I recently purchased a 93 e-150 van. While the recommendation is 41 psi on XL tires, it came with non-XL tires in the front rated at a max of 35 psi and LT tires in the rear rated at a max of 60 psi.

I don't want to replace the tires, since I bought the van to go on one long trip (moving out of state) and I'm on a tight budget.

I'm not sure what to inflate the tires to. I don't want to put excess pressures on the rear rims, and it sounds bad to have a substantial mismatch in front and rear pressures. I was thinking maybe 35psi in front and 41 psi in back, but I'm concerned that the rear pressure may be too low for the tires.

And thoughts?

 

Tire pressure for tires that are the same size is based on load. An empty van has more weight on the front, so a higher tire pressure will yield the same profile front and rear for that situation. Pressure is not really based on the tire, it is based on the load. However, tires of different sizes present more or less area to the ground and therefore require different pressure for the same load. Of course, limitations of tire pressure maximums must be followed.

My E250 had 80psi E rated tires that are inflated at 45 front, 40 rear.

 

Non XL/LT tires on an E150 can be deadly. The XL on the P235/75R15 XL means the tire is rated to run at a higher pressure in order to handle more load.

That said, inflate the front tires to 35, and the rears to 41. In fact, the factory sticker on my E150 states this is how it should be done. The LT rating on your rear tires just means they can be inflated to a higher pressure, not that they MUST be at that pressure. They cannot haul their rated maximum unless they are at their maximum pressure however. I run my LT C-Rated (30x9.5R15, a larger offroad tire) at 35 front and 41 rear. At this PSI, their capacity easily exceeds the vans maximum capacity, so no sweat. Your front axle GAWR is probably 3600, with a 3800 rear.

Double check your spare while you are at it. Make sure it has good air pressure, and is in good shape.

If you are towing, things get a bit complex. Remember that weight added to the van reduces its towing capacity. You vans axles combined cannot exceed your GVWR (usually 7k). Your trailer plus loaded van cannot exceed the GCWR. I usually recommend you load the trailer to its weight capacity before you put ANYTHING into the van. Then hit some scales if you can.

 

OK, this raises a very interesting discussion when it comes to vans. The mfg. does not know what is in your van when they put that sticker on the door. So, 35/41 is a nice safe suggestion when the load is unknown. Let's assume the load limit is 945 lb for a 93 E150. If you put 945 pounds in the back of an e150, then the profile of the tires at 35/41 is about the same. 20% more weight balanced to the rear. 18% higher pressure in the rear. This makes sense and results in a safe configuration.

An empty van has the opposite configuration. Heavy in the front, light in the rear. Hence a higher pressure needed for front tires. When the van is loaded, add pressure to the rear.

 

On E150s of that generation, the front GAWR will be up to 3600, the rear GAWR up to 3800. The GVWR is up to 7000, depending on flavor. An empty 5.8L E150 of this generation usually curbs right around 4700 with a bit of fuel and a pretty heavy driver (Yo!). Their actual payload is (supposedly) 2100lbs, and I suppose the rest is padding for equipment/options/fatter drivers.

One of these days I will figure out why its considered a 'quarter ton' van when it clearly hauls 'one ton' of cargo.

The recommended tire PSI seems to be partially based on the load carrying capacity of the tire at that inflation level, but that doesnt explain why they want 6 more PSI (~18%) for a Loaded capacity difference of 200 lbs (~5%). I would expect higher PSI at the front unless they just accepted the limitations of available tires in that size when developing the recommendations for the rear. I kinda think vehicle dynamics would be considered, but the PSI selection may be as simple as "XL rated tires only go up to 41PSI, and that's what we will set the rear to." Or, it may be that Ford expects you to put most of your load on the back axle of the van, much like their pickups.

Either way, 35 up front, 41 out back, seems like a nice starting point. Adjust as needed!

 

I suppose it doesn't hurt to be prepared for a load to be added. Empty, it will oversteer, which is a lot better than the alternative. My van is always empty, essentially, so I balance the profile by having more pressure up front. The profile then looks, and probably is, identical. But, then, it's an empty van.

 

I'm on my 3rd e 150 and always use the numbers on the tires (235-16 coopers now @ 41#). just thought the tire maker knew better....J

 

So I let out the front tires from about 40psi (overinflated by the tire specifications) to 35 psi (underinflated by the van specifications). And inflating the rear tires up from about 30psi to 41psi.

The rear tires look better, but now the front tires look a bit flat at the very bottom.

How dangerous is the current configuration? How comparably dangerous would it be to exceed the tire's pressure specifications as they were before?

These are the front tires if it makes a difference:
Radial T/A | BFGoodrich Tires
p235/70r15 102s m+s
Rated for 1896 pounds at 35 psi.

If it also makes a difference, the van is currently empty, but won't be later.

 

Ford put XL truck tires on it for a reason, any good tire shop will tell you not to mix load ranges and never to put on lesser load range tire than factory spec...... I use to sell BFGs back in the day!

 

Check your door sticker, but 35PSI should be correct by van standards...

 

The sticker says 41 psi for both front and rear.

 

Hmm... If its a conversion van perhaps they replaced the sticker. Since you are operating out of spec (non XL rated front tires) I cant really say its safe. I have seen a fair number of vans running on non XL rated tires though. I wouldn't EXPECT it to be a problem myself, but I am paranoid, and would replace the tires if i could find it in my budget. I know here locally (Memphis) I can find appropriate used LT tires for about 45/each mounted.

 

I have a 2004 E-450 SuperDuty.
The door jam sticker put there by ford indicates 60psi Front 80psi rear.
I put 80 psi in all tires as what the tire manufacturer stamps on the sidewall of the tire.

 

this topic has been thrown around in many threads. the consensus always remains the same: the pressure must match the load. too much pressure for the weight produces poor traction, too little pressure causes excessive deformation of the tire, which results in heat and catastrophic failures.
so if you're carrying a factory-assumed load, use factory specs. if not, stop by the truck scales when you're fully loaded and do some math. 3/4 of the tire weight rating should get about 3/4 of the tires rated pressure. your numbers will vary, so be smart about it, and of course, don't go below the factory numbers if you can help it.
for the OP, run those fronts at 35-38 until you can get something stronger up there, and the rears at the 41 they specify.

 

I do something similar on my '00 E250 that weighs right at 7800# as a daily driver work truck. Running Michelin LTX 245 @ 70psi I have a good compromise between handling, traction & ride comfort (which is highly subjective! )

Since my load almost never changes and I don't tow other than checking for proper inflation periodically I don't adjust my TP ever.