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Bobtailing

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ACinSC View Drop Down
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Joined: 16 Dec 2015
Location: South Carolina
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ACinSC Quote  Post ReplyReply Direct Link To This Post Topic: Bobtailing
    Posted: 16 Oct 2020 at 7:59pm
Been wondering this for a long time . When I was a truck driver 40 years ago we could only drive 45mph bobtailing . What's different now that 70 mph is ok ? Thanks
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Brian Jasper co. Ia View Drop Down
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Joined: 11 Sep 2009
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian Jasper co. Ia Quote  Post ReplyReply Direct Link To This Post Posted: 16 Oct 2020 at 8:14pm
I have driven spring ride and air ride tractors. On a rough road no way would I drive an unloaded spring ride 70. The tandem dumps the state has can get a little squirrely empty on a rough road, I can only imagine how fun they would be as an incomplete vehicle.

Edited by Brian Jasper co. Ia - 16 Oct 2020 at 8:15pm
"Any man who thinks he can be happy and prosperous by letting the government take care of him better take a closer look at the American Indian." Henry Ford
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tomNE View Drop Down
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Joined: 13 Sep 2009
Location: dorchester, ne
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tomNE Quote  Post ReplyReply Direct Link To This Post Posted: 16 Oct 2020 at 8:40pm
35yrs ago we drove the speed limit; which varied widely throughout the states!
AC from the start of my families farming career till the end!
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klinemar View Drop Down
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Joined: 14 Sep 2009
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Post Options Post Options   Thanks (0) Thanks(0)   Quote klinemar Quote  Post ReplyReply Direct Link To This Post Posted: 17 Oct 2020 at 6:02am
Brian,I agree with you about State Highway Plow Trucks ! The one I drove had Hendrickson suspension and when scraping snow with an underbody blade you wanted to keep a sharp eye for frost heaves in the road as the suspension would throw the truck about! Some guys claimed they could scrape at 45 mph. I didn't!
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ACinSC View Drop Down
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Joined: 16 Dec 2015
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ACinSC Quote  Post ReplyReply Direct Link To This Post Posted: 17 Oct 2020 at 8:22am
We were told that if you hit the brakes bobtailing the tractor might spin like a top . Thanks !
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Lars(wi) View Drop Down
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Joined: 14 Sep 2009
Location: Permian Basin
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Lars(wi) Quote  Post ReplyReply Direct Link To This Post Posted: 17 Oct 2020 at 8:26am
I remember back when semi tractors didn’t have brakes on the steer axles.
I tried to follow the science, but it was not there. I then followed the money, and that’s where I found the science.
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DMiller View Drop Down
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Joined: 14 Sep 2009
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DMiller Quote  Post ReplyReply Direct Link To This Post Posted: 17 Oct 2020 at 8:38am
Can remember REMOVING Steer brakes on road tractors in the 70s as was NOT illegal yet.  

With ABS there is a false sense of security in being able to stop while bobtail or even just empty trailer.  I still leave stopping distance gaps as they will still slide even with ABS as the system ONLY works if one wheel still retains traction telling the controls that have wheel lockup on the others, they ALL lock down same time ABS does not see a problem.
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TomC View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TomC Quote  Post ReplyReply Direct Link To This Post Posted: 17 Oct 2020 at 8:40am
I was an owner operator from 1974 until this past April & retirement. Roads haven't changed much except for way more congestion, trucks haven't changed except way more power. What has changed way,way,way more is big nuts right behind the steering wheel,, and not for the better.
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DMiller View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DMiller Quote  Post ReplyReply Direct Link To This Post Posted: 17 Oct 2020 at 8:41am
Them be LOOSE Big Nuts behind the wheels!!
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ACinSC View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ACinSC Quote  Post ReplyReply Direct Link To This Post Posted: 17 Oct 2020 at 8:57am
Way back when I drove we had a paper graph that tracked our speed . Thanks
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Coke-in-MN Quote  Post ReplyReply Direct Link To This Post Posted: 17 Oct 2020 at 9:18am
When I quit driving tractor/tanker the company went from 68 MPH to 62 MPH limit in computer - and it seems local driving and home every night became Omaha , Chicago, Mandan SD , and a few more routes where freeways speeds were 70 and you impeded traffic with you foot to the floor ..
 Bobtailed a few times to pick up new trailers in WI , Ill, and Iowa but most times drop a trailer at a place to get it certified and run to another place to pick another trailer up 100 miles or so away . Air ride Pete as the tractor . 
 Ya Hendricks suspension on a dump when empty can give quite a ride on rough road - counter-steering to keep front end straight in direction of travel as rear decided which way it was going to go next. 
Faith isn't a jump in the dark. It is a walk in the light. Faith is not guessing; it is knowing something.
"Challenges are what make life interesting; overcoming them is what makes life meaningful."
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TomC View Drop Down
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Joined: 24 Nov 2017
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TomC Quote  Post ReplyReply Direct Link To This Post Posted: 17 Oct 2020 at 10:07am
Suspensions make a difference in the ride, the big difference in bobtailing is the ability to slow down ,stop or control. On wet roads it's going to be 2 to 3 times longer to stop,on ice or snow??? You are not going to stop or slow down, an empty trailer is a little better but not much. From what I saw in the past 10 years and only gets worse by the week is a large percentage of the people these companies are putting in trucks these days are not able to grasp just plain old walking around sense.
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DMiller View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DMiller Quote  Post ReplyReply Direct Link To This Post Posted: 17 Oct 2020 at 11:08am
Originally posted by ACinSC ACinSC wrote:

Way back when I drove we had a paper graph that tracked our speed . Thanks

I remember Tachographs, can remember drivers destroying the charts as they could get into them or knowing how to 'Unplug' Speedo.  If could not do that as with the old haulers in STL they just beat the mechanisms until quit and claimed were trying to get them to function so would not get fired, worked for a few.
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ACinSC View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote ACinSC Quote  Post ReplyReply Direct Link To This Post Posted: 17 Oct 2020 at 11:36am
Some driver's put rubber bands on the needle arm so it would show 10 mph slower . Remember one guy had his too tight and the graph never got over 15 mph . Uh oh !
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ac fleet View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ac fleet Quote  Post ReplyReply Direct Link To This Post Posted: 19 Oct 2020 at 2:51pm
only had to do it a few times ----- that was one thing I refused to do and boss respected my wishes. When I did it I never ran anywhere near the limit and on wet roads even slower---on snow and ice----they sent somebody else. I am still alive and still enjoy part time runs now and then.
http://machinebuildersnetwork.com/
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DMiller View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DMiller Quote  Post ReplyReply Direct Link To This Post Posted: 19 Oct 2020 at 4:48pm
Was instructed DECADES ago now that a Tandem Dual Wheel semi has LESS CONTACT SURFACE Weight on the back wheels bobtailing than a standard VW Beetle on four tires, looks impressive but contact surface weight spread means there is next to nothing gluing that machine to pavement.  Hit the brakes all the weight shifts forward so the rears lock out or ABS Kicks in and NO STOPPING in any reasonable distance.  We were then told NO MORE than 2/3 maximum speed of the machine when bobtail and DOUBLE stopping distances.
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TomC View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote TomC Quote  Post ReplyReply Direct Link To This Post Posted: 19 Oct 2020 at 5:14pm
I believe it was put to me like this" it's like trying to roller skate uphill "
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ACinSC View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ACinSC Quote  Post ReplyReply Direct Link To This Post Posted: 19 Oct 2020 at 7:13pm
Thanks for all the replies . Guess it's still a good idea to take it easy bobtailing .
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Dakota Dave View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dakota Dave Quote  Post ReplyReply Direct Link To This Post Posted: 19 Oct 2020 at 7:57pm
back in the 70s we had no traction bias ply lump lump till they warmed up tires almost no brakes front drums and no antiskid. the trucks we drive now are much better they will for the most part stop even on wet slushy roads brakes are more controllable the old ones were on or off pretty much in between. the massive power increase makes it much easier to spinout accelerating empty.  i dont rember farm trucks having that problem back then we usually couldnt get up to hiway speed with a full truck
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SteveM C/IL Quote  Post ReplyReply Direct Link To This Post Posted: 19 Oct 2020 at 8:23pm
Bobtailing 600hp is like driving a sports car!
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TomC View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TomC Quote  Post ReplyReply Direct Link To This Post Posted: 19 Oct 2020 at 8:31pm
Let me know which way you are going,,, cause I am headed the other direction
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