Tire pressure with LOADED FWC Hawk on truck?

[Bucky]

Hi Gang,

My 2012 Sierra 1500 ext. cab, 5.8L, 4x4, Z71 has Wrangler AT/S tires with recommended 35 psi front and back on the doorpost label. I normally run the truck at 35 psi with and without the 1200 lb 2004 FWC Hawk on the truck. It's just a great ride either way. And the tires look new at just over 30k miles.

However, I'm moving a bunch of stuff from Mass. to North Carolina (700+ miles) next weekend; the camper is crammed with boxes, etc. in every available space, nook and cranny, total added weight approximately 800 lbs (each box/item individually weighed). I loaded the heaviest boxes on the floor and in front of the rear axle.

The Torklift Quick Disconnect Stableloads are handling the big load nicely; the truck sits pretty much level. If I were to describe the ride, it reminds me of a Chevy Express 3500 extended van, built up like our 2008 Roadtrek Popular 210 (8,300 lb GVWR). Definitely NOT zippy like an unloaded 1/2-ton pickup or even with the normal camping-weight Hawk in the bed.

I know I'm exceeding the truck's 7,000 lb. GVWR big time, and plan to take it easy, not exceeding 65mph, using tow mode on hills and in traffic (gearing down in tow mode helps stop sooner.) We've taken lots of stuff (including a dining table and LazyBoy love seat!) down in the camper before, but never a load this heavy. FWIW, I'm experienced at driving long distances with this camper/truck combination.

My question: Would you air up the Wranglers another 5 lbs to 40 psi? Sidewall has maximum 44 psi.

Thanks!

Bucky

 

[pugslyyy]

Hi Gang,

My 2012 Sierra 1500 ext. cab, 5.8L, 4x4, Z71 has Wrangler AT/S tires with recommended 35 psi front and back on the doorpost label. I normally run the truck at 35 psi with and without the 1200 lb 2004 FWC Hawk on the truck. It's just a great ride either way. And the tires look new at just over 30k miles.

However, I'm moving a bunch of stuff from Mass. to North Carolina (700+ miles) next weekend; the camper is crammed with boxes, etc. in every available space, nook and cranny, total added weight approximately 800 lbs (each box/item individually weighed). I loaded the heaviest boxes on the floor and in front of the rear axle.

The Torklift Quick Disconnect Stableloads are handling the big load nicely; the truck sits pretty much level. If I were to describe the ride, it reminds me of a Chevy Express 3500 extended van, built up like our 2008 Roadtrek Popular 210 (8,300 lb GVWR). Definitely NOT zippy like an unloaded 1/2-ton pickup or even with the normal camping-weight Hawk in the bed.

I know I'm exceeding the truck's 7,000 lb. GVWR big time, and plan to take it easy, not exceeding 65mph, using tow mode on hills and in traffic (gearing down in tow mode helps stop sooner.) We've taken lots of stuff (including a dining table and LazyBoy love seat!) down in the camper before, but never a load this heavy. FWIW, I'm experienced at driving long distances with this camper/truck combination.

My question: Would you air up the Wranglers another 5 lbs to 40 psi? Sidewall has maximum 44 psi.

Thanks!

Bucky

So you probably want to be somewhere between 35 and 44. All tire manufacturers have inflation tables that tell you what to inflate to for a given axle weight. To do it right, roll through a weigh station once loaded up and then use the table. This is the RV one, may or may not have your tire listed. http://www.goodyeartrucktires.com/pdf/resources/publications/2010%20RV%20Care%20and%20Maintenance%20Guide.pdf

 

[brian90744]

over weight ??

On your tire it give maximum weight for that tire, now time 4 should give you the maximum weight load. you could rent a trailer if you have over-load in the camper.
just FYI=brian

 

[Bucky]

I just put air in the cold tires, OAT (outside air temperature) 78F.

43 psi on tire pressure gauge; TPMS reads 41 psi all four tires. i can already see a higher sidewall and much less bulge.

Will evaluate over the next few days for ride, handling, and hotter temps by the end of the week. Then I'll be off to NC for a couple months!

(Maximum load per tire is 2535 lbs. at 44 psi. I'm well within that, but still exceeding GVWR, like most truck campers going down the road.)

Thanks for your replies and suggestions.

Bucky

 

[Overland Hadley]

Are these load range C tires?

I would definitely air up from what is on the doorpost, 40-45 is good.

 

[Bucky]

Load range is SL, according to the tire specs.

From ehow.com: P-metric sized tires--tires with sizes starting with a "P" such as P235/75R15--are given a load range rating of either SL or XL. SL stands for Standard Load and XL indicates extra load. An SL-rated tire has its maximum load capacity at an inflation pressure of 35 psi. XL tires can carry a heavier load when inflated to 41 psi. Read more : http://www.ehow.com/about_6642758_load-sl-truck-tire-mean_.html

This, also from the ehow.com article, is very interesting: Warning
The load capacity for P-metric tire sizes is for passenger cars. If a P-metric tire is mounted on a truck or SUV, the maximum load capacity is reduced by 9 percent. If our P235/75R15 tires are used on a truck or SUV, the maximum load per tire is 2,028 times 91 percent or 1,845 pounds. The total weight for the vehicle should not exceed 7,380 pounds. The load capacity of an SL load range tire does not increase by inflating the tire to more than 35 psi. The tire will have a maximum tire pressure greater than 35 psi, but the max load capacity is reached at 35 psi.l

So, I guess the maximum load rating is attained at 35 psi (the door post recommended psi). Airing up to 41 psi will mean less sidewall flex and more stability, I'm thinkin'.

When it's time to replace these Wrangler passenger tires, I'm going with light truck tires, either D or E range.

Bucky

 

[Overland Hadley]

Go for the E rated.

 

[Regcabguy]

Astounds me that 1/2 ton manufacturers are allowed to put passenger rated tires on 1/2 ton LT's. I'd run to the tire store for E-rated tires.
We met a Canadian guy in one of the Yosemite campgrounds off of Hwy 120. He was towing a 22' TT with a newer Tundra TRD and sought my advice why the handling was so precarious. Without looking at the truck I suspected P-rated tires. Sure enough,Toyota supplied p-rated tires but upgraded the shocks to Bilstein's. Aside from dismal towing economy of 6-9 mpg he loved the braking and performance of the truck.

 

[bob91yj]

I don't get the "P" rated tires on a truck either. "LT" for light truck should be pretty self explanatory!

 

[Bucky]

Go for the E rated.

Roger that!

 

[Bucky]

Astounds me that 1/2 ton manufacturers are allowed to put passenger rated tires on 1/2 ton LT's. I'd run to the tire store for E-rated tires.

I agree. My 2003 Sierra 1500 had Firestone Steelex light truck tires. The best tire I've ever had; got 80k+ miles out of them. Still had good tread, but the sidewalls had dry rot. Replaced them with Firestone LT Destination.

I plan on getting E-load range light truck tires when these passenger Wranglers go. They've served me well. And I am within the 4-tire load range (minus 9 per cent because they're on a truck . . . that's pretty crummy!). No more trips with such a heavy load, after this one.

Bucky

 

[DEnd]

If you are getting near the end of service life with these tires, it's probably a good idea to just go ahead and replace them, especially if you have been running them regularly at a high load condition. The Ford explorer tire failures resulted from running tires for a long time at too high of a load condition.

 

[Bucky]

If you are getting near the end of service life with these tires, it's probably a good idea to just go ahead and replace them, especially if you have been running them regularly at a high load condition. The Ford explorer tire failures resulted from running tires for a long time at too high of a load condition.

Just over 30k miles on the P-metric tires; lots of tread left. They handle the 1200-lb FWC Hawk very well under normal circumstances.

I think the problem with the Ford Explorer was under inflation of the tires, a problem with any load, light or heavy.

I've aired up, and I should be good to go this weekend. The Torklift Quick Disconnect Stableloads have prevented rearend sag, giving the truck a level stance, and handling the side-to-side movement of the heavily loaded camper well.

This trip with the 1-ton (1200 lb camper stuffed with 800 lbs of boxed things) in the truck's bed is an exception, not the rule. Not exceeding 65mph, taking it easy all the way down to NC.

Definitely going with E-rated tires when it's time to replace the P-metric Wranglers!

Bucky

 

[Overland Hadley]

I think the problem with the Ford Explorer was under inflation of the tires, a problem with any load, light or heavy.

Yes, under-inflation.

 

[DEnd]

Just over 30k miles on the P-metric tires; lots of tread left. They handle the 1200-lb FWC Hawk very well under normal circumstances.

I think the problem with the Ford Explorer was under inflation of the tires, a problem with any load, light or heavy.
Bucky

At 30,000 miles you are already over the UTQC rating for that tire. Over or under inflation is related to load. The explorer tire failures resulted from heat build up because the tires were under inflated for the load they were carrying. unfortunately tread wear is not a direct correlation to the heat build up in a tire. I'm going to assume that you have not found any problems like these: http://www.maxxis.com/media/197662/tire_damage.pdf unfortunately those are problems that arise only after the initiating damage is already done, meaning the tire can be damaged and still be absent those problems. Regardless you should still closely inspect your tires during your stops.