Tire Pressure Question

[mburklu]

Probably a dumb question, but the van I just got has Goodyear Wrangler Duratrac LT235/85R16 tires. The only thing I can find is that the max pressure is 80 psi. Any ideas on what a good average psi would be. Thanks.

 

[digitaldelay]

If it's the E350 Quigley Diesel, I would probably run 80 psi on-road unless otherwise specified. Off-road (at low speeds) you can experiment.

Jason

P.S. - Did Quigley remove the factory placard in the driver's door jamb? If so, they should have the correct pressures listed somewhere.

 

[mburklu]

Thanks. Is it ok to run at the max pressure when it's really hot out?

Nope, no placard.

 

[digitaldelay]

It's safer to run the max pressure on a heavy vehicle like yours if you're not sure what it should be. The higher "cold" pressure (before driving) will prevent sidewall deflection and overheating, especially at highway speeds on a hot day. It may be a harsher ride than necessary but you will avoid blowouts.

Jason

 

[mburklu]

Thanks for the info.

 

[Bikersmurf]

The placard on my 97 E350 ambulance with Duallys has 65 front and 55 rears. This pressure is for 225/75R16 tires. I'd run 65psi all around and then use a chalk test on the tires to determine contact patch on the tires.

Empty, it weighs 8300 lbs... When it was in service it would've been more like 9500 lbs.

 

[mburklu]

I read about the chalk test when I was doing a search. I'll have to give it a try. Thanks.

 

[Bikersmurf]

On my fj40, the tire shop inflated the 33x10.50 R15s to 35 psi. Only 3-4" in the Center of the tire touched the ground, and the handeling was downright scary. At 25, they're slightly overinflated, but steering is lighter, handeling is acceptable, and wear should be decent. They're 50 psi max, at 50 even with a 4700 lb truck they'd be way too hard.

 

[spencyg]

I run my 9k lb rig at 75psi all around when on pavement. The tires are 285-75-16 load range E and at 75psi they behave well. Off pavement I usually go down to 35 or so. Any lower and I get some tread heating which of course is not a good thing...

SG

 

[stormlover]

Why run the max recommended psi when your rig weights 9,000 or 10,000 pounds and the tires are rated to nearly 16,000 lbs? Maybe if your pulling a trailer but otherwise I would air down a bit for a better ride.

 

[digitaldelay]

and the tires are rated to nearly 16,000 lbs?

Just over 12,000 lbs. but I hear what you are saying. I'm just suggesting he run max until he can prove otherwise.

Jason

 

[Bikersmurf]

I hear you...

Quiglley conversions add a bit... Specs must be around for a stock E350... Then add some to factor in for the extra 1000 lbs.

The chalk test has served me well over the last 22 years... I'm running to the high side, but low enough that 80-85% of the tire width is contacting the road.

If your pressure is too high, ride, handeling, tread wear, and safety will all be negatively impacted.

 

[Antichrist]

It's safer to run the max pressure on a heavy vehicle like yours if you're not sure what it should be. The higher "cold" pressure (before driving) will prevent sidewall deflection and overheating, especially at highway speeds on a hot day. It may be a harsher ride than necessary but you will avoid blowouts.

Overinflated will also wear the tires out quicker.

 

[digitaldelay]

Overinflated will also wear the tires out quicker.

I know, I'm just saying it's better than a blowout until he can figure out the correct pressures.

Jason

 

[stormlover]

Spirited discussion of whether it is prudent to air down E-rated tires here: http://www.expeditionportal.com/forum/threads/135520-Tires-E-or-D