Tire Pressure When Not Towing

[Hurk]

I drive a 2014 Dodge Ram 3500 20" tires and when towing 13,000 lb FW I put 80 psi in rear tires and 65 in front as per specs. When not towing the ride is very ruff especially the rear end bouncing over bumps. I believe it would be ok to reduce rear psi to 65psi same as front as rear unloaded is lighter than front. Your thoughts?

[Super Thirty]

I have same make, series and Year truck but my tires are 18's. The spec is 80 rear and 60 front. I reduced the rear tires to 60 when running empty to get more consistent tire wear. The ride has benefited somewhat as well.

[Old-Biscuit]

I have a 2007 3500

I run 55# front ALL the time (towing/non towing)
Rears:
Towing 14K 5vr....80#
Not towing-------45#

Run Michelin
Get 60K per set......not down to wear bars just anal about having good tires

Even wear ...no cupping, scalloping etc

[SmokeyWren]

Originally Posted by Old-Biscuit

I have a 2007 3500

I run 55# front ALL the time (towing/non towing)
Rears:
Towing 14K 5vr....80#
Not towing-------45#

That's close to right for Load Range E tires, whether 18" or 20". You want the 80 PSI max in the rear tires when hauling 2,800 pounds of pin weight. But when hauling nothing but a good suntan, then 45 PSI is about right.

Here is the TRA load/inflation table for the probable sizes of tires under discussion for an SRW:

PSI------------ 35 ---40----45----50---55---60-----65---70---75----80 -LR -LI
LT275/65R18 1940 2130 2310 2535 2660 2825 3000 3150 3305 3415 (E) 123

LT275/65R20 2080 2280 2475 2680 2850 3030 3195 3375 3540 3750 (E) 126So 35 PSI is the minimum, and 80 PSI is the max. the 20s are a bit stronger than the 18s, but not enough to get excited about.

At 45 PSI, the 18s can support 4,620 pounds on the rear axle. That should be more than enough for an empty pickup. The 20s can support 4,950.

[SmokeyWren]

Originally Posted by SmokeyWren

At 45 PSI, the 18s can support 4,620 pounds on the rear axle. That should be more than enough for an empty pickup. The 20s can support 4,950.

That's assuming the 20s are LT tires with Load Index 123. If they are P-series tires with load index of about 112 to 116, then that's a different load/inflation table, and the max load on the pair would be a lot less than 4,950 pounds.

[jadatis]

I answered your question a few minutes ago on RV-forum via goodsamsclub.
There you did not give the towed weight.

And answer to SmokeyWren

His tires also on car must be LT , otherwise the 80 psi ( cold) would be much to high for the P-tire . 80 psi is the AT-pressure of an E-load/LRE LT tire.
Not saying TS has LT tires , though he asumes it. So Hurk, look at the sidewall of your tires for the sises, Loadindex, and loadrange ( fi 80 psi =E-load /LRE) and the speedcode of tire.

I call it AT-pressure because on LT its often given next "maximum load xxxx lbs AT yyy psi( cold). On P-tires the maximum allowed cold pressure is given on sidewall of between 44 and 51 psi for SL and sometimes up to 60 psi for XL//, AT pressure is SL 35 psi and XL// 41 psi in USA system , and as far as I know no exceptions, Eur system SL 36 psi with exeptions to lower ,XL 42 psi with exeptions.

You also gave a list of the TRA but these are made with a formula that leads to to high loadcapacity's for the pressure in the lower pressures.
Better would be to use a P/LC list of same AT-pressure ( 80 psi) and loadindex ( that 123 or 126 you gave) of European tyre, because its made with a formula that gives lower loadcapacity's for the pressure, and is proven to be saver.

American TRA swiched over to this formula, as late as 2006 , but only for P-tires ( standard load and XL/reinforced/Extraload) and left LT and Truck-tires to the old ( Less worse then P-tires) formula. European ETRTO uses this saver formula ( wich I once got hold of and went running with) since decades for every kind of tyre , From standard load up to Truck-tyre.

[jadatis]

Oh what , I will give you here the copy of my reaction to you on the RV-forum.

It all depends on what the weight on the axles, or better seperate wheel(pairs) is when not towing.

If you then ride fully loaded , it is only the weight on the towbar that is missing.

This weight on towbar is for American trailers minimum 10% and maximum 15% of total weight of trailer ( I case of middle axle trailers, but mayby experts make me wiser here).

so it depends of howmuch you are allowed to tow, or better of howmuch you tow in real.

Take 10 to 15% of that, and that is towbarweigth
This weight is on about 4 to 6 foot behind the rear axle, depending on the overhang behind.
This puts more weight on rear axle than that 10 to 15%, and lifts up the front axle a little.
Rough estimation,knowing nothing about your car, asume 500 lbs on towbar, gives about( roughly estimated) 750 lbs extra on rear axle and 250 lbs less on the front axle.

So front axle dont need to be lowered in pressure, sooner a bit higher pressure, and rear can be lower.
This is if, besides the towbarload, nothing else chanches in the loading of the car.

But howmuch lower on rear , all depends on the weights and other demensions of the car.
Wheelbase is one ( distance between front- and rear-axle).

If you can produce as much possible data ( weigts on axles,and tire-data), I , as selfdeclared tirepressurespecialist, am able to calculate the pressure for you, with some reserve.

Even determined a verry discussable bumping border.
For comfort that is is real weight on wheel is lower then 85% of the weigth the pressure is calculated for for up to 160km/99m/h, that then bumping begins. Verry subjective and open for discussion, and it all is about the deflection the tire gets, below a sertain deflection discomfort begins but also gripp is less.

[SmokeyWren]

Originally Posted by jadatis

You also gave a list of the TRA but these are made with a formula that leads to to high loadcapacity's for the pressure in the lower pressures.

Better would be to use a P/LC list of same AT-pressure ( 80 psi) and loadindex ( that 123 or 126 you gave) of European tyre, because its made with a formula that gives lower loadcapacity's for the pressure, and is proven to be saver.

In the USA, the authority is the United States Tire and Rim Association (TRA). The load/inflation tables developed by the engineers at TRA are the official load/inflation tables to be used by the tire industry and vehicle manufacturers that sell tires, rims, and vehicles in the USA.

And IIRC, Canada also uses the TRA load/inflation tables.

So regardless of the load/inflation tables used in England or Germany or Japan or Australia, here in the USA we use the TRA tables.

And those load/inflation tables are difficult to find for the average web surfer. They are updated and published annually in the TRA annual report, but that report goes only to members of the TRA (generally, manufacturers of tires, rims [wheels], and vehicles), and membership is expensive. So no, I'm not a member.

Way back when, the TRA load/inflation tables were made available by all tire manufacturers that sell tires in the USA. But most of those sources have stopped making the tables available for P-Series and LT tires. Even the Toyo tables quoted above are very hard to find now. If you simply go to toyotires.com, you probably won't find them. Michelin, Goodyear, Goodrich, Cooper, Firestone/Bridgestone and others no longer include the load/inflation tables for P-Series and LT tires on their websites. They all now say to follow the vehicle manufacturer's load/inflation instructions.

[Tireman9]

Originally Posted by Hurk

I drive a 2014 Dodge Ram 3500 20" tires and when towing 13,000 lb FW I put 80 psi in rear tires and 65 in front as per specs. When not towing the ride is very ruff especially the rear end bouncing over bumps. I believe it would be ok to reduce rear psi to 65psi same as front as rear unloaded is lighter than front. Your thoughts?

Does your owners manual indicate a Heavy or full load and light load inflation? Some do some do not. The ones that do not probably do not because they know that many people simply forget or do not bother to re-inflate their tires when hooking up the trailer.

[jadatis]

Originally Posted by SmokeyWren

In the USA, the authority is the United States Tire and Rim Association (TRA). The load/inflation tables developed by the engineers at TRA are the official load/inflation tables to be used by the tire industry and vehicle manufacturers that sell tires, rims, and vehicles in the USA.

And IIRC, Canada also uses the TRA load/inflation tables.

So regardless of the load/inflation tables used in England or Germany or Japan or Australia, here in the USA we use the TRA tables.

And those load/inflation tables are difficult to find for the average web surfer. They are updated and published annually in the TRA annual report, but that report goes only to members of the TRA (generally, manufacturers of tires, rims [wheels], and vehicles), and membership is expensive. So no, I'm not a member.

They all now say to follow the vehicle manufacturer's load/inflation instructions.

They say that for reasons of responcibility, Tire-and car-maker nowadays can be held responcible if the pressure advice they give , leads to tire-failure, and accident , and damage to car and people, even if it is by some overloading and unequall loading R/L, and inacurate reading of pressure.

So if you want to use a different pressure then they advice, you yourselfes are responcible for the savety .
Then I see advices of even 45 psi , wich could be OK , but probably to low.
And then its better to determine the weights and speed first , and tire-data.
So if you want to take the responcibility yourselfes, do it by using acurate determined data, and use a system that sertainly dont lead to to low pressure, so to much deflection , so to much heatproduction.

Now there is a system the tiremakers use, wich is different in USA and EUR, and there is science, and laws of nature.
Laws of nature always rule above things organisations agreed, thoug they try base it on laws of nature.

Tires are basically the same all over the world, so if you have a sertain sise and AT-pressure tire, it is allowed to carry a sertain load up to a sertain speed AT the pressure it is given for, without overheating any part of the rubber.
For lower loads the pressure must be calculated so , that the deflection stays the same , so heatproduction too.

A man of a tiremaker of Dutch origen , told me this in a long telephone comversation, that its all for the temperature of the rubber not getting to high, then to many sulfur bridges form and the rubber gets hard on those spots.

That one organisation uses an other formula, that leads to higher loadcapacaty for the same pressure of same tire, then another organisation, can never be to laws of nature.
Would mean that a Chinese tirefirm that makes tires for EUR and USA, could use a lower pressure in America then in Europe for a sertain lower load then maximum load , for excactly the same tire.
Ofcource then the print on sidewall is different in EUR and USA.

So if you want to take your own responcibility in determining the right pressure for your situation, use a system that is best to laws of nature.

And Pigheaded as I am, I think my system is coming closest to those laws of nature, mayby even pessimistic, so always on the save side.
But if you use inacurate determined data , the outcome could still be to low , so tire damage.
But using the official USA TRA calculation togeter with those inacurate data, would even give lower pressure ,so sooner tire-damage.

Once the damage to the structure of rubber by overheating is done, there is no way back. every bending of it, by the deflection about 10 times a second of every segment of the tire, then tears those hardened rubberparts a bit further , and mayby even after 3 years suddenly blowing tire, with the missery that can go with it.

And you did not see me giving a specific advice here, I first stated what was important to determine first to get a save advice for your not towing situation.

[Tireman9]

Originally Posted by SmokeyWren

In the USA, the authority is the United States Tire and Rim Association (TRA). The load/inflation tables developed by the engineers at TRA are the official load/inflation tables to be used by the tire industry and vehicle manufacturers that sell tires, rims, and vehicles in the USA.

And IIRC, Canada also uses the TRA load/inflation tables.

So regardless of the load/inflation tables used in England or Germany or Japan or Australia, here in the USA we use the TRA tables.

And those load/inflation tables are difficult to find for the average web surfer. They are updated and published annually in the TRA annual report, but that report goes only to members of the TRA (generally, manufacturers of tires, rims [wheels], and vehicles), and membership is expensive. So no, I'm not a member.

Way back when, the TRA load/inflation tables were made available by all tire manufacturers that sell tires in the USA. But most of those sources have stopped making the tables available for P-Series and LT tires. Even the Toyo tables quoted above are very hard to find now. If you simply go to toyotires.com, you probably won't find them. Michelin, Goodyear, Goodrich, Cooper, Firestone/Bridgestone and others no longer include the load/inflation tables for P-Series and LT tires on their websites. They all now say to follow the vehicle manufacturer's load/inflation instructions.

I think you can find the Load/Inflation info on this page from my blog. There are 7 other posts ged to "Load Inflation Table" info according to index on left side of the page.

[09 harley]

Toyo tires has a table that shows all tire sizes and the pressures needed to carry various weights. Pretty simple. A tire can utilize different pressures without damage. You just need to be very careful to change it based on towing or not. This is not rocket science!
I just went to the Toyo website and it is still up and running.

[spock123]

My Silverado 3500 is 60 front and 80 towing, to much trouble to keep changing the air

[09 harley]

Originally Posted by spock123

My Silverado 3500 is 60 front and 80 towing, to much trouble to keep changing the air

Lots of people do exactly the same as you do. I just happen to prefer having a smoother ride during the majority of time my vehicle is not used for towing. I have a compressor in my garage and it is simple to adjust the pressure. Since I'm sure we all check our pressure either manually or with built in TPMS then this makes it even simpler.
In my brothers dually if he doesn't reduce his pressure you come off the rear seat when going over a small speed bump in parking lots. He obviously lowers his pressure to improve his ride quality and also to even out the tire wear from sidewall to sidewall.