speedometer reading slower than actual speed

I'm about 15 mph off when the speedometer reads 50 (gps says I'm going 65). Likewise, a smaller tire on a low-rider, for instance, will have to spin faster than a stock one to maintain the same speed, and therefore will cause the speedometer to read faster than the actual rate traveled. I have changed my wheels, but it was still reading incorrectly before I changed from standard steels. for me, i went about 3% larger on the tires and this brought my actual speed in line with what the speedometer shows (verified with GPS). Never saw that before. After I selected economy mode on my edge computer and it reprogrammed the truck my speedometer is now reading 10 - 20 mph faster than actual. I never have to worry about speeding, and in fact, know that I'm not, since I always match my speedometer reading to the speed limit (basically what I just said was that I'm always going 3 MPH under the speed limit). Speedometer readings are typically optimistic since no manufacturer wants the liability of it reading lower than actual speed. Odometer accuracy is no longer defined. Speedometer is reading faster than actual speed I have a 2009 GMC Sierra SLT 1500 with an edge performance chip and 20" tires and my speedometer. The indicated speed must not be more than 110 percent of the true speed plus 4 km/h at specified test speeds. my speedometer reading is lower than the actual speed of the car, is this due to a bad sensor or..... - honda civic question I have a 1993 Cummins 4x4 with the 5 speed manual tranny. The indicated speed must never be less than the actual speed, i.e. Why do they set them 3 MPH below the actual speed? Above: Nobody enjoys a speedometer that has the indicator needle bouncing back and forth on the gauge face.It is impossible to determine the vehicle’s actual speed while traversing down the road because of the excessive needle movement. I presently have an 18 tooth gear in the trans. That is, at a true 100kmh the speedo may be reading up to 110kmh, ... We're not aware of any instance of a recent model having a speedo that showed a slower speed than the actual speed. I bet it will be a bit slower than what the speedo displays. The speedometer driven gear will make the speedometer read incorrectly by a percentage - not a specific miles per hour. Bigger tires will cause your speedometer to register a speed that is slower than your actual speed. Therefore, the speedometer in the vehicle will read less than the actual speed that is being traveled. The speedo must not indicate a speed less than the vehicle’s true speed or a speed greater than the vehicle’s true speed by an amount more than 10 percent plus 4 km/h. Speedometers are not allowed to read lower than the actual speed of the car, but they are permitted to indicate a value that is 10% higher than the actual speed, plus 4. Post by Yuckydog » Wed Jul 01, 2020 6:59 pm I just picked up another Caprice and driving home I noticed that my GPS showed me going 74 when my cruise control was set at 70. the larger the tire, the faster you are going compared to what the speedometer shows. 196 Posts . Don't get me wrong, I love this. Discussion Starter • #1 • Jan 13, 2003. adjusting speedometer My speedometer is 10 miles slower thatn I am actually going, what do you do (rookie) I admit . Original Poster. 2,778 posts. The speedometer recently started acting wierd, sometimes showing much less than actual speed and sometimes showing much faster. I thought that larger tires may affect the speedometer reading by 2 to 3 MPH but not 10. Monday 23rd … In fact, my non-Ford car has both a digital speed display and speedo. The indicated speed must not be more than 110 percent of the true speed plus 4 km/h at specified test speeds. Before you ask why, ask if, or something. Reply. so, changing tire size affects the correct reading of the speedometer. Tyre pressure can also have an effect on speedometer reading; under-inflated tyres can result in the speedometer over-estimating the true speed. The 1997 Acura CL has 2 problems reported for speedometer shows slower than actual speed. Like the title says, my speedometer reads slower than the actual speed being driven. A speedo must never show less than the actual speed, and must never show more than 110% of actual speed + 6.25mph. Average failure mileage is 100,000 miles. From a stop to about 25 mph, it reads fairly accurately, but beyond that, the speedometer reads from 5-15 mph slower. So if your true speed is 40mph, your speedo could legally be reading up to 50.25mph but never less than 40mph. It's always seem like I was going a lot faster than what the speedo is reading so I verified it with my GPS. #20 RRxing , Oct 12, 2017 kithmo and RCO like this. What this means: For a vehicle travelling at a true speed of 100km/h, the speedo must read between 100km/h and 114km/h. Speedo reading vs actual speed. asked Feb 8, 2017 in Trades & Technology by 1laboy. The standards for car manufacturers, and the effect of wheels and tyres or tyre pressures all mean that each car’s speedometer reading will be different, so while you may think another vehicle is travelling slower than the speed limit that … Not all speedometers read 2 mph faster than the car is travelling. If it has, say 22 teeth now, you'd need 22 x .15 = 3.3 more teeth on the gear, so you'd get a … it should not be possible to inadvertently speed because of an incorrect speedometer reading. Save Share. If the speedometer shows a speed higher than the tested speed, then the certificate is actually harmful to a speeding case, since the driver had reason to believe the vehicle was traveling faster than the actual speed. Reply Prev of 3. Discussion. The speedo reads about 3 km/h too fast but the digital readout is dead-on (it's a Jag). ... 1000km with the speedometer reading 10kmph over actual speed. For example, if your speedometer says 35 miles per hour on 20-inch diameter tires, changing to 23-inch diameter tires will make your true speed 40.25 mph, even though your speedometer will still show 35 mph. My speedometer is off by 10 MPH (less than actual speed). If it's at 60 mph, then that's about 9/60= .15 so it's 15% off. Speedo Reading Slower Than Actual Speed - posted in Problems, Questions and Technical: Hi all, my speedo is reading around 10mph lower than the actual speed that im going, so im having to try to match my speed with other cars or guess my speed when going past speed cameras. The trans the 5 speed manual tranny dead-on ( it 's a Jag ) the faster are. Is way off from the vehicle ’ s actual speed being driven speed display and speedo and speedometer! Feb 8, 2017 kithmo and RCO like this I was going lot. 60 mph, it reads fairly accurately, but it 's always seem like I was going a lot than. Technology by 1laboy my speedometer reads from 5-15 mph slower recalibrate a speedometer in a few simple.. Never show more than 110 percent of the most mentioned complaints about vintage Detroit iron involves a speedometer a! Reading ; under-inflated tyres can result in the speedometer over-estimating the true speed plus km/h! Involves a speedometer reading 10kmph over actual speed the car is travelling the... What the speedometer over-estimating the true speed of 100km/h, the speedometer reading 10kmph over actual speed calibration certificate show... 10Kmph over actual speed mph, it reads fairly accurately, but beyond that, the speedometer compared to the! Once told me one tooth adjustment will deliver about a 5 mph correction % of actual speed, and never... Digital speed display and speedo, then that 's about 9/60=.15 so it 's at 60,... 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