Questions About Tire Pressure

[Texas Jim]

Good Morning Boys and Girls,

Would like your opinions on tire pressure and tire wear, handling and the trade offs.

I recently bought a 2006 DTS Performance Sedan. Tires are 18 inch 255x50. The tires have max pressure of 44psi on the sidewall, but the sticker on the door says 30 psi front and 30 psi rear.

I currently have 34psi front and 32psi rear. It rides a little rougher than with 30psi, but seems to handle a lot better.

But at over $1000.00 to replace the set of tires, I am wondering how much different pressures will affect tire wear and if the better handling is all in my head.

Long ago, <longer than I care to remember> I used to drive 1/4 mile dirt tracks a little bit, so I "THINK" I can tell the difference.

[Ranger]

Higher pressures will benefit fuel milage and lower will benefit ride. Too high will wear then ion the center and too low will wear them on the edges. I'd say you are just about in the right place now.

[JIMDTS]

I have had good luck running an 01 dts with 32psi(cold) all around It rides better at lower pressures 30psi I would not want to drive it with anymore than 32psi One time at the tire shop they aired the tires to 40psi I had to pull off the freeway to let some air out the car rode VERY hard Lucky I had an air gauge with me

Jim

One quick question how do you like the 06 DTS

I ran across one the other day & I'm tempted to grab it the price is rite with 13k on the clock Hard for me to justify getting rid of the 01 it has Low milage(48k) & runs great

Jim

[JasonA]

My suggestion would be to get a tread depth gauge and keep an eye on the tread depths in all four main grooves (or however many grooves your tires have).

My '97 Seville calls for 30/30 front/rear, but I think that's in interest of ride quality. All the tires that have been on this car have suffered from severe edge wear...underinflation, especially on the front. I currently run at 40/30 front/rear. I can't tell a large difference in ride quality, but the ride/handling does get comparatively "squishy" when I set the fronts as low as 30, as Cadillac instructs. I think I may back down to about 35 front and see where the wear lies.

[BodybyFisher]

My question is, is that 44 psi on the side wall, the max pressure HOT or the max pressure COLD.. my guess is HOT.

I tend to run my tires at higher pressure for better handling and better gas mileage. Now I am running with 35 in the front and 34 in the rear (cold). Right now I am only concerned with better gas mileage.

[JasonA]

The max pressure moulded into the sidewall is the maximum pressure COLD. The PSI will increase with temperature, so the PSI indicated isn't the absolute maximum a tire can handle. It's the most air you should ever put in cold.

[BodybyFisher]

The max pressure moulded into the sidewall is the maximum pressure COLD. The PSI will increase with temperature, so the PSI indicated isn't the absolute maximum a tire can handle. It's the most air you should ever put in cold.

Thanks for that Jason, I didn't know that

[GreenMachine]

Also your door sticker is based off the stock tires that came from the factory. If you got a dealer package that included the better tires go by what the tire says.

If you could get ahold of the tire manufacture that would be the surpreme answer because then you could match up the weight of your car to the PSI they recommend.

30 PSI has been (for a number of years) basically the "safe spot" for tires. Almost any tire can be filled to 30 and ride safely.

My 98 has Perilli tires that on the sidewall say 35PSI max.

Well when you are driving a good rule of thumb is you want the the hot range in the 40-42PSI range (for these tires anyway). So I checked and with my car they get to that if I place in 33-35 PSI. most of the time I stick them right around 33, that way if the weather gets cold, they wont be underinflated at first, and when the weather is warm they wont be too hot to start off.

Basically do what the tire recommends, the door is for the stock michelins or goodyears.

I like the firmer ride with this pressure setup, my deville's suspension is plenty soft so in a way this only helps

[JimD]

....

I recently bought a 2006 DTS Performance Sedan. Tires are 18 inch 255x50. The tires have max pressure of 44psi on the sidewall, but the sticker on the door says 30 psi front and 30 psi rear....

Consider the door sticker to be the "minimum" safe inflation pressure as determined by the GM legal department (remember the Ford Exporers that blew tires and caused injuries and worse? Underinflation!).

Find your sweet spot between 30 and 44 psi and motor on down the road.

[Texas Jim]

One quick question how do you like the 06 DTS

I ran across one the other day & I'm tempted to grab it the price is rite with 13k on the clock Hard for me to justify getting rid of the 01 it has Low milage(48k) & runs great

Jim

I really like the '06 DTS. Just finished a 3500 mile road trip. It did great. About 21/22 mpg and if it wasn't for my heavy foot it would have probably got a lot better, but I can live with that.

[JasonA]

Basically do what the tire recommends, the door is for the stock michelins or goodyears.

Actually, you will almost NEVER put the inflation pressure at what is indicated on the sidewall.

Again, what is moulded on the sidewall is the SAFE MAXIMUM inflation pressure for THAT TIRE -- NOT the recommended inflation pressure for YOUR VEHICLE.

Most tires have a maximum inflation pressure of either 35 psi, 44 psi, or 51 psi. For tires rated as low as 35 psi, you MIGHT be putting that much in the tires, but again, not because that's what the tire says. If you have a tire model that has a 44 psi max pressure, you don't want to put that much in the tires. And you certainly don't want to put 51 psi in the tires, even though that's what some tires are safe to.

Again, go by what's on the VEHICLE DECAL as your starting point. Go up from there if you like. Don't exceed the pressure moulded on the tire, but you probably won't have that issue, unless your tires are only safe to 35 psi.

[GreenMachine]

I did indicate that you should contact your tire manufacturer for the "safe" PSI for your car and you could match up the weight to it and did say the 30 PSI is the safe spot. No big deal its just a pet peeve of mine when people pull one line out of something and disregard the rest If I was unclear about contacting and checking with the manufacture to see what PSI goes with what wieght on the car (then again 30PSI in the tires of a real small car takes more air to make more pressure, where as with a big car less air creates more pressure, generally speaking).

Also your door sticker is based off the stock tires that came from the factory. If you got a dealer package that included the better tires go by what the tire says.

If you could get ahold of the tire manufacture that would be the surpreme answer because then you could match up the weight of your car to the PSI they recommend.

30 PSI has been (for a number of years) basically the "safe spot" for tires. Almost any tire can be filled to 30 and ride safely.

My 98 has Perilli tires that on the sidewall say 35PSI max.

Well when you are driving a good rule of thumb is you want the the hot range in the 40-42PSI range (for these tires anyway). So I checked and with my car they get to that if I place in 33-35 PSI. most of the time I stick them right around 33, that way if the weather gets cold, they wont be underinflated at first, and when the weather is warm they wont be too hot to start off.

Basically do what the tire recommends, the door is for the stock michelins or goodyears.

I like the firmer ride with this pressure setup, my deville's suspension is plenty soft so in a way this only helps smile.gif

Basically do what the tire recommends, the door is for the stock michelins or goodyears.

Actually, you will almost NEVER put the inflation pressure at what is indicated on the sidewall.

Again, what is moulded on the sidewall is the SAFE MAXIMUM inflation pressure for THAT TIRE -- NOT the recommended inflation pressure for YOUR VEHICLE.

Most tires have a maximum inflation pressure of either 35 psi, 44 psi, or 51 psi. For tires rated as low as 35 psi, you MIGHT be putting that much in the tires, but again, not because that's what the tire says. If you have a tire model that has a 44 psi max pressure, you don't want to put that much in the tires. And you certainly don't want to put 51 psi in the tires, even though that's what some tires are safe to.

Again, go by what's on the VEHICLE DECAL as your starting point. Go up from there if you like. Don't exceed the pressure moulded on the tire, but you probably won't have that issue, unless your tires are only safe to 35 psi.

[JasonA]

The reason I called out that one individual line is because that was the only part of your post that was inaccurate.

The door sticker is NOT just for the stock Goodyears or Michelins. That's for any tire in general, and is Cadillac's *recommendation* on what the tires should have to give the "best performance" from the car. What Cadillac defines as "best performance" may be different from what you and I define as "best performance". Cadillac probably prioritizes a smooth ride at the expense of fuel economy and handling. If you took a stock Goodyear or Michelin (or now Continental) tire and aired it up over 30 psi, you'd see the same changes that you do with an aftermarket tire. Decreased fuel consumption, better handling, worse ride.

My Grand Caravan specifies 36 psi front and rear. Dodge obviously prioritizes fuel economy in those ratings. I run the front tires at about 36 and the rears at about 33 on the Dodge. But the tires have a maximum inflation pressure of 44 psi.

When you say "do what the tire recommends", that shouldn't be misunderstood by someone reading that the correct inflation pressure is that which is moulded into the sidewall. That's why I called it out.

[kcd1184]

I have found that in most vehicles, you need to tune the tires pressure by experimenting yourself. The door numbers are just that, numbers. I found that with my Cooper Lifeliners, H rated, to get the best all around handling, wear, and ride, I run 32lbs front and 26lbs rear.

If you compare the squish (spread) of the front and rear tires, the rears still don't spread like the fronts, but I don't want to go any lower in pressure.

Kent

[Texas Jim]

A big thank you to everyone for the tire pressure info.

I have 34psi front and 32psi rear now. I will experiment with different pressures to see what I like best and what gives a good combination of ride and decent handling.

[JasonA]

Kent brought up a good point about the "squish" factor between the fronts and the rears. When running at an even 30/30 or even 32/32, that's probably a little underinflated for the front, and probably a little overinflated for the rear. However, in theory, because we're all diligent in tire rotation, that uneven wear will "even out" over time.

I prefer (as does Kent apparently) to run what I feel are the "correct" pressures at each end, even if it means adjusting air pressure everytime I rotate. I don't prefer to go as low as 26 in the rear, but that's all personal preference.