Accurate Tire Pressure Measure with Dry Ice

dbdawson · 07-13-2006, 11:47 PM

Hello fellow Toyota Prius owners,

I'm a new owner of a 2006 Barcelona Red, package #2. I haven't added any mods yet, but I plan on adding some LCDs to each seat and I might go buy some Rockford Phosgates...I'm not sure yet.

Anyway...

After reading a few posts about accurately measuring tire pressure, I have a couple ideas.

First, let me guide others as to what I'm talking about.

There are a few threads on the PriusChat that talk about accurately measuring tire pressure. Accurately measuring your tire pressure can help get better mileage (a possible increase of 2 mpg...a total savings of approximately $8,000 over the life of your home mortgage!!).

The problem is that normal gauges in normal weather just aren't good enough. Your tires have to be very cold in order for the measurement to be accurate. It could say 42 psi, but really, in actuality, your tires are at 41 psi. That's a DIFFERENCE of 1 psi!(in this example)

That 1 psi could end up costing your son or daughter 5 credits at a nice private university.

However, I think I've figured out a way to beat the system.

In Minnesota, we have a company called Simon Delivers. They deliver groceries. Sometimes its a little spendy, but it is basically a way for the world to cut down on gas. Instead of everyone driving to the grocery store, and the truck drivers driving from the warehouse to the store, we now have the ability to have several drivers deliver from the warehouse to our house. Thus, the world cuts down on its gas consumption.

But this isn't where the advantages end. To keep things cold, Simon Delivers uses Dry Ice. The Dry Ice is FREE!

Let's see here:

1. I need better gas mileage.
2. I need good tire pressure.
3. In order to get good tire pressure, I need cold.
4. Simon Delivers gives me free Dry Ice.
5. I'm going to use my free dry ice to measure my tires accurately.

What I'd like to know is:

a) Is this safe for someone who has little to no knowledge of dry ice other than Mr. Wizard episodes?

What types of tools and equipment will I need other than medical forceps?

brandon · 07-13-2006, 11:51 PM

<div class='quotetop'>QUOTE(Dudley @ Jul 13 2006, 10:47 PM) [snapback]286056[/snapback]</div>

Quote:

The problem is that normal gauges in normal weather just aren't good enough. Your tires have to be very cold in order for the measurement to be accurate...

5. I'm going to use my free dry ice to measure my tires accurately.
[/b]

KTPhil · 07-14-2006, 12:06 AM

"In order to get good tire pressure, I need cold."

People have been setting tire pressure for 100 years without dry ice.

Just be consistent and measure it in the morning. Since no one knows what the "best" pressure is anyway, and experiment until they find their own personal compromise between comfort, handling, and mileage, the absolute number is meaningless anyway! Play with it until you ar ehappy, then measure it the next morning.

Skwyre7 · 07-14-2006, 07:53 AM

This has nothing to do with tire pressure, but the dry ice gave me an idea. What if you were to "mount" some dry ice under your car. The "fog" it produces would look really cool when you were stealthing around.

dbdawson · 07-14-2006, 07:54 AM

Morning cannot guarantee the type of cold I'm looking for. Only dry ice can provide me with the consistency I'm looking for. You cannot overlook the consistency of dry ice.

And the post above brings me to another question for everyone:

Since I'm getting all this free dry ice:

What other stuff can I use dry ice for on the Prius? (other than the tires and fogging....thanks for the fogging tip Skwyre...I'll probably use it at the next gala I attend)

daronspicher · 07-14-2006, 08:07 AM

Remove the tire from the car.

Pack it in dry ice for about an hour.

Using the tongs, peel back enough dry ice to get at the valve stem.

Air the tire up to 42psi.

put the dry ice back over it, close it up for another 20 minutes.

Check the pressure again, top off if necessary.

Once you have a steady reading on your tire psi and it's at 42 (you want full tires for best mpg)... put it back on the car and repeat the process for the other 3 tires.

Now that you've used science to properly inflate all 4 tires, hit the road... For the best test, hopefully, it's about 95 degrees outside and you have some fresh blacktop to ride on at freeway speed. (60ish, we don't want to waste any gas).

Give this about 30 miles and then recheck your tire pressure. I'm betting (if the tires haven't blown yet) that your tire pressure is upwards of 90psi.

If the tires haven't blown yet, keep driving, they will. Once they blow, get a new set and start from the top with the dry ice.

For me.. I'm gonna stick with the 42/40psi at operating temperature. The key word being.. 'operating' temperature.

If, by chance you are going to be driving on dry ice for many miles, it does make sense to pack your wheels in dry ice to inflate them to 42psi. You'd get the reverse effect if you had 42psi tires on average day temperatures and then drove in an environment that is -150c. Your tires would either get too stiff to go flat, or they would go flat.

Let us know how the dry ice experiment goes... Wear your seat belt.

Alnilam · 07-14-2006, 01:29 PM

Some of us need new Social Directors! Brain surgery isn't this complicated. (At least the way I do it.)

naterprius · 07-14-2006, 01:29 PM

"Cold" is defined as not having been driven on yet that day, not the temperature of dry ice. I think you will destroy your tires with dry ice.

Nate

brandon · 07-14-2006, 01:36 PM

<div class='quotetop'>QUOTE(naterprius @ Jul 14 2006, 12:29 PM) [snapback]286266[/snapback]</div>

Quote:

"Cold" is defined as not having been driven on yet that day, not the temperature of dry ice. I think you will destroy your tires with dry ice.[/b]

Well said.

tnthub · 07-14-2006, 01:40 PM

Ture pressure will vary throughout a regular day, even with the car sitting still. At the drag strip I will run 13 1/2 to 14 1/2 pounds, cold. Depending on the day I may have to add or subtract air between each round. Even having one side of the car in the sun can change the tire pressure which is why most people use vinyl tire covers.

The only way I am aware to minimize this problem is to use nitrogen instead of oxygen.

07-14-2006, 08:07 AM	#6
daronspicher Join Date: Sep 2005 Posts: 1,205 My Car: Package: Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	Remove the tire from the car. Pack it in dry ice for about an hour. Using the tongs, peel back enough dry ice to get at the valve stem. Air the tire up to 42psi. put the dry ice back over it, close it up for another 20 minutes. Check the pressure again, top off if necessary. Once you have a steady reading on your tire psi and it's at 42 (you want full tires for best mpg)... put it back on the car and repeat the process for the other 3 tires. Now that you've used science to properly inflate all 4 tires, hit the road... For the best test, hopefully, it's about 95 degrees outside and you have some fresh blacktop to ride on at freeway speed. (60ish, we don't want to waste any gas). Give this about 30 miles and then recheck your tire pressure. I'm betting (if the tires haven't blown yet) that your tire pressure is upwards of 90psi. If the tires haven't blown yet, keep driving, they will. Once they blow, get a new set and start from the top with the dry ice. For me.. I'm gonna stick with the 42/40psi at operating temperature. The key word being.. 'operating' temperature. If, by chance you are going to be driving on dry ice for many miles, it does make sense to pack your wheels in dry ice to inflate them to 42psi. You'd get the reverse effect if you had 42psi tires on average day temperatures and then drove in an environment that is -150c. Your tires would either get too stiff to go flat, or they would go flat. Let us know how the dry ice experiment goes... Wear your seat belt. __________________ My Lifetime MPG is: Lifetime Stats Down with VFTW, KeepTheBestIdol.com instead...

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07-13-2006, 11:47 PM	#1
dbdawson Join Date: Jul 2006 Posts: 2 My Car: Package: Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	Hello fellow Toyota Prius owners, I'm a new owner of a 2006 Barcelona Red, package #2. I haven't added any mods yet, but I plan on adding some LCDs to each seat and I might go buy some Rockford Phosgates...I'm not sure yet. Anyway... After reading a few posts about accurately measuring tire pressure, I have a couple ideas. First, let me guide others as to what I'm talking about. There are a few threads on the PriusChat that talk about accurately measuring tire pressure. Accurately measuring your tire pressure can help get better mileage (a possible increase of 2 mpg...a total savings of approximately $8,000 over the life of your home mortgage!!). The problem is that normal gauges in normal weather just aren't good enough. Your tires have to be very cold in order for the measurement to be accurate. It could say 42 psi, but really, in actuality, your tires are at 41 psi. That's a DIFFERENCE of 1 psi!(in this example) That 1 psi could end up costing your son or daughter 5 credits at a nice private university. However, I think I've figured out a way to beat the system. In Minnesota, we have a company called Simon Delivers. They deliver groceries. Sometimes its a little spendy, but it is basically a way for the world to cut down on gas. Instead of everyone driving to the grocery store, and the truck drivers driving from the warehouse to the store, we now have the ability to have several drivers deliver from the warehouse to our house. Thus, the world cuts down on its gas consumption. But this isn't where the advantages end. To keep things cold, Simon Delivers uses Dry Ice. The Dry Ice is FREE! Let's see here: 1. I need better gas mileage. 2. I need good tire pressure. 3. In order to get good tire pressure, I need cold. 4. Simon Delivers gives me free Dry Ice. 5. I'm going to use my free dry ice to measure my tires accurately. What I'd like to know is: a) Is this safe for someone who has little to no knowledge of dry ice other than Mr. Wizard episodes? What types of tools and equipment will I need other than medical forceps?

07-14-2006, 12:06 AM	#3
KTPhil Senior Member Join Date: Jan 2005 Posts: 1,201 My Car: Package: Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	"In order to get good tire pressure, I need cold." People have been setting tire pressure for 100 years without dry ice. Just be consistent and measure it in the morning. Since no one knows what the "best" pressure is anyway, and experiment until they find their own personal compromise between comfort, handling, and mileage, the absolute number is meaningless anyway! Play with it until you ar ehappy, then measure it the next morning.

07-14-2006, 07:53 AM	#4
Skwyre7 What's the catch? Join Date: Apr 2006 Location: Richmond, VA Posts: 2,302 My Car: 2005 Prius Package: #4 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 1	This has nothing to do with tire pressure, but the dry ice gave me an idea. What if you were to "mount" some dry ice under your car. The "fog" it produces would look really cool when you were stealthing around.

07-14-2006, 07:54 AM	#5
dbdawson Join Date: Jul 2006 Posts: 2 My Car: Package: Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	Morning cannot guarantee the type of cold I'm looking for. Only dry ice can provide me with the consistency I'm looking for. You cannot overlook the consistency of dry ice. And the post above brings me to another question for everyone: Since I'm getting all this free dry ice: What other stuff can I use dry ice for on the Prius? (other than the tires and fogging....thanks for the fogging tip Skwyre...I'll probably use it at the next gala I attend)

07-14-2006, 01:29 PM	#7
Alnilam The One in the Middle Join Date: Jun 2006 Location: Carlsbad, CA Posts: 760 My Car: 2006 Prius Package: #8 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	Some of us need new Social Directors! Brain surgery isn't this complicated. (At least the way I do it.)

07-14-2006, 01:29 PM	#8
naterprius Senior Member Join Date: Mar 2004 Location: USA Posts: 1,830 My Car: Other Non-Hybrid Package: N/A Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	"Cold" is defined as not having been driven on yet that day, not the temperature of dry ice. I think you will destroy your tires with dry ice. Nate

07-14-2006, 01:40 PM	#10
tnthub Senior Member Join Date: Jun 2006 Posts: 462 My Car: Package: Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	Ture pressure will vary throughout a regular day, even with the car sitting still. At the drag strip I will run 13 1/2 to 14 1/2 pounds, cold. Depending on the day I may have to add or subtract air between each round. Even having one side of the car in the sun can change the tire pressure which is why most people use vinyl tire covers. The only way I am aware to minimize this problem is to use nitrogen instead of oxygen.