PSI

[rlawson4]

To start out, I simply love my FFH. I have about 700 miles on it. I wanted to find out what PSI people recommend? My car came with tires at 35 PSI. (in the morning parked in a garage in Atlanta). I don't know how much the PSI has gone up throughout the day. Is 35 just about right for a morning PSI? In the winter, my garage should be warmer than the ambient air. So, where should my morning winter PSI be? Thanks. I am new to even caring about things like PSI and even getting good milage. It has been great fun. I am averaging about 38 mpg in mixed driving. Thanks all for your help.

[lrymal]

Great gasoline mileage!!!! Compare that to any mid-sized car, or another Fusion without the hybrid technology. Mixed driving for most mid-sized cars will give about 25 mpg.

 

Also check your tire pressure while the tires are cold, or as cool as they can get in summer. This means, no summer sun shining on them. Your garage should be fine. Use the PSI on the door sill decal. Some enthusiats will inflate a couple of extra pounds PSI to the tires to try to get more gas mileage, but this will harshen the ride a bit if your road is not all that smooth.

[akirby]

Cold tires really just means don't check them right after you've driven on them. The ambient air temp doesn't matter much. I usually run mine 2-3 psi higher than the door sticker for better handling and fuel mileage. It also gives me a bigger safety net if I forget to check them for awhile.

[rlawson4]

Cold tires really just means don't check them right after you've driven on them. The ambient air temp doesn't matter much. I usually run mine 2-3 psi higher than the door sticker for better handling and fuel mileage. It also gives me a bigger safety net if I forget to check them for awhile.

 

I looked at the door and it says 33PSI Cold. I was surprised it was not a range. My car came at 35PSI and it has been great. I think I will keep it that way.

[akirby]

I looked at the door and it says 33PSI Cold. I was surprised it was not a range. My car came at 35PSI and it has been great. I think I will keep it that way.

 

It's never a range - always a single number although it can vary front to rear. Consider that the minimum pressure.

[cchaos]

I keep mine at 40 psi.

[rlawson4]

It's never a range - always a single number although it can vary front to rear. Consider that the minimum pressure.

 

I appreciate the response. How do I know the maximum and an optimal PSI?

[akirby]

I appreciate the response. How do I know the maximum and an optimal PSI?

 

Maximum is on the tire itself - do not exceed this. Adding 2-3 psi usually won't hurt the ride quality too much - more than that and it will ride much harsher but will handle better and get a few tenths better mpg. I keep mine around 36.

[aggoodin]

Pump those puppies up to the max rating on the sidewall. Unless you are some kind of snob you won't notice the ride difference after a couple days. I'll give up a tiny bit of comfort for some gain on MPG's any day.

[treeofliberty]

After reading this thread last week, curiousity got the better of me and I checked mine, since I've only had the car for a couple of weeks. Surprisingly, they were at 42 pounds (from the dealership), with a maximum rating of 44. This would explain, at least in part, the wonderful mileage I'm getting.

 

This does bother me slightly. With the oversized tires on my Wrangler, inflating them near the maximum would result in reduced contact patch, right down the middle of the tread. These are certainly different tires, a different car, and different driving paradigm. However, I cannot get past the feeling that 42 pounds will reduce my contact with the road, wear the tires prematurely, and make them more susceptable to puncture.

 

My next experiement will be to reduce the pressure by a couple pounds at a time, watching the impact to mileage.

[aggoodin]

After reading this thread last week, curiousity got the better of me and I checked mine, since I've only had the car for a couple of weeks. Surprisingly, they were at 42 pounds (from the dealership), with a maximum rating of 44. This would explain, at least in part, the wonderful mileage I'm getting.

 

This does bother me slightly. With the oversized tires on my Wrangler, inflating them near the maximum would result in reduced contact patch, right down the middle of the tread. These are certainly different tires, a different car, and different driving paradigm. However, I cannot get past the feeling that 42 pounds will reduce my contact with the road, wear the tires prematurely, and make them more susceptable to puncture.

 

My next experiement will be to reduce the pressure by a couple pounds at a time, watching the impact to mileage.

 

Its my feeling that the pressure rating on the sidewall is the maximum inflation rating that achieves the manufacturers minimum requirement for contact patch with the average weight of the vehicle it is intended for.

 

I'm guessing that the weights figured for the contact patch by the tire manufacturers are the average weights of the vehicles intended for the tires, but it sounds plausible. So oversize tires on your Wrangler were probably designed for a heavier vehicle and thats why your contact patch is crap at the near maximum inflation.

[jeff_h]

Its my feeling that the pressure rating on the sidewall is the maximum inflation rating that achieves the manufacturers minimum requirement for contact patch with the average weight of the vehicle it is intended for.

 

I'm guessing that the weights figured for the contact patch by the tire manufacturers are the average weights of the vehicles intended for the tires, but it sounds plausible. So oversize tires on your Wrangler were probably designed for a heavier vehicle and thats why your contact patch is crap at the near maximum inflation.

 

The label on the door says 33, the tires say max of 44, I will go to 40 and see if the ride is greatly affected and adjust from there. I've noticed that when the tires are max rated for 44 and I have them at 32-35, the outer edges seem to wear out faster and to me indicates under-inflation. So I will go to 40, I had the Prius (said 32 on the door sticker) at 40 and the tire wear was much more even across the entire tread instead of on the inner and outer edges.

[Oman]

Mine came from the dealer at 40, which surprised me. At 35PSI the ride is a fair bit better. I went back to 40 until I find out what the story is. It seems they are all coming in at 40 or so from Ford.

 

Jon

 

 

The label on the door says 33, the tires say max of 44, I will go to 40 and see if the ride is greatly affected and adjust from there. I've noticed that when the tires are max rated for 44 and I have them at 32-35, the outer edges seem to wear out faster and to me indicates under-inflation. So I will go to 40, I had the Prius (said 32 on the door sticker) at 40 and the tire wear was much more even across the entire tread instead of on the inner and outer edges.

[Waldo]

Its my feeling that the pressure rating on the sidewall is the maximum inflation rating that achieves the manufacturers minimum requirement for contact patch with the average weight of the vehicle it is intended for.

 

I'm guessing that the weights figured for the contact patch by the tire manufacturers are the average weights of the vehicles intended for the tires, but it sounds plausible. So oversize tires on your Wrangler were probably designed for a heavier vehicle and thats why your contact patch is crap at the near maximum inflation.

 

The contact patch size is a function of only two things, pressure and vehicle weight. If you increase the pressure, you reduce the patch size. If you increase the vehicle weight, you increase the contact patch size. The type, size or max inflation pressure of the tire has no effect on the contact patch whatsoever. The smaller the contact patch, the more wear (uneven wear) you'll get, plus braking and handling will be greatly reduced.

 

The maximum inflation pressure printed on the sidewall is a result of tests done by the tire companies using a standard test procedure to determine what is the maximum pressure the tire can withstand before it blows out. I believe it's tested at the max load rating of the tire, with nothing to do with the vehicle it's actually used on. But with the trends to bigger wheels and heavier cars these days, most OEM tires are already close to the max load rating once you put in a couple passengers and luggage.

 

As for the manufacturers minimum requirements, they are all tested at the pressure printed on the door label. All braking, handling, EPA fuel mileage and tire wear testing is done at the printed pressure. The OEMs don't care what the max pressure of the tires are, they never test it. If you slide off the road and crash and try to sue Ford, if they find out you're tires are at 44psi they will likely dismiss the lawsuit, just as if you had any other aftermarket modification done to the suspension.

 

So why do they ship from the factory at 40psi? Simple, the higher pressure (smaller contact patch), reduces the tire's chance to be flatspotted during shipping and any time sitting at the dealership.

[Oman]

That makes sense to me, but I thought part of the dealer prep was putting the correct pressure in the tires (I think there was a check-box for that) - so if the sill plate is 33/5, why are the dealers setting them to 40? Just curious... I don't want to prematurely wear the tires. I already went through that with my wife's run flats, or should I say expensive and useless tires.

 

Jon

 

 

The contact patch size is a function of only two things, pressure and vehicle weight. If you increase the pressure, you reduce the patch size. If you increase the vehicle weight, you increase the contact patch size. The type, size or max inflation pressure of the tire has no effect on the contact patch whatsoever. The smaller the contact patch, the more wear (uneven wear) you'll get, plus braking and handling will be greatly reduced.

 

The maximum inflation pressure printed on the sidewall is a result of tests done by the tire companies using a standard test procedure to determine what is the maximum pressure the tire can withstand before it blows out. I believe it's tested at the max load rating of the tire, with nothing to do with the vehicle it's actually used on. But with the trends to bigger wheels and heavier cars these days, most OEM tires are already close to the max load rating once you put in a couple passengers and luggage.

 

As for the manufacturers minimum requirements, they are all tested at the pressure printed on the door label. All braking, handling, EPA fuel mileage and tire wear testing is done at the printed pressure. The OEMs don't care what the max pressure of the tires are, they never test it. If you slide off the road and crash and try to sue Ford, if they find out you're tires are at 44psi they will likely dismiss the lawsuit, just as if you had any other aftermarket modification done to the suspension.

 

So why do they ship from the factory at 40psi? Simple, the higher pressure (smaller contact patch), reduces the tire's chance to be flatspotted during shipping and any time sitting at the dealership.

[WPWoodJr]

Mine came from the dealer at 40, which surprised me. At 35PSI the ride is a fair bit better. I went back to 40 until I find out what the story is. It seems they are all coming in at 40 or so from Ford.

 

Jon

My tires are at 35 after almost a month. Haven't touched them since I picked the FFH up at the dealer.

[Waldo]

That makes sense to me, but I thought part of the dealer prep was putting the correct pressure in the tires (I think there was a check-box for that) - so if the sill plate is 33/5, why are the dealers setting them to 40? Just curious... I don't want to prematurely wear the tires. I already went through that with my wife's run flats, or should I say expensive and useless tires.

 

Jon

 

 

The dealers are supposed to do a lot of things, but with everyone demanding to pay invoice pricing or less, they are cutting a lot of corners.

[aggoodin]

The contact patch size is a function of only two things, pressure and vehicle weight. If you increase the pressure, you reduce the patch size. If you increase the vehicle weight, you increase the contact patch size. The type, size or max inflation pressure of the tire has no effect on the contact patch whatsoever. The smaller the contact patch, the more wear (uneven wear) you'll get, plus braking and handling will be greatly reduced.

 

The maximum inflation pressure printed on the sidewall is a result of tests done by the tire companies using a standard test procedure to determine what is the maximum pressure the tire can withstand before it blows out. I believe it's tested at the max load rating of the tire, with nothing to do with the vehicle it's actually used on. But with the trends to bigger wheels and heavier cars these days, most OEM tires are already close to the max load rating once you put in a couple passengers and luggage.

 

As for the manufacturers minimum requirements, they are all tested at the pressure printed on the door label. All braking, handling, EPA fuel mileage and tire wear testing is done at the printed pressure. The OEMs don't care what the max pressure of the tires are, they never test it. If you slide off the road and crash and try to sue Ford, if they find out you're tires are at 44psi they will likely dismiss the lawsuit, just as if you had any other aftermarket modification done to the suspension.

 

So why do they ship from the factory at 40psi? Simple, the higher pressure (smaller contact patch), reduces the tire's chance to be flatspotted during shipping and any time sitting at the dealership.

 

Before I file this into my brain as the tire pressure/contact patch gospel, please tell me that you are in the tire industry and this is the absolute truth.

[akirby]

Before I file this into my brain as the tire pressure/contact patch gospel, please tell me that you are in the tire industry and this is the absolute truth.

 

I'm not in the tire industry but I can tell you this is the absolute truth - just do a few googles. It's basically common sense.

[WPWoodJr]

Before I file this into my brain as the tire pressure/contact patch gospel, please tell me that you are in the tire industry and this is the absolute truth.

Here's and interesting article about tire pressure on police cars:

http://www.cleanmpg.com/forums/showthread.php?t=11652

 

Myths about pressure

 

Let’s put to rest some common misconceptions. The tires will not balloon out creating a peak in the center portion of the tread when tire pressure is above 35 psi. There is a steel belt that prevents this from happening. Also, you are not overstressing the tire with higher pressure, and the tire will not be forced off the rim with higher pressure. The picture above is Bobby Ore of Bobby Ore Motorsports driving a Ford Ranger on two wheels. The tires on the left side have 100 psi in them, and they happen to be tires and rims from a 1999 Crown Victoria! This is a dramatic example of how pressure holds the tire in shape, and how much stress a tire can handle.

[rfruth]

I plan to use a few more PSI then recommend (per the drivers door jam, not the max pressure on the tire sidewall) but if that causes safety and or driveability issues uneven wear etc its back to the recommended pressure for me - hope the TPMS likes this idea ...

[aggoodin]

I plan to use a few more PSI then recommend (per the drivers door jam, not the max pressure on the tire sidewall) but if that causes safety and or driveability issues uneven wear etc its back to the recommended pressure for me - hope the TPMS likes this idea ...

 

Funny you bring that up. It seems to me that the TPMS only knows the pressure it was programmed at and then goes off after "x" % of air is lost. I reprogrammed all mine after I pumped up the tires to max. I want it to go off when there is like 35psi in there and not 25 psi.

[Waldo]

Funny you bring that up. It seems to me that the TPMS only knows the pressure it was programmed at and then goes off after "x" % of air is lost. I reprogrammed all mine after I pumped up the tires to max. I want it to go off when there is like 35psi in there and not 25 psi.

 

"Reprogramming" them won't do it. The cut-off is fixed in the memory of the computer, it has nothing to do with what the pressure is when you program the sensor. Programming the sensor just tells the computer the serial number of the sensor and which tire it's in.

[rfruth]

I saw this on how-to train the tires (thanks fordfusionclub.com and all) ((would I need to reprogram the wheel sensors if there is NO new sensors)) ?

 

reset TPMS link

[Oman]

I thought that the NTSB required the TPMS system to be temperature aware now, not the old dumb type. The TPMS reset is supposed to be done with the tires cold so that the computer gets a baseline and then tracks the rise/fall of the pressures with temperature. It will alarm for several reasons, not just for a low-pressure cutoff. I suppose if that wasn't required and Ford went cheap then there could just be a cutoff - which would suck because those things false all the time when you live in an area where the temperatures can vary 40 degress in an hour or two.

 

Jon

 

 

I saw this on how-to train the tires (thanks fordfusionclub.com and all) ((would I need to reprogram the wheel sensors if there is NO new sensors)) ?

 

reset TPMS link