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Tire Pressure

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Fordwerke

CEG'er
Joined
Jan 27, 2008
Messages
157
Location
Bay Harbor Islands, FL
Since last Saturday, I'm back in the Contique league. I've a V6 Mystique now, and to improve gas-mileage I put the pressure on all four wheels on 40psi, and the tires say that 40psi shouldn't be exceeded.

Dunno, is there anything I should know driving w/ tires at 40psi? Braking may take a (bit?) longer? On wet roads aquaplaning may occurr easier?

What are your thoughts?
 
Try deleting your duplicate thread first. For those tires, it *might* be ok. Our cars aren't that heavy, so I'm sure you're below the max load for them.. which I believe is what the max psi is based off of. Personally, I currently run 43f / 38r... which will result in a pretty even wear across my tires, but my tires also state max psi of 51. I'm guessing that your centers will wear out way before your corners at that psi, with those tires. Also, keep in mind that as your tires get hot, their psi will increase.
 
Last edited:
morbid said:
Also, keep in mind that as your tires get hot, their psi will increase.
Click to expand...


But thats figured into the speed rating and the max cold pressure. Still that doesnt mean you should run the tires at max pressure and wait for the gas savings.
 
You'll have a slightly rougher ride with the tires at full pressure. That's the only thing I know for certain. I can't imagine that hydroplaning would be an issue. I just maxed my pressure on my Fuzion ZRIs to 50 lbs. Ride quality suffered a little bit, but they still stick to the pavement like glue.
 
Be careful with maxing it right to the limit. Air temperature plays a big deal in pressure... 40psi at 60 degrees is 42psi at 80 degrees... so you're actually over the safe limit.
 
But that 40psi is max cold pressure. I assume the manufacturer figures in temp raising the pressure. That being said I'm not comfortable running at max pressure after I popped a tire off the rim hitting a pothole a few tears ago.
 
Cold pressure means the tire is the same temperature as the air temperature. When you have a pressure number, it's for 70 degrees F. So the sticker on my car says 34psi... but it stays in the 20s here during the winter here. So during the winter, 29psi would actually be spot-on... you adjust 1psi for every 10 degrees of air temperature; down for colder, and up for warmer.

Still, I see no reason to run max pressure. You have to give tolerances for the outside air temperature, air pressure gauge being off a bit, etc. If it says 35psi on the door sticker, why run higher than a couple psi above that?
 
I'll never understand why people run max pressure. :shrug:

Past a certain psi, you'll only make the car ride like crap and handle like crap. Every car and tire has an ideal pressure. Don't always go exactly by what the sticker will say. For example, on my Blizzak WS-50's, I have to run the pressure at least 4 psi over the stock rating. The sidewall is too soft for the factory recommended pressure.

Remember that when the tires a warm, the pressure will be up probably another 4 psi.
 
This is another one of those topics that gets to me. There are a few considerations to take into account when choosing what tire pressure to run. First is wheel and tire size. Then you have the load on the tire at a standstill and max load under acceleration, deceleration, and cornering conditions. Sidewall stiffness and flex is another issue. The duties a tire is going to see is another consideration. One of the least things to be concerned about under normal daily driving is the tempiture. It still needs to be considered, but the change of pressure and tempiture during normal driving is a lot less than most people seem to realize for some reason. I've heated my tire up to 220+ degrees and saw a 6 psi increase. Granted the starting temp was around 100, I was on a race track and had to drive very hard to get it that hot. So for most people, running tires at or near max tire pressures is the most logical thing. Running tires at higher pressures increases steering response (wich is directly related to increased sidewall stiffness), hydroplane resitance, and decrease rolling resistance. Running lower but not too low pressures will increase overall grip at the trade-off of a less stable more unpredictable ride. I could go on all day with details, instances, and scenarios, but why? If anyone has any questions, I'll be happy to awnser them.
 
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