditionOz 4WD Skills - Sand Driving

Take special note of the comments on width and tread patterns as applies to sand.

My brother-in-law lives in Australia, has a diesel 105 and I've been in it with him driving in stuff I couldn't handle due to lack of experience... But I can tell you skinny+sand handled properly is just as capable as the fattest tires you could fit. Maybe even more so.

 

[RoderickGI]

I've driven plenty of sand in Australia. When the LX was standard, and weighed around 2600 Kg with me in it, I ran the tyres (tires for you Americans) at about 18 to 20 psi and only had trouble in the really really fine and deep sand near Robe in South Australia. At these pressures I still managed to roll a tyre off a front rim when I had to turn suddenly to avoid a drop off.

Now that my LX weighs 3200 Kg unloaded, 3500 Kg when I'm out on a trip, I run at least 24 psi on deep soft sand. It doesn't work as well as a lighter vehicle with lower pressures, but I got across the Simpson desert with it, and handled most of the fine white sands over near Lancelin in Western Australia. If I had to, I would run lower pressures to get out of a situation, but very carefully and not for too long or at speed.

On the road I run 40 psi front and rear. The ride is a little harsh, but any lower and the tyres bellow out too much for my liking. I prefer a slightly harsh ride to low mileage and badly worn tyres.

I run Silverstone AT-117 Specials. They are 275/70, rated 114S, 1180 Kg max. In a tyre comparison I used they were rated 2 out of 5 on sand, but were average or above on road, fire trails, gravel and mud, so a good choice for me at the time. An unusual choice, but they worked very well for five years, and are still okay at seven years, but need replacing now.