Ram 2500 tire pressure

wintersun wrote:
I have never seen where a truck manufacturer recommends a lower tire pressure based on no load. In my own experience the tire manufacturers' charts result in underinflated tires with uneven tread wear and shorter life.

Underinflated tires will also negatively impact road handling and stopping distance and the greater amount of sidewall flexing will make them run hotter - this was why the Ford Explorer's were experiencing blow-outs and killing people.

Anyone who has gone up a load range with the tires on their truck has experienced better handling from the stiffer tires. The offset is a harsher ride.

A 200# fiberglass cap will do a lot to smooth out the ride on a heavy truck when there is no weight on the hitch. You could achieve the same by putting a couple bags of sand in the bed.

When I have looked at trucks on dealers' lots I have noticed wide variations in the payload ratings of the trucks based on the tires that were provided at the factory. I have seen factory supplied truck tires with load capacity ratings from 2200 up to 3200 lbs. on heavy duty models.

I was thinking the exact same way until I started having a second hard look at the Ram 2500 Longhorn. Here is what the door jamb decal reads. This is for a new 2013 crew cab, diesel, 4x4:

Max load: Front = 60 lbs and Rear = 70 lbs

Light load: Front = 50 lbs and Rear = 40 lbs.

On top of this, Ram has the ability to adjust the tire pressure monitor for both Max and Light load readings.

All that said there are a couple posts that make complete sense now that I go back and read about them supporting the Max / Light tire pressures and the benefits of following the manufacturers recommendations. In fact, if you go to the Ram site, you can download the manual,and the complete detail regarding the suggested 2 sets of tire pressures can be found in 490 to 521.

I know - at first I thought there must be some mistake or I misunderstood what was going on with the Ram 2500's as I never heard of doing this before. Then again, I'm an "amateur" when it comes to tow vehicles of this size!

I have never seen where a truck manufacturer recommends a lower tire pressure based on no load. In my own experience the tire manufacturers' charts result in underinflated tires with uneven tread wear and shorter life.

Underinflated tires will also negatively impact road handling and stopping distance and the greater amount of sidewall flexing will make them run hotter - this was why the Ford Explorer's were experiencing blow-outs and killing people.

Anyone who has gone up a load range with the tires on their truck has experienced better handling from the stiffer tires. The offset is a harsher ride.

A 200# fiberglass cap will do a lot to smooth out the ride on a heavy truck when there is no weight on the hitch. You could achieve the same by putting a couple bags of sand in the bed.

When I have looked at trucks on dealers' lots I have noticed wide variations in the payload ratings of the trucks based on the tires that were provided at the factory. I have seen factory supplied truck tires with load capacity ratings from 2200 up to 3200 lbs. on heavy duty models.

Agree and that deflection is about #1 Heat generation #2 control

#1 squirm, wave, etc are some of the terms, along with deflection. Bending and
the heat generated from bending/flexing.

This is what is left of a tire found on the side of the road and took it for
this type of discussion

The side wall bend back is small on low aspect ratio tires, but this one flexed
till the side wall broke down. Obviously heat damaged sidewall from
close inspection


Another one saw and took pic for this type of discussion, but it held together
till the whole carcass broke down and the tread separated



This one had the chance to talk to the lady, who said she asked her husband to
lower the pressure for a softer ride. Used this opp to teach the kid why and how
this happened









#2 control and what meant by keeping the tire's shape. Mainly during maneuvers
(braking, acceleration, cornering, etc)

Slip angle changes with PSI vs max PSI rating. Rim width also factors slip angle


In order to calculate, need the specifications of the tire and only
the OEM's test data can do...or develop your own empirical data...why
posted the chalk and tape method for the general owner without benefit
of OEM data

@ Benk

When the load on the tire is low , the deflection of the tire is the same , that is what the calculation of pressure for lower loads is meanth for.
So for lower loads you dont need the pressure needed for the maximum load. If you use that the deflection is less so the bending of the sidewall is less.

What I need to make a better estimation of the load on the axles is the empty weigt of the "truck" and the loads that are on it for not towing and towing condition. Then a pressure can be calculated , that is save for those situations. Also try to find the GAWR's and GVWR, mostly on the same plate as the pressure advices.

Also need the maximum load and pressure needed for that ( called maxloadpressure or reference-pressure and is lower then the maximum pressure) , wich is probably 80 psi for your tires( because of the 70 advice back for towing, wich is higher then the loadrange D below that with 65 psi) , and is written on the sidewall mostly or can be made up by the Loadrange ( E-load/10 ply = almost always 80 psi).

Many car-makers automatically describe that 80 psi , thoug the tires are probably oversised for the loads. Could be that even for your GAWR back ( gross axle weigt rating) with a comfortable reserve , you only need for instance 60 psi. But to be shure we have to calculate.

NebraskaNative wrote:
I can agree with BenK above except for the last line: "If not, then use the chalk or masking tape method to determine the proper PSI for 'that' loading during that test"

Bad advice, tire manufacturers have load tables for this exact reason. Using an arbitrary method to determine something as important as tire pressures is asking for trouble.

Thanks for the confirmation and say to the one point...said if not stock
or something like that...then must re-engineer for 'that' new, non-OEM
sized tire/wheel

How else would they figure out what the re-engineered tire/wheel's
PSI should be?

There was a 'try' at developing a system whereby the wheel center
down to pavement vs PSI, but that didn't fly. BFG was about the only
OEM that actually published spec's for their KO-AT series

How many folks actually go out and weigh their trucks in order to
use the OEM tables? Most won't and they come here asking HOW2 or "just
tell me a PSI and I'll use that"





Found this one posted by someelse on another forum and show the
typical 3 conditions of #1 under inflation, #2 over inflation and
#3 just right

Notice in #1, under inflation, it is holding up the weight and goes
to my comment that pressure has more to do with maintaining the shape
of the tire than just weight carry

These are on or with-in that tire's recommended rim width

Static and the dynamic will have the wheel roll over while the tire
side wall rolls over.




These images found showing the difference in cornering between the
old bias-ply vs then new radial, but is a good image to visualize
conceptually how tire will roll over during any change in direction


Bias-ply

Radial


Too low PSI will have the sidewall roll over even more






Sidewall bend-back. Image from Michelin's try in a new type of
bead, but saved it to show how lower pressure allows more sidewall
bend back, therefore more potential for roll over during a change
in direction.





This shows the PSI vectors working on the insides of a tire. They
are in all directions. Only 'ONE' is 'up', or holding up weight. The
others are maintaining the tire shape
http://img.photobucket.com/albums/v77/bentoy/Tire%20Wheel/Tirecarrysidewallpic.jpg~original



All this trying to answer the OP's question:

So my question:

Does anyone drop the rear tire pressure from 70 lbs when not towing, to the recommended 40 lbs, or some other pressure for a better ride? What has been your experience and your thoughts as Ram owners of this 'light load' concept?

Yes, but it won't handle as well and not all TV's will do well with
such a low PSI.

That the 40PSI is out of context...it depends on the vehicle in question,
tire size vs OEM, and how/where you drive

One neighbor has a CTD and drives like a little old lady. He does
drop his PSI, but when I've driven it...mushy and he did notice that
the out side tread ribs wore more than when he drove it

Nephew has a CTD and drives very much like me...his is aired up to
max sidewall *ALL* the time

Saying that it depends if the adviser drives just like you do, would
their advice then apply to you. Terrain and ambient too

pronstar wrote:
I air up/down all the time, depending on what I'm doing with the truck.
50 front/38 rear on my Toyo MT's empty.
Sidewall max when towing heavy.

Same here +/-.
It will not increase your treadwear if you keep the proper pressure for the load. Think about it this way, weight on the rear axle, empty between a 1500 and a 3500 diesel is not much different for the same wheel base, less than 500lbs I'd guess.
Would you feel the need to air up to 80psi in the 1500 before putting 500lbs in the bed? No, you'd keep it at 35-40psi whatever reccomended.
In fact too high of tire pressure running empty will wear the center of your tread prematurely.
I like the Ram switchable light load for the TPMS. You can lower Fords Superduty pickups too, but it's a 1 time deal and the dealer has to do it. Tire shops wont due to liability.
SOme dealers will tell you it can't be done. I had to call 3 before I found one that didn't play dumb with me. 30psi is the min the TPMS will go.
I jsut had mine dropped to 30 on all 4 corners then I can air up or down as needed form sand/snow to heavy hauling and the TPMS will still kick in if it's about to go flat.
Not sure about GM.

Thanks for all the input - greatly appreciated!

I can agree with BenK above except for the last line: "If not, then use the chalk or masking tape method to determine the proper PSI for 'that' loading during that test"

Bad advice, tire manufacturers have load tables for this exact reason. Using an arbitrary method to determine something as important as tire pressures is asking for trouble.

I run 75f and 80r during camping season and lower to 65f and 45r in the
winter. There is a big difference in ride quality at the lower pressure.
Ed

Tire pressure advice is all about load on the ( seperate) tires.
So if you know the exact load on the axles or better seperate tires for the condition you drive it ,you can calculate the needed pressure for that with some reserve for pressureloss in time, unequal loading R/L, incidental extra load or loadshifting etc.

But as long as you dont know the excact weights on the sepetate axles or wheels , you have to be extra carefull.

Risk is that you take to low pressure and it even gives better comfort and gripp , but at a sertain moment your tires get that much damaged, that you have a blow-out, with all the missery that goes with it.