Question about increased PSI while driving

[Nokones]

Sure, tread design, carcass weight, ambient and inflated air temp, asphalt temp, speed all play a part. One week is usually not enough. There my be tire "break in" as well.

Tire break-in is called "Heat Cycling" and if you want to have longevity in your tires, you need to properly heat cycle the tires. Heat cycling will change the molecular construction in the rubber compound.

Some tire distributors will heat cycle your tires, of course, for a fee.

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[Chuckster3]

My BFG k02 stayed at 35psi for the first 13 months and now if I inflate them to 35psi they will go as high as 40psi. Now the first 13 months our temperature went as high as 90 degrees to -20 degrees with 155 inches of snow? I am glad someone else is also asking this question.

 

[Left Field]

On my normal routes here in FL, I am used to seeing a 4 or 5 PSI increase in my tires while driving, per TPMS. However, last week I purchased new tires, the same size as the old ones, and the PSI, on the same roads, same speed and duration, I am only having a 1-2 PSI increase. The TPMS sensors were not replaced.

All gases, whether nitrogen, air, water vapor, etc. follow the same laws of pressure/volume/temperature (Boyle's Law, Charles Law) which means the gas filling the tire wouldn't appear to be relevant to a pressure increase.
It also seems unlikely (but maybe possible?) that the tire volume is increasing more with the Toyo's, thereby reducing the pressure increase. Most likely seems that the Toyo's are running cooler. This could be due to either better heat dissipation or less heat created by improved tire materials and design.

TLDR:
The latter seems likely and if true it should be evidenced by a slight improvement in your fuel economy. Any data?

LF

 

[Wabujitsu]

All gases, whether nitrogen, air, water vapor, etc. follow the same laws of pressure/volume/temperature (Boyle's Law, Charles Law) which means the gas filling the tire wouldn't appear to be relevant to a pressure increase.
It also seems unlikely (but maybe possible?) that the tire volume is increasing more with the Toyo's, thereby reducing the pressure increase. Most likely seems that the Toyo's are running cooler. This could be due to either better heat dissipation or less heat created by improved tire materials and design.

TLDR:
The latter seems likely and if true it should be evidenced by a slight improvement in your fuel economy. Any data?

LF

Tim, the tires are each 10.6 pounds lighter than the Falkens they replaced. My MPGs have increased by 3.

 

[Nokones]

All gases, whether nitrogen, air, water vapor, etc. follow the same laws of pressure/volume/temperature (Boyle's Law, Charles Law) which means the gas filling the tire wouldn't appear to be relevant to a pressure increase.
It also seems unlikely (but maybe possible?) that the tire volume is increasing more with the Toyo's, thereby reducing the pressure increase. Most likely seems that the Toyo's are running cooler. This could be due to either better heat dissipation or less heat created by improved tire materials and design.

TLDR:
The latter seems likely and if true it should be evidenced by a slight improvement in your fuel economy. Any data?

LF

Am I understanding you correctly, if the same tire and wheel filled with either Nitrogen or compressed air won't make a difference in pressures when the tire and wheel heats up under the same ambient and pavement conditions? Tires will heat up regardless how they are driven.

 

[Pape]

Am I understanding you correctly, if the same tire and wheel filled with either Nitrogen or compressed air won't make a difference in pressures when the tire and wheel heats up under the same ambient and pavement conditions?

to be expected, standard air is composed of 78% of nitrogen. where the data change is the purity and the water vapor. Water Vapor as pointed out in this thread will expend more.

 

[Nokones]

to be expected, standard air is composed of 78% of nitrogen. where the data change is the purity and the water vapor. Water Vapor as pointed out in this thread will expend more.

Exactly.

 

[Aonarch]

What expensive machines or equipment are you talking about. Other than the pressure regulator having the proper fitting to connect to the nitrogen supply tank, what other special machine and equipment is needed?

I have been using nitrogen for well over 30 years, mainly for my race shocks, besides the regulator having the appropriate fitting, the shocks require a special shock tool, there is no other special equipment. If you are thinking about a machine that will evacuate the old air out of the tires in order to benefit from pure nitrogen in the tires, that is way unnecessary and the difference is non-measureable.

Insofar as if nitrogen is a scam, it is not a scam. There is no scam providing you're getting the nitrogen and not compressed air, and the nitrogen will prevent the tires from growing so how is that a scam? The nitrogen does do what it is intended to do. The bullshit sales pitch as to if it is needed for your grocery getter tires is what is bullshit.

You just need to ask yourself, do you need nitrogen service for your tires for a passenger car on a public highway and what are the benefits? There are not any and so what if your tires grow by 2-4 pounds when driving to get your groceries.

There are no direct or measureable/substantiated benefits for a grocery getter vehicle having nitrogen in the tires for use on a public highway.

I didn't say nitrogen is a scam, I said most shops scam customers selling expensive "nitro fill" packages.

I used to manage a chain of performance shops, I'm very familiar with the industry. Most of our business was tires, balancing and alignments on performance cars. And yes we did have a purge station, which as you said is unusual.

Most tire shops are not going to properly setup nitrogen, refill the tanks, and maintain them. It costs money.

Tire shops will typically have one massive compressor with over a dozen lines running in the ceiling to each bay for air tools and air chucks.

So you need a separate air system just for nitrogen. Again, shops aren't going to want to run lines to each bay for that, or have nitrogen tanks setup at each bay. And when you get new tires, they are filling them up at the tire mounting station, with regular atmospheric air anyways. Maybe a decent shop will let a little air out and refill with nitrogen, but I doubt they are pulling valve cores to let the regular air out, then refilling with nitrogen. That is a bunch of extra steps and time.

So generally you'll have one nitrogen fill station somewhere in the shop. Techs have to bring the wheels and tires there to fill. Maybe they will have multiple lines, but again leaks happen, you don't want expensive nitrogen leaking out.

Again, my shops did this properly for the most part, but we were very expensive and a specialty business.

 

[Pape]

I didn't say nitrogen is a scam, I said most shops scam customers selling expensive "nitro fill" packages.

I used to manage a chain of performance shops, I'm very familiar with the industry. Most of our business was tires, balancing and alignments on performance cars. And yes we did have a purge station, which as you said is unusual.

Most tire shops are not going to properly setup nitrogen, refill the tanks, and maintain them. It costs money.

Tire shops will typically have one massive compressor with over a dozen lines running in the ceiling to each bay for air tools and air chucks.

So you need a separate air system just for nitrogen. Again, shops aren't going to want to run lines to each bay for that, or have nitrogen tanks setup at each bay. And when you get new tires, they are filling them up at the tire mounting station, with regular atmospheric air anyways. Maybe a decent shop will let a little air out and refill with nitrogen, but I doubt they are pulling valve cores to let the regular air out, then refilling with nitrogen. That is a bunch of extra steps and time.

So generally you'll have one nitrogen fill station somewhere in the shop. Techs have to bring the wheels and tires there to fill. Maybe they will have multiple lines, but again leaks happen, you don't want expensive nitrogen leaking out.

Again, my shops did this properly for the most part, but we were very expensive and a specialty business.

The green cap was all the rage 5 ~6 years ago, today they are rare. I guess consumer are wising up.
On the other hand possible the shop have a good water / air separator on their air system.

 

[Ratbert]

Insofar as if nitrogen is a scam, it is not a scam. There is no scam providing you're getting the nitrogen and not compressed air, and the nitrogen will prevent the tires from growing so how is that a scam? The nitrogen does do what it is intended to do. The bullshit sales pitch as to if it is needed for your grocery getter tires is what is bullshit.

Exactly. It's a scam for anything but specific scenarios. For the scenarios discussed here: it's a scam.

Nitrogen does not prevent the tires from growing. It merely reduces their expansion by 20 to 25% (for the tire volumes discussed here). That is, a 4 PSI increase could be diminished to about 3 PSI.

It'd be completely different if we were talking about low profile, extreme performance tires on a race track, but in the scenarios discussed here: it's a scam.

 

[2nd 392]

I didn't say nitrogen is a scam, I said most shops scam customers selling expensive "nitro fill" packages.

I used to manage a chain of performance shops, I'm very familiar with the industry. Most of our business was tires, balancing and alignments on performance cars. And yes we did have a purge station, which as you said is unusual.

Most tire shops are not going to properly setup nitrogen, refill the tanks, and maintain them. It costs money.

Tire shops will typically have one massive compressor with over a dozen lines running in the ceiling to each bay for air tools and air chucks.

So you need a separate air system just for nitrogen. Again, shops aren't going to want to run lines to each bay for that, or have nitrogen tanks setup at each bay. And when you get new tires, they are filling them up at the tire mounting station, with regular atmospheric air anyways. Maybe a decent shop will let a little air out and refill with nitrogen, but I doubt they are pulling valve cores to let the regular air out, then refilling with nitrogen. That is a bunch of extra steps and time.

So generally you'll have one nitrogen fill station somewhere in the shop. Techs have to bring the wheels and tires there to fill. Maybe they will have multiple lines, but again leaks happen, you don't want expensive nitrogen leaking out.

Again, my shops did this properly for the most part, but we were very expensive and a specialty business.

What size will we need to carry to air up after airing down, possibly several times before getting a refill ?

 

[Wabujitsu]

Here’s a thought. If over time you top-off your tire pressure due to the smaller O2 and CO2 molecules leaking out before the nitrogen, won’t you eventually end up with just nitrogen in your tires anyway??

 

[Nokones]

Exactly. It's a scam for anything but specific scenarios. For the scenarios discussed here: it's a scam.

Nitrogen does not prevent the tires from growing. It merely reduces their expansion by 20 to 25% (for the tire volumes discussed here). That is, a 4 PSI increase could be diminished to about 3 PSI.

It'd be completely different if we were talking about low profile, extreme performance tires on a race track, but in the scenarios discussed here: it's a scam.

Tires with nitrogen, the pressures do not increase or decrease. When I mean regarding the tires will grow, I mean the pressures do not increase. It is a racing thing. The changing tire pressures is not the only factor when it comes to traction. The changing of pressures also will affect the corner balance and center of gravity that will have major affect on the handling of a racecar. Nitrogen will prevent the pressures increasing.

Also, another reason they use nitrogen in shocks besides for preventing the oil from fosming up so the pressure does not increase when the shock heats up changing the shock rate.

 

[2nd 392]

Here’s a thought. If over time you top-off your tire pressure due to the smaller O2 and CO2 molecules leaking out before the nitrogen, won’t you eventually end up with just nitrogen in your tires anyway??

 

[Aonarch]

I fill up with helium +20 extra mpg.

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