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50 Psi??

babyburb

babyburb

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A couple weeks back I went to make sure all my tires were properly aired up for a road trip. The sidewall of my tire said max 50 PSI. Is this the optimal pressure for MPG, good tire wear and drivability.

I run 275/60 20's on the Ram and looking for new tires. I wanted to know before I put some new rubber on?
 
Optimal all the way around is what the door jam on the truck said.

Tires are rated at what they CAN run, not what is best. Issue is loading. If the load is too light, and PSI too high, you wear out the centers. Too low and you wear out the edges. Not to mention more heat generation at lower pressures, and worse ride at higher pressures.

Better mileage but faster wear out is no savings when tires are as expensive as they are. :)
 
babyburb said:
So whatever tire I choose, go with the door jam pressure?
Click to expand...

Only if it is the same size and equivalent type/make of tire.

Just like the tire sidewall states, the number is the "max" pressure you can put in the tire. It doesn't say "optimal" pressure. ;)
 
The max pressure is for the max load. You need about 0psi for 0 load. Any load inbetween you can interpolate.

If you run 50psi without the full load it will ride like crap, wear out the centers and could handle weird.
 
I'm gonna amend my answer...optimal pressure for stock tires is in the door jamb.

Apparently tire manufacturers have a tire load/inflation table for their tires which is what you use to determine pressure, like this: http://www.goodyear.com/rv/pdf/rv_inflation.pdf I see much reference to the tables, but can't find any car/light truck tables from BFG for instance, online.

Found these:
http://www.olderogtire.com/pdf/light_truck_load_and_inflation_tables.pdf (that chart is from the US tire spec folks)

http://marktg.toyotires.com/file/loadinflationtable.pdf tons of reading

http://www.yokohamatire.com/pdf/Load_Inflation.pdf
 
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i thought most tires have nominal psi on the sidewall along w/the max, which i was told the max is for mounting the bead. like my tires say 34psi nominal/60psi max
 
If you read one of the links above I think they talk about it. Some tires are also labeled for single/dual use as well. Problem seems to be there are two or three "standards" out there.

Since weight determines the pressure to run, no idea how any manufacturer could put a "nominal" PSI on their tires, unless they were only used on one vehicle.
 
If it geos by load, wouldn't the front tires be a different PSI having to carry the weight of the engine compared to the rear which is much lighter?
 
Some vehicles are that way. People don't look at the door jam.

I *suspect* that on our trucks, if front to rear is the same, then it takes into account some sort of load.

Not only that, it's also probably a more modern deal (don't recall hearing about front/rear different pressure on older vehicles) where they take into account things like weight distribution. Kind of odd, since people can't or won't check their own tire pressure as it is nowadays.

I don't believe the front to rear load balance is as bad as people might think it is in these trucks, at least the K5's. I bet that data is out there.

You'd need to scale the front and rear tires to see what kind of load each is taking. From the charts, looks like the difference in weight required to change pressure is fairly large.
 
I've never seen a tire that has a "nominal" pressure rating on it, only the max pressure. I've also never seen a graph or table from a tire manufacture that lists anything but the max.

It is not uncommon for newer cars and trucks (I deal with them all the time at work) to have different recommend pressures on the door jam between the front and rear. This is typically based on the weight distribution from front to rear at the GVWR.....a lot of cars and SUV's have a close to 50/50 weight distribution and this includes K5's. Pickups (especially heavier duty versions) usually have the largest variance between tire pressure front to rear, with the fronts generally being lower than the rear. While the front is much heavier on a pickup empty, when you put the maximum payload in the back it gives you more weight on the rear tires. For liability reasons they make the number for the worst case scenario. For examply my '03 2500HD states 65 psi front and 80 psi rear, even though with no load (most of the time) the front weights a lot more. I understand tire pressures, so I run the back tires more along the lines of 50-55 psi empty but always make sure to add air when towing or hauling a load.
 
The links above show some of the charts from the tire manufacturers that aren't the max. Basically it's the adjustment in tire pressure for a given tire size with a given weight.

I saw reference to it in regards to the "+ sizing" you hear about from tire stores nowadays. Interesting how that's all tied together.
 
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