Tire question, yes again

[J-N-Lham]

Just what is cold considered to be in checking tire pressure? the tag says 85psi cold. At home it would be simple generally in the 50's night time mid to upper 60's morning 70's and up from there.
Now where I am at it is 89 already probably
headed to the mid to upper 90's. I do have tire covers on there is sun shining lots of it.

The tire dealer said they just fill them to 90psi all the time. any body havde a formula they use or like?
Thanks

[TonyMac]

Weigh all corners to ensure you are below placard weights, then fill to placard recommendations. If the ride is good, you're done. NEVER fill to sidewall limits.

[jeff0210]

https://www.irv2.com/forums/attachme...1&d=1653661966

First time adding a file. I hope this works.

Don't forget to read the notes at bottom of chart.

[hamm2018]

Originally Posted by J-N-Lham

Just what is cold considered to be in checking tire pressure? the tag says 85psi cold.

Cold is before you start traveling.

[Skip426]

Originally Posted by hamm2018

Cold is before you start traveling.

Driving has way more effect on pressure build up than ambient temp.

I would also add ; if you set your pressure; for your RV weight ; at home at 60f , and you're checking at 80f , do not lower the pressure, unless it exceeds the max cold on the side wall , or you'll be looking for a compressor tomorrow , when temp is 70f.

[Kid Gloves]

Originally Posted by J-N-Lham

Just what is cold considered to be in checking tire pressure? the tag says 85psi cold. At home it would be simple generally in the 50's night time mid to upper 60's morning 70's and up from there.
Now where I am at it is 89 already probably
headed to the mid to upper 90's. I do have tire covers on there is sun shining lots of it.

The tire dealer said they just fill them to 90psi all the time. any body havde a formula they use or like?
Thanks

“Cold” is the temperature in the morning, before the tires have been exposed to direct sunlight and before the coach has been driven. It’s really that simple. There’s is no formula. Just check the pressure when “Cold” and be on your way.

[Gary RVRoamer]

The "Cold" on the tires sidewall means "not driven more than one mile in the previous 4-6 hours". It has nothing to do with ambient temperature.

[astrnmrtom]

This is a very common question and is understandable because of the term "cold" makes people think of, well, cold.

Cold refers to any ambient temperature BEFORE the vehicle has been driven or BEFORE any tires have been heated by sunlight. I bet there'd be less confusion if tire pressure instructions dropped the temp "cold" and used ambient.

If you get up in the morning on a day of travel and it's 32 out and your tires haven't been sitting in the sun, 32 is the "Cold" temp. If it's 75 degrees out in the same circumstances, 75 is "Cold."

Some people check and adjust their pressure every time before they leave. I prefer to not micro manage my tire pressure. I check it before traveling, but say the last time I adjusted air pressure, ambient temps were 65, and a week later it's travel day and the temps are 68. I will not adjust pressure for a could degrees difference in ambient temperatures. However, there have been times where there's a larger change in temperatures, especially in the spring and fall, and at those times, I'll adjust as often as needed.

If you stop and think about it, tires are incredibly resilient and dependable. There's millions and millions of vehicles going down the road every day who's owners never check tire pressure unless they notice a tire looks low, and yet the highways aren't littered with disabled vehicles because of over or under inflated tire failures.

The key is to just pay attention. How many degrees of variation in ambient temperature triggers action on your part is personal preference. After all, tires can experience temperature and pressure changes on any given day. Driving from the desert to the snowcapped mountains, and back on a day trip doesn't require several stops to adjust tire pressure.

[Chargerman]

Originally Posted by TonyMac

Weigh all corners to ensure you are below placard weights, then fill to placard recommendations. If the ride is good, you're done. NEVER fill to sidewall limits.

Sorry but this is not really accurate. You weigh the Coach and then fill the tires to the tire manufacturers weight/pressure chart. Personally I go 5 psi above the chart. This just assures I have a little extra carrying capacity for the PSI.
Also, saying NEVER to fill to the sidewall limit is not an accurate statement either. Based on the my weight my steer tires are at the maximum 120psi. of the manufacturers sidewall which also happens to match what is on my Coach manufacturers placard. There are many with this same situation.

[Kid Gloves]

Originally Posted by Gary RVRoamer

The "Cold" on the tires sidewall means "not driven more than one mile in the previous 4-6 hours". It has nothing to do with ambient temperature.

Following that guidance, if we pull in to spot at noon, do you believe it is acceptable to check pressures at 6pm, when temperatures are 100F and the tires on one side of the coach have been exposed to direct sunlight for the past few hours? What do you suppose those pressures will be the next morning if the temperature is 60F?

Tire pressure will increase approximately 2% with every 10F increase in ambient temperature. The tire that we inflated to 100psi at 100F, while in direct sunlight could be at 90psi or less the next morning. Would you drive on that tire if the recommended “cold” pressure was 100psi?

[Persistent]

Originally Posted by Kid Gloves

Following that guidance, if we pull in to spot at noon, do you believe it is acceptable to check pressures at 6pm, when temperatures are 100F and the tires on one side of the coach have been exposed to direct sunlight for the past few hours? What do you suppose those pressures will be the next morning if the temperature is 60F?

Tire pressure will increase approximately 2% with every 10F increase in ambient temperature. The tire that we inflated to 100psi at 100F, while in direct sunlight could be at 90psi or less the next morning. Would you drive on that tire if the recommended “cold” pressure was 100psi?

There are reasons to check tire pressure when driving and when exposed to sun light. A leaking tire will drop pressure. Of course that is bad and detecting and correcting is good.

On the other hand expect pressure to rise while driving and with ambient temperature rise. Don't remove air to lower pressure until tires cool down to ambient and are shielded from the sun or other heat sources. Tires are designed to work under these conditions. They do not require intervention.

[rtaggio]

Originally Posted by jeff0210

https://www.irv2.com/forums/attachme...1&d=1653661966

First time adding a file. I hope this works.

Don't forget to read the notes at bottom of chart.

Thank you very much for posting this file, it answered all my questions and more.

Seems very self explanatory and simple to understand.

[Jkwilson1989]

Originally Posted by Skip426

Driving has way more effect on pressure build up than ambient temp.

I would also add ; if you set your pressure; for your RV weight ; at home at 60f , and you're checking at 80f , do not lower the pressure, unless it exceeds the max cold on the side wall , or you'll be looking for a compressor tomorrow , when temp is 70f.

Hot tires are always going to exceed the max cold rating on the sidewall. Don’t drop the pressure on hot tires. The cold rating allows for pressure increase with heat, and lowering the pressure in a hot tire can cause it to be under inflated even if the pressure is higher than the maximum sidewalk rating.

[Winemaker2]

Originally Posted by Gary RVRoamer

The "Cold" on the tires sidewall means "not driven more than one mile in the previous 4-6 hours". It has nothing to do with ambient temperature.

Mostly correct, it is no specific temp, but it does have to do with ambient conditions. check in morning not late afternoon and not when sun is beating on one side of MH and respective tires.