Tire Psi Question.

[intellivised]

OK. So I'm starting to get into actually understanding cars and my Lexus. It was only a matter of time; I find it really interesting and live in a town small enough to walk everywhere if I have to (in case of a major breakdown). As anything learned later on in life, there are a lot of gaps in my knowledge. The big thing I'm curious about now all the sudden is this:

What PSI should I have my tires at? I want to make sure I have them set right on my 1992 LS400. I got my winter tires off a month ago (yes, winter and snowy roads go all the way to May here) and my summer tires are on. I always check the tires before I go to Fort Collins, CO since it's through the mountains and I go once every 2-4 weeks. I noticed, though, when I got the car back from the garage the PSI was in the 40's and it was even all around (looked intentional). Hadn't been driving for the day and the gas station was across the street, so it was accurate. The manual says 35. I've read that more is better, or at least being way under is bad. And being way over is bad for different reasons. A few articles on Tire Rack can be a dangerous thing; so I'm seeking input.

Also - just so this isn't a total n00bfest at my expense, I will also say a few things about my winter tires. I bought a set of Hankook iPike's. I've had them two seasons now and it's important now to mention that I live in Wyoming at 7000' next to the highest point on the US interstate. Long story short: We get a lot of snow. And ice. Hail capital of the world, so I'm told. Mostly the snow is the powder kind (but we also get the gross stuff in early Spring like what you see in MI where I grew up). This last winter saw a LOT of snow, and I had a few encounters with unreal conditions on highways that shut down behind me and can saw that the iPikes were great. They were a budget minded choice - I had thought about Blizzaks but these were cheaper. I've only gotten stuck once in two years and that required some outright hoonage in an empty K-Mart parking lot to do. The tires themselves have proven to give me a lot of confidence and ability to control in severe conditions.

So.... thoughts on PSI's?

[Brett in AK]

OK. So I'm starting to get into actually understanding cars and my Lexus. It was only a matter of time; I find it really interesting and live in a town small enough to walk everywhere if I have to (in case of a major breakdown). As anything learned later on in life, there are a lot of gaps in my knowledge. The big thing I'm curious about now all the sudden is this:

What PSI should I have my tires at? I want to make sure I have them set right on my 1992 LS400. I got my winter tires off a month ago (yes, winter and snowy roads go all the way to May here) and my summer tires are on. I always check the tires before I go to Fort Collins, CO since it's through the mountains and I go once every 2-4 weeks. I noticed, though, when I got the car back from the garage the PSI was in the 40's and it was even all around (looked intentional). Hadn't been driving for the day and the gas station was across the street, so it was accurate. The manual says 35. I've read that more is better, or at least being way under is bad. And being way over is bad for different reasons. A few articles on Tire Rack can be a dangerous thing; so I'm seeking input.

Also - just so this isn't a total n00bfest at my expense, I will also say a few things about my winter tires. I bought a set of Hankook iPike's. I've had them two seasons now and it's important now to mention that I live in Wyoming at 7000' next to the highest point on the US interstate. Long story short: We get a lot of snow. And ice. Hail capital of the world, so I'm told. Mostly the snow is the powder kind (but we also get the gross stuff in early Spring like what you see in MI where I grew up). This last winter saw a LOT of snow, and I had a few encounters with unreal conditions on highways that shut down behind me and can saw that the iPikes were great. They were a budget minded choice - I had thought about Blizzaks but these were cheaper. I've only gotten stuck once in two years and that required some outright hoonage in an empty K-Mart parking lot to do. The tires themselves have proven to give me a lot of confidence and ability to control in severe conditions.

So.... thoughts on PSI's?

You can't go wrong with what your owners manual or sticker suggests. Regarding high PSI vs. low I would opt for the high if it wasn't excessively so. Bear in mind that your tire wear in the center will be faster and the ride will be harsher. Point to remember, when the temperatures warm up in the spring and summer you normally will have to readjust the tire pressure again. Just as a matter of curiosity, when you checked the tire pressure after you got the car back from the garage, was that after driving home, or after sitting at home and giving the tires a chance to cool down? The reason I bring this up is the tire pressure will increase exponentially as the tire or ambient temperature increases. I'm pretty religious about keeping up with the tire PSI's and the other day when I checked my "other" vehicle they were all at 40 PSI, up from the recommended 36.

[HRP]

Tire pressure has been discussed at length here and on about every discussion board about cars.

Briefly, your tires are used by the engineers and designers in helping to adjust your ride. Many of us who prefer a firmer ride and quicker handling run our tires at a higher pressure than suggested by the manufacturer. If you search tire pressure on the web, you'll find that many state highway patrol departments recommend 40 lbs for handling (and this commonly on Ford Crown Vics which are of comparable waight to an LS). If you watch your tread wear, you'll find that under-inflated tires wear on both the outer and inner aspects of the tread. Over-inflated tires wear on the tread crown. Then adjust tire pressure accordingly. I generally run high quality Michelin all season tires on our vehicles which weigh in at around 4000 lbs and run cold tire pressures of 38 lbs. I get firm handling, a slightly stiff ride, and good traction as well as even wear. I do rotate, balance, and 4 wheel align at least every 5k. I also check tire wear and pressures every couple of weeks.

I would not run tires at less than your vehicle manufacturers recommended pressures or higher than your tire manufacturer's recommendations. Look up "how to read your tire information on your sidewalls". This will tell you the maximum cold tire pressure (usually around 44 lbs for most Michelins and other automobile premium tires). And increasing your tire pressure usually will improve fuel milage a bit.

Hope this info helps.

[1990LS400]

The manual says 35.

Are you certain? The manual for the gen 1 1990 LS400 I drove for 13 1/2 years recommended only 30 psi for non-winter tires.

The manual for my current 2000 LS400 recommends an even lower pressure - 29 psi. The manual for my 1990 LS400 recommended bumping up the pressure on snow tires by 4 psi. The manual for my 2000 LS400 does not recommend doing that. Many snow tires, including Blizzaks (which I use in winter), have a fairly low maximum inflation limit -- 35 psi.

I've found that the best combination of ride, handling and tire life on an LS400 is when the tire pressure is kept at the low end of the recommended range. I keep the tires on my 00 LS400 at about 32 psi mainly to keep the pressure from dropping below 29 psi due to temperature fluctuations.

During the nearly 300,000 miles I've driven LS400s over the past 19+ years, I haven't found it necessary to balance tires on an LS400 very often unless there is some other suspension problem that is causing uneven tire wear. And I've rarely found it necessary to have the alignment checked more than every 30,000 miles and, even then, sometimes the car is still in perfect alignment.

[intellivised]

OK. So I'm starting to get into actually understanding cars and my Lexus. It was only a matter of time; I find it really interesting and live in a town small enough to walk everywhere if I have to (in case of a major breakdown). As anything learned later on in life, there are a lot of gaps in my knowledge. The big thing I'm curious about now all the sudden is this:

What PSI should I have my tires at? I want to make sure I have them set right on my 1992 LS400. I got my winter tires off a month ago (yes, winter and snowy roads go all the way to May here) and my summer tires are on. I always check the tires before I go to Fort Collins, CO since it's through the mountains and I go once every 2-4 weeks. I noticed, though, when I got the car back from the garage the PSI was in the 40's and it was even all around (looked intentional). Hadn't been driving for the day and the gas station was across the street, so it was accurate. The manual says 35. I've read that more is better, or at least being way under is bad. And being way over is bad for different reasons. A few articles on Tire Rack can be a dangerous thing; so I'm seeking input.

Also - just so this isn't a total n00bfest at my expense, I will also say a few things about my winter tires. I bought a set of Hankook iPike's. I've had them two seasons now and it's important now to mention that I live in Wyoming at 7000' next to the highest point on the US interstate. Long story short: We get a lot of snow. And ice. Hail capital of the world, so I'm told. Mostly the snow is the powder kind (but we also get the gross stuff in early Spring like what you see in MI where I grew up). This last winter saw a LOT of snow, and I had a few encounters with unreal conditions on highways that shut down behind me and can saw that the iPikes were great. They were a budget minded choice - I had thought about Blizzaks but these were cheaper. I've only gotten stuck once in two years and that required some outright hoonage in an empty K-Mart parking lot to do. The tires themselves have proven to give me a lot of confidence and ability to control in severe conditions.

So.... thoughts on PSI's?

You can't go wrong with what your owners manual or sticker suggests. Regarding high PSI vs. low I would opt for the high if it wasn't excessively so. Bear in mind that your tire wear in the center will be faster and the ride will be harsher. Point to remember, when the temperatures warm up in the spring and summer you normally will have to readjust the tire pressure again. Just as a matter of curiosity, when you checked the tire pressure after you got the car back from the garage, was that after driving home, or after sitting at home and giving the tires a chance to cool down? The reason I bring this up is the tire pressure will increase exponentially as the tire or ambient temperature increases. I'm pretty religious about keeping up with the tire PSI's and the other day when I checked my "other" vehicle they were all at 40 PSI, up from the recommended 36.

The 40ish reading was the next morning after sitting in my garage for the night. The temperature variation here is pretty extreme due to the elevation; i.e. it can get to the high 70s or 80s during the day and it'll still get down to the 40's or even 30's at night (I really enjoy that).

[intellivised]

Tire pressure has been discussed at length here and on about every discussion board about cars.

Briefly, your tires are used by the engineers and designers in helping to adjust your ride. Many of us who prefer a firmer ride and quicker handling run our tires at a higher pressure than suggested by the manufacturer. If you search tire pressure on the web, you'll find that many state highway patrol departments recommend 40 lbs for handling (and this commonly on Ford Crown Vics which are of comparable waight to an LS). If you watch your tread wear, you'll find that under-inflated tires wear on both the outer and inner aspects of the tread. Over-inflated tires wear on the tread crown. Then adjust tire pressure accordingly. I generally run high quality Michelin all season tires on our vehicles which weigh in at around 4000 lbs and run cold tire pressures of 38 lbs. I get firm handling, a slightly stiff ride, and good traction as well as even wear. I do rotate, balance, and 4 wheel align at least every 5k. I also check tire wear and pressures every couple of weeks.

I would not run tires at less than your vehicle manufacturers recommended pressures or higher than your tire manufacturer's recommendations. Look up "how to read your tire information on your sidewalls". This will tell you the maximum cold tire pressure (usually around 44 lbs for most Michelins and other automobile premium tires). And increasing your tire pressure usually will improve fuel milage a bit.

Hope this info helps.

I went with 35 because I thought that's what the manual said and 40-42 what the garage put them at seemed really high to me. If it ends up being a little higher, I might just keep it at 35 for the benefit of a slightly stiffer ride and sharper handling; I don't think that should compromise tire handling too much? I'll be honest - I don't worry about tire rotation on my summer tires. Before you all scream !Removed! murder! understand that I really only have them on my car for 6 months or less and since Laramie is such a compact town - it's hard for me to put 5000 miles on them a season; even when you include a few trips to Denver/Boulder. So my rotation is done at the annual tire change. My winter tires get even less mileage but I'm thinking this next year will be there last. The snow is unpredictable and I had a few trips to the airport on dry roads with the iPikes.

[IS400]

When the car stops getting taller when you inflate the tires, you are at the optimum pressure for gas mileage.

When the tire is slack enough so you can flex the sidwall side to side with your body weight, you are at optimum traction.

Drag racers do the first for the fronts and the latter for the rears.

Being a forced induction notchback 5.0 crew member in the past, I know the guys sweated tire pressures for an advantage.

FYI, the corrected elevation and ambient temperature have to be included in deciding what actual pressure reading is right.

The durometer and elastomeric index of the tire compound are also important if statistically siginificant results are what you are after.

[Brett in AK]

OK. So I'm starting to get into actually understanding cars and my Lexus. It was only a matter of time; I find it really interesting and live in a town small enough to walk everywhere if I have to (in case of a major breakdown). As anything learned later on in life, there are a lot of gaps in my knowledge. The big thing I'm curious about now all the sudden is this:

What PSI should I have my tires at? I want to make sure I have them set right on my 1992 LS400. I got my winter tires off a month ago (yes, winter and snowy roads go all the way to May here) and my summer tires are on. I always check the tires before I go to Fort Collins, CO since it's through the mountains and I go once every 2-4 weeks. I noticed, though, when I got the car back from the garage the PSI was in the 40's and it was even all around (looked intentional). Hadn't been driving for the day and the gas station was across the street, so it was accurate. The manual says 35. I've read that more is better, or at least being way under is bad. And being way over is bad for different reasons. A few articles on Tire Rack can be a dangerous thing; so I'm seeking input.

Also - just so this isn't a total n00bfest at my expense, I will also say a few things about my winter tires. I bought a set of Hankook iPike's. I've had them two seasons now and it's important now to mention that I live in Wyoming at 7000' next to the highest point on the US interstate. Long story short: We get a lot of snow. And ice. Hail capital of the world, so I'm told. Mostly the snow is the powder kind (but we also get the gross stuff in early Spring like what you see in MI where I grew up). This last winter saw a LOT of snow, and I had a few encounters with unreal conditions on highways that shut down behind me and can saw that the iPikes were great. They were a budget minded choice - I had thought about Blizzaks but these were cheaper. I've only gotten stuck once in two years and that required some outright hoonage in an empty K-Mart parking lot to do. The tires themselves have proven to give me a lot of confidence and ability to control in severe conditions.

So.... thoughts on PSI's?

You can't go wrong with what your owners manual or sticker suggests. Regarding high PSI vs. low I would opt for the high if it wasn't excessively so. Bear in mind that your tire wear in the center will be faster and the ride will be harsher. Point to remember, when the temperatures warm up in the spring and summer you normally will have to readjust the tire pressure again. Just as a matter of curiosity, when you checked the tire pressure after you got the car back from the garage, was that after driving home, or after sitting at home and giving the tires a chance to cool down? The reason I bring this up is the tire pressure will increase exponentially as the tire or ambient temperature increases. I'm pretty religious about keeping up with the tire PSI's and the other day when I checked my "other" vehicle they were all at 40 PSI, up from the recommended 36.

The 40ish reading was the next morning after sitting in my garage for the night. The temperature variation here is pretty extreme due to the elevation; i.e. it can get to the high 70s or 80s during the day and it'll still get down to the 40's or even 30's at night (I really enjoy that).

If you enjoy the temperature changes, you ought to move up here to Alaska. You'll get a bigger bang for the buck as you see upwards of a 160 degree swing between summer and winter. Also depending on where you come to you can escape the Laramie wind.

[aarman4]

The glovebox in my 91 LS recommends 30 for the front and back, and then 35 for the backs under a high load condition. I keep all of my tires at 35 PSI all around for the most part in the summer, and at 30 in the winter unless I am loaded.

Chek your glovebox, or driver door sticker, and go by that, and you cannot go wrong. Experiment as you research more on your own about the effects of lower and higher pressures.