Tire inflation

[Shoe2728]

Got E rated tires installed, 80psi max, Tire guy said it would be better to run around 65-70 psi as tires heat up. Always thought I should run max cold rating 80psi. FW weight is around 9000 lbs hooked up to truck.

[jadatis]

allen8106 wrote:
I have a similar situation. I have a 5ver the weighs in at 10,500 unhooked. Now I haven't yet weighed the axles or the truck axles. I just upgraded from GY Marathons with a D rating to Maxxis with an E rating. My problem is that the aluminum wheel is supposedly only rated for 65 PSI yet the tires are rated for up to 80 cold. I just completed a 2000 mile round trip to Mesa, AZ and ran the tires a 65 PSI cold. I have a TPMS and observed that the tire pressure grew from the 65 cold to as much as 80 PSI running down the road on a day where the ambient air temp was 65 degrees.

Going from 65 cold to 80 warm means a pressure rising of 23% wich makes the inside tire temp to be warm about 165 degr F , wich is to warm, Normal rising only by driving is about 10% pressure rising so warm inside of about 110 to 115 degr F.
This means that your E rated tires are deflecting to much.

A stiffer tire ( E-load stiffer then D-load) needs more pressure for the same load, so if for D-load 65 is enaugh , E loads needs for instance 70 psi.

I would rather risk the rimms leaking by to hing pressure then the tires to fail and blow when driving at speed.
Most likely the 65 psi of the rimms is cold pressure and some rising for warm is calculated in , yust as is done for tires and valves.

Once read a story on Dutch caravantrekker ( traveltrailersite) about rimms leaking when they chanched from P-tire to D-load with using the 65 psi pressure , wich was apperantly to much for the rimms. By the forces on the rimm the rimm went leaking.
But this was for a rimm that was made probably for 35 psi and now used for 65psi.
This is the only case I found, so asume this leaking of the rimm does not happen that soon, there must be a large reserve in that for rimms.

So highen up the pressure until warm is about that 10% higher then cold, and your tires are save.
Risk is that you have damaged your tires already by the to low pressure and so the tire will blow when filled to 80 psi.
then the high pressure is not the blame but the to low pressure before.

Best is to calculate it with my made spreadsheet , or let me do it.

[rhagfo]

sidney wrote:
My trucks tire label lists 65 psi for the front and 80 psi for the rear... No other inflation info is provided. I can only assume the label is referring to max payload operation.

Empty... I believe 80 psi is over inflated for the rear. I run 65 psi in the rear when empty.

But 35 psi from the chart seems way to low to me.

I run 65 loaded current 50 empty going for 35 in the morning.

[sidney]

My trucks tire label lists 65 psi for the front and 80 psi for the rear... No other inflation info is provided. I can only assume the label is referring to max payload operation.

Empty... I believe 80 psi is over inflated for the rear. I run 65 psi in the rear when empty.

But 35 psi from the chart seems way to low to me.

[wilber1]

The top of the chart says "tire load limits at various cold inflation pressures". It says nothing about being the proper pressure or the recommended pressure. Do you think it is a good idea to run a tire near its maximum rated load when it has much more capacity? I sure don't.

If you look at your truck manufacturers recommended pressure for your truck empty, I bet it is more than 35 psi. That should give you a clue.

[rhagfo]

sidney wrote:

rhagfo wrote:

wilber1 wrote:
If you look at tire inflation tables they say they are load limit tables not recommended pressures. If you match the table pressure to your actual load, you are running the tire at its rated limit for that pressure. These are load limit pressures, nowhere do they say they are recommended pressures.

WHY go to the trouble of load and pressure chart IF the recommendation was to always run the MAX pressure?

The way I read the chart is for this load, this is the correct pressure. More pressure would be over inflated and less would be under inflated.

Much like an Antifreeze chart, the 50/50 most run is NOT the best protection, nor is 100%, it is about 70/30 antifreeze to water. I use that ratio, as it also provides the best over heat protection.
You should have seen the dumb look on the parts house counter guy when I asked for antifreeze back in the summer of 1967!!!

I regress to graphics!!

OK... given my circumstances in my previous post above... with the 3600 lb load are you recommending running at 35 psi per Firestone's chart?

The chart states you should be good to 4,140# for both tires, my tires if Firestone should carry 3,820,so I will see what it feels and looks like at 35 psi. Then i will get the Michelin chart.

[sidney]

rhagfo wrote:

wilber1 wrote:
If you look at tire inflation tables they say they are load limit tables not recommended pressures. If you match the table pressure to your actual load, you are running the tire at its rated limit for that pressure. These are load limit pressures, nowhere do they say they are recommended pressures.

WHY go to the trouble of load and pressure chart IF the recommendation was to always run the MAX pressure?

The way I read the chart is for this load, this is the correct pressure. More pressure would be over inflated and less would be under inflated.

Much like an Antifreeze chart, the 50/50 most run is NOT the best protection, nor is 100%, it is about 70/30 antifreeze to water. I use that ratio, as it also provides the best over heat protection.
You should have seen the dumb look on the parts house counter guy when I asked for antifreeze back in the summer of 1967!!!

I regress to graphics!!

OK... given my circumstances in my previous post above... with the 3600 lb load are you recommending running at 35 psi per Firestone's chart?

[rhagfo]

wilber1 wrote:
If you look at tire inflation tables they say they are load limit tables not recommended pressures. If you match the table pressure to your actual load, you are running the tire at its rated limit for that pressure. These are load limit pressures, nowhere do they say they are recommended pressures.

WHY go to the trouble of load and pressure chart IF the recommendation was to always run the MAX pressure?

The way I read the chart is for this load, this is the correct pressure. More pressure would be over inflated and less would be under inflated.

Much like an Antifreeze chart, the 50/50 most run is NOT the best protection, nor is 100%, it is about 70/30 antifreeze to water. I use that ratio, as it also provides the best over heat protection.
You should have seen the dumb look on the parts house counter guy when I asked for antifreeze back in the summer of 1967!!!

I regress to graphics!!

[wilber1]

sidney wrote:

wilber1 wrote:
If you look at tire inflation tables they say they are load limit tables not recommended pressures. If you match the table pressure to your actual load, you are running the tire at its rated limit for that pressure. These are load limit pressures, nowhere do they say they are recommended pressures.

This is a good point.

I have Firestone Transforce LT275/70R/18E tires on my SRW RAM 3500.

The empty rear axle weight is ~3600 lbs.

According to Firestone's INFLATION CHAT The inflation is 35 psi for this load.

Would you run at 35 psi?

What psi would you run at?

I would run the truck manufacturer's recommended pressure and add a bit if I wasn't actually "empty".

[rhagfo]

sidney wrote:

wilber1 wrote:
If you look at tire inflation tables they say they are load limit tables not recommended pressures. If you match the table pressure to your actual load, you are running the tire at its rated limit for that pressure. These are load limit pressures, nowhere do they say they are recommended pressures.

This is a good point.

I have Firestone Transforce LT275/70R/18E tires on my SRW RAM 3500.

The empty rear axle weight is ~3600 lbs.

According to Firestone's INFLATION CHAT The inflation is 35 psi for this load.

Would you run at 35 psi?

What psi would you run at?

I think I just may try tomorrow, currently at 50 psi and a little hard!

[sidney]

wilber1 wrote:
If you look at tire inflation tables they say they are load limit tables not recommended pressures. If you match the table pressure to your actual load, you are running the tire at its rated limit for that pressure. These are load limit pressures, nowhere do they say they are recommended pressures.

This is a good point.

I have Firestone Transforce LT275/70R/18E tires on my SRW RAM 3500.

The empty rear axle weight is ~3600 lbs.

According to Firestone's INFLATION CHAT The inflation is 35 psi for this load.

Would you run at 35 psi?

What psi would you run at?

[Shoe2728]

I had St 235 80R 16E went to BF Goodrich Commercial T/A All-Season 235 85R 16E GVW of FW is 12000. I have looked for a pressure weight table but mostly all I fine is max inflation rate is 80 psi. I have a 2011 crossroads cruiser 305skp

[FastEagle]

Shoe2728 wrote:
Got E rated tires installed, 80psi max, Tire guy said it would be better to run around 65-70 psi as tires heat up. Always thought I should run max cold rating 80psi. FW weight is around 9000 lbs hooked up to truck.

The minimum inflation pressures for everyday use is found on your tire placard. The guy "that said" could have you stranded on the side of the road.

FastEagle

[wilber1]

If you look at tire inflation tables they say they are load limit tables not recommended pressures. If you match the table pressure to your actual load, you are running the tire at its rated limit for that pressure. These are load limit pressures, nowhere do they say they are recommended pressures.

[Cummins12V98]

Dennis M M wrote:
I don't think there is another subject on RV forums that generates more misinformation and pure guess work!

It is very simple:

1. weigh your rig - axle weights are fine, but individual wheel weights are better.

2. Find the weight/pressure chart for your brand and size of tire - they are all out there on the web.

3. Set your pressures cold according to the chart and relax.

4. Get a good tire monitor system for peace of mind if you are rolling up miles.

This is what Michelin says about RV tire inflation:
An underinflated or overloaded tire will build up more
heat that could go beyond the endurance limits of the
rubber and radial cords. This could cause sudden tire
failure. Underinflation will also cause poor handling, faster
and/or irregular tire wear, and can decrease fuel economy.

Overinflation, on the other hand, will reduce the tire’s
contact area with the road, which reduces traction, braking
ability, and handling. A tire that’s overinflated for the
weight it’s carrying is more prone to a harsh ride, uneven
tire wear, and impact damage.

WE HAVE A WINNER

[rhagfo]

allen8106 wrote:
I have a similar situation. I have a 5ver the weighs in at 10,500 unhooked. Now I haven't yet weighed the axles or the truck axles. I just upgraded from GY Marathons with a D rating to Maxxis with an E rating. My problem is that the aluminum wheel is supposedly only rated for 65 PSI yet the tires are rated for up to 80 cold. I just completed a 2000 mile round trip to Mesa, AZ and ran the tires a 65 PSI cold. I have a TPMS and observed that the tire pressure grew from the 65 cold to as much as 80 PSI running down the road on a day where the ambient air temp was 65 degrees.

Interesting, if the 5er weighs 10,500 total, then the pin would be between about 2,500# and 1,500# so seeing how this is most assumptions anyway, say pin is 2,000#.
Then the axle weight would be 8,500#, assuming 235/85-16 E rating is 3,042# X 4 = 12,168#, 8,500/12,168 = 70% of total tire capacity. Not having an inflation chart 80*70% = 56 psi, likely an inflation chart would be at 60 to 65 psi.

Contact your dealer for an inflation chart.