Question about increased PSI while driving

[Wabujitsu]

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.

This baffles me, and I am curious why there is a difference. I went from a 35x12.50R17E Falken Wildpeak MT to the same size and load rated Toyo Open Country R/T Pro (a very new model, a hybrid MT). Any ideas?

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[azwjowner]

The same reason why Falken tires are extremely heavy and mostly made in Thailand -- they aren't exactly using the latest and greatest tire technology. I've read that they use an older steel belt technology that is very heavy.

The Falkens clearly heat up more, resulting in increased pressure. What is the temperature rating on the tires? Tires are rated A, B, C, etc. The A rated tires heat up the least, B more, C even more.

My KO2s also heat up only 1-2 PSI. I'm not surprised that Toyos, which are quality tires, are likewise.

 

[dstevens]

Might depend on how dry the air was that went into the tire, but almost certainly the difference is from the layup of the tire resulting in a difference in hysteresis (essentially rolling resistance). In that case you should see a difference in fuel economy too.

BTW the tire temperature rating is how resistant to temperature a tire is, which may not be the same thing as to how much the tire heats up.

 

[calemasters]

Maybe the sidewalls are stiffer and less sidewall/tread flex so less heat is generated.

 

[Jeffy56]

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.

 

[ijp4fun]

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.

This baffles me, and I am curious why there is a difference. I went from a 35x12.50R17E Falken Wildpeak MT to the same size and load rated Toyo Open Country R/T Pro (a very new model, a hybrid MT). Any ideas?

I run two different sets of the same size tires you run, with identical rims on my Jeep and have noticed the same thing.
My Toyo AT3's load C weigh 61 pounds and increase 2 psi.
My Mickey Thompson BBMT's load D weigh 76.5 pounds and increase 4 psi.

I loose about 3 mpg with the Mickey Thompson tires pushing the extra 62 pounds and more aggressive tread pattern.

I assume the extra weight and tread pattern is retaining more heat causing the increased psi.

 

[jadmt]

10% rule at play. Your cold psi is too high. Lower it until you go up 10% when fully warmed up ie if cols psi is 30 when fully warm should be 33 psi.

 

[2nd 392]

It’s that lead infused rubber Falken uses. …
Only half kidding, not a complete shit post.

 

[Jeep Wick]

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.

This baffles me, and I am curious why there is a difference. I went from a 35x12.50R17E Falken Wildpeak MT to the same size and load rated Toyo Open Country R/T Pro (a very new model, a hybrid MT). Any ideas?

Taller tread blocks of the new tires are dissipating more heat, acting as cooling fins. If the old tread was really low, there was more surface area and more friction.

 

[Pape]

Did you get the fancy shop that put the green tip schrader cap ?

 

[Nokones]

The increase in the pressure is related to both the tire/wheel temperature heating up and the amount of water molecules in the air in your tires. The amount of water molecules in the tires will be dependent on the ambient humidity at the time when you fill the tires with air from the compressor.

If you want to eliminate the tires from growing when they heat up, use nitrogen which has no water molecules. That is what most racers use.

 

[Aonarch]

The increase in the pressure is related to both the tire/wheel temperature heating up and the amount of water molecules in the air in your tires. The amount of water molecules in the tires will be dependent on the ambient humidity at the time when you fill the tires with air from the compressor.

If you want to eliminate the tires from growing when they heat up, use nitrogen which has no water molecules. That is what most racers use.

The problem with nitrogen is, it is mostly a scam. Most shops that sell you "nitro-fill" don't actually have the proper equipment to do so.

Those machines are expensive and require proper maintenance.

Plus most techs are probably too lazy to pull up to the machine and fill the tires even if the shop does have a machine.

 

[Wabujitsu]

Taller tread blocks of the new tires are dissipating more heat, acting as cooling fins. If the old tread was really low, there was more surface area and more friction.

Wick, thanks. When the Falkens were new, they still heated up 4-5 PSI.

 

[Nokones]

The problem with nitrogen is, it is mostly a scam. Most shops that sell you "nitro-fill" don't actually have the proper equipment to do so.

Those machines are expensive and require proper maintenance.

Plus most techs are probably too lazy to pull up to the machine and fill the tires even if the shop does have a machine.

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.

 

[Wabujitsu]

10% rule at play. Your cold psi is too high. Lower it until you go up 10% when fully warmed up ie if cols psi is 30 when fully warm should be 33 psi.

Thanks, Jeff. 30 PSI cold was what I told them to put in the new tires when they mounted them. I have to chalk-test the tires. I’m pretty sure 30 will be the sweet spot, though, as all E-rated tires I’ve run all chalked out to 30.

I have to say, so far I am very impressed with this new Toyo model of tire! They have an extremely aggressive tread, yet handle significantly better on-road.

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