Community Forums

JohnH12 · 09-08-2021, 10:53 AM

For those with 5th wheels:
My Ram 3500 B pillar shows 80 PSI for the front tires and 65 PSI for the rear dual tires.
The 5th wheel we are getting has about a 3000# hitch weight. Of course that plus any cargo I have in the bed of the truck.
Should the rear tire pressures be adjusted because of the added load? The owner's manual doesn't mention anything regarding cargo weight effecting tire pressure recommendations.
Thanks.

chrisicool · 09-08-2021, 12:08 PM

Quote:

Originally Posted by JohnH12

For those with 5th wheels:
My Ram 3500 B pillar shows 80 PSI for the front tires and 65 PSI for the rear dual tires.
The 5th wheel we are getting has about a 3000# hitch weight. Of course that plus any cargo I have in the bed of the truck.
Should the rear tire pressures be adjusted because of the added load? The owner's manual doesn't mention anything regarding cargo weight effecting tire pressure recommendations.
Thanks.

The back tires should still run at the same recommended levels. For verification I would check your tire manufacturers specifications. The tire will have a load index and recommended PSI. You should be fine with your payload weight; However, there's a lot of variables that play into it. Temp being a big one. Check your tire pressure prior to load as well. Running too low or too high can be dangerous.

kdauto · 09-08-2021, 05:27 PM

Quote:

Originally Posted by JohnH12

For those with 5th wheels:
My Ram 3500 B pillar shows 80 PSI for the front tires and 65 PSI for the rear dual tires.
The 5th wheel we are getting has about a 3000# hitch weight. Of course that plus any cargo I have in the bed of the truck.
Should the rear tire pressures be adjusted because of the added load? The owner's manual doesn't mention anything regarding cargo weight effecting tire pressure recommendations.
Thanks.

Those weights and pressures almost mirror my truck. You should run it at 65 psi. Running it higher it will be rough riding and almost to the point of being unsafe when unladen, say, unhooking and doing a grocery run. The rear of the truck will bounce on the tiniest of bumps on curves, not fun.

You will notice 65 psi with your tires, surely load range E, will coincide with max axle ratings for your truck or a bit higher. You won't be gaining much by raising over 65 psi on rear tires.

jimcumminsw · 09-09-2021, 09:03 AM

In fact if you raise the rear tire pressure over the recommend pressure for your DRW truck, the tires could rub each other. That is why on every LT tire the air pressure for a SRW truck is higher and a DRW truck has a lower tire pressure reading. This is to prevent the tires from rubbing each other if you used just one air pressure setting.

00 Buckshot · 09-09-2021, 09:14 AM

The tire info on the door is for the max load of your truck. I run 75 in the front and 65 in the rear duals hauling a 17K gvw 5th wheel.

**hamm2018** · 09-09-2021, 10:44 AM

Quote:

Originally Posted by JohnH12

For those with 5th wheels:
My Ram 3500 B pillar shows 80 PSI for the front tires and 65 PSI for the rear dual tires.
The 5th wheel we are getting has about a 3000# hitch weight. Of course that plus any cargo I have in the bed of the truck.
Should the rear tire pressures be adjusted because of the added load? The owner's manual doesn't mention anything regarding cargo weight effecting tire pressure recommendations.
Thanks.

We haul a 2017 Road Warrior, 21,000 lbs loaded with around 4500lb pin weight. With other items in truck, plus a 55 gal under bed fuel tank we run 65psi in the rear tires. We replaced the 36 gal tank with a Titan 55 gal tank Feb 2020.
If you adjust the PSI for the added load are you going to adjust for when you are not hauling, then adjust again when hooked up?????

mjdenn · 09-09-2021, 11:58 AM

The B pillar label should be good to your max GVW. Note that the tires have different load capacity in a DRW versus a SRW. If you are running empty you can actually reduce pressures to improve the ride. My Ford uses 65 PSI for a RAWR of 9900 LBS.

kdauto · 09-09-2021, 12:42 PM

Quote:

Originally Posted by jimcumminsw

In fact if you raise the rear tire pressure over the recommend pressure for your DRW truck, the tires could rub each other. That is why on every LT tire the air pressure for a SRW truck is higher and a DRW truck has a lower tire pressure reading. This is to prevent the tires from rubbing each other if you used just one air pressure setting.

On all the duallies I've seen and worked on there was ample space between the tires in the air and loaded on the ground. I had a solid 1"+ clearance, enough to widen all tires from 235s to 245s, and I still have ample clearance. Width of an LT tire when inflated from 65 to say 80 psi will not measurably change, "maybe" 1mm at most.

twinboat · 09-09-2021, 12:49 PM

Quote:

Originally Posted by jimcumminsw

In fact if you raise the rear tire pressure over the recommend pressure for your DRW truck, the tires could rub each other. That is why on every LT tire the air pressure for a SRW truck is higher and a DRW truck has a lower tire pressure reading. This is to prevent the tires from rubbing each other if you used just one air pressure setting.

Tires are rubber to keep the air in and have nylon or steel cords to hold their shape.

The only way a tire will get wider is if the cords are damaged or way under inflated, causing them to bulge under the weight.

chaps2018 · 09-09-2021, 02:51 PM

Quote:

Originally Posted by mjdenn

…My Ford uses 65 PSI for a RAWR of 9900 LBS.

Similarly, my 2016 RAM 3500 DRW label indicates

65 PSI for RAWR of 9750

Funny thing tho, my 2006 RAM 3500 DRW specified for the rears: 65 PSI for non-towing and 80 PSI for towing. That truck had much less RAWR but don’t recall what it was. Go figure.

xc-mark · 09-09-2021, 05:40 PM

my truck has TPM system , I run 64 psi cold in the rear and 70 up front. loaded or unloaded. the front weight never changes with a 5th wheel so 80 psi up front really is to much.

Skilletface · 09-10-2021, 05:13 AM

Quote:

Originally Posted by JohnH12

For those with 5th wheels:
My Ram 3500 B pillar shows 80 PSI for the front tires and 65 PSI for the rear dual tires.
The 5th wheel we are getting has about a 3000# hitch weight. Of course that plus any cargo I have in the bed of the truck.
Should the rear tire pressures be adjusted because of the added load? The owner's manual doesn't mention anything regarding cargo weight effecting tire pressure recommendations.
Thanks.

What is the actual weight coming to bare on your rear axel? An air psi. adjustment may not be required. No manufacturers manual or nomenclature will ever publish a recommendation of exceeding what is published.

jimcumminsw · 09-10-2021, 09:58 AM

Quote:

Originally Posted by kdauto

On all the duallies I've seen and worked on there was ample space between the tires in the air and loaded on the ground. I had a solid 1"+ clearance, enough to widen all tires from 235s to 245s, and I still have ample clearance. Width of an LT tire when inflated from 65 to say 80 psi will not measurably change, "maybe" 1mm at most.

I stand by my statement.

When static the tires are probably OK.

When the tire heats up as due to the rolling resistance from the road surface and the weigh of the load on the rear axle. The tires will increase in size so, if you over inflate the tire to start with the tire size will increase proportionately to that new inflated air pressure. You need the distance between the tires to prevent over heating and rubbing that can occur.

kdauto · 09-10-2021, 01:13 PM

I guess we will just have to disagree then. I have checked the spacing cold and hot. Obviously, I am checking when it isn't rolling, but theoretically, the spacing will increase the faster you go due to centrifugal force and tire expansion radially, not laterally.

If a dually tire setup is that close to each other it isn't stock, either wrong wheels/offset or way too wide a tire. As I said, I widened mine from 235s to 245s with no measurable difference in spacing between them.