Tire Pressures for Tow Rig

[MontanaMike]

I got a dumb question related to tow vehicle tire pressures. My truck (2015 RAM 3500 SWD) lists the cold tire inflation levels at 60PSI front and 80PSI rear and the tires (BFGoodrich KO2's LT275/70R 18E) say max cold PSI 80. Simple enough...when the tires are cold, inflate them to 60 in the front and 80 in rear however when they get hot, they can read up to 70-75 in the front and 85+ in the rear. I'm worried about getting a blowout when towing in hot weather.

So my questions is: Am I the only one worried about it? Is that worry unfounded? My truck is rated at 4340lbs (cargo and occupants) at those tire pressures. The pin weight on my tow hauler is 3060lbs however my dealer says that's a dry weight and if I have toys and such in the garage, it will actually be lighter.

Any help/comments/observations would be appreciated.

[JRTJH]

Here is one explanation from"the experts": http://www.tirerack.com/tires/tirete...jsp?techid=196

"A tire's maximum inflation pressure is the highest "cold" inflation pressure that the tire is designed to contain. However the tire's maximum inflation pressure should only be used when called for on the vehicle's tire placard or in the vehicle's owners manual. It is also important to remember that the vehicle's recommended tire inflation pressure is always to be measured and set when the tire is "cold." Cold conditions are defined as early in the morning before the day's ambient temperature, sun's radiant heat or the heat generated while driving have caused the tire pressure to temporarily increase.

For the reasons indicated above, It is also normal to experience "hot" tire pressures that are up to 5 to 6 psi above the tire's recommended "cold" pressure during the day if the vehicle is parked in the sun or has been extensively driven. Therefore, if the vehicle's recommended "cold" inflation pressures correspond with the tire's maximum inflation pressure, it will often appear that too much tire pressure is present. However, this extra "hot" tire pressure is temporary and should NOT be bled off to return the tire pressure to within the maximum inflation pressure value branded on the tire. If the "cold" tire pressure was correctly set initially, the temporary "hot" tire pressure will have returned to the tire's maximum inflation pressure when next measured in "cold" conditions.

A tire's "maximum inflation pressure" may be different than the assigned tire pressure used to rate the tire's "maximum load." For example, while a P-metric sized standard load tire's maximum load is rated at 35 psi, many P-metric sized standard load performance and touring tires are designed to contain up to 44 psi (and are branded on their sidewalls accordingly). This additional range of inflation pressure (in this case, between 36 and 44 psi) has been provided to accommodate any unique handling, high speed and/or rolling resistance requirements determined by the tire and vehicle manufacturers. These unique tire pressures will be identified on the vehicle placard or the vehicle's owner's manual.

The tire's maximum inflation pressure is indicated in relatively small-sized print branded near the tire's bead (adjacent to the wheel) indicating the appropriate value. Because tires are global products, their maximum inflation pressure is branded on the tire in kilopascals (kPa) and pounds per square inch (psi). These values can also be found in the industry's tire load & inflation charts."

I did a "google search" for "cold vs hot tire pressure" and found a number of sources of information about the topic.

As for your "pin weight", your dealership is correct, it will "change" depending on your trailer loading. The only "sure fire" way to know what your pin weight and tow vehicle/combined weights are is to pay a visit to a "CAT scale" or other local scale and actually weigh your rig when it's loaded as you'd use it for a trip. Don't forget to take along all the passengers, pets and cargo you'd normally carry in the truck as well as in the trailer.

[canesfan]

I'll keep my reply short and simple, I'm sure you'll get a lot of feedback on this.

Cold = BEFORE you start driving.

Hot = AFTER you have been driving.

Tire pressure changes with air temperature and as the tire rolls down the road.

Never lower the tire pressure after you've been driving because it went up. This is normal.

If you travel from a cold location to a hot location, or reverse, you may need to readjust tire pressure the next day before you start out depending on how great the change in air temperature.

[Ken / Claudia]

I check mine before and while traveling. Most extreme rear was 80psi at home around 40 degrees. Hours later near Redding Ca. temps 105. Rear tires 96 and 94 psi. What can you do about it, nothing. Set psi when cold, when carrying wt. such as a RV and high outside temps will have higher psi. Before I went to all metal high pressure valve stems I had 2 blow outs. Those were about 6 bucks each and made the difference over the free rubber valve stems. Those tires are rated 3710lbs max, 80 psi cold. 285/75/16 toyo.

[notanlines]

All of the above is good advice. Your info from the dealer "my dealer says that's a dry weight and if I have toys and such in the garage, it will actually be lighter" is something that you need to look at with very narrow eyes. Remember the "CAT scale" advice? Keep in mind that 1400 pounds of toys in the garage doesn't even come close to taking that much off the pin weight. And leave your tires alone. 80 in the rear and 60 up front and go ahead on hot days.

[mtofell]

Funny timing... I was just thinking about this today as I was towing. When I left home my rear psi was 75 (per the DIC). Once rolling for an hour they both read 85. It was a pretty mild day - around 65 and rainy. I figured the 80 max cold psi would include a buffer for hot and/or towing temps but it's a good question.

[nellie1289]

I have firestone AT 285's on my ram, and mine says 65 front 80 rear. that's what I roll when towing. when im not going to two for a while I will lower the rears down to 65 to improve the ride. I just had my tires rotated at the dealer as I was getting my oil changed at 9000 miles for second time (that's right 9000 miles in 2 years lol). I noticed the dealer didn't bother to readjust the air pressure so now I have 80 front/65 rear. Need to adjust that today!

[CWtheMan]

Your tire’s manufacturer uses a law of thermodynamics known as thermal equilibrium, in part, to provide an explanation about tire temperatures rising while in use. Because of individual building formulas the temperature increase will not normally transfer from manufacturer to manufacturer. So if its something you’re really concerned with you should find and study the tire data book for the tires you’re using.

Here is an example of a paper on the subject.

http://papers.sae.org/2012-01-0796/

Best answer...The tire engineers have factored the process into the final product.

[CaptnJohn]

Originally Posted by nellie1289

I have firestone AT 285's on my ram, and mine says 65 front 80 rear. that's what I roll when towing. when im not going to two for a while I will lower the rears down to 65 to improve the ride. I just had my tires rotated at the dealer as I was getting my oil changed at 9000 miles for second time (that's right 9000 miles in 2 years lol). I noticed the dealer didn't bother to readjust the air pressure so now I have 80 front/65 rear. Need to adjust that today!

9000 in 2 years!!!???!!! My truck is almost 4 months old and over 12,000. By 6 months it will be 15,500 - 16,500.

[nellie1289]

Originally Posted by CaptnJohn

9000 in 2 years!!!???!!! My truck is almost 4 months old and over 12,000. By 6 months it will be 15,500 - 16,500.

Yeah. I only drive it when towing my boat or trailer. Have a car I drive the rest of the time and I travel a lot for work so it sits a lot. I change the oil once a year because I don't care if the manual says earlier of six months or 15000. They don't change the oil in trucks that sit on lot a long time. I plan on several longer road trips this summer so should put some miles on it lol

Oh or the record I rounded up its only 8900 lol

[Tbos]

My Silverado 1500 says 35 lbs front and back. My tires say max 51. When I tow I run 51. I have 20K on them. Rotate every 6k or so. When they wear out I will replace with LT tires. I wish it had LT tires now but I can't justify the expense right now. When not towing I run about 40 lbs. the ride is a little harder but tires wear more evenly.

[MontanaMike]

Originally Posted by CWtheMan

Your tire’s manufacturer uses a law of thermodynamics known as thermal equilibrium, in part, to provide an explanation about tire temperatures rising while in use. Because of individual building formulas the temperature increase will not normally transfer from manufacturer to manufacturer. So if its something you’re really concerned with you should find and study the tire data book for the tires you’re using.

Here is an example of a paper on the subject.

http://papers.sae.org/2012-01-0796/

Best answer...The tire engineers have factored the process into the final product.

Thats what I was looking for!

Thanks for all the responses.

[EVMIII]

I know this is an older thread, but I just replaced tires so here's what I learned. If you are using the original size tire, use the inflation rates on your vehicle. If you have changed sizes (or significantly changed tire characteristics), the tire manufacturer will provide specific guidance for your application.

My example
2007 Chevy 3500HD DRW
Original placard states
215/85/R16
Front 70 PSI
Rear 65 (dually)

Previous owner changed to 235/85/R16

New tires are Michelin Defender LTX M/S
235/85/R16

Per Michelin


Hello Bud,

Thanks for contacting the Michelin Consumer Care Team. My name is Dale and I look forward to helping you out. You’ve been assigned case number 8696473. This will allow my team to quickly pull your claim details if any further questions arise.

Let’s see how we can help.

Regarding your email stating:

--------------------------------------------------------------------------
Need recommended tire pressure
2007 Chevy 3500 HD DRW

Just put on Michelin Defender LTX M/S 235/85R16

Original Equipment 215/85R16
Pressure front 70 PSI
Rear 65 (dually)

I pull a 13,000lbs 5th wheel (5% of time)

What is the recommended tire pressure for daily driving and towing.

Thanks.

Bud

--------------------------------------------------------------------------

For tire size LT235/85R16 LRE on your dually, daily driving would be 60 psi front and 55 psi rear.

Psi for towing would depend on additional weight transferred to the vehicle from the trailer. Following are load/psi capacities for size LT235/85R16 LRE:

55 psi = 2335 lbs

60 psi = 2485 lbs.

65 psi = 2623 lbs.

70 psi = 2765 lbs.

75 psi = 2905 lbs.

80 psi = 3042 lbs.

Remember to check the psi when the tires are cold.

We hope that your issue has been resolved or addressed to your satisfaction. If we can assist you further, please respond to this email or call us at 866-866-6605 (toll-free) between 8:00 a.m. and 8:00 p.m. EST Monday through Friday or between 8:30 a.m. and 4:30 p.m. EST on Saturday.

We appreciate your business and thank you for choosing Michelin.

Sincerely,
Dale
Consumer Care Department
Certified Michelin Product Expert


I've heard many opinions in tire pressure varying significantly, but I guess I'll go with what the manufacturer recommends. I did up the pressure slightly in the rear to account for hitch, tool box full of heavy stuff. I'm running 60 all the way around right now, I'll beef up the rears to about 65. when towing. Safe travels all, see you on the road.

[Ken / Claudia]

Bud, thanks for sharing that. Nice they responded and gave some numbers.
As a police officer, I can tell all psi matters in all vehicles.. Maybe you will never drive a vehicle hard as I needed to many times. Besides psi adding to a softer or harder ride. It will also help with handling as in stopping and turning. Stopping with all of the tire tread on the surface shortens the stopping length vs. a tire over inflated and partly in contact with the road. Over inflated front tires will cause the vehicle to slide when turning hard or fast. More on gravel or wet than dry surface. Under inflated causes different problems, like rear of vehicle sways or driving on side walls as vehicle bounces. In one of those oh **** situations it may mean crashing or not.

[Stircrazy]

every tire manufacture have load/weight/psi charts you just have to dig for them, every tire is different. find the one for your tires and scale the loaded truck and adjust psi according to the chart. my f250 I need to do 45 psi front 70 psi rear on my tires.

Steve

[CWtheMan]

Originally Posted by EVMIII

I know this is an older thread, but I just replaced tires so here's what I learned. If you are using the original size tire, use the inflation rates on your vehicle. If you have changed sizes (or significantly changed tire characteristics), the tire manufacturer will provide specific guidance for your application.

My example
2007 Chevy 3500HD DRW
Original placard states
215/85/R16
Front 70 PSI
Rear 65 (dually)

Previous owner changed to 235/85/R16

New tires are Michelin Defender LTX M/S
235/85/R16

Per Michelin


Hello Bud,

Thanks for contacting the Michelin Consumer Care Team. My name is Dale and I look forward to helping you out. You’ve been assigned case number 8696473. This will allow my team to quickly pull your claim details if any further questions arise.

Let’s see how we can help.

Regarding your email stating:

--------------------------------------------------------------------------
Need recommended tire pressure
2007 Chevy 3500 HD DRW

Just put on Michelin Defender LTX M/S 235/85R16

Original Equipment 215/85R16
Pressure front 70 PSI
Rear 65 (dually)

I pull a 13,000lbs 5th wheel (5% of time)

What is the recommended tire pressure for daily driving and towing.

Thanks.

Bud

--------------------------------------------------------------------------

For tire size LT235/85R16 LRE on your dually, daily driving would be 60 psi front and 55 psi rear.

Psi for towing would depend on additional weight transferred to the vehicle from the trailer. Following are load/psi capacities for size LT235/85R16 LRE:

55 psi = 2335 lbs

60 psi = 2485 lbs.

65 psi = 2623 lbs.

70 psi = 2765 lbs.

75 psi = 2905 lbs.

80 psi = 3042 lbs.

Remember to check the psi when the tires are cold.

We hope that your issue has been resolved or addressed to your satisfaction. If we can assist you further, please respond to this email or call us at 866-866-6605 (toll-free) between 8:00 a.m. and 8:00 p.m. EST Monday through Friday or between 8:30 a.m. and 4:30 p.m. EST on Saturday.

We appreciate your business and thank you for choosing Michelin.

Sincerely,
Dale
Consumer Care Department
Certified Michelin Product Expert


I've heard many opinions in tire pressure varying significantly, but I guess I'll go with what the manufacturer recommends. I did up the pressure slightly in the rear to account for hitch, tool box full of heavy stuff. I'm running 60 all the way around right now, I'll beef up the rears to about 65. when towing. Safe travels all, see you on the road.

Michelin has left out the most important factor, tire industry standards require replacement tires to provide an equal or greater load capacity when compared to the Original Equipment tires. Did you quote the tire placard cold inflation pressures? If so, your minimum recommended (correct) cold inflation pressures for your replacement tires are 61 PSI - minimum - for the front and 56 PSI - minimum for the rears in (dual configuration).

From Michelin tire inflation chart your front OE tires provided 2430# of load capacity @ 70 PSI. The replacements provide 2464# of load capacity @ 61 PSI. The OE rears (dual) provided 2150# ea of load capacity @ 65 PSI. The replacements will provide 2177# of load capacity @ 56 PSI.

[Desert185]

I went up in size and load capacity with my last tire change. Unloaded, with the 265's, I ran 65 front and 60 rear. Now, with the 285's, I run 65 front and 50 rear in order to maintain a nice, rear contact patch for longevity (and a more comfortable ride). Within load capacity.

Loaded/towing the fiver, its the recommended 65/80.

Nitto Terra Grapplers, BTW. I like them.

[EVMIII]

Originally Posted by CWtheMan

Michelin has left out the most important factor, tire industry standards require replacement tires to provide an equal or greater load capacity when compared to the Original Equipment tires. Did you quote the tire placard cold inflation pressures? If so, your minimum recommended (correct) cold inflation pressures for your replacement tires are 61 PSI - minimum - for the front and 56 PSI - minimum for the rears in (dual configuration).

From Michelin tire inflation chart your front OE tires provided 2430# of load capacity @ 70 PSI. The replacements provide 2464# of load capacity @ 61 PSI. The OE rears (dual) provided 2150# ea of load capacity @ 65 PSI. The replacements will provide 2177# of load capacity @ 56 PSI.

The numbers quoted were the cold pressures from OEM placard. I did miss quote what I'm running now, 65 up front and 60 rear. So do I need to increase pressure in the rears before I tow, pin weight on my Alpine is about 2500lbs?

[CWtheMan]

Originally Posted by EVMIII

The numbers quoted were the cold pressures from OEM placard. I did miss quote what I'm running now, 65 up front and 60 rear. So do I need to increase pressure in the rears before I tow, pin weight on my Alpine is about 2500lbs?

The placard pressures are appropriate up to the truck's GAWR values. Many owners (wrongly) load their trucks using the axle manufacturer's load limits. If you do that you will have to know the actual weights on the rear axles and then inflate the tires to a psi value that will support the axles actual loads. Your truck manufacturer will not recommend overloading the axles above GAWR values.

[EVMIII]

Originally Posted by CWtheMan

The placard pressures are appropriate up to the truck's GAWR values. Many owners (wrongly) load their trucks using the axle manufacturer's load limits. If you do that you will have to know the actual weights on the rear axles and then inflate the tires to a psi value that will support the axles actual loads. Your truck manufacturer will not recommend overloading the axles above GAWR values.

Ok, so to be sure I understand,(not so sure I do)

61 PSI front
56 PSI back

At these pressures with these tires I am at GAWR of my truck. If this is true, why provide additional inflation levels for additional load capacity that would exceed my axle limits. I'm sure I'm making this more difficult than it needs to be but it's just not making sense to me. In the mean time, I'm running 65/60 and the truck feels good. Thanks.