Today's the day - Big trucks can now do 65 mph in Ohio on interstates

[piper1]

If the engine can be in it's sweet spot, slower will ALWAYS give you better fuel mileage.

Wind resistance above 55 MPH goes up exponentially, meaning the rate of HP needed to overcome the air rises much faster than the rate of speed.

A lot of trucks got geared so that they were at the bottom end of the sweet spot (say 1350 rpm) while they were at 65MPH, these trucks when you back them down to 55MPH are now operating in an rpm range that the engine has poor volumetric efficiency, in other words the engine becomes a very poor air pump and wastes a lot because it can't inhale and exhale very well (think 95 year old on the golf course in July). There are trucks out there with direct drive transmissions and things like 2.97 rear ends that are designed to run at 65, and not much else, BUT, most trucks are geared with a bit of flexibility in them and you can slow down and SAVE.

The other thing that happens is some guys will slow down and then they get flappy with the fuel pedal, that is they cruise along and when they need a little umph, they floor it. If you drive any truck and use your foot on the throttle the same way you use your foot on the clutch pedal, good fuel mileage will not follow.

 

[OntarioVanMan]

I was at the "J" in Perrysburgh Today and Overheard a Couple of Drivers talking about the Speed Limit Change in Ohio! They were Saying That Since the Speed Limit Changed That The D.O.T. Is Now Working the Ohio Turnpike and That They Saw 5 Seperate Diesel Bears working it from The Indiana Line to Cleveland. Anyone Know If that's True?

Ohio is pretty anal about fuel spot checks at harvest time...looking for dyed diesel..I got checked on #2 last year....

Some farmers take their farm trucks of produce to market and forget? about the dye thingee...one heck of a fine for that!

 

[Doggie Daddy]

Now, if Il & Ca would follow suit, the interstates would be far safer, IMO.

Let's not forget Oregon,still 55 for trucks there.

 

[greg334]

I drive 65 in california, they are 55 there?

I also drive through atlanta....

 

[DougTravels]

In Cali, I noticed when southbound from Oregon the signs said "Trucks over 3 axles 55". When headed East or West into or out of LA they just say trucks 55.

 

[inkasnana]

I was driving on US 35 in Ohio and there were places where the 55 mph truck speed signs had been covered over, leaving just the 65 mph sign so they are applying that single speed limit to some US highways as well. It was just in places here and there so you have to watch the signs.

 

[Jack_Berry]

just because the max speed allowed is 65 or 60 or 70 it does not mean you are not allowed to go slower. it is a maximum speed.


now...what can be done about that idiot in the gravel truck who just H-A-S to invade my 2 second space so he can get off the tollway in front of me? would it have killed him to get behind me for 1/2 mile? next time i will just fill that space when the signal goes on.

 

[mjolnir131]

just because the max speed allowed is 65 or 60 or 70 it does not mean you are not allowed to go slower. it is a maximum speed.


now...what can be done about that idiot in the gravel truck who just H-A-S to invade my 2 second space so he can get off the tollway in front of me? would it have killed him to get behind me for 1/2 mile? next time i will just fill that space when the signal goes on.

love the one with the signs that warn you to stay back 50 or 100 feet kinda hard to do when he's almost clipping your front bumper when they merge

 

[Crazynuff]

just because the max speed allowed is 65 or 60 or 70 it does not mean you are not allowed to go slower. it is a maximum speed.


now...what can be done about that idiot in the gravel truck who just H-A-S to invade my 2 second space so he can get off the tollway in front of me? would it have killed him to get behind me for 1/2 mile? next time i will just fill that space when the signal goes on.

Yesterday as I got off the north end of the Natcher Parkway in KY to head towards 60 East , a dump truck owned by Scott and Ritter passed me at over 65 m.p.h. less than a half mile before the end of the parkway . Another of their trucks tailgated me after I was on the bypass while a third on passed us in the left lane even though he needed to be in the right lane when the bypass ended in less than a mile .
The Riverton Trucking trucks working construction on I-64 in IN are just as bad . I had 7 of them pass me within 5 miles while I was doing the speed limit . Two of these were in the 45 m.p.h. construction zone .
When ATA and Road Safe America were pushing for speed limiters a few years ago they stated excessive speed was a factor in 8% of truck accidents but failed to mention 80% of the time the excessive speed was below 65 m.p.h. (and the most common violators were ATA governed trucks trying to make up time in 55 m.p.h. and construction zones )

 

[moose]

Ye'p , Speed limiters will make you Speed.
we see it every day.

 

[Dakota]

Still 55 on 30 between Vanwert and Indiana border

 

[mjolnir131]

Now this is totally from a physicists point of view.and it's one of the bones of contention that you can tell the difference between a physicist and and engineer.
wind tunnels do a great job of telling you how to improve the shape of your design ,where parts met, transition lines etc, etc. but that is where your good data ends anything above that is pure guess work more related to torrot card and prodicting the weather than science,you can get some raw data from them but it's still up to drastic interpatation mainly becouse said object being tesed is not powering itself during the test.

AirTabs are a great example here. the data for them are all over the board with the big"super accurate" tunnels claiming there is no savings or MPH increase,the smaller tunnels ranging from a fair to drastic increase,most all are disproven when the tabs are put on a truck and driven in the RW, the milage does increase.

 

[Turtle]

The wind tunnel data on my Sprinter matched nearly perfectly with my real world experiences.

 

[mjolnir131]

are you talking the MPG on your stiker i believe most stickers use a base avgerage taken from a random rumber of vehicles that are driven over a closed course.