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Car Forum / Toyota / Toyota Cars / October 2006Inaccruate speedometers...
I've been suspicious for some time, but now I've gone out to prove it. I always though the speedometers on new cars are too fast than actual speed, but now I've gone out and prove it. I took my 1990 Corolla and drive 65 mph and have my wife drive our new Camry 2007 SE V6 behind me. We talk over walkie-talkie. She told me when my Corolla says 65 it says 70 mph on her Camry. Then I speed up to 70 mph and the Camry, matching my speed, says 75-77mph. I slow down to 50 mph and the Camry says 55 mph. I did the same test drive on my 2000 Maxima, same result (Maxima faster than Corolla at "same" speed) Interesting huh? Was the speedometer in your Corolla recently certified? If not, how do you know that your 1990 Corolla is accurate? "Big Blue" <aclaritan@gmail.com> wrote in message 9fj6k2teeiapsgr7hvo0las8d7803bi402@4ax.com... > I've been suspicious for some time, but now I've gone out to prove it. > I always though the speedometers on new cars are too fast than actual [quoted text clipped - 10 lines] > > Interesting huh? > Was the speedometer in your Corolla recently certified? If not, how do you > know that your 1990 Corolla is accurate? Or look at it this way: if the Camry and the Maxima match and the Corolla does not match, the vote is 2 to 1 that the Corolla's speedometer is inaccurate, especially if the Corolla does not have the original factory sized tires.  SignatureRay O (correct punctuation to reply) > > "Big Blue" <aclaritan@gmail.com> wrote in message [quoted text clipped - 14 lines] >> >> Interesting huh? Use a GPS to more accurately measure actual speed - not pacing with another car. > I've been suspicious for some time, but now I've gone out to prove it. > I always though the speedometers on new cars are too fast than actual [quoted text clipped - 10 lines] > > Interesting huh? > Use a GPS to more accurately measure actual speed - not pacing with > another car. That is what I use also. Used to use a watch with a second hand on it and the mile markers on the interstate. On level ground the cruse control will usually hold the speed steady enough to check the milage. I have also heard the mile markers may not be exectally one mile either. >> Use a GPS to more accurately measure actual speed - not pacing with >> another car. [quoted text clipped - 3 lines] > will usually hold the speed steady enough to check the milage. I have > also heard the mile markers may not be exectally one mile either. Except for cases where the markers might be missing for whatever reason, I'd guess that they are within 25 feet of being in the right place. Surely they are in the right place by a margin that would not affect your speed / stopwatch measurements. Having said that, the GPS is an excellent way to validate the speedo's accuracy. I use a stop watch because I'm a cheap bastard and never bought a GPS to replace the one I've lost. I own several stop watches though (one is actually an official stopwatch, not a feature of a wrist watch). Travel through South Carolina -- State Troopers will help you out. I got stopped about 15years ago and told the trooper that my Speedometer said that I was traveling 62 mph. He told me that I needed to get it checked as he gave me a ticket for 72 in a 60. I always made better time in that car than any other that I have owned. > I've been suspicious for some time, but now I've gone out to prove it. > I always though the speedometers on new cars are too fast than actual [quoted text clipped - 10 lines] > > Interesting huh? > I've been suspicious for some time, but now I've gone out to prove it. > I always though the speedometers on new cars are too fast than actual [quoted text clipped - 10 lines] > > Interesting huh? No. Not interesting at all. Sorry. You are comparing a beat up old base-model car with a brand new top-of-the-line car. In one, they throw a pile of pieces together and proclaim, "it works, let's sell it," and in the other they go to great pains to make sure the parts all work together just the way a driver might want them to. The approach to building the car makes a big difference in what the car tells you. And, if the Corolla came with tiny little tires, and somebody along the ownership line opted for a larger tire, then the speedo would be reading slow -- which is what yours is doing. I'd give odds that the new cars are MUCH more accurate than your Corolla. The actual way to test this is to set the cruise control and use a stopwatch to time how long it takes to go a measured mile. Mile markers are placed at half-mile intervals along the shoulder of the highway for this purpose. (Well, the purpose they are there might be different, but they can be used for this purpose.) As you pass a mile marker with the cruise set, click the stop watch and keep your eyes peeled for the next marker at which point you stop the watch. Divide 3600 by the time it takes to go a mile, and the result is your actual speed. 3600 / 65 = 55mph 3600 / 60 = 60mph 3600 / 51 = 70mph 3600 / 45 = 80mph Due to the magic of mathematics, you can divide 3600 by your speed to calculate the location of the next mile marker. Since you know that if you pass the markers at 51 second intervals, then you are going 70. If you are going 70, then you can calculate that the mile marker will appear 51 seconds after the previous marker. If a marker is missing, the next marker should appear after about 102 seconds. (Actually, 70 takes 51.4 seconds, so the next marker after the missing one should come at closer to 103 seconds.) I challenge you to run this test in your Corolla and your Camry and see which speedo is more accurate. I suspect you will find that the Camry is going 80 on the speedo, it is really doing about 77 on the ground. Given the numbers you cited, the Corolla at 80 should be doing about 83 on the ground. (I suggest you run the test at the legal speed limit, but your tolerance for pain will dictate what speed(s) you actually test.) The cars that I own and have tested are doing an actual 78.5 when the speedo reads 80. I've checked the odometer on my nearly brand new 2006 Sienna against my Garmin 76CS GPS (extremely accurate). As posted about a month ago: Odometer: 464.2 GPS: 469.86 Another poster noted that this might be purposely done by Toyota to account for later tire wear - makes sense. I've also noticed that the Sienna speedometer registers about one or two mph higher than the GPS. Strange, because it's inversely related to the data shown above. Arthur Hass > I've been suspicious for some time, but now I've gone out to prove it. > I always though the speedometers on new cars are too fast than actual [quoted text clipped - 10 lines] > > Interesting huh? Interesting that a couple of the posts mention speedometer readings that just happen to be 3 MPH high. My 1997 Camry also reads 3 MPH high. Curiously, it's constant, not proportional - as in 25 reads 28, and 55 reads 58. It's possible that the speedo is just pointing to 3 mph when the car is at rest. > Interesting that a couple of the posts mention speedometer readings > that just happen to be 3 MPH high. My 1997 Camry also reads 3 MPH high. > > Curiously, it's constant, not proportional - as in 25 reads 28, and 55 > reads 58. I'm not sure, but I think the error is more accurately expressed as a percent than an absolute. My guess is that the speedo is off by 2% (or whatever) and at high speed, this is 3 mph, but at city traffic speeds, the error is more like 1.5mph. > Interesting that a couple of the posts mention speedometer readings > that just happen to be 3 MPH high. My 1997 Camry also reads 3 MPH high. > > Curiously, it's constant, not proportional - as in 25 reads 28, and 55 > reads 58. > I've checked the odometer on my nearly brand new 2006 Sienna against my > Garmin 76CS GPS (extremely accurate). As posted about a month ago: [quoted text clipped - 10 lines] > > Arthur Hass Your experience is the mathematical affect of having a speedo (odometer actually) that is 98.8% accurate. I give that one high marks. > I've checked the odometer on my nearly brand new 2006 Sienna against my > Garmin 76CS GPS (extremely accurate). As posted about a month ago: > > Odometer: 464.2 > GPS: 469.86 the GPS is constantly bouncing signals off satellites, so "as the crow flies" would be an apt analogy. your odo is measured by the rubber actually meeting the road. > Another poster noted that this might be purposely done by Toyota to > account for later tire wear - makes sense. >> I've checked the odometer on my nearly brand new 2006 Sienna against >> my Garmin 76CS GPS (extremely accurate). As posted about a month ago: [quoted text clipped - 6 lines] > > your odo is measured by the rubber actually meeting the road. The GPS is recording every second. The GPS measurement is an accumulation of several thousand measurements (about 24,000) in the above statistic. I checked the entire track log. There were no errors of any magnitude. If there would have been, I could have eliminated them. The GPS measurement can have error, but if obvious errors are eliminated, the GPS measurement, in reality, would be shorter than the odometer since it is summing straight line segments as opposed to a continuous line (rubber meeting th road). But, in the data above, the reverse is true. Thus, the odometer was clearly measuring short. Arthur Hass >> Another poster noted that this might be purposely done by Toyota to >> account for later tire wear - makes sense. What really bugs me is inaccurate spelling... > I've been suspicious for some time, but now I've gone out to prove it. > I always though the speedometers on new cars are too fast than actual [quoted text clipped - 10 lines] > > Interesting huh? > I've been suspicious for some time, but now I've gone out to prove it. > I always though the speedometers on new cars are too fast than actual > speed, but now I've gone out and prove it> > Interesting huh? 77 on my speedo = 70 on my GPS in both my '91 Celica, fathers BMW and '96 Landcruiser. Brothers JDM surf is 4mph out though. |
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