# tire pressure



## Robby (Mar 1, 2013)

35 PSI is the recommended operating pressure for best ride and general day to day usage.

The maximum cold operating pressure is printed into the tire sidewall.....in your case I believe it will say 44 psi maximum cold pressure.

So, your actual operating range is from 35 to 44 psi.

All this to say, there is no action necessary at this time.

Rob


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## draco_m (Dec 28, 2014)

Pressure will indeed drop over time. But it should be very slow to drop.

I just bought a Cruze yesterday. I inflated each tire to 36 PSI cold. 

I guess 38 would work fine too. Might be a little rougher ride.


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## obermd (Mar 3, 2012)

As Robby said, anything between 35 (door placard) and 44 (Max sidewall) PSI cold is where your car should be running. Find the happy medium between handling and ride comfort.


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## Tomko (Jun 1, 2013)

Drawing back on my high school chemistry class of PV=nRT, Boyle's law tells us that a pressure of a gas in a sealed container is directly proportional to its temperature. 

For tires that means that every 10 degree Celsius change in temperature will result in a corresponding change of 2.5 PSI. 

Therefore tires set at 35 PSI at a temperature of 25 degrees Celsius (77 Fahrenheit) will drop to 25 PSI at -15 degrees Celsius (5 Fahrenheit).


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## Psychomidgit (Jun 9, 2013)

And will go up as the temperature of the tires rises, as it does when driving. As long as you don't go over the max psi while driving (once the tires heat up), then you should be fine.


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## Robby (Mar 1, 2013)

Psychomidgit said:


> And will go up as the temperature of the tires rises, as it does when driving. As long as you don't go over the max psi while driving (once the tires heat up), then you should be fine.


Incorrect info.....but an easy trap to fall into.

The example, maximum COLD pressure as stated on the sidewall, means just that.
The manufacturer is well aware of the fact the tire will be operating at a pressure above the COLD pressure maximum at speed.
This has been taken into consideration at the design stage.......so, if starting off with pressure at, in this case 44 psi, and it rises to say, 46/48 psi, there is no concern.......probably rides hard but as long as it's not being used on a track, no worries.

Rob


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## obermd (Mar 3, 2012)

Tomko said:


> Drawing back on my high school chemistry class of PV=nRT, Boyle's law tells us that a pressure of a gas in a sealed container is directly proportional to its temperature.
> 
> For tires that means that every 10 degree Celsius change in temperature will result in a corresponding change of 2.5 PSI.
> 
> Therefore tires set at 35 PSI at a temperature of 25 degrees Celsius (77 Fahrenheit) will drop to 25 PSI at -15 degrees Celsius (5 Fahrenheit).


Which is why you need to physically check your tire pressure at least once a month.


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## obermd (Mar 3, 2012)

Psychomidgit said:


> And will go up as the temperature of the tires rises, as it does when driving. As long as you don't go over the max psi while driving (once the tires heat up), then you should be fine.


Aside from Robby's point, I used the TPMS in my ECO MT to validate this. It turns out that the OEM Goodyear FuelMax assurance top out around 53-54 PSI regardless of starting pressure. When running 45 cold they would climb to 52-53 PSI and when running at 51 cold they would only climb to 54 PSI, even in the middle of the summer heat. I measured this both in my daily commute and while driving across Kansas in 100+ temperatures.

Given this information it's also easy to understand why higher PSIs tend to wear slower - there's less heat buildup in the sidewall to be transferred to the tread compound. The bulk of your heat buildup is a result of sidewall flexing.

I did some quick testing of the Perelli's I'm currently riding on and they appear to have a similar heat buildup characteristic.


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## spacedout (Dec 7, 2010)

I don't know how all you can stand riding on rock hard tires in the winter, only have 35psi in mine.


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## obermd (Mar 3, 2012)

spacedout said:


> I don't know how all you can stand riding on rock hard tires in the winter, only have 35psi in mine.


Potholes hurt at 50 PSI. However, the benefit is a much more predictable response from the car when I need to steer. Both my Transport and Montana were this way as well even at 35 PSI (door on both was 32) so I got used to the harsher ride.


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## Phil2 (Nov 22, 2014)

*What gives?*

My 2013 Cruze LT with the RS suspension recommends 30 P.S I. on the door sticker and not 35 P.S I.. Does anyone know why there's a difference?


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## obermd (Mar 3, 2012)

Different suspensions and the desire to reduce rolling resistance in the three ECO trims (AT, MT, and CDT). The easiest way to reduce rolling resistance is to increase tire pressure. The bulk of your rolling resistance comes from sidewall flex. With radial tires vehicle weight, within reason, isn't a determining factor in tire pressure. The ECO MT is the lightest version of the Cruze and the CDT is the heaviest - both have higher tire pressure recommendations than the LS, LT, and LTZ.


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## 170-3tree (Nov 4, 2014)

Hmm my '13 lt rs says 35. 

I run my summer tires at 43/ just a hair under sidewall. My blizzaks runat 40, unless I know that weather is coming, thenI drop to 34-36 for increased traction.


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## BlkGrnetRS (Jul 21, 2013)

Phil2 said:


> My 2013 Cruze LT with the RS suspension recommends 30 P.S I. on the door sticker and not 35 P.S I.. Does anyone know why there's a difference?


Really? Mine says 35


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## Phil2 (Nov 22, 2014)

I'll double check this with the GM dealership. There must be a reason for the difference. I'll get back to you on this, thanks for the reply.


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## obermd (Mar 3, 2012)

Phil2 said:


> I'll double check this with the GM dealership. There must be a reason for the difference. I'll get back to you on this, thanks for the reply.


What does the door placard say?


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## spacedout (Dec 7, 2010)

The reason some are seeing the 30PSI door placard, they have LTZ 18in wheels. ALL OTHER TRIMS ARE 35PSI door placard.


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## Phil2 (Nov 22, 2014)

30 psi front and 30 psi rear! Could it be because of the RS suspension and 225 50 R 17 tires that come with it? Maybe the RS suspension gives a firmer ride so they lowered the tire pressure to give a soften the ride.


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## obermd (Mar 3, 2012)

Phil2 said:


> 30 psi front and 30 psi rear! Could it be because of the RS suspension and 225 50 R 17 tires that come with it? Maybe the RS suspension gives a firmer ride so they lowered the tire pressure to give a soften the ride.


Possible, but it's more likely the door placard is for an LTZ and not an LT. Run those tires at 35 PSI and see how you like it.


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## Danny5 (Dec 22, 2011)

obermd said:


> Which is why you need to physically check your tire pressure at least once a month.


Does looking at my DIC screen count? 

I run mine 42psi cold. Over time, I'll let them drop to 38 cold, and then I fill them again.

People SAY they can feel a difference of 3 or 4 psi (38 over 35 for instance) but I think its all in their mind. I drove my GF's soul around and the tires were at 25. Stopped to fill them to 35, barely noticed a difference.


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## obermd (Mar 3, 2012)

Danny5 said:


> Does looking at my DIC screen count?
> 
> I run mine 42psi cold. Over time, I'll let them drop to 38 cold, and then I fill them again.


Yes, especially since you're using it to alert you to time to actually go inflate them as needed.



Danny5 said:


> People SAY they can feel a difference of 3 or 4 psi (38 over 35 for instance) but I think its all in their mind. I drove my GF's soul around and the tires were at 25. Stopped to fill them to 35, barely noticed a difference.


I can feel a five PSI difference. The car handles differently.


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## Danny5 (Dec 22, 2011)

obermd said:


> I can feel a five PSI difference. The car handles differently.


Oh, are we talking track days? I was generalizing about street comfort, where I drive on freeways and highways for 95% of my time. I couldn't tell you the difference in 5psi on a tire.

I have over 100 hours of track time in specially prepared street cars. 2 psi difference is all it would take to make a slow car fast. 

But if I am approaching that kind of limit on any road, straight, twisty, school zone, then I should be arrested and have the book thrown at me.

Let me say this one more time - on the street in a passenger car, I can't tell the difference in 5psi. I say pump your tires to 40.


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## jblackburn (Apr 14, 2012)

I couldn't stand the FR710 at anything above 38. When it got above 40, I could feel it. 

I'm actually thinking of knocking my new tires down to the recommended 35 as they do ride harsher than the Firestones in freezing temps. 

I can easily feel a 5 PSI difference on the Bridgestones on the GFs car as well - it handles like crap at 29, handles well and rides rough at the recommended 35.


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## obermd (Mar 3, 2012)

I don't track my Cruze, but 5 PSI makes a huge difference how the LRR tires handle corners. I do tend to corner hard on the theory that if I don't slow down I don't have to waste energy accelerating again.


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## Phil2 (Nov 22, 2014)

Maybe your both right. If you check on the Tire Rack site, lets say you want a high performance all season tire for example. Tire Rack will list all the different tire manufacturers with that type of tire. You'll notice that some perform better than others regardless of price. Some give a harsher ride and some soft. You would have to check on that site to see how the tires you have perform in all categories. If you have tires that gives you a soft ride you can put 5 psi over the placard and may not notice the difference. It's good to check Tire Rack first before buying tires, then you can choose the tire that performs the way you want. I learned from them that every tire manufacturer make great and/or bad tires. It could also be the way the suspension is set up, can it take higher tire pressure, every car is different. Worn shocks really affect the ride. If you follow a car with worn shocks, you can notice the wheels hopping up and down off the road surface. Good luck with that!


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## BU54 (Nov 24, 2014)

obermd said:


> Which is why you need to physically check your tire pressure at least once a month.


My '13 1LT displays tire pressure on the DIC. Very nice.


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## spacedout (Dec 7, 2010)

Danny5 said:


> Let me say this one more time - on the street in a passenger car, I can't tell the difference in 5psi. I say pump your tires to 40.


The stock firestones or even the hankooks I replaced them with its very easy to feel a 5 PSI difference. 35PSI initial steer in will cause slight body roll when the sidewall of the tire compresses, at 40PSI this is drastically reduced. 

Now if your not one to take corners at speed whipping the wheel into the turn then this might not be noticed.... however the harsher ride sure is.


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## obermd (Mar 3, 2012)

BU54 said:


> My '13 1LT displays tire pressure on the DIC. Very nice.


I'd still check with a gauge. My 2012 ECO MT's TPMS can be off by as much as 3-4 PSI.


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## BU54 (Nov 24, 2014)

obermd said:


> I'd still check with a gauge. My 2012 ECO MT's TPMS can be off by as much as 3-4 PSI.


On the other hand I think my stick gauge is off. Especially when it's cold. It doesn't slide as well.


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## Danny5 (Dec 22, 2011)

obermd said:


> I'd still check with a gauge. My 2012 ECO MT's TPMS can be off by as much as 3-4 PSI.


Mine is dead on accurate. Verified with at least half a dozen tire shops, and my own Longacre pressure gauge. 

Just like any other gauge in your car, you should verify it's accuracy before quoting as gospel.


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## jblackburn (Apr 14, 2012)

Mine are within 1-2 PSI of gauge and air pump readings - close enough for me. They do take some time to update after first turning on the key, though.


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## obermd (Mar 3, 2012)

Danny5 said:


> Mine is dead on accurate. Verified with at least half a dozen tire shops, and my own Longacre pressure gauge.
> 
> Just like any other gauge in your car, you should verify it's accuracy before quoting as gospel.


That's why I said "my ECO MT". Although I wonder if this difference changes when you replace the TPMS sensors because I had my tires inflated to 50 PSI last week by the dealership and my TPMS now shows 50 PSI. I replaced the sensors when I replaced the OEM tires and that was the last time I verified the TPMS readings against a calibrated pressure gauge.


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## Danny5 (Dec 22, 2011)

obermd said:


> That's why I said "my ECO MT". Although I wonder if this difference changes when you replace the TPMS sensors because I had my tires inflated to 50 PSI last week by the dealership and my TPMS now shows 50 PSI. I replaced the sensors when I replaced the OEM tires and that was the last time I verified the TPMS readings against a calibrated pressure gauge.


Well yah! It is the sensor reading the pressure after all. 

What you pay for new sensors?


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## obermd (Mar 3, 2012)

Danny5 said:


> Well yah! It is the sensor reading the pressure after all.
> 
> What you pay for new sensors?


I think it was $80 for all four wheels. Basically $20 a wheel installed. I also replace my valve stems whenever I replace the tires. Rubber rots and metal corrodes.


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## Danny5 (Dec 22, 2011)

obermd said:


> I think it was $80 for all four wheels. Basically $20 a wheel installed. I also replace my valve stems whenever I replace the tires. Rubber rots and metal corrodes.


That's flipping cheap! I think Tire Rack wants $200. I need to find this deal


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