Front tire pressure for 3500 long bed pulling 5th wheel

Grit dog wrote:

Durb wrote:
Let's see, 17 replies, 5 say go with the Ram engineers, the other 12 suggest tire pressures that differ from each other and the factory, sometimes quite a bit. What is the OP to do?

Realize that if you don't want to or can not discern/understand, the relationship between tire size/rating/pressure/load then use the "engineers" reccomendation. It's the "safe for max load" scenario.
All valid points, comment on the higher pressure, less traction/contact patch is also true, but with that realize what is "enough" vs what may be "better." You're not going to wear your tires out by tomorrow or skid to a fiery death with nominal over inflation, in the context we are discussing here. You WILL have an unnecessarily stiff ride and maybe get .1mpg better fuel economy.

Regarding engineers' design parameters, I'm a civil engineer but work on the construction side. One of the projects I'm looking after is a design build, and alMost DAILY I'm able to economize a preliminary design from our designer that may not take into account real world conditions or limitations. It's just different views or knowledge on the same subject, and just like auto mfgs design parameters, they are not able to take into account individual conditions/uses, so the design needs to be as absolutely conservative as practical to envelope the greatest majority of conditions/uses.
From there, if one understands what they're dealing with, modifications or improvements can be had.....for free. Because they were there already, hiding behind an ultra conservative design.

Excellent post!

Electronics engineer here and the same design parameter concept exists in my world .

You also have to consider that tire pressure, like many other things consists of trade-offs. In this case between load capacity, ride quality, braking contact patch, cornering ability, puncture resistance, tread wear and likely more I missed.

As you say, knowing what you're after and what you may need more of versus what you can spare factors in. Consider too that if braking is what you're after, loaded vehicles tend to add plenty of that load to the front when you are braking the most. Loads are not static,

Just to add to Grit dog's point - look into the owner's manual of German sport sedans, often you'll see multiple psi specs, one for each speed and payload bracket. Even in my subcompact Mini, the range goes from 35psi (low payload, under 120 km/h) to 50 psi (max payload, 220 km/h top speed).

That's an example of the OEM engineer trying to tailor a design spec to each end user application. In Germany, probably the most engineering oriented culture, it works.

In our sue happy North American culture where people never read a manual, and talk to their lawyer the minute their tire blows, OEMs are forced to take a different approach.

Durb wrote:
Let's see, 17 replies, 5 say go with the Ram engineers, the other 12 suggest tire pressures that differ from each other and the factory, sometimes quite a bit. What is the OP to do?

Realize that if you don't want to or can not discern/understand, the relationship between tire size/rating/pressure/load then use the "engineers" reccomendation. It's the "safe for max load" scenario.
All valid points, comment on the higher pressure, less traction/contact patch is also true, but with that realize what is "enough" vs what may be "better." You're not going to wear your tires out by tomorrow or skid to a fiery death with nominal over inflation, in the context we are discussing here. You WILL have an unnecessarily stiff ride and maybe get .1mpg better fuel economy.

Regarding engineers' design parameters, I'm a civil engineer but work on the construction side. One of the projects I'm looking after is a design build, and alMost DAILY I'm able to economize a preliminary design from our designer that may not take into account real world conditions or limitations. It's just different views or knowledge on the same subject, and just like auto mfgs design parameters, they are not able to take into account individual conditions/uses, so the design needs to be as absolutely conservative as practical to envelope the greatest majority of conditions/uses.
From there, if one understands what they're dealing with, modifications or improvements can be had.....for free. Because they were there already, hiding behind an ultra conservative design.

Me Again wrote:

wnjj wrote:

kzspree320 wrote:
I'll stick with the door sticker recommendations for air pressure at axle weight ratings. For me that's 60 front and 80 rear. The fifth wheel adds no real weight to the front axle so I don't get the need to increase it so much.

Weight on the front is only part of it. Higher pressure up front may reduce some of the wiggle (sway). Tires see much more than just down force.

Over inflated tires have a smaller contact patch which reduces braking ability and they are more likely to receive impact damage! I noted 5 additional pounds of inflation for those concerned. 20 pound more = NO WAY.

Agreed.

Use a Scale to find the real Load. And stay inside vehicle manufacturer rating.

My towing combo is over 17k. And I still get over 100k on those too soft for some Michelins. Pressure according to Load. Test for pressure rise, and you're done.

wnjj wrote:

kzspree320 wrote:
I'll stick with the door sticker recommendations for air pressure at axle weight ratings. For me that's 60 front and 80 rear. The fifth wheel adds no real weight to the front axle so I don't get the need to increase it so much.

Weight on the front is only part of it. Higher pressure up front may reduce some of the wiggle (sway). Tires see much more than just down force.

Over inflated tires have a smaller contact patch which reduces braking ability and they are more likely to receive impact damage! I noted 5 additional pounds of inflation for those concerned. 20 pound more = NO WAY.

kzspree320 wrote:
I'll stick with the door sticker recommendations for air pressure at axle weight ratings. For me that's 60 front and 80 rear. The fifth wheel adds no real weight to the front axle so I don't get the need to increase it so much.

Weight on the front is only part of it. Higher pressure up front may reduce some of the wiggle (sway). Tires see much more than just down force.

Grit dog wrote:
To Durb, those pressures on the door jamb are arbitrary......but generally safe, for those that don't know how to adjust for tire size, weight, conditions. That's why the newer 2500s all got 80 psi idiot lights in them when most people on mOst days (running empty) would be much better served with significantly lower tire pressure.

To everyone else, some good reccomendations, some not applicable, like those quoting pressures for a dually with pizza cutter tires when OP is asking about a srw truck with presumably different tires.
Tire size and capacity also play as large a role as actual applied weight.

YnotTurbo caused the confusion, as he has a dually when OP has a SRW. Chris

I'll stick with the door sticker recommendations for air pressure at axle weight ratings. For me that's 60 front and 80 rear. The fifth wheel adds no real weight to the front axle so I don't get the need to increase it so much.

70 to 80 in front, 80 rear towing on my 2500 4x4.

Know your loads and use the weight/inflation chart for your tires to determine proper psi.