Max tire pressure increase when hot?

hlh1 · 06-01-2022, 06:25 AM

What would be a max hot tire pressure percentage increase over the cold tire pressure? My tires max load is at 35 psi, would a 20% psi increase when hot be a max air pressure before they pop? Or 25% psi increase?

Or I could ask it this way; what would be the max hot psi that I should sustain with these tires?

**sourdough** · 06-01-2022, 06:35 AM

What kind/size of tires do you have that the max psi is 35 lbs.?? IIRC my last 1/2 ton had a max psi of 44 on the P rated OE tires (maybe 51??). I don't see how you could drop much weight of any kind on such soft tires.

wiredgeorge · 06-01-2022, 06:48 AM

I think my riding mower has about 35 PSI in the tires. Seriously, buy some LT tires for that truck.

hlh1 · 06-01-2022, 07:11 AM

I should have researched more before posting. My tires show a max PSI of 51. So, I'll set the cold at 35 psi for max load and then not worry too much until they get towards 51 psi.

When last towing the tires got up to 43 psi in air temps of 97 degrees. My infrared temp reader showed the tires at 130 degrees. The Carlisle trailer tires went from 63 psi to 70 psi and only showed 120 degrees.

bsmith0404 · 06-01-2022, 07:18 AM

You’re going to see a big variance in pressure gain depending on outside temps, concrete or blacktop road surface. A percentage is hard to say but o personally wouldn’t get concerned unless it increased more than 10 psi. Again that’s even debatable. On my truck I typically see around a 6-7 psi increase, my RV is more around 10-15. Temps would be more of a concern than pressure, however, higher pressure increases could be an indicator of higher temps.

hlh1 · 06-01-2022, 07:19 AM

Quote:

Originally Posted by wiredgeorge

I think my riding mower has about 35 PSI in the tires. Seriously, buy some LT tires for that truck.

This is a good idea. I have a spare set of rims for this.

**sourdough** · 06-01-2022, 07:29 AM

If you've been pulling that trailer on P tires inflated to 35 psi 1) they're going to get hot because they're overloaded and 2) the tires are probably damaged/weakened from the overloading.

Pulling a 7k trailer with a 1/2 ton would/should require LT tires. They will not only provide more support, but more importantly, more strength to resist and minimize the squishing and wiggling inherent in P tires with a load.

As far as the psi when they are running; obviously if you have been towing at 35psi that temp has soared. Air the tires to the max of 51psi and then start checking. My tires vary a lot depending on lots of factors so don't know exactly what numbers you will get when you tow. Just realize they vary and compare the tires when taking temps. Sun side will be hotter than shade side etc. One tire that has a big variance from the others is a problem.

Some might say to refer to an inflation chart to find possibly a lower pressure for your tires. I would disagree. A 7k trailer on P tires needs ALL the support it can get....and then some.

hlh1 · 06-01-2022, 07:39 AM

I'm seeing my current P tires have a load range of "SL" and Max Load of 2756lbs.

I'm looking at some Goodyear LT tires that have a load range "E" and Max Load of 3417lbs.

**sourdough** · 06-01-2022, 07:55 AM

What is the tire size on the truck?

wiredgeorge · 06-01-2022, 08:24 AM

Lee's "about me" says he has an 1892 lb payload and he has that tow package. Would they put car tires on a 1/2 ton with that much payload and the max tow package? 35 PSI? My missus Crown Vic has tires that have a max inflation of over 50 PSI (go figure) although I keep them aired at 35 PSI.

hlh1 · 06-01-2022, 08:37 AM

Quote:

Originally Posted by wiredgeorge

Lee's "about me" says he has an 1892 lb payload and he has that tow package. Would they put car tires on a 1/2 ton with that much payload and the max tow package? 35 PSI? My missus Crown Vic has tires that have a max inflation of over 50 PSI (go figure) although I keep them aired at 35 PSI.

One thing I'm seeing is that my "P" tires that the truck came with at rated "max load" of 2756 lbs, which should handle what the truck is rated for. But, like you all I like a higher safety margin.

I should have been running these "P" tires towards 50 psi cold.

hlh1 · 06-01-2022, 08:38 AM

Quote:

Originally Posted by sourdough

what is the tire size on the truck?

275/65/r18.

bsmith0404 · 06-01-2022, 08:41 AM

Quote:

Originally Posted by hlh1

I'm seeing my current P tires have a load range of "SL" and Max Load of 2756lbs.

I'm looking at some Goodyear LT tires that have a load range "E" and Max Load of 3417lbs.

The 2756 is enough load capacity for a 1/2 truck, but P tires are a softer sidewall so an upgrade to LT will definitely help. 3471 is a bit of an overkill, not going to hurt anything, but will ride a bit rougher. That’s the kind of tire you put on a 3/4 or 1 ton. You’ll never get close to 7000 lbs on the rear of a 1/2 ton. In fact your rear axle is probably only rated for around 5k lbs. If it weee mine, I’d probably look for a LR D around 3k lb capacity.

hlh1 · 06-01-2022, 09:07 AM

Quote:

Originally Posted by bsmith0404

The 2756 is enough load capacity for a 1/2 truck, but P tires are a softer sidewall so an upgrade to LT will definitely help. 3471 is a bit of an overkill, not going to hurt anything, but will ride a bit rougher. That’s the kind of tire you put on a 3/4 or 1 ton. You’ll never get close to 7000 lbs on the rear of a 1/2 ton. In fact your rear axle is probably only rated for around 5k lbs. If it weee mine, I’d probably look for a LR D around 3k lb capacity.

The door sticker shows:

Front GAWR: 3375 lb
Rear GAWR: 3800 lb

So, my tires are fine, load wise, with the axle rating. But, I can see the benefit of a stiffer LT tire when towing.

**sourdough** · 06-01-2022, 09:15 AM

In your tire size the only LT tires I find are LRE which max inflation is 80psi. If that is the case I would put them on and run at 80psi when loaded with the trailer. If not loaded I would air them down because they will be really stiff on a 1/2 ton and provide more support than your axles can carry. On my 1 ton I air down to 65psi when unloaded. On the 1/2 ton you could run 60 psi, maybe even a little less if you scaled the truck. No matter, I would upgrade the tires to LTs asap IMO.

**JRTJH** · 06-01-2022, 09:27 AM

Quote:

Originally Posted by hlh1

The door sticker shows:

Front GAWR: 3375 lb
Rear GAWR: 3800 lb

So, my tires are fine, load wise, with the axle rating. But, I can see the benefit of a stiffer LT tire when towing.

Your tires do meet the axle load rating with no problems. Your "major concern" is going to be "tire squirm when towing" and with P series tires, even the XR/XL (extra load construction), the 51PSI max pressure isn't going to be enough to keep the sidewalls from flexing. That said, you have NO worries about inflating those tires to 51PSI Cold pressure and feeling that they "might pop when they get hot"... Trust me when I say that tire engineers are well advanced from the dark ages and they are fully aware that tire pressure goes up when the tire gets hot. All of that is engineered into the tire performance standards and the tires are constructed to support any and ALL tire pressure increases that will occur during normal use, even when towing. So, rest assured, your tires will support the pressure increases that occur when the tire temperature goes up during use. THEY WON'T POP AT 52PSI !!!!!

All that said, I don't believe that LT tires are available in LRD (8 ply) construction in the 275 65R18 size. They are available in LRC (6 ply) and in LRE (10 ply) ratings, The LRC max pressure is 50 PSI, so I don't think you'll see much improvement over your current tires if you inflate them to 51PSI during towing. You'll get, I believe, a near comparable amount of sidewall flex from both the LT LRC's and your current tires at those similar pressures.

If you do go to LT LRE tires, expect a rougher ride both at lower non-towing pressure and at 80PSI when towing.

While you might want to consider LT tires, I think, before spending that kind of money, you might want to simply try towing with maximum sidewall pressure on your current tires and see if the handling improves enough to satisfy your needs.

No need to spend $1000 on new tires and find that what you currently have will suffice with the increased pressure.....

IMO, it's worth the try to see how the current tires perform when towing at 51PSI. You may be well satisfied with the results and save a substantial amount of money to boot.....

hlh1 · 06-01-2022, 09:38 AM

John, That's a good idea. I'll delay the LT truck tires for now and Next time out I'll go with 50 psi cold and see how it does. Last time out it towed fine, I was just not very knowledgeable about tire temps and pressures.

**JRTJH** · 06-01-2022, 10:16 AM

Quote:

Originally Posted by hlh1

John, That's a good idea. I'll delay the LT truck tires for now and Next time out I'll go with 50 psi cold and see how it does. Last time out it towed fine, I was just not very knowledgeable about tire temps and pressures.

Your tires are engineered to operate at an increased air pressure safely. Inflating them to 51PSI cold, will cause them to operate somewhere significantly above that pressure when they get hot from towing on a sunny highway. I can't tell you if they will increase to 85PSI or to 105PSI, but the tire engineers that designed and built them tested their design in all "normal operating environments" so your tires are safe to operate at the maximum cold sidewall inflation pressure and all of the pressure increase attributable to towing, driving, hot temperatures has already been tested and verified safe...

You don't need to worry about your tires "popping unless you let some air out of them".... They will be safe at maximum cold pressure with the anticipated pressure increases as the tires warm up during use. They won't "pop from too much pressure buildup"..... Now, if you hit a rough patch of highway that's filled with deep potholes and speed up as you cross that area, the tires may explode from tire damage due to the potholes, but not from too much hot air inside them.....

**flybouy** · 06-01-2022, 10:32 AM

To answer the original question the air pressure increase is fine. The load capacity of your tires is appropriate for the rated load of the truck. If your scaled weight is within the truck specs and If you're happy with the way it tows stop there and motor on.

I would suggest first getting the rig across the scales to eliminate any guesswork about the rear axle and tires being overloaded. Then I suggest experimenting with the rear cold inflation tire pressures. You may THINK it tows "great" but you don't know what you don't know. You may find out that increasing the air pressure IMPROVES the way it tows. The cost is merely a little time and easily reversable.

hlh1 · 06-01-2022, 10:44 AM

Quote:

Originally Posted by flybouy

To answer the original question the air pressure increase is fine. The load capacity of your tires is appropriate for the rated load of the truck. If your scaled weight is within the truck specs and If you're happy with the way it tows stop there and motor on.

I would suggest first getting the rig across the scales to eliminate any guesswork about the rear axle and tires being overloaded. Then I suggest experimenting with the rear cold inflation tire pressures. You may THINK it tows "great" but you don't know what you don't know. You may find out that increasing the air pressure IMPROVES the way it tows. The cost is merely a little time and easily reversable.

That's so correct, that I "don't know what I don't know". Where do I find scales? Do I just pull up to the truck scales that I see on the Interstates?

You may also like: