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Discussion Starter #1
So I just got my Metris & saw that the tires looked low. The tires themselves say the max pressure is 50 psi, but the owner's manual says the tire pressure should be 39. I swear even at 50 it looks like it's sitting on the sidewalls and I'm concerned about how the tires will wear. This is for the passenger model. What do all of you have your pressure at? Thanks
 

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Which tires - the Hankook's? I ran my Hankook's in the high 40's and I do the same with my Michelins as well. But I like a firm ride and have the van fully/heavily loaded.
 

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Inside the door says 44 front, 45 rear so that's what I run.
I was unknowingly running 36 for a couple months until last week.
 

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If you don’t recall the era when all tires weren’t oversized rubber bands, a bit of deformation from weight is both normal and desirable- it increases contact patch and thus grip.
 

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Inside the door says 44 front, 45 rear so that's what I run.
I was unknowingly running 36 for a couple months until last week.
don't forget the secret tire pressure label behind the fuel door. iirc I've been running between 42 and 44 and it seems to do fine without any wear caused by tire pressure changes.
 

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Discussion Starter #9
Yes, they are the Hancook, and from what I'm reading on other posts they are a POS. I keep forgetting to look inside the fuel door but the owner's manual says 39. Why put tires with a 50 psi on a vehicle you only want 39 in? And, excuse my naivete, but does it really make a difference for the vehicle if I use the higher #? Also, why didn't my sensor go on when they were only @ 30-35 when I got the car? How low does the tire need to be for the sensor to go on?
 

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Yes, they are the Hancook, and from what I'm reading on other posts they are a POS. I keep forgetting to look inside the fuel door but the owner's manual says 39. Why put tires with a 50 psi on a vehicle you only want 39 in? And, excuse my naivete, but does it really make a difference for the vehicle if I use the higher #? Also, why didn't my sensor go on when they were only @ 30-35 when I got the car? How low does the tire need to be for the sensor to go on?
The sidewall number is the maximum air pressure. It’s specific to the tire, not the vehicle. So if that tire were hypothetically mounted on a Metris or a Prius, that’s the most psi they say you should run. Just like you likely don’t run your van at it’s maximum payload all day just because you can, you also don’t run your tires at maximum air pressure just because you can. They are worst case figures, not ideal ones.

The tire pressures on the van’s stickers are specific to the Metris, and were calculated by Mercedes engineers to provide the optimum combination of ride comfort, treadwear, and handling and braking performance at the indicated load ranges. Those should be your reference figures.
 

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Because it wears evenly on the tires, also a hair improvement on MPG.

One more thing, if I forget or just be lazy I'll still have longer time to inflate them. It's like I've never run them under inflated tires.
Wait, what? You run lower pressure in the rear???
 

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On a cargo van you also want more air in the rear because that's where you're carrying the weight when loaded. When you increase the load on a tire, the contact patch increases. That causes more friction, thus more heat. An underinflated tire with a heavy load on it can expand the contact patch to the point where it overheats and ultimately fails. Increasing the air pressure (assuming one stays under the maximum tire psi) counteracts this.
 

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Discussion Starter #17
The sidewall number is the maximum air pressure. It’s specific to the tire, not the vehicle. So if that tire were hypothetically mounted on a Metris or a Prius, that’s the most psi they say you should run. Just like you likely don’t run your van at it’s maximum payload all day just because you can, you also don’t run your tires at maximum air pressure just because you can. They are worst case figures, not ideal ones.

The tire pressures on the van’s stickers are specific to the Metris, and were calculated by Mercedes engineers to provide the optimum combination of ride comfort, treadwear, and handling and braking performance at the indicated load ranges. Those should be your reference figures.
Ok, I get it. However, each part of the vehicle has a different psi. The door says 44 & 45 and the fuel door says 39.
 

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It depends on load; unladen, 39 is good. With full load 44 front, 45 rear. With loads in between... well you get the idea. I suggest investing in a decent 12v air compressor- I have a decent (read: old) Craftsman. But I’m pretty sure Rigid, Bosch, and Snap-On all make them.

It is also a godsend if you get a slow leak in the middle of nowhere. I mostly use it to reflate several leaky tires on Rudolf because there is no world in which spending money on tires for an unregistered car makes sense.
 
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