At 105 mph in 6th, I was using gas to defeat down hill compression slowing.
I think it was 3500.
I would not mind going 105 in NEUTRAL.
What would be the problem? I’m not counting on compression.
(The only thing I was counting on was the level then upgrade to slow the vehicle.)
But unless I had sufficent engine RPM, much greater than idle RPM, I’d be cooking and damaging the transmission.
“I would not mind going 105 in NEUTRAL.”
If you really meant this (rather than attempting to make a joke), then you are truly a hazard on the road, specialized training or not.
No, you CAN’T clearly see the road surface at 105 m.p.h. Slowing down for a questionable or unknown road surface? Are you kidding? You’ve just described ANY road surface. Ever hear of a tire tread, car part, rock, tree limb, pothole?
It’s impossible to react quickly enough to those at the speed you’re talking, unless you’re Superman. If that’s the case, you’d be better off flying.
rockstar–It is becoming ever more obvious that Mr. Gift is either just bragging about driving this top-heavy behemoth as unsafe speeds, or that he is trying to rationalize his bone-headed behavior, or that he just doesn’t get it.
Whatever the case, it is also becoming more and more obvious that this guy is a hazard on the road.
Yes, I would go 105 in Neutral if the engine revs were sufficient to keep the transmission fluid flowing enough.
Why not?
To try to answer Robert’s question from post number 80. While less flexing of the tire and causing less heat may be desirable, the loss of traction due to the overinflation is a bad result to have to deal with. Remember that the speed rating of the tire exceeds the maximum possible speed of the vehicle. Therefore, it is not necessary to overinflate the tire.
Try to remember that overinflation is not desirable and that it is actually overinflation without the load to go with it. The load is what dictates the necessity of higher tire pressure,
Usually, it has been found that if you push every factor to its rated maximum capacity the results will be catastrophic a lot sooner than when you operate the equipment toward the middle range of its capacity.
Operating at maximum is like designing everything to minimum standards. Disasters are much more likely to happen.
Therefore it is reasonable to back it down a bit. I think that you have and will give your speed some careful consideration.
I also hope that in reality, people are not going as far as you seem to be to justify whatever they feel like doing. I faithfully believe that much of what you are asking and telling is rhetorical and an honest search for answers. Much knowledge is found by asking the most extreme questions.
It causes premature wear on the transmission. Not to mention the thought of seeing a huge truck barreling down the highway at 105 in neutral (sacrificing control of the car) would be terrifying at best. Imagine if someone can’t merge out in time. They’d be toast.
Dodgevan,
I hope you understand that I am trying to correct a misconception.
The speed capability of a tire is indeed a function of the inflation pressure. It is recommended that the pressure be increased for higher operating speeds - and I think 105 mph qualifies.
As you said, pushing every factor to its maximum could result in catastrophy, so while it might not be necessary to overinflate, it certainly is desireable.
I’m referring to an Expedition, not a huge loaded truck.
If the engine RPM is enough that sufficient fluid is flowing, how does it wear the transmission?
Engine compression through an automatic transmission does not add that much retard. The brakes would control the vehicle.
There were no on ramps nor other vehicles. Otherwise I would not have gone that fast there.
What’s mind-boggling is that so many people on this thread seem to know better than the person who was there just what is safe.
Given that he has said he was addressing an emergency, knew his tires were adequately inflated, had lights going, was not in traffic and his vehicle was handling smoothly, his speed seems appropriate to me. 105 in those conditions in an Expedition is not reckless or particularly more dangerous than the same speed in a sedan. My 1999 handled it easily, on the flats. It wouldn’t be safe on curves of any size or without clear visibility for hundreds of yards ahead, or on any road with oncoming or crossing traffic.
Robert, regarding optimum speed for best gas mileage:
If you have the gas and the time, and if your Exp. is equipped with speed control and instantaneous gas mileage computer, you can find it out yourself by driving the same stretch of non-busy, straight-and-level highway over and over at different speeds.
The optimum speed is probably somewhere between 45 and 65 mph (maybe below 45 mph, but I assume you were talking about highway speeds), although theoretically it should be better at slower rather than faster speeds. There is also probably little meaningful difference in gas mileage at any speed within that range. Gas mileage falls off sharply over 75 mph.
As a test, I once drove my 1999 V8 Expedition to the Grand Canyon and back (150 miles round trip) with four people on board. According to the on-board computer, which is pretty accurate, I averaged just under 20 mpg while driving at the posted speed limits, which were in the 45 to 65 mph range, winter temperatures, dry surfaces.
My experience is that mileage is much more affected by slowing, accelerating, stopping and starting than it is by driving speed, especially in a heavy vehicle like the Expedition.
I should have added:
Your best gas mileage should be obtained at the slowest speed you can maintain above the speed where your transmission shifts into its highest gear. With many vehicles, that is at 40 mph. Whatever that speed is, driving slower than that will usually hurt your mileage because your transmission will frequently be down-shifting to maintain speed as you come to inclines or hills to climb.
If the Max rated pressure is 44 psi, then 44 psi is not “overinflation.”
Thanks.
That is excellent gas mileage for such a vehicle with four occupants!
The manual is not here. I’ll have to find out if it can indicate fuel/mileage.
I look ahead and, when possible, coast to red signals and stopped traffic.
Often I need not apply brakes - the vehicles begin moving as I get to them.
I also accelerate gently.
Going up hills, I try to not increase speed. I try to attain a reasonable speed and then keep the throttle at the same level up the hill.
Sometimes slowly advancing throttle to maintain the speed.
Wish I could get rid of the light bar.
It is not overinflation for the tire.
However, given the vagaries of vehicle chassis design, handling, and weight distribution, it could definitely be overinflated for some of the many types of vehicles that take the same size tire.
That is why one should always adhere as closely as possible to the vehicle manufacturer’s tire inflation recommendations, in order to not wind up with bizarre, dangerous handling. As just one example, if you owned an early '60s Corvair and decided to inflate all 4 tires to the maximum pressure listed on the tire sidewall, you probably would not have survived the first curve on a rainy day.
For improved handling and better tread life, I like to run my tires with about 3 psi over the vehicle mfr’s recommendation, making sure to preserve the specified front/rear bias in inflation pressure. If I was to inflate those tires according to the guidelines on the tire sidewall, the tires would be grossly overinflated, and the car’s handling–particularly on slick surfaces–would suffer
The vehicle placcard recommends 35 front and rear.
Are they doing that to impress with a smootheride
-at the owner’s expense of poorer fuel mileage?
I have never counted on handling - I don’t even knowhat it is.
I go more gently around curves and turns.
But the better handling might improve successful outcome in an emergency maneuver.
Would 40 psi be OK?
I definitely recall that some of us explained this concept to you some time ago in another of the threads that you created. At that time, you were told that one size tire will fit a wide variety of vehicles, with a wide variety of handling characteristics, and that this is why one should adhere as closely as possible to the vehicle manufacturer’s inflation guidelines.
After reading about your previous defense of driving at 105 mph in this behemoth that is unsuited for those speeds, it is REALLY frightening to read your latest admission–“I have never counted on handling - I don’t even knowhat (sic) it is.” You continue to claim that you are operating this vehicle in complete safety at triple digit speeds, but you clearly have no clue regarding some of the most basic principles of safe driving.
“Would 40 psi be OK?” That depends on what Ford’s inflation guidelines for this vehicle might be. If they recommend…let’s say…30 psi, then, NO, 40 psi is not okay. Please tell us what is printed on the placard affixed to the driver’s door jamb.
Thanks.
Ford’s placcard reads 35 front and rear.
Tires, Bridgestone Dueller, (stock?) read 44 psi max.
Not knowing what handling is means that I have never pushed this vehicle, or any SUV, in turning and weaving and maneuvering extremes.
Ford guys agree, nothing wrong with going 110 mph down a hill on dry, clean, fairly new interstate pavement.
If Ford’s placard states 35 psi, then 40 psi should be safe.
However, as to, “Ford guys agree, nothing wrong with going 110 mph down a hill on dry, clean, fairly new interstate pavement.”, you might want to consider making plans right now for these words to be placed on your tombstone.
What do you think will happen?
My concern was tire blowout and drive shaft deflection.
Tires are always inspected and in good condition at 40 psi.
No vibrations or noise detected.
Vehicle felt very smooth and stable.
Good epitaph! But I’m to be cremated.