# Why are 18-wheelers called "semi's"? **URL:** \ **Category:** Factual Questions\ **Created:** [August 11, 2008, 5:40pm UTC](https://boards.straightdope.com/t/why-are-18-wheelers-called-semis/459630 "2008-08-11T17:40:15Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Dinsdale](https://avatars.discourse-cdn.com/v4/letter/d/97f17d/32.png) [@Dinsdale](https://boards.straightdope.com/u/Dinsdale)\ **Post date:** [August 11, 2008, 9:04pm UTC](https://boards.straightdope.com/t/why-are-18-wheelers-called-semis/459630/21 "2008-08-11T21:04:36Z")
[QUOTE=brewha] Since cab-overs are no longer neccesary, they aren’t gettting built or used much anymore. [/QUOTE] Thanks. I was surprised, however, that I did not see a single cab-over. And this was on the truck-heavy stretch of 294, 80/94, around Chicago and the bottom of Lake Mich. Saw literally hundreds of trucks. Would have expected to see at least a couple of old dinosaurs still in service. ---
**Author:** ![hibernicus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hibernicus/32/2802_2.png) [@hibernicus](https://boards.straightdope.com/u/hibernicus)\ **Post date:** [August 11, 2008, 9:09pm UTC](https://boards.straightdope.com/t/why-are-18-wheelers-called-semis/459630/22 "2008-08-11T21:09:15Z")
[QUOTE=Freddy the Pig] Wow. Future generations will have _no idea_ what C.W. McCall was talking about when he spoke of a “cab-over Pete”. [/QUOTE] The “cab-over” configuration is so nearly universal here in Ireland that I wasn’t even aware there was a name for it. ---
**Author:** ![SeanArenas](https://avatars.discourse-cdn.com/v4/letter/s/df705f/32.png) [@SeanArenas](https://boards.straightdope.com/u/SeanArenas)\ **Post date:** [August 11, 2008, 9:12pm UTC](https://boards.straightdope.com/t/why-are-18-wheelers-called-semis/459630/23 "2008-08-11T21:12:27Z")
[QUOTE=Freddy the Pig] Wow. Future generations will have _no idea_ what C.W. McCall was talking about when he spoke of a “cab-over Pete”. [/QUOTE] Oh that wonderful song about a fateful June 6th! Cab-over Pete is smokin a reefer! Care to explain what a swindle sheet is? (Also a trucking term from that song) ---
**Author:** ![ParentalAdvisory](https://avatars.discourse-cdn.com/v4/letter/p/53a042/32.png) [@ParentalAdvisory](https://boards.straightdope.com/u/ParentalAdvisory)\ **Post date:** [August 11, 2008, 9:15pm UTC](https://boards.straightdope.com/t/why-are-18-wheelers-called-semis/459630/24 "2008-08-11T21:15:59Z")
[QUOTE=Sunspace] A tractor is a machine that pulls other equipment. A farm tractor pulls farm equipment. [/QUOTE] But most of the farm tractors that I’m used to also dig and push dirt around. That’s why it’s funny to me when semi’s are called tractors. Yes, even after you’ve given me the definition. ---
**Author:** ![DSYoungEsq](https://avatars.discourse-cdn.com/v4/letter/d/c6cbf5/32.png) [@DSYoungEsq](https://boards.straightdope.com/u/DSYoungEsq)\ **Post date:** [August 11, 2008, 9:22pm UTC](https://boards.straightdope.com/t/why-are-18-wheelers-called-semis/459630/25 "2008-08-11T21:22:53Z")
[QUOTE=ParentalAdvisory] But most of the farm tractors that I’m used to also dig and push dirt around. That’s why it’s funny to me when semi’s are called tractors. Yes, even after you’ve given me the definition. [/QUOTE] How could a farm tractor “dig” or “push” dirt? I’ve never seen a tractor with a front end loader or a back hoe attached… ---
**Author:** ![tomndebb](https://avatars.discourse-cdn.com/v4/letter/t/b9e5f3/32.png) [@tomndebb](https://boards.straightdope.com/u/tomndebb)\ **Post date:** [August 11, 2008, 9:37pm UTC](https://boards.straightdope.com/t/why-are-18-wheelers-called-semis/459630/26 "2008-08-11T21:37:38Z")
[QUOTE=SeanArenas] Care to explain what a swindle sheet is? (Also a trucking term from that song) [/QUOTE] Truckers keep a log to demonstrate to their employers that they have worked enough hours to get paid while demonstrating to the government that they have not worked an illegally excessive number of hours to be considered safe. The swindle sheet is the nickname for the log they must keep to prove their hours. It is taken from the same word used in accounting to describe an expense account (from the frequent practice of padding accounts to swindle employers out of more cash). ---
**Author:** ![Gorsnak](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gorsnak/32/7587_2.png) [@Gorsnak](https://boards.straightdope.com/u/Gorsnak)\ **Post date:** [August 11, 2008, 9:39pm UTC](https://boards.straightdope.com/t/why-are-18-wheelers-called-semis/459630/27 "2008-08-11T21:39:26Z")
[QUOTE=DSYoungEsq] How could a farm tractor “dig” or “push” dirt? I’ve never seen a tractor with a front end loader or a back hoe attached… [/QUOTE] Surely you aren’t serious. [But just in case you are…](http://images.google.ca/images?client=firefox-a&rls=org.mozilla%3Aen-US%3Aofficial&hl=en&q=loader+tractor&btnG=Search+Images&gbv=2) ---
**Author:** ![tomndebb](https://avatars.discourse-cdn.com/v4/letter/t/b9e5f3/32.png) [@tomndebb](https://boards.straightdope.com/u/tomndebb)\ **Post date:** [August 11, 2008, 9:48pm UTC](https://boards.straightdope.com/t/why-are-18-wheelers-called-semis/459630/28 "2008-08-11T21:48:34Z")
[QUOTE=DSYoungEsq] How could a farm tractor “dig” or “push” dirt? I’ve never seen a tractor with a front end loader or a back hoe attached… [/QUOTE] Probably not the monsters used on the prairies to pull twenty-bottom plows or thousand gallon sprayers, but on smaller farms, tractors often have front loaders and backhoes. [front loader](http://www.techsystractor.com/images/Implements/Front%20End%20Loader.jpg) [back hoe](http://www.techsystractor.com/images/Implements/Back%20Hoe.jpg) [front loader](http://www.wurzwitz.com/front_end_loader.jpg) [back hoe](http://www.anderton-kitchen.com/pagecontent/backhoe/backhoe-loader.jpg) I have misplaced my photo, but my FIL attached a front end loader (not a snow blade) to his [Oliver](http://www.tractorshed.com/cgi-bin/shed.cgi?oc05-018.jpg) every winter to clear rhe driveway of snow. ---
**Author:** ![SeanArenas](https://avatars.discourse-cdn.com/v4/letter/s/df705f/32.png) [@SeanArenas](https://boards.straightdope.com/u/SeanArenas)\ **Post date:** [August 11, 2008, 10:21pm UTC](https://boards.straightdope.com/t/why-are-18-wheelers-called-semis/459630/29 "2008-08-11T22:21:28Z")
[QUOTE=Gorsnak] Surely you aren’t serious. [But just in case you are…](http://images.google.ca/images?client=firefox-a&rls=org.mozilla%3Aen-US%3Aofficial&hl=en&q=loader+tractor&btnG=Search+Images&gbv=2) [/QUOTE] It’s still pushing and pulling a load, the load just happens to be dirt instead of a semi-trailer (in the case of trucking), or a wandering probe (in the case of Star Trek), although the tractor beam could surely move a lot of dirt if it wanted to. ---
**Author:** ![tomndebb](https://avatars.discourse-cdn.com/v4/letter/t/b9e5f3/32.png) [@tomndebb](https://boards.straightdope.com/u/tomndebb)\ **Post date:** [August 12, 2008, 12:04am UTC](https://boards.straightdope.com/t/why-are-18-wheelers-called-semis/459630/30 "2008-08-12T00:04:48Z")
Just over a couple of months ago, we had a related thread on the topic of cargo vehicles: [An automobile question too stupid for GQ…](http://boards.straightdope.com/sdmb/showthread.php?t=469930) (that was not really a stupid question). ---
**Author:** ![danceswithcats](https://avatars.discourse-cdn.com/v4/letter/d/9e8a1a/32.png) [@danceswithcats](https://boards.straightdope.com/u/danceswithcats)\ **Post date:** [August 12, 2008, 1:46am UTC](https://boards.straightdope.com/t/why-are-18-wheelers-called-semis/459630/31 "2008-08-12T01:46:29Z")
[QUOTE=brewha] Since cab-overs are no longer neccesary, they aren’t gettting built or used much anymore. [/QUOTE] IIRC cabover Mack tractors are still popular with UPS. Realistically, if you don’t operate routes which require a co-driver or sleeper cab, e.g. nothing long haul, a cabover is the VW of trucking. ---
**Author:** ![Princhester](https://avatars.discourse-cdn.com/v4/letter/p/3e96dc/32.png) [@Princhester](https://boards.straightdope.com/u/Princhester)\ **Post date:** [August 12, 2008, 3:32am UTC](https://boards.straightdope.com/t/why-are-18-wheelers-called-semis/459630/32 "2008-08-12T03:32:00Z")
[QUOTE=Mister Rik] With the exception of faux-intellectuals who use “at the present time” when “now” would work better. [/QUOTE] It’s hardly limited to “faux-intellectuals”. It seems to be used in “official speak” all the time: it drives me batty when travelling in the US that every announcement gives instructions as to what must happen “at this time”. If I say “would all passengers for flight xy223 please proceed to boarding gate F” would people actually think I meant “at some later time” if I didn’t tack “at this time” on the end of my announcement? ---
**Author:** ![J\_Cubed](https://avatars.discourse-cdn.com/v4/letter/j/c6cbf5/32.png) [@J\_Cubed](https://boards.straightdope.com/u/J_Cubed)\ **Post date:** [August 12, 2008, 4:16am UTC](https://boards.straightdope.com/t/why-are-18-wheelers-called-semis/459630/33 "2008-08-12T04:16:10Z")
[QUOTE=Broken Hoe] Okay, but why is the whole assembly called “a semi”? [/QUOTE] [Synecdoche](http://en.wikipedia.org/wiki/Synecdoche). The formal term for what the others said. [QUOTE=Princhester] If I say “would all passengers for flight xy223 please proceed to boarding gate F” would people actually think I meant “at some later time” if I didn’t tack “at this time” on the end of my announcement? [/QUOTE] While I believe that these formulations occur because most people who use public address systems are not scholars of oral English, they do have a saving grace: in the chaotic environment of an airport, communication benefits from redundancy. More truckin’ questions: do they use the same tractors to pull full trailers so that there are more than 18 wheels, or does it still work out to be 18? I wonder if anyone has cause to throw around terms like 16- or 20-wheeler. Or 13-wheeler. ---
**Author:** ![usedtobe](https://avatars.discourse-cdn.com/v4/letter/u/ec9cab/32.png) [@usedtobe](https://boards.straightdope.com/u/usedtobe)\ **Post date:** [August 12, 2008, 4:56am UTC](https://boards.straightdope.com/t/why-are-18-wheelers-called-semis/459630/34 "2008-08-12T04:56:28Z")
Remember a patient hooked up to weiths and pulleys? He was said to be in: “Traction” Traction = pull “Tractor” = that which pulls Thanks for the explanation of “semi” - another old Q I never got aroung to asking. While we’re on heavy trucks: Many years ago I drove across the US, mainly driving at night (avoid idiots and drunks, btw). Consequently, I dealt with truck stops - lots of truck stops. I noticed many truckers paying for fuel with an enormous roll of bills. Being discrete, I decided not to approach, and so never got to asking: How much fuel do those open-road beasts carry? Some tanks extend from front to aft - and that is behind the sleeper - huge. I once spend some time on Freightliner and Mack sites looking for such specs, and came up empty, Thanks! ---
**Author:** ![dbuzman](https://avatars.discourse-cdn.com/v4/letter/d/9de0a6/32.png) [@dbuzman](https://boards.straightdope.com/u/dbuzman)\ **Post date:** [August 12, 2008, 6:21am UTC](https://boards.straightdope.com/t/why-are-18-wheelers-called-semis/459630/35 "2008-08-12T06:21:09Z")
[QUOTE=SeanArenas] Cab-over Pete is smokin a reefer! [/QUOTE] No, Cab-over Pete had a reefer on (was pulling a refrigerated trailer). ---
**Author:** ![TheLoadedDog](https://avatars.discourse-cdn.com/v4/letter/t/35a633/32.png) [@TheLoadedDog](https://boards.straightdope.com/u/TheLoadedDog)\ **Post date:** [August 12, 2008, 6:58am UTC](https://boards.straightdope.com/t/why-are-18-wheelers-called-semis/459630/36 "2008-08-12T06:58:11Z")
In my part of the world, a “prime mover” hauls a “trailer (or trailers)”. Non-articulated truck = “truck” Prime mover + 1 trailer = “semi trailer” or “semi” Prime mover + 2 trailers (one “semi” and one fully-wheeled) = “B Double” Prime mover + \>2 trailers = “road train” (only in remote areas) The American “tractor trailer” still sounds a little weird to me, but it makes perfect sense, as described in **usedtobe** ’s post. ---
**Author:** ![danceswithcats](https://avatars.discourse-cdn.com/v4/letter/d/9e8a1a/32.png) [@danceswithcats](https://boards.straightdope.com/u/danceswithcats)\ **Post date:** [August 12, 2008, 7:37am UTC](https://boards.straightdope.com/t/why-are-18-wheelers-called-semis/459630/37 "2008-08-12T07:37:44Z")
[QUOTE=usedtobe] How much fuel do those open-road beasts carry? Some tanks extend from front to aft - and that is behind the sleeper - huge. [/QUOTE] Twin 150 gallon saddle tanks with a separate belly tank for the reefer APU (if needed) sticks in my head as typical. Custom units can always be larger. ---
**Author:** ![tomndebb](https://avatars.discourse-cdn.com/v4/letter/t/b9e5f3/32.png) [@tomndebb](https://boards.straightdope.com/u/tomndebb)\ **Post date:** [August 12, 2008, 7:57am UTC](https://boards.straightdope.com/t/why-are-18-wheelers-called-semis/459630/38 "2008-08-12T07:57:55Z")
[QUOTE=J Cubed] More truckin’ questions: do they use the same tractors to pull full trailers so that there are more than 18 wheels, or does it still work out to be 18? I wonder if anyone has cause to throw around terms like 16- or 20-wheeler. Or 13-wheeler. [/QUOTE] Different rigs can have any number of wheel combinations. Supermarkets/groceries are often served by large volume/short haul/moderate weight rigsd that may have only a single axle on the semi-trailer and/or a single driving axle on the tractor. This would make them 10-wheelers. Some heavy duty steel haulers have several extra supporting axles, making them 24-wheelers (or more!). However, all those specialty rigs are overwhelmingly outnumbered by the standard 18-wheel configuration, so the term “18 wheeeler” has come into general use as a generic term, regardless of the number of wheels on a specific truck. (You can always load an 18-wheeler with your grocery resupply if a 10-wheeler is not handy or load a bit fewer steel coils onto an 18-wheeler if a 24-wheeler is not available, so the more common configuration remains the 18-wheeler.) ---
**Author:** ![TheLoadedDog](https://avatars.discourse-cdn.com/v4/letter/t/35a633/32.png) [@TheLoadedDog](https://boards.straightdope.com/u/TheLoadedDog)\ **Post date:** [August 12, 2008, 8:01am UTC](https://boards.straightdope.com/t/why-are-18-wheelers-called-semis/459630/39 "2008-08-12T08:01:30Z")
[QUOTE=TheLoadedDog] Prime mover + 2 trailers (one “semi” and one fully-wheeled) = “B Double” [/QUOTE] I tell a lie. A lot of them have a turntable on the back of the first trailer, so both trailers are semis. ---
**Author:** ![Horatio\_Hellpop](https://avatars.discourse-cdn.com/v4/letter/h/e5b9ba/32.png) [@Horatio\_Hellpop](https://boards.straightdope.com/u/Horatio_Hellpop)\ **Post date:** [August 12, 2008, 8:09am UTC](https://boards.straightdope.com/t/why-are-18-wheelers-called-semis/459630/40 "2008-08-12T08:09:58Z")
What is the greatest number of trailers a tractor will pull? Out west, I see as many as three, but around here, just one. [Previous page](https://boards.straightdope.com/t/why-are-18-wheelers-called-semis/459630.md?page=1) [Next page](https://boards.straightdope.com/t/why-are-18-wheelers-called-semis/459630.md?page=3)