Under inflation is neglect. Over inflation like my Ranger was no accident but could have cause one and that's my whole point! Over inflation is self inflected, lack of knowledge or a defective air guage.

Being crass is the general rule of thumb in this forum! That wasn't a personal attack just a general statement.

If 99% of articles outline how to properly inflate tires, why would anybody ignore that?? I can't believe that everybody including the NHTSA would be wrong! The NHTSA study on under inflated tires was the actual tire air pressure compared to what? Of course, it was the manufactures suggested air pressure and not the MAX LOAD tire pressure marked on the sidewall.

 

My question still remains. If "over inflation" is dangerous and can happen to even the best of us (like Bill), why wouldn't the NTHSA take the steps to put an upper limit on the TPMS requirement? Why not the same warning at 25% over vehicle manufacturer recommended PSI? Then again... that would be 44psi for vehicles with a 35psi recommendation.

This is from the 2008 FEH owners guide under the Tires, Wheels and Loading section:
"Maximum Permissible Inflation Pressure is the tire manufacturer’s
maximum permissible pressure and/or the pressure at which the
maximum load can be carried by the tire."

My interpretation is that while Ford recommends 35psi, they also find it permissible to allow inflation up to 44psi on the stock Conti's. So if you're inflated up to 44psi on the stock tire, you're still within the permissible range set by Ford.

 

Because neglect or under inflation is a bigger problem.

I'm glad that you posted that quote. What part of "maximum load" can't you understand?? That's 44psi at maximum load. Are you carrying maximum load all the time?? It's plain and simple, MAX PSI at MAX LOAD!

My suggested tire pressure by Ford is 30psi. I assume yours is 35psi because a FEH is heavier than a FE.

If you take your GVW minus your curb weight, that'll be your maximum load you can carry and at which point you should have 44psi.

From the Tire Rack:

Disadvantages of Underinflation

An underinflated tire can't maintain its shape and becomes flatter than intended while in contact with the road. If a vehicle's tires are underinflated by only 6 psi it could weaken the tire's internal structure and eventually lead to tire failure. Lower inflation pressures will allow more deflection as the tire rolls. This will build up more internal heat, increase rolling resistance (causing a reduction in fuel economy of up to 5%) and reduce the tire's tread life by as much as 25% while increasing the probability of irregular treadwear. Drivers would also find a noteworthy loss of steering precision and cornering stability. While 6 psi doesn't seem excessively low, it typically represents about 20% of a passenger car tire's recommended pressure.

Disadvantages of Overinflation

An overinflated tire is stiff and unyielding and the size of its footprint in contact with the road is reduced. If a vehicle's tires are overinflated by 6 psi, they could be damaged more easily when encountering potholes or debris in the road, as well as experience irregular tread wear. Higher inflated tires cannot isolate road irregularities as well causing the vehicle to ride harsher and transmit more noise into its interior. However, higher inflation pressures reduce rolling resistance slightly and typically provide a slight improvement in steering response and cornering stability. This is why participants who use street tires in autocrosses, track events and road races run higher than normal inflation pressures

 

Why not address both problems while you're at it? You've already got the sensors and alert system right there...

Me too... see there's an "and/or" in there that indicates to me that Ford is fine with running at max sidewall no matter what the load (as long as it's under the vehicle and tire's maximum load rating).

There's no argument that tire pressure should be raised as load increases.

What I don't agree with you is that tire pressure has to be lowered as load decreases.

There are two max load figures involved. You have GVW (from Ford) and the max load listed on the tire (from Continental).

What happens if the FEH's max GVW is less than the tire's max load (I'm pretty sure it is because no manufacturer would risk the legal ramifications for setting the GVW above the tires/chassis/drivetrain they provided to carry that load)? How come Ford says it's OK to go to max sidewall pressure in the manual when they limit GVW to less than the max tire load limit?

The only logical solution is that Ford is OK with max sidewall pressure at less than max tire load limit as set by the tire's manufacturer. The tire manufacture can't know the vehicle's GVW limit so they have to be OK with max sidewall pressure up to the tire's max load.

 

I think that your confused. That is the tire manufacturers maximum pressure for that tire and they don't build vehicles. I assume that you left out where it tells you to go by the door pillar sticker, correct?? What's the point of the sticker??

Keep an open mind if that's possible and do some Googling on tire pressure. I'm sure you'll find some cautions as I did about over inflating tires. Granted moreso on under inflating though but you still have something to worry about!

 

This is my take and personal experience with the present tires available for my '05 and '09 FEH. I only purchase the highest quality Michelins for my FEH which are the OEM tires on 16" rims. I don't recommend to anyone exceeding the MAX cold sidewall pressure on the tire. That said, I run 50psi and exceed the Maximum by 6psi at 80F. The ride is only noises if I hit other than smooth road surfaces because a hard riding tires will transmit the shock loads to the suspension and reduce the a tire’s ability to withstand road impacts. This is acceptable to me because of the other benefits of 50psi. Over inflating tires does not increase load carrying capacity which I'm not interested in anyway. The tire spring characteristic is very important to the vehicle's ride but so is avoiding as many imperfections in the road as you can. Many of the inperfections are marked with engine oil that's shaken off cars with fluid leaks.

Under inflation is more of a safety concern and causes far more accelerated tire wear problems than over inflation IMO. The suspension is very giving in the '09 FEH but not so giving as my '05 FEH. Still, I've never seen any sort of vehicle bounce like trailers being towed without shocks. If anything, I have far more control of my FEH at 50psi than I have at 35psi.

Mileage was the original reason I went above 44psi and tested 50psi in my FEH. Other benefits like vehicle control, traction, tire wear and less chance of hydroplaning made me convinced it was safer to keep them at 50psi for me. With my temperature variations low in South Florida, I can safely set a cold tire pressure at 80F degrees at 50psi.

"Temperature Effects

Air pressure is affected by temperature. The air under pressure in a tire is no exception. Typically, an inflation pressure can change by 1 psi for every 10 degrees Fahrenheit of temperature change. Higher temperature means increased pressure.

For example, if a tire is inflated to 35 psi on an 80-degree day in July, it could have an inflation pressure of 23 psi on a 20-degree day 6 months later in January. This represents a normal loss of 6 psi over the six months and an additional loss of 6 psi due to the 60-degree temperature change. At 23 psi, this tire is severely under-inflated.

If the rear tire is inflated to 40 psi on a summer morning with a temp of 60 and a high of 90-degrees--tire pressures can reach around 44 psi."

On average, I only have a small swing down to 70F in the morning and a high of 90F during the day. If your setting your cold tire pressure at 35psi on a cold day at 30F and it gets up to 80F during the week your getting a 40psi ride. If you set your tires at 35psi at 80F and it get below freezing in the area your driving, you could have very under inflated tires. Even more if you set your tires below 32psi. The tire manufactures take temperatures under consideration so a cold 44psi maximum is within the safety margins of a cold morning with a hot day like in a desert.

The '09 FEH cannot be loaded as much as the '09 FE V6 yet they come with the same tire and load range. This thread therefore has little to do with the maximum load at 44psi because the FEH GVW will never allow those loads approved by the tire manufacture. All the dangers mentioned in this thread about over inflating to 44psi I haven't seen at 50psi for 4 years of experience. If I saw any of the these dangers I would reduce my tire pressure and warn everyone else on these forums. Most of what is said or quoted in this thread is from people who have no real experience with our FEH or the OEM tires at 44psi or 50psi.

The funny thing about tire stores and car manufactures is their main concern is about liability. As stated, the TPS is for LOW tire pressure not high tire pressure. When I ask a large tire chain store to put 50psi in my tires, the store manager had a list of reasons why I should not run that PSI. While waiting for my tires I didn't know a guy I was talking to was the chain store trainer and was getting my opinion on that stores service. All three of us then discussed the issue and the trainer addmitted the issue was liabilty. When I got home and checked my tires thinking they needed air, they were all at ~52psi and I only requested 50psi.

GaryG

 

GaryG:

Nice post but what do you "actually" do if/when you see a pothole in front of you at 50psi?

Why do you think there is a liabilty issue associated deviating from manufacturer's suggested air pressure?

 

Try to avoid it like everyone else?

 

Road hazards is the key bad point of using MAX or higher air pressure. It can cause tire damage or loss of steering control because of wheel bounce. If you live in the South, you can probably get away with it but not in the North as roads are rough. I can't imagine hitting a pothole at 50psi! Many times you just can't avoid them.

 

Hi Bill

I admit I thought increasing my tires to 50psi would pose all kinds of dangers prior to actually doing it. The liability issue was a big concern then also. I have none of these concerns anymore. There has been no wheel bouncing as you indicate because the normal tire spring is just not that much anyway at 35psi. The suspension handles the rough roads just fine and my steering and handling is much better because the contact patch stays put in those hard turns. In fact, I take hard turns because I now have the traction and better control even in the rain. I would have less traction and wear out my tires faster with 35psi. I've seen the results in both my FEH's. The '05 OEM tires started wearing on the inside even after an alignment. I notice this stopped after increasing the tire pressure to 50psi. The Goodyear manager told me that he sees inside wear on all the FE's and mine was set to spec. I think Ford sets the alignment this way to help prevent rollovers. I think 50psi also helps prevent rollovers also.

As far as liability, I'm not going after Ford, the tire manufacture or the tire shop if my tires fail at 50psi. I don't recommend exceeding the tire manufactures maximum tire pressure for liability reasons only. I'm just stating what works for me in my FEH's. Some people say a few MPG is not worth the dangers or the ride and that's fine with me because I don't buy their tires or gas and I want them to feel safe. Some people are just scared to increase their tire pressure above the door label for all types of reasons. Maybe knowing I'm very pleased with the results with my experiences with 50psi they might try raising the pressure a little and see the results themselfs. Or maybe my experience will just make someone maintain 35psi more often.

I share any and all the techniques I use for safety and great gas mileage but no one should use my experiences if they feel their safety is at risk.

Lifetime '09 FWD FEHL mileage average so far:
http://www.cleanmpg.com/index.php?page=garage&displayunits=MPG(US)&viewcar =2612

GaryG