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Tires and Tire Pressure


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57 replies to this topic

#41 OFFLINE   GaryG

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Posted 30 August 2013 - 04:31 PM

WhhhhhhhhhhhhhhhhhhhhhhhhaaaaaaaaaaaaaaaaaaaaaaaaT??

 

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

 

I'm sure I said 58psi, and I keep 58psi in them. All of my vehicles have over 50psi including my Focus, Explorer, and the Energi. Read this tread and you'll know why.

 

Gary


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#42 OFFLINE   drdiesel1

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Posted 30 August 2013 - 09:54 PM

I'm sure I said 58psi, and I keep 58psi in them. All of my vehicles have over 50psi including my Focus, Explorer, and the Energi. Read this tread and you'll know why.

 

Gary

I know why, I just didn't think you were setting them that high.  Maybe I'll have a test run with it :wink:



#43 OFFLINE   ITFlyer

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Posted 04 September 2013 - 07:42 AM

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. 

 

You're correct, and I did mention that I was simplifying the calculations. I did not take into account anything like sidewall or carcass rigidity, which also increase contact patch size.



#44 OFFLINE   Gyrobob

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Posted 01 October 2013 - 02:06 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.

It also means less propensity for hydroplaning.



#45 OFFLINE   Gyrobob

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Posted 01 October 2013 - 02:11 PM

Don, on 28 Aug 2013 - 8:43 PM, said:snapback.png

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

I disagree with Gary.  Don is just a plain dumb ass, not a complete dumb ass.



#46 OFFLINE   GaryG

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Posted 01 October 2013 - 02:26 PM

 

Don, on 28 Aug 2013 - 8:43 PM, said:snapback.png

I disagree with Gary.  Don is just a plain dumb ass, not a complete dumb ass.

 

 

Lets not get into the details we both agree about.

 

Gary



#47 OFFLINE   Don

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Posted 01 October 2013 - 02:27 PM

Gyro- I see your loneliness has you begging for attention again. I found, on another forum, you list one of your favorite pastimes is being annoying. Good job on digging up a comment from over a month ago to support your pastime. :wink:

          Truly refreshing to see that you avoided whining about how the gas engine does not charge the battery in this latest post, you seem to be making progress.

 

Gary- How's the suppercharging going? Just to be clear is that something that you do during dinner? :hysterical3:  Have you made any more discoveries on how to waste a bunch of time, money and energy for no net benefit? :hysterical3: How 'bout that tire pressure conspiracy 

           got anymore kooky ideas on how the car manufactures are creating specs that would hurt sales of cars but increase sales of tires? :hysterical3:

 

From the Versys site, Gyrobobs interests: Gyrocopters, digital photography, computers, guitars, guns, annoying liberals
 


Edited by Don, 01 October 2013 - 03:12 PM.


#48 OFFLINE   GaryG

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Posted 01 October 2013 - 05:03 PM

Gary- How's the suppercharging going? Just to be clear is that something that you do during dinner? :hysterical3:  Have you made any more discoveries on how to waste a bunch of time, money and energy for no net benefit? :hysterical3: How 'bout that tire pressure conspiracy 

           got anymore kooky ideas on how the car manufactures are creating specs that would hurt sales of cars but increase sales of tires? :hysterical3:

 

 

Supercharging is going extremely well. I've modified it to work very quickly on a standard fully charged battery, just before my trips. When I don't have long trips, and don't have a lot of time and don't supercharge, the drive reminds me of how fast the battery discharges without supercharging.

 

Today, I replaced the two front tires on my Explorer at 51,044 miles. I have never rotated or removed them from the front since new. The Service Dept. at Lake Park Mullinax Ford couldn't believe how my tires were wearing with 55psi, and I bet many of them are going to follow my advise with their tires. The back tires should go another 40,000 miles easy before needing to be replaced. There was a note on my work order to put max sidewall at 51psi in my tires, and my SA agreed and put the note there. The people know me at my dealership and have seen Fox News 29 here play repeat video of me hypermiling my FEH every time gas prices shoot up around here. The reporters that filmed me were fascinated by my results, and did a great story on me hypermiling. Good Morning America did a great story also in 2007, when I won 1st place at the 2007 MPG Challenge at Hybridfest in Madison WI. No one has come close to my results to this day.

 

You can follow as a dumb ass or lead.

 

Gary


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#49 OFFLINE   Gyrobob

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Posted 01 October 2013 - 07:18 PM

Gyro- I see your loneliness has you begging for attention again. I found, on another forum, you list one of your favorite pastimes is being annoying. Good job on digging up a comment from over a month ago to support your pastime. :wink:

          Truly refreshing to see that you avoided whining about how the gas engine does not charge the battery in this latest post, you seem to be making progress.

 

Gary- How's the suppercharging going? Just to be clear is that something that you do during dinner? :hysterical3:  Have you made any more discoveries on how to waste a bunch of time, money and energy for no net benefit? :hysterical3: How 'bout that tire pressure conspiracy 

           got anymore kooky ideas on how the car manufactures are creating specs that would hurt sales of cars but increase sales of tires? :hysterical3:

 

From the Versys site, Gyrobobs interests: Gyrocopters, digital photography, computers, guitars, guns, annoying liberals
 

don, don, don,.... You are once again dumbassness personified. I admire your having so much free time you can scour the internet for info on me.  I guess I should be flattered, but since no one cares about my Versys profile, you'd be a lot more interesting and worthwhile here if you'd spend less time on invective, and more on the subjects.  Let's use the bandwidth for C-Max Energi discussions, shall we?  Let's see if you can make a comment here that actually adds to the discussion.



#50 OFFLINE   Gyrobob

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Posted 01 October 2013 - 07:19 PM

Lets not get into the details we both agree about.

 

Gary

okay



#51 OFFLINE   Don

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Posted 01 October 2013 - 08:11 PM

Supercharging is going extremely well. I've modified it to work very quickly on a standard fully charged battery, just before my trips. When I don't have long trips, and don't have a lot of time and don't supercharge, the drive reminds me of how fast the battery discharges without supercharging.

 

Today, I replaced the two front tires on my Explorer at 51,044 miles. I have never rotated or removed them from the front since new. The Service Dept. at Lake Park Mullinax Ford couldn't believe how my tires were wearing with 55psi, and I bet many of them are going to follow my advise with their tires. The back tires should go another 40,000 miles easy before needing to be replaced. There was a note on my work order to put max sidewall at 51psi in my tires, and my SA agreed and put the note there. The people know me at my dealership and have seen Fox News 29 here play repeat video of me hypermiling my FEH every time gas prices shoot up around here. The reporters that filmed me were fascinated by my results, and did a great story on me hypermiling. Good Morning America did a great story also in 2007, when I won 1st place at the 2007 MPG Challenge at Hybridfest in Madison WI. No one has come close to my results to this day.

 

You can follow as a dumb ass or lead.

 

Gary

That's good to hear. Exactly how many Watts from the wall does it take to get how many more miles out of the battery?

Also good to hear that your dealer is doing what you want them to do. Of course you do drive slow and use drafting etc. and you have not driven the car in the same way with recommended pressure so you really have no comparative data to make any conclusions with do you :wink: .



#52 OFFLINE   Don

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Posted 01 October 2013 - 08:35 PM

don, don, don,.... You are once again dumbassness personified. I admire your having so much free time you can scour the internet for info on me.  I guess I should be flattered, but since no one cares about my Versys profile, you'd be a lot more interesting and worthwhile here if you'd spend less time on invective, and more on the subjects.  Let's use the bandwidth for C-Max Energi discussions, shall we?  Let's see if you can make a comment here that actually adds to the discussion.

Gyro- I think you have been sitting in that rattletrap of vibration too long and am guessing your brain has vibrated loose and turned over a few times. You seem to like being insulted since you keep coming back for more, oh wait you actually like being annoying so I guess you like being annoyed also. Your Welcome :smile2: .



#53 OFFLINE   PJFW8

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Posted 02 October 2013 - 06:24 AM

Gyro- I think you have been sitting in that rattletrap of vibration too long and am guessing your brain has vibrated loose and turned over a few times. You seem to like being insulted since you keep coming back for more, oh wait you actually like being annoying so I guess you like being annoyed also. Your Welcome :smile2: .

Please! Let's keep the forum civil. Everyone C-Max Energy owner on this forum is a little off the beam...me included. Who else would buy a first year plug in!? I love my car, but Gyrobob is not the only "interesting" member. Keep it positive!
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#54 OFFLINE   Gyrobob

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Posted 02 October 2013 - 12:28 PM

Every forum has its trolls that seem to focus on attacking those trying to discuss the issues.  They are easily dismissed/ignored so the rest of us can work the issues and try to learn cool stuff about this really cool car.
I truly value the folks that experiment, learn what works and doesn't work, then let us know of the results.  Did you ever notice, though, how those folks usually have arrows in their backs?

Thanks large, Gary, for all the info about "supercharging" the battery.  I'll try it next time the car gets used.

 


Edited by Gyrobob, 02 October 2013 - 12:28 PM.


#55 OFFLINE   Don

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Posted 03 October 2013 - 06:14 AM

Please! Let's keep the forum civil. Everyone C-Max Energy owner on this forum is a little off the beam...me included. Who else would buy a first year plug in!? I love my car, but Gyrobob is not the only "interesting" member. Keep it positive!

Robert is looking for moderators, perhaps you would like to volunteer.



#56 OFFLINE   Don

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Posted 03 October 2013 - 10:19 AM

Every forum has its trolls that seem to focus on attacking those trying to discuss the issues.  They are easily dismissed/ignored so the rest of us can work the issues and try to learn cool stuff about this really cool car.
I truly value the folks that experiment, learn what works and doesn't work, then let us know of the results.  Did you ever notice, though, how those folks usually have arrows in their backs?

Thanks large, Gary, for all the info about "supercharging" the battery.  I'll try it next time the car gets used.

 

That is SOP when folks make grandiose claims and do not have a valid data set to support them. None of the claims made have any controlled experiments, with proper isolation of variables, to give reason for validity. If one wishes to publish claims of "discovery" they should be prepared to stand up to critic and criticism and support their claims with proper data.

 

There is real concern for danger when I hear someone is running equipment in out of spec conditions especially when they encourage others to try.

 

Running tire pressure, above those that the car manufacture considers safe, is bad enough but running pressure higher than the sidewall rating of the tire is......

 

Charging the HVB in a method that is not documented or tested by the manufacture, and encouraging others to do so, without all the proper testing is just plain arrogant. It is entirely possible that there is long term negative impact to battery life and or other components by keeping the car plugged in and in the run position.

 

I can't always stop lemmings from following the leader over the cliff but I will continue to try.


Edited by Don, 03 October 2013 - 10:50 AM.


#57 OFFLINE   Kenowen

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Posted 15 December 2015 - 03:51 PM

I had a VW Dasher station wagon that had Goodyear Arrivas on it. Door said 28 but I found that 32 gave the best handling and no degradation in traction including stopping. A quick oil change place changed my tire pressure to 35 psi and when I had to do a panic stop I slid all four tires on dry pavement and hit the car in front of me. Luckily it had good bumpers and sustained no damage. I thought no way. I checked and they had raised the pressure to the max tire at 35 psi. I dropped it back to 32 and it performed like I thought. Had it been at 32 psi there is no doubt that I would have stopped. The next time I went there I told them I was there for an oil change and to leave my tires alone. They did not and I refused to pay until they returned my tires to the 32 psi. I stopped recommending them because they tampered with my tires. That was a lighter car than the C-max.

 

Without naming the tire that you are adjusting the pressure higher I will not take any recommendations here. I will research myself and when I find the point of the braking distances and turning traction degrade I will not go any higher.  Under no circumstances will I exceed the tire maximum pressure.

 

Nitrogen filled tires start with one atmosphere of 20% oxygen and then you pump to almost 3 so technically it is now around 6% oxygen and not 100% nitrogen.



#58 OFFLINE   ptjones

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Posted 15 December 2015 - 05:35 PM

That's an interesting note on the Nitrogen, from Wikipedia: By volume, dry air contains 78.09% nitrogen, 20.95% oxygen,[1] 0.93% argon, 0.039% carbon dioxide, and small amounts of other gases. Air also contains a variable amount of water vapor, on average around 1% at sea level, and 0.4% over the entire atmosphere.  It's the water vapor in the tires that changes tire pressure mostly.  I guess Race Car Drivers feel every little bit helps, sounds like a sales gimmick. LOL   Just a side note you would think Plants are suffocating with only .039% of 1% of the atmosphere to grow on. IMO.  As far as tire pressure goes I run 50 psi and I got 64K mi. on my first set and 52k mi. so far on my second set which I expect to get 70K mi.  Both sets i'm getting even wear which tells me that it is a good pressure to use.  Add to that last month my wife and I almost hit a deer but I slammed on the brakes and the CMAX stopped so fast that everything lose in the car came flying to the front and we slammed into our shoulder belts.  Running 50 psi didn't hurt our stopping ability at all and our shoulders were sore too. I would imagine the deer was lucky too. LOL  With 116K mi. I have tested my CMAX a lot. IMO  :smile2: 

 

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