chanka98 Posted September 7, 2011 Report Share Posted September 7, 2011 ok, so I've had my 2011 Edge Sport for almost 3 weeks now and this morning I got a low tire pressure warning. Can someone tell me how to find out which tire is low ? The warning does not specify. Also, my dealership was trying to sell me nitrogen for life for my tires for $80. Sice they are not around the corner from me I did not buy this option (yet). I can't seem to find any compelling evidence that nitrogen is so much better than air for the average driver but with the 22" Pirelli's I want to make sure I do everything possible to make them last as long as they can. Does anyone use strictly nitrogen for their tires? It didn't seem to stop my brand new tires from losing pressure, unless I have a nail or something. Thanks. Quote Link to comment Share on other sites More sharing options...
akirby Posted September 7, 2011 Report Share Posted September 7, 2011 ok, so I've had my 2011 Edge Sport for almost 3 weeks now and this morning I got a low tire pressure warning. Can someone tell me how to find out which tire is low ? The warning does not specify. Is this a trick question? You take out the tire pressure gauge and check each one. The onboard system is not a substitute for regularly checking your tire pressure. It can be low before the warning goes off. Also, my dealership was trying to sell me nitrogen for life for my tires for $80. Sice they are not around the corner from me I did not buy this option (yet). I can't seem to find any compelling evidence that nitrogen is so much better than air for the average driver but with the 22" Pirelli's I want to make sure I do everything possible to make them last as long as they can. Does anyone use strictly nitrogen for their tires? It didn't seem to stop my brand new tires from losing pressure, unless I have a nail or something. Thanks. You don't need Nitrogen. The biggest advantage is that it's drier than regular air. All the other benefits are very minor or non-existent for street driving. It's certainly not worth $80. Just use that new tire pressure gauge that you're going to buy and check the pressure once a month and you'll be just fine. Quote Link to comment Share on other sites More sharing options...
chanka98 Posted September 7, 2011 Author Report Share Posted September 7, 2011 Thanks for the (sarcastic & patronizing) response. I actually do know how to use a tire pressure gauge, but when the warning light comes on while I am driving down the interstate at 75mph it would be nice to have more info (which tire is low and what the pressure is) so that I know if I ran something over, have a slow leak, and if one of my front tires might be compromised to the point where I should slow down and get to the nearest gas station or garage to get air in it. It actually looks like there is an issue with the 22's holding pressure so I guess I'll have to keep an eye on them. Thanks for the info on the nitrogen too. I'm glad to know I am not being remiss with the care of my wheels. Quote Link to comment Share on other sites More sharing options...
cal3thousand Posted September 7, 2011 Report Share Posted September 7, 2011 Thanks for the (sarcastic & patronizing) response. I actually do know how to use a tire pressure gauge, but when the warning light comes on while I am driving down the interstate at 75mph it would be nice to have more info (which tire is low and what the pressure is) so that I know if I ran something over, have a slow leak, and if one of my front tires might be compromised to the point where I should slow down and get to the nearest gas station or garage to get air in it. It actually looks like there is an issue with the 22's holding pressure so I guess I'll have to keep an eye on them. Thanks for the info on the nitrogen too. I'm glad to know I am not being remiss with the care of my wheels. You, like many of, expected a TPMS that was advanced enough to supply individual tire pressure readings. Maybe there will be an app that will bring this to SYNC someday. Quote Link to comment Share on other sites More sharing options...
McEdge Posted September 7, 2011 Report Share Posted September 7, 2011 You, like many of, expected a TPMS that was advanced enough to supply individual tire pressure readings. Maybe there will be an app that will bring this to SYNC someday. My Acura which is 5 years old has TPMS and warns on an individual tire basis. My Edge?, just the basic warning light. Synch is cool, but useful technology is even better. Quote Link to comment Share on other sites More sharing options...
akirby Posted September 7, 2011 Report Share Posted September 7, 2011 Thanks for the (sarcastic & patronizing) response. I actually do know how to use a tire pressure gauge, but when the warning light comes on while I am driving down the interstate at 75mph it would be nice to have more info (which tire is low and what the pressure is) so that I know if I ran something over, have a slow leak, and if one of my front tires might be compromised to the point where I should slow down and get to the nearest gas station or garage to get air in it. It actually looks like there is an issue with the 22's holding pressure so I guess I'll have to keep an eye on them. Thanks for the info on the nitrogen too. I'm glad to know I am not being remiss with the care of my wheels. Sorry, I take things literally. Sounds like you meant to ask "How do I tell which tire or how low it is before stopping". I'm not sure whether the computer knows the actual pressure or if it's just getting a fault from the TPMS sensor or whether it knows which tire (depends on whether it has a sensor at each wheel or one for the entire vehicle. Either way it does not display this information. Some vehicles do but Ford has not implemented this feature. So you gotta stop and take out the tire gauge. Quote Link to comment Share on other sites More sharing options...
Dingo Posted September 7, 2011 Report Share Posted September 7, 2011 It does not know what the actual pressure is. It just knows there's a difference of several psi between that wheel and the others. If you air all four down to 10 psi, you'll still have no warning. Quote Link to comment Share on other sites More sharing options...
NatG Posted September 7, 2011 Report Share Posted September 7, 2011 I agree with Akirby, checking the tires routinely with a pressure gauge is a must. TPMS can fail, and from my experience most don't respond until there is a drastic variation. IF the tire stays too low for too long, it can be hazardous, consume more fuel, and possible effect the condition of the tire. Quote Link to comment Share on other sites More sharing options...
chanka98 Posted September 8, 2011 Author Report Share Posted September 8, 2011 Just checked my tires and all four were below 30psi. Seems like the dealership never checked it before I picked it up. Either that or they are losing pressure REAL fast, even with the nitrogen. Anyway, I brought them all up to 35psi so we'll see how long that lasts. Thanks for all the input. Quote Link to comment Share on other sites More sharing options...
Dingo Posted September 8, 2011 Report Share Posted September 8, 2011 Also keep in mind that most of the cheap gauges can be off by as much as 8 psi when you buy it. Quote Link to comment Share on other sites More sharing options...
seabee78 Posted September 8, 2011 Report Share Posted September 8, 2011 I was lead to believe that nitrogen keeps a more constant pressure and does not fluctuate tire pressures in heat or cold as air does. Quote Link to comment Share on other sites More sharing options...
akirby Posted September 8, 2011 Report Share Posted September 8, 2011 I was lead to believe that nitrogen keeps a more constant pressure and does not fluctuate tire pressures in heat or cold as air does. Pure nitrogen does not expand as much under heat but that's only a problem if you're a Nascar driver and you're worried about a quarter pound of pressure. There are benefits (drier, not as heat sensitive, doesn't leak out as fast) but they don't really matter to everyday drivers. Quote Link to comment Share on other sites More sharing options...
dr.edge Posted September 8, 2011 Report Share Posted September 8, 2011 I was lead to believe that nitrogen keeps a more constant pressure and does not fluctuate tire pressures in heat or cold as air does. Studies have shown that tire pressure remains more consistent with nitrogen since the oxygen and water vapor in compressed air are absorbed or transmitted at a faster rate through the sidewall than the nitrogen (oxygen 4 times faster, water vapor 10 times faster). Left unchecked, an under-inflated tire has more rolling resistance and consequently lower gas mileage, shorter life span, etc. Best course of action, check your tire pressure regularly when cold, and make sure it's at the recommended level. Another aspect of this, is that since compressed air is 78% nitrogen and 21% oxygen, as the oxygen and water vapor is slowly absorbed into the sidewall and you replace it with more compressed air, the over all percentage of nitrogen will increase. So over time, assuming all the gas in the tire is not purged and then replaced with fresh compressed air, you will begin to approach a pure nitrogen gas. I'll leave it to someone else out there to do the math and determine how long that would take and if it would even occur in your lifetime. 1 Quote Link to comment Share on other sites More sharing options...
Waldo Posted September 8, 2011 Report Share Posted September 8, 2011 (edited) It does not know what the actual pressure is. It just knows there's a difference of several psi between that wheel and the others. If you air all four down to 10 psi, you'll still have no warning. This is 100% false. The system does know what the exact pressure is and by federal regulations it must be able to recognize if all 4 tires drop at exactly the same time. What you describe is only true of the old ABS-based systems like GM used to use, but they cannot be used anymore as they don't meet the federal requirements. To the OP, looks like you're in Florida, which from what I hear has had a pretty cold week this week. I suspect your tires are all low because the temperature has dropped. Putting air back in as you did is the only solution, but don't blame the dealer if it was much hotter when you took delivery. Edited September 8, 2011 by Waldo Quote Link to comment Share on other sites More sharing options...
cal3thousand Posted September 8, 2011 Report Share Posted September 8, 2011 I was lead to believe that nitrogen keeps a more constant pressure and does not fluctuate tire pressures in heat or cold as air does. This is actually one "mis"-fact about Nitrogen. Gasses at atmospheric, or in this case, near atmospheric (2~3 BAR), behave the same, under the ideal gas laws. So a change in temperature of both gasses will cause the same pressure change in both gasses. This is especially true of this relationship since "air" is 75%+ Nitrogen. Quote Link to comment Share on other sites More sharing options...
akirby Posted September 8, 2011 Report Share Posted September 8, 2011 (edited) This is actually one "mis"-fact about Nitrogen. Gasses at atmospheric, or in this case, near atmospheric (2~3 BAR), behave the same, under the ideal gas laws. So a change in temperature of both gasses will cause the same pressure change in both gasses. This is especially true of this relationship since "air" is 75%+ Nitrogen. Upon further research I think it is true that oxygen and nitrogen would behave about the same as far as expansion under heat. However, air contains a lot of water vapor whereas nitrogen contains almost none and I believe that is what makes Nitrogen more stable and causes less variation in pressure between hot and cold conditions. However, the difference is still relatively small and inconsequential to a passenger car or truck. Edited September 8, 2011 by akirby Quote Link to comment Share on other sites More sharing options...
NatG Posted September 8, 2011 Report Share Posted September 8, 2011 Studies have shown that tire pressure remains more consistent with nitrogen since the oxygen and water vapor in compressed air are absorbed or transmitted at a faster rate through the sidewall than the nitrogen (oxygen 4 times faster, water vapor 10 times faster). Left unchecked, an under-inflated tire has more rolling resistance and consequently lower gas mileage, shorter life span, etc. Best course of action, check your tire pressure regularly when cold, and make sure it's at the recommended level. Another aspect of this, is that since compressed air is 78% nitrogen and 21% oxygen, as the oxygen and water vapor is slowly absorbed into the sidewall and you replace it with more compressed air, the over all percentage of nitrogen will increase. So over time, assuming all the gas in the tire is not purged and then replaced with fresh compressed air, you will begin to approach a pure nitrogen gas. I'll leave it to someone else out there to do the math and determine how long that would take and if it would even occur in your lifetime. Interesting Point. So essentially people filling up the tires with Nitrogen are paying a premium for a 20-22% difference, and may never see any benefit. I used to be a supervisor at a store that sold balloons. We would fill wall displays with Nitrogen since it wouldn't leak like compressed air or, more importantly, compressed helium. But the cost was significantly higher and we didn't have 1 quarter of a 4200lbs vehicle on the balloon. Considering all the factors, I don't see the benefit of utilizing nitrogen. Although to be honest, I had never considered it until reading this topic. Quote Link to comment Share on other sites More sharing options...
chanka98 Posted September 9, 2011 Author Report Share Posted September 9, 2011 Waldo.... I guess you can say it's been cooler lately as the high temp is barely hitting 90 now as opposed to 95 when I bought the car 3 weeks ago... :-). I'll monitor the pressure weekly and see how long they stay around 35psi. Just to answer another point made by another member above, I did not use a cheap gauge so I'm pretty confident in my initial readings. Again, thanks to all for the feedback and very interesting commentaries! Quote Link to comment Share on other sites More sharing options...
Dingo Posted September 9, 2011 Report Share Posted September 9, 2011 (edited) This is 100% false. The system does know what the exact pressure is and by federal regulations it must be able to recognize if all 4 tires drop at exactly the same time. What you describe is only true of the old ABS-based systems like GM used to use, but they cannot be used anymore as they don't meet the federal requirements. To the OP, looks like you're in Florida, which from what I hear has had a pretty cold week this week. I suspect your tires are all low because the temperature has dropped. Putting air back in as you did is the only solution, but don't blame the dealer if it was much hotter when you took delivery. Ford used to use the ABS system too, in the Windstar. And apparently, you're partially right. I'm concerned that 2 of my last 3 Fords wouldn't trip a light when I aired them down. Apparently, the sensors know the temperature and pressure of each tire individually, but the receiver doesn't. It only knows if one or more tires hits a threshold that's 25% below whatever pressure the door sticker reads. Just thought I'd clear up my previous statement, which incidentally, was told to me by a Ford engineer. Apparently, he was misinformed. Edited September 9, 2011 by Dingo Quote Link to comment Share on other sites More sharing options...
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