Born Free Leap'n Lions RV Club Info & Discussion Forum

I'm sure this has been addressed, but I just can't find it.

Have a 2000 26' RSB, and am going to be towing a 2018 Camry on a dolly. The Camry weighs in at about 3300# and the dolly at just under 400#.

BF manual recommends (without towing I presume) 60 psi front, 65 psi rear, and 55 psi air lift. I haven't had a chance to get weighed with the car in tow and provisioned for a trip, but last weigh had 10080 pounds on the rear axle.

Question is, should I up the pressure on the rear tires, and/or raise pressure on the air lift? In the general Internet world, some recommend maxing out the tire pressure (in my case 80 psi) to prevent overheating the tires. I'm looking for the best tire wear, best fuel "economy", and best ride. And yes, everything is a compromise. I have a ScanGauge so I can experiment a little bit to try to find a sweet spot.

According to Bridgestone, the rears can handle a total of 9880 lbs @ 80 psi (2470 lbs load/tire), with any additional weight being addressed by the air lift. Assuming a rear axle weight of 10500 to 10700 lbs with the car in tow (10% - 15% tongue weight and rounding up), the air lift would only need to be 20 psi - 25 psi. At the BF recommended pressures, the rear axle should be able to handle 10800 lbs (65 psi tires, 55 psi air lift).

I know it would be best to get all four corners weighed and adjust individually, but that's not really an option right now.

Any general (or specific) advice on how to balance tire rear tire pressures and air lift pressure would be greatly appreciated. My priorities are safety first, comfort second. My main concern is risking a blowout with incorrect tire pressures.

Thanks!!

With your rear dual tires inflated to the maximum rated 80 psi, the maximum rear axle load is due tires is limited to 9880 lb (4 x 2470). However, your E450 chassis is equipped with a Dana 80 rear axle which is weight rated for a maximum load of 9600 lbs. Adding pressure to your airbags does not allow you to load the rear axle above 9600 lbs. Every brand of your size E rated tires will have this same 2470 lb limitation when used in rear dual configuration. So unfortunately if your rear axle weight is 10080 lbs you are overloaded in the rear both over your rear axle rating and your tire limitations. Adding any more weight such as the tongue weight from the car dolly will overload the rear axle and tires even worse.

I am always trying to learn and follow discussions on tires after my two blowouts. If one two with 4 wheels down how it that calculated as any added weight to the rear axle? Just curious to understand.

Towing 4 wheels down only adds about half the weight of the tow bar to the rear axle weight - maybe around 10 lbs or less.

perleys wrote: ↑Sun Sep 18, 2022 7:20 pm I am always trying to learn and follow discussions on tires after my two blowouts. If one two with 4 wheels down how it that calculated as any added weight to the rear axle? Just curious to understand.

Michelin now offers a Commercial tire that has a higher weight capacity than an LT tire. Check out their C-metric , Agilis Cross Climate tires. We have a 2008 27 RSB and I’ve found loading on rear axle is at or above capacity, with what I’d consider average loading in back ( nothing extremely heavy) . I’ve been pleased with the Michelins so far, about 4,000 miles, with a toad. They provide about an extra 2,000 lb of tire capacity over LTs, ( 3080# each for our size). Of course this won’t change axle capacity, but I bet tire failure is more common than an axle bearing. I don’t like maxing out tire capacity and prefer to have a reserve capacity to handle heat, road hazards or emergency maneuvers.