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Tires and Tire Pressure


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57 replies to this topic

#21 OFFLINE   Mr. Fusion

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Posted 19 May 2013 - 07:17 PM

I N glide in my FEH all the time. I just haven't done it yet in the Energi, probably because of my commute. I run EV later on the highway and I don't like pulsing and gliding on the highway.

The A/C is great on the Energi, especially compared to my 09 Escape Hybrid, especially since I get 28 miles on a charge (as high as 30). So with A/C, I still get over 21 miles.

Gary, what miles are you showing on a full charge? I do think the Fusion is more aerodynamic than the C-Max, which probably helps the plugin miles.

I will go from 45 PSI to 50 and see if I notice any difference.







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#22 OFFLINE   GaryG

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Posted 20 May 2013 - 04:48 PM

My wife drove the Energi with a full charge for first time since I've had it Sunday, so I don't know how far I can go on a full charge yet. I did a few coasting test today, and found little difference in dropping the tire pressure 4psi. There at 58psi now and I'll do more test with lower pressure soon. I conduct the test by getting up to 30mph in EV at my starting line and glide in "N" till I come to a stop on this back road west of town. I paint a line on the pavement at the stopping point for comparison. If the distance stays near the higher tire pressure, I continue to drop psi until the distance decreases. No need in having to much tire pressure with little benefits.

 

I'm already using "N" and "L" in my Energy and I'm running the A/C constantly because it takes no gas in EV anyway and it's hot here now. Folks must realize not using E10 in their tanks for thousands of miles in EV, will cause the gas to go bad in storage. I'm having that problem in my '09 FEH with just an 1/8 of a tank left. I need to burn that off and fill with fresh gas for the new buyer.  

 

Gary



#23 OFFLINE   mikeb

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Posted 21 May 2013 - 04:01 AM

The Energi has a 'fuel freshness mode' where it burns some gas if you haven't been using any, but the rate is very slow. Check the owners manual for details. I do enough weekend trips that it's never going to happen for me, but someone with a nearly pure EV drive pattern will eventually see it happen.



#24 OFFLINE   Mr. Green Jeans

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Posted 22 May 2013 - 06:29 AM

In the past, I have always increased air pressure 1 to 3 pounds over the amount suggested by the auto maker, but always less than the tire manufacturer maximum.  After I got home with my new energi, I noticed that the valve caps were green.  My son says that the tires are nitrogen filled.  Anyone had any experience with this?  Thoughts?

 

I googled and found this....http://www.edmunds.c...h-nitrogen.html

 



#25 OFFLINE   ArizonaEnergi

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Posted 22 May 2013 - 06:38 AM

Nitrogen is a marketing scheme and has little value in an automotive tire.

 

I'm running mine at 40 psi, which is "good enough" and helps insures I'm not under-inflated by a poorly calibrated gauge.  I did note that mine had lost NO pressure since checking and inflating before my last interstate trip in March.  I like that.



#26 OFFLINE   Mr. Green Jeans

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Posted 22 May 2013 - 07:03 AM

There was no charge for the nitrogen filled tires, but I was surprised by the fact that they had them.  I will air them up myself at home.



#27 OFFLINE   jeffegg2

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Posted 22 May 2013 - 11:00 AM

In the past, I have always increased air pressure 1 to 3 pounds over the amount suggested by the auto maker, but always less than the tire manufacturer maximum.  After I got home with my new energi, I noticed that the valve caps were green.  My son says that the tires are nitrogen filled.  Anyone had any experience with this?  Thoughts?
 
I googled and found this....http://www.edmunds.c...h-nitrogen.html


Oh no! I believe the safety placard says "Air" pressure! You are not in compliance! Warning Will Robertson!

#28 OFFLINE   Mr. Green Jeans

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Posted 22 May 2013 - 12:36 PM

Oh no! I believe the safety placard says "Air" pressure! You are not in compliance! Warning Will Robertson!

 

 

Kaboooooom?



#29 OFFLINE   paladinfello

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Posted 22 May 2013 - 02:02 PM

In the past, I have always increased air pressure 1 to 3 pounds over the amount suggested by the auto maker, but always less than the tire manufacturer maximum.  After I got home with my new energi, I noticed that the valve caps were green.  My son says that the tires are nitrogen filled.  Anyone had any experience with this?  Thoughts?

 

I googled and found this....http://www.edmunds.c...h-nitrogen.html

 

I've purchased my tires at Costco in the past and they use the green caps for nitrogen filling.  When I've needed to top-off, I've pulled up to the tire center and they've handed me the hose to fill up myself.

 

 

Oh no! I believe the safety placard says "Air" pressure! You are not in compliance! Warning Will Robertson!

Technically air is 80% nitrogen 20% oxygen sooo..... (sorry couldn't resisit)



#30 OFFLINE   GaryG

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Posted 23 May 2013 - 08:24 AM

I N glide in my FEH all the time. I just haven't done it yet in the Energi, probably because of my commute. I run EV later on the highway and I don't like pulsing and gliding on the highway.

The A/C is great on the Energi, especially compared to my 09 Escape Hybrid, especially since I get 28 miles on a charge (as high as 30). So with A/C, I still get over 21 miles.

Gary, what miles are you showing on a full charge? I do think the Fusion is more aerodynamic than the C-Max, which probably helps the plugin miles.

I will go from 45 PSI to 50 and see if I notice any difference.

 

Now I know what your question was gettig at. I've been noticing when I get a partial charge that the battery miles showed 19 miles when I was no where near fully charged. This morning after a full charge, I noticed 25 miles on the battery indicator. That is 25 miles with the A/C because I keep it set On 72F all the time. Now this is getting very interesting! It may be possible to squeeze 40 miles out of the battery without the A/C once I really turn on my hypermiling tricks and skills.

 

This happen when I got my '05 FEH new. Ford said it would go up to 25mph in EV. The day I got the FEH, I was doing over 33mph in EV and latter on I could set the cruise at 35mph here on flat roads.

 

I'm thinking we need a thread for people to post and show pictures of record miles on a fully charged battery. I can see now that I own the C-Max Energi, that someone's lifetime MPG could be in the thousands and even ten thousands of miles if they just use EV miles. Great Car!

 

Gary


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#31 OFFLINE   Mr. Fusion

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Posted 23 May 2013 - 02:48 PM

I'm lurking on the C-Max site because of more owner activity than the Fusion Energi site, but I did start a "Big battery miles" thread over there.

http://www.fordfusio...en-on-the-dash/

I got a 31mile reading (Consistently getting 28) and all I do is drive it normally with the exception of 45 PSI in the tires. No neutral gliding. I'm not convinced pulsing and neutral gliding in EV will help, so maybe you can prove that wrong. The best part of this car is that it's a no compromise hybrid. Just drive it and get great results.

#32 OFFLINE   drdiesel1

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Posted 21 August 2013 - 01:49 PM

I currently run 42 PSI in my Michellin 225/50/17's and I'm looking to move up to 45 with these big tires.

I've ran 42 and 44 in my 08 Prius and in my 2013 Prius C. I have about 7 hybrid years of running higher tire pressures.

I've never had a flat, my tires have never suffered from premature wearout and my MPG numbers have always been in the 50+ range without any special driving techniques. The maximum pressure on the tire is a rating for maximum load. I always stay under that number and make sure my tires wear evenly. Running 51 in a tire rated for 51 shouldn't cause any issue's.

They have at least a 10% margin on that number.

 

I find the mid 40's work best for my tastes and driving habits. YMMV :victory:

There is no right or wrong, just personal preference. I prefer better MPG's over the recommended rating on the door jamb. 

Try it before you knock it :shift:


Edited by drdiesel1, 30 August 2013 - 06:29 AM.


#33 OFFLINE   ITFlyer

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Posted 28 August 2013 - 12:26 PM

Something to think about when considering running higher-than-normal tire pressures:

 

The size of the contact patch is directly related to both the load on the tire, and the air pressure in the tire.

 

Take the load (in pounds) applied to the tire, divide it by the pressure (in PSI) inside the tire, and you will arrive with the size of the contact patch (the amount of rubber touching the road), in square inches.

 

If all four tires have equal pressure, you can average it out. Say the car, with fuel and passengers, weighs 3500 lbs. Your four tires have 44 psi in them. That's 79.5 square inches total area of contact patch. Distributed among four tires, that's 19.8 square inches of contact patch per tire. Obviously it won't be that in reality, as the car is not balanced perfectly, and there is different load on each tire, but for argument's sake, we'll assume the load on each tire is the same.

 

Now we pump up the tires to 51 psi. That's 68.6 square inches of contact patch in total, which is an almost 14% reduction in the overall contact patch size. That 14% reduction in contact area means less rolling resistance - but it also means a 14% reduction in the braking and cornering ability of your car.

 

This is why it helps to deflate your tires somewhat if you are stuck in the snow. Less air pressure = larger area in contact with the snow = more traction.



#34 OFFLINE   GaryG

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Posted 28 August 2013 - 03:23 PM

I'm about to change the front tires on my '11 Explorer. It came new with 20" Hankook tires and have handled like a dream with 55psi in them. Very little road noise and the higher pressure saved my tires and rims when I hit a high curb and jumped completely over it with all four tires. I predicted tire wear at 20,000 miles to go to 50,000 miles on the front, and 90,000 miles on the rear tires. I have a little over 50,000 miles on the two front tires that never have been rotated. So, I've not spent one dime on repairs, rotating or balancing. They wore evenly across the entire contact patch, so I know the alignment is not that bad. It doesn't mean the alignment is perfect, because high tire pressure also corrects tire wear alignment problems. I know this from experience with my '05 Ford Escape Hybrid (FEH). Ford purposely aligns the wheels on all the older Escapes so the inside of the tires wear out first to prevent rollovers in that SUV. This has been confirmed by many Escape owners and alignment shops. In fact, many Escape owners had their Escapes alignment modified to prevent this problem. At about that time when I seen my tires wearing on the inside, I took my Escape back to Goodyear who aligned my Escape at my first rotation and the manager check the alignment again and confirmed all Escapes have that problem at that time. I had finely been convinced by some top hypermilers to put at least 50 psi in my tires for the first time. This was when I discovered not only the increase in MPG, but my alignment problem stopped wearing the inside of my tires on the Escape.

 

I no longer rotate any of my tires and keep the tire pressure above max sidewall on all of my vehicles. Everything has been positive as far as tire wear, handling, MPG, hydroplaning and traction. Everything the hypermilers were telling me back then are true. Even the  top training officer of the San Jose Police Dept teaches this in their driving course.

 

It's going to cost me $600 to replace the two front Hankook tires after 50,000 miles. That beats the hell out of leaving the tires at the recommended Ford pressure and changing 4 tires at 40,000 miles and risking the safety of family and friends.

 

Gary



#35 OFFLINE   dr61

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Posted 28 August 2013 - 04:10 PM

Actually your calculation is way high because tires are not balloons.  The relationship (air pressure vs contact patch size) is not linear for a modern radial tire because it has a very strong structure.  There is a much smaller change in contact patch in the working range of pressures for a modern tire than your calculation suggests.  The air pressure increase also increases stability and reduces distortion of the contact patch, which may, up to a point, increase cornering ability, and increase transient response especially.  These changes are small across large changes in pressure. 

 

Now we pump up the tires to 51 psi. That's 68.6 square inches of contact patch in total, which is an almost 14% reduction in the overall contact patch size. That 14% reduction in contact area means less rolling resistance - but it also means a 14% reduction in the braking and cornering ability of your car.



#36 OFFLINE   Don

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Posted 28 August 2013 - 04:43 PM

Bottom line is that safety is compromised when running at other than the car manufactures' recommended pressure. The recommended pressures are determined by running many "controlled" tests on "controlled" track conditions containing the many common hazards and weather conditions found on our roadways. The folklore of people observing "better" results is mostly folklore since they have not done any "controlled" testing or plotted any curves to make a convincing case. Car manufacturers have thousands of hours of combined testing experience to determine optimum operating parameters and are all held to meet SAE, DOT, etc. requirements for safety.

 

In our modern engineering world all the parameters are subject to DOE analysis and optimized in a controlled and scientific way. Those making arrogant claims that the manufactures are either involved in conspiracy to sell more tires or that they simply don't know what they are doing are just being arrogant and foolish.

 

The recommended tire pressure is a huge issue from a liability point of view. If a manufacture, I.E. Ford, made a higher pressure recommendation but it is later determined that a death or injury could have been avoided if the pressure recommendation was a bit lower, to give more controlled handling or shorter stopping distance, Ford would have their hands held to the fire (this is the primary reason the recommended pressure is what it is).


Edited by Don, 28 August 2013 - 04:51 PM.


#37 OFFLINE   GaryG

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Posted 28 August 2013 - 07:10 PM

Bottom line is that safety is compromised when running at other than the car manufactures' recommended pressure. The recommended pressures are determined by running many "controlled" tests on "controlled" track conditions containing the many common hazards and weather conditions found on our roadways. The folklore of people observing "better" results is mostly folklore since they have not done any "controlled" testing or plotted any curves to make a convincing case. Car manufacturers have thousands of hours of combined testing experience to determine optimum operating parameters and are all held to meet SAE, DOT, etc. requirements for safety.

 

In our modern engineering world all the parameters are subject to DOE analysis and optimized in a controlled and scientific way. Those making arrogant claims that the manufactures are either involved in conspiracy to sell more tires or that they simply don't know what they are doing are just being arrogant and foolish.

 

The recommended tire pressure is a huge issue from a liability point of view. If a manufacture, I.E. Ford, made a higher pressure recommendation but it is later determined that a death or injury could have been avoided if the pressure recommendation was a bit lower, to give more controlled handling or shorter stopping distance, Ford would have their hands held to the fire (this is the primary reason the recommended pressure is what it is).

 

What a complete dumb ass.

 

Gary



#38 OFFLINE   pb5927317

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Posted 30 August 2013 - 05:28 AM

I'd like to share what I've experienced after changing my tire beliefs 8 years ago. Since that time, I've seen amazing  improvements in handling, traction, hydroplaneing, tire wear, tire weight and MPG. The San Jose Police Department Training Officer has confirmed most of hypermiler's recommendations for tire pressure. At first, I was reluctant about increasing tire pressurers for all the myths I've heard during my lifetime about high tire pressure. I thought it would cause the center of the tire to wearout before the outer edges. This may have been true before steelbelted tires came out, but it is no longer a problem today.

 

The vehicle handles better because the tires don't ride on the sidewalls in a turn. I thought traction would be reduced because the tires were harder. It turns out with steelbelted tires, the tire patch remains flat, so the tread contact with the road is the best. I've found that it's the wear that reduces traction as the tire tread wears down. For instance, my front tires on my '11 Explorer are getting near the life of the tread, and I'm noticing some increases in slippage under hard exceleration on wet pavement and even a little on dry pavement. Because my front tires wear flat accross the tread, traction is still good in hard turns on wet pavement.

 

Hydroplaneing has improved because the tread is doing what it was designed to do, push the water away from the tread. Lower tire pressure increases the area of the tire patch like a larger ski on the water.

 

Tire wear is most important to me because of cost, handling over the life of the tire for safety, traction, and tire weight. If you can wear the tread evenly across the tire, weight decreases which decreases roll resistance. I've experimented with lighter factory rims and the same worn factory LRR tire vs a heavier factory (Limited) rim with new factory LRR tires. The difference with the lighter setup can be as much as 3 - 5 tank MPG.

 

Look at having higher tire pressure as the key of hypermiling. It all starts there because higher tire pressure increases the glide distance in any gear. It allows you to maintain your speed from dropping faster compared with lower tire pressure. I think Ford increased the recommented tire pressure from 35psi to 38psi on the Michelin Energy that comes with the C-Max. The Max sidewall is 51psi, so I'll most likely run 55psi on my new C-Max Energi. 

 

Gary 

Gary I agree with my Mercury Mariner Hybrid, inflated them 5lbs over and went 120k miles on my first set of tires.  I am at 42lbs on my Energi, I will probably go to 48 this weekend.



#39 OFFLINE   GaryG

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Posted 30 August 2013 - 03:04 PM

Gary I agree with my Mercury Mariner Hybrid, inflated them 5lbs over and went 120k miles on my first set of tires.  I am at 42lbs on my Energi, I will probably go to 48 this weekend.

 

I posted on cleanmpg.com about this and a poster said the Michelin Energy's really need higher pressure for everything. I have mine at 58psi and they ride excellent.

 

Gary



#40 OFFLINE   drdiesel1

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Posted 30 August 2013 - 04:13 PM

I posted on cleanmpg.com about this and a poster said the Michelin Energy's really need higher pressure for everything.

I have mine at 58psi and they ride excellent.

 

Gary

WhhhhhhhhhhhhhhhhhhhhhhhhaaaaaaaaaaaaaaaaaaaaaaaaT??

 

Are you sure you don't mean 48 ???  :hysterical3: 51 is the MAX at MAx load 


Edited by drdiesel1, 30 August 2013 - 04:15 PM.









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