# Why do cars have tachometers? **URL:** \ **Category:** Factual Questions\ **Created:** [January 25, 2009, 1:41pm UTC](https://boards.straightdope.com/t/why-do-cars-have-tachometers/482916 "2009-01-25T13:41:28Z")\ **Posts on this page:** 16\ **Page:** 2
**Author:** ![HoboStew](https://avatars.discourse-cdn.com/v4/letter/h/f17d59/32.png) [@HoboStew](https://boards.straightdope.com/u/HoboStew)\ **Post date:** [January 25, 2009, 6:52pm UTC](https://boards.straightdope.com/t/why-do-cars-have-tachometers/482916/21 "2009-01-25T18:52:24Z")
These explanations are all well and good, but I am about to give the super secret REAL reason. It’s fun to say “tachometer” ---
**Author:** ![Jophiel](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jophiel/32/66_2.png) [@Jophiel](https://boards.straightdope.com/u/Jophiel)\ **Post date:** [January 25, 2009, 7:17pm UTC](https://boards.straightdope.com/t/why-do-cars-have-tachometers/482916/22 "2009-01-25T19:17:55Z")
Going with some of the above, even though I drive an automatic, I like having an additional data point for how well the car is handling. It seems as though everything else is handled by idiot lights so it’s nice to have something that constantly feeds me information instead of waiting until something’s gone wrong. I don’t know that I’d absolutely refuse to buy a car without one but, between two similar cars, it’d easily tip the scales for me. That aside, it’s not as though the tachometer is taking up valuable real estate that’d be used for something else. The spedometer is large enough as is so what else would they put there? ---
**Author:** ![Philster](https://avatars.discourse-cdn.com/v4/letter/p/13edae/32.png) [@Philster](https://boards.straightdope.com/u/Philster)\ **Post date:** [January 25, 2009, 7:45pm UTC](https://boards.straightdope.com/t/why-do-cars-have-tachometers/482916/23 "2009-01-25T19:45:05Z")
American car companies put tachs in their auto-tranny cars because the Japanese and Euro brands had them. It is that simple. Japanese and Euro brands had tachs because their cars were actually being driven with manual transmissions in their home markets. That’s how it played out over the years. Sure, some American sports cars had tachs, but the above-mentioned facts solve the riddle for the OP. ---
**Author:** ![squeegee](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/squeegee/32/14537_2.png) [@squeegee](https://boards.straightdope.com/u/squeegee)\ **Post date:** [January 25, 2009, 8:06pm UTC](https://boards.straightdope.com/t/why-do-cars-have-tachometers/482916/24 "2009-01-25T20:06:44Z")
I concur with **Rick** , above. Tachs used to be uncommon, until auto mfr’s started adding them as a gimmick to make commonplace automatic cars “sexier” or “sportier”. Until recently, I drove manual transmission cars exclusively, and a tach is quite useful with manuals. And, yes, you can tell the engine revs by sound and feel, but I like to listen to music and ignore the engine roar, so a tach is a very good placeholder for this information. My current car has an automatic transmission, with a tiptronic-ish shifter (although it seems to me that the driver just casts a “vote” for when to shift, rather than having actual control). I find the tach slightly useful when downshifting, but wouldn’t miss it very much if it disappeared. ---
**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\ **Post date:** [January 25, 2009, 8:58pm UTC](https://boards.straightdope.com/t/why-do-cars-have-tachometers/482916/25 "2009-01-25T20:58:57Z")
> [@yabob](#): > > [http://www.carpages.co.uk/mini/mini\_images/mini\_cooper\_s\_interior\_17\_08\_06.jpg](http://www.carpages.co.uk/mini/mini_images/mini_cooper_s_interior_17_08_06.jpg) > > Bloody thing can be read not only by everyone in the vehicle, but from other cars pulling up alongside it. Surely, the only person who needs to read the speedo easily is the driver. I’ve seen other cars with the speedo in the center, I always figured it was so they could use the same dash (or very similar) in cars where the driver is on the right side. ---
**Author:** ![Rick](https://avatars.discourse-cdn.com/v4/letter/r/9f8e36/32.png) [@Rick](https://boards.straightdope.com/u/Rick)\ **Post date:** [January 25, 2009, 10:25pm UTC](https://boards.straightdope.com/t/why-do-cars-have-tachometers/482916/26 "2009-01-25T22:25:02Z")
> [@Philster](#): > > American car companies put tachs in their auto-tranny cars because the Japanese and Euro brands had them. It is that simple. > > Japanese and Euro brands had tachs because their cars were actually being driven with manual transmissions in their home markets. > > That’s how it played out over the years. Sure, some American sports cars had tachs, but the above-mentioned facts solve the riddle for the OP. Actually many early Japanese imports did not have tachs as standard. Pre 1970 or so Toyota Corona, and Corollas did not have them. Japanese sports cars did, and they gradually moved across the model line. ---
**Author:** ![Magiver](https://avatars.discourse-cdn.com/v4/letter/m/4491bb/32.png) [@Magiver](https://boards.straightdope.com/u/Magiver)\ **Post date:** [January 26, 2009, 12:02am UTC](https://boards.straightdope.com/t/why-do-cars-have-tachometers/482916/27 "2009-01-26T00:02:54Z")
> [@Crafter\_Man](#): > > Yea, I can understand its usefulness w/ manual transmissions and in special circumstances. But most cars nowadays have automatic transmissions, and most cars are used for run-of-the-mill transportation tasks. > > I’m not saying a tachometer has no purpose in your average car, just that the size and prominence of the tachometer dial seems rather disproportionate when compared to its actual usefulness. Probably the main reason that it’s in the car was already stated by Joey P. It’s cheaper to standardize parts on a car than it is to customize it on the assembly line for customers. With that said I also have a Saturn with an automatic and I look at the tach to see if I’m in high gear. I can get it to shift at 40 mph if I’m light on the pedal. ---
**Author:** ![spinky](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@spinky](https://boards.straightdope.com/u/spinky)\ **Post date:** [January 26, 2009, 1:21am UTC](https://boards.straightdope.com/t/why-do-cars-have-tachometers/482916/28 "2009-01-26T01:21:44Z")
> [@Crafter\_Man](#): > > Yea, I can understand its usefulness w/ manual transmissions and in special circumstances. But most cars nowadays have automatic transmissions, and most cars are used for run-of-the-mill transportation tasks. Sure, it’s not often that I drive my truck (with an automatic transmission) up or down a steep hill but when I do, it’s really good to have a tachometer so I can keep an eye on engine speed. It’s also pretty rare that I specifically put the truck in first gear, but there it is, right on the pernuddle.\* Also, claiming that a good driver should be able to gauge engine speed by feel is kind of bogus. Sure, I know what it feels like when my wife’s car (automatic, no tach) shifts, but I can only guess as to what RPM it is or how close to redlining I’d be if I had to downshift at a given speed. It forces you to be extra conservative because you’ve never been able to calibrate your gut feeling against a real number. And claiming people only need a tach in a manual so they can “pretend [they] are a hotshot race car driver and shift at exactly the correct rpm” is called “mocking others for being less ignorant than yourself.” If you’ve never heard of rev-matching, consider yourself unqualified to speak on the subject of manual transmissions. Rev-matching, which a tachometer helps with, not only extends the life of your clutch, but when done well will give your passengers a smoother ride (as well as being something hotshot race car drivers and their wannabe counterparts do). - this is what my grandfather called an automatic transmission. It’s actually spelled “PRNDL” 😃 ---
**Author:** ![snailboy](https://avatars.discourse-cdn.com/v4/letter/s/97f17d/32.png) [@snailboy](https://boards.straightdope.com/u/snailboy)\ **Post date:** [January 26, 2009, 1:28am UTC](https://boards.straightdope.com/t/why-do-cars-have-tachometers/482916/29 "2009-01-26T01:28:47Z")
> [@AHunter3](#): > > Tachometers are useful in automatic-transmission cars where the speedometer only goes up to 120 MPH (or even lower). Gives you some highly useful feedback about how far you’ve gone beyond that. True, except the benefit isn’t dependant on the type of transmission. > [@aerodave](#): > > Pointless but somewhat appropriate anecdote: In college my girlfriend (now wife) had a Chevy Beretta with a manual transmission. It had no tachometer. Her friend had a Chevy Cavalier built in the same year, with an automatic. And it did have a tach. So two cars built at the same time from the same maker had it completely ass-backwards. Didn’t make sense…but this was in the era when GM still used different keys for a car’s ignition and doors, so the lack of common sense in Detroit shouldn’t be too shocking. I’ve noted that, especially among 80’s cars, cheaper cars were less likely to have tachometers than higher-end cars. Economy cars were less likely to have them than luxury cars. On the other hand, cheaper cars were more likely to have manual transmissions. I don’t know whether the Cavalier or Beretta was the cheaper car so I’m not sure if this applies to your case. And relying on feel to judge engine RPM isn’t accurate at all. Even Formula 1 drivers have tachometers on their steering wheels. I hate driving manuals without them. ---
**Author:** ![SmackFu](https://avatars.discourse-cdn.com/v4/letter/s/53a042/32.png) [@SmackFu](https://boards.straightdope.com/u/SmackFu)\ **Post date:** [January 26, 2009, 5:39am UTC](https://boards.straightdope.com/t/why-do-cars-have-tachometers/482916/30 "2009-01-26T05:39:04Z")
In the late 80’s, my parents had a decent car, but in the base model with no options. It had a massive dial clock on the dash in the place where the tach would go. I think it was a Nissan Stanza. ---
**Author:** ![Colophon](https://avatars.discourse-cdn.com/v4/letter/c/f05b48/32.png) [@Colophon](https://boards.straightdope.com/u/Colophon)\ **Post date:** [January 26, 2009, 12:59pm UTC](https://boards.straightdope.com/t/why-do-cars-have-tachometers/482916/31 "2009-01-26T12:59:16Z")
The tachometer, as the name suggests, exists to measure the tackiness of the car. ---
**Author:** ![Dog80](https://avatars.discourse-cdn.com/v4/letter/d/6bbea6/32.png) [@Dog80](https://boards.straightdope.com/u/Dog80)\ **Post date:** [January 26, 2009, 4:31pm UTC](https://boards.straightdope.com/t/why-do-cars-have-tachometers/482916/32 "2009-01-26T16:31:21Z")
> [@yabob](#): > > Related question - what is the idea of the speedometer on some Mini Coopers, and similar vehicles? What I refer to is a freaking HUGE speedometer placed in the middle of dash: > > [http://www.carpages.co.uk/mini/mini\_images/mini\_cooper\_s\_interior\_17\_08\_06.jpg](http://www.carpages.co.uk/mini/mini_images/mini_cooper_s_interior_17_08_06.jpg) > > Bloody thing can be read not only by everyone in the vehicle, but from other cars pulling up alongside it. Surely, the only person who needs to read the speedo easily is the driver. The original mini had a similar speedo: [http://www.aronline.co.uk/images/mini\_10.jpg](http://www.aronline.co.uk/images/mini_10.jpg) Obviously they designed the new mini so that it resembles the old one. But since the dashboard on the new mini is cluttered with a million lights and switches they had to make the speedo really HUGE so it could stand out. ---
**Author:** ![Omegaman](https://avatars.discourse-cdn.com/v4/letter/o/e480ec/32.png) [@Omegaman](https://boards.straightdope.com/u/Omegaman)\ **Post date:** [January 26, 2009, 4:51pm UTC](https://boards.straightdope.com/t/why-do-cars-have-tachometers/482916/33 "2009-01-26T16:51:09Z")
> [@Rick](#): > > Now a tachometer is a customer expectation in pretty much all cars. (Yeah, maybe you don’t want it, but survey 1000 customers and more will expect it than not) > You will also get trashed in the automotive reviews in the car magazines if you don’t have a tach. > Implemented across an entire product line, I doubt that the tach costs much. > \*Sometimes known as adding showpower. This is how I see it. It’s all for show, pretty much. The days when you had to worry about fragging a motor because of overreving are pretty much gone with the invention of engine management systems. Don’t forget the lighted and refrigerated cupholders. ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [January 26, 2009, 5:14pm UTC](https://boards.straightdope.com/t/why-do-cars-have-tachometers/482916/34 "2009-01-26T17:14:45Z")
It helps if the car seems to idle rough, to see what is happening. Also helps notice if overdrive has engaged on the highway. During cold starts the RPM’s sometimes are higher then they should be to shift into drive/reverse, having the tach helps you notice that. Before the car is warmed up to operating temps it is sometimes recommended to keep rpm’s under a certain value. engine braking / preventing overspeed Many cars now have a ‘manumatic’ auto trany, where manual shifting in a ‘sporty’ mode is possible When tach’s became popular many autotrans were not electronically controlled and sometimes had a operating range short of the engine’s red line, aggressive driving could overspeed the engine or AT. ---
**Author:** ![brad\_d](https://avatars.discourse-cdn.com/v4/letter/b/50afbb/32.png) [@brad\_d](https://boards.straightdope.com/u/brad_d)\ **Post date:** [January 26, 2009, 6:56pm UTC](https://boards.straightdope.com/t/why-do-cars-have-tachometers/482916/35 "2009-01-26T18:56:53Z")
They’re nice to have, but hardly essential (IMO) on an automatic. I’ve been a die-hard manual driver for decades, but our family is now down to two vehicles with automatics - a Honda Accord and a Honda Odyssey. Both have tachs, but I really don’t spend much time looking at them. The information they convey is of little value in day-to-day driving unless there’s a problem, and most problems I’ve encountered are of the sort that you’d notice something felt or sounded wrong first, and then look to the tach for quantitative confirmation. I feel somewhat more strongly that a tach really should be present on a manual transmission, but again - you can get by without one. My dad used to have a late-80’s or early-90’s Mazda pickup (before they became rebadged Rangers) that had a manual tranny and no tachometer. One could drive it just fine, and rev-match by ear & feel - you could tell if you’d gotten it right or not, and fairly quickly converged to driving it with no more difficulty than my own car, which had a tachometer. I did have to be careful when really gunning it to get on the freeway, since I didn’t know where I was in relation to the redline. That could be worked around - mostly just by driving conservatively - but it would have been a huge issue in a racing vehicle (which this truck most definitely was not). Aside: This question is somewhat prone to being no-true-Scotsman’ed: “If you don’t think a tachometer is vital then you don’t really know how to drive properly and thus your opinion is of little value. When we leave out _those_ people, it’s unanimous! QED.” ---
**Author:** ![MonkeyMensch](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@MonkeyMensch](https://boards.straightdope.com/u/MonkeyMensch)\ **Post date:** [January 26, 2009, 7:48pm UTC](https://boards.straightdope.com/t/why-do-cars-have-tachometers/482916/36 "2009-01-26T19:48:07Z")
I am always reminded, when seeing this subject come up, of Graham Hill’s remark on Johnny Carson’s Tonight Show, lo these many years ago. He said, “A tachometer in a street car lets the driver know the engine’s running.” I use the tach in my truck to know how fast I am going, since the speedometer’s needle has been bent to where it touches the dial face and doesn’t really move much. I know the rev-gear combos for all the common speed limits and drive accordingly. So for me it’s a emergency-auxilary speedometer.🙂 [Previous page](https://boards.straightdope.com/t/why-do-cars-have-tachometers/482916.md?page=1)