Believe it or not the speedometer reading 4 MPH higher than your actual speed is normal for this vehicle. When you add larger tires to your Jeep, the speedometer is reading slower values on a LINEAR slope, it doesn't read "5-7mph off" all of the time, only at a certain speed. My Harley speedo reads about 3MPH faster than actual, as verified with my GPS and those speed limit signs that display your speed. In these transmissions, each tooth added or deleted changes your speedometer reading. I've repeated the tests using a dash cam with GPS speed so you can observe the actual speed and the actual speedometer reading and clearly see they are way way off. Any ideas on why this is happening, and a fix? Over Reporting speedo (speedo 120kmh actual speed 115kmh) 2. I have a 2004 2500HD pickup with diesel and 95,000 miles. 40/43. In these transmissions, each tooth added or deleted changes your speedometer reading. Many jurisdictions place strict limits on speedometer accuracy - but the range is not symmetric typically the legal range for the speedometer display is 100-110% of actual speed. Analog speedometer, digital odometer if it matters. With my L8 ABS, at our speed limit, which is 100 kph, I seem to blend in with most other traffic or maybe I'm even a tad faster, but all speedo's will indicate slightly faster than the real speed for reasons already mentioned a few post up from here.. This is on my 96 AWD with stock 14" tires. Yup and Honda also got sued for it, because when your speedometer runs fast, your odometer also runs fast. They will read high, but it’s for a different reason. Back to the basics, if your speedometer is indicating too slow for a given roadspeed then you have to turn it faster. So if your true speed is 40mph, your speedo could legally be reading up to 50.25mph but never less than 40mph. Please let us know what you find. The speed offset was Not a constant. The reason for this might be one of two or both: 1. speed The UK law is based on the EU standard, with some minor changes. I came to Harley from metric bikes and it's a well known fact that metric speedos read 5-10% higher than actual speed. Thus, with each revolution you are traveling further than before. And I'm usually bold enough to use the GPS speed to set my cruise rather than speedometer, without getting pulled over. I just put new tires on (OEM 245 75R16) but there has been virtually no change. OP, for the speedometer to read FASTER than actual speed would mean the speedometer cable would have to be spinning faster than it should. For example, if your speedo reads 5% higher than actual speed then your Odometer is also reading the miles 5% faster. What would cause the speedometer to indicate you are doing 65 when you are actually traveling 58? There is no calibration for the speedometer. I am having an issue with my speedometer, it reads slower than my actual speed. The EU says "The indicated speed must never be less than the actual speed, i.e. this would be correct with 355 gears installed inplace of 308 without changing the speedometer gear. Changing the stock gearing on a modern sportbike is practically manditory for honest sport riding. 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. 07 G35 Sporter wrote:Hello forum Just registered since I am a brand new G owner. This speed signal is a big factor in the overall performance equation. VSS– A faulty speed sensor will often be accompanied by the P0500 (VSS circuit malfunction) trouble code. Below are some examples of what it's reading. I found the stock 26" setting gives a speedometer reading that is 1 MPH faster than the actual speed as shown via the GPS. 50/54. Dec 3, 2012. Thus, with each revolution you are traveling further than before. Your speedometer is reading how many revolutions your tires are making not how fast they are spinning. GPS speedometers work with the NMEA 0183 antenna that receives satellite signals to determine speed over land. GPS speedometers are more accurate than a regular speedometer using a pitot tube, as there is no need to calibrate for wind current. Plus, this system can be interfaced with GPS plotters and fish finders. If it … Do bigger tires throw off odometer? Each bus, truck, and truck-tractor must be equipped with a speedometer indicating vehicle speed in miles per hour and/or kilometers per hour. The speedometer must be accurate to within plus or minus 8 km/hr (5 mph) at a speed of 80 km/hr (50 mph). If my speedometer says I'm going faster than I really am does that mean my odometer is registering more miles than I'm really driving? Tire size is 225 75R15 so pretty close to stock size. If you want to know with GPS verified accuracy, grab a couple of zip ties, download a free speedometer app, zip tie your phone to your bars (so you can see the screen and the speedo at the same time), turn on the app (turn off the auto … I have been driving past a construction area for the past week that has one of those radar stations with a display that shows your speed. Speedometer reporting faster than actual speed So over the weekend my wife, brother-in-law, and I were sitting around talking and all came to the same conclusion that our speedo's were off, saying we were going faster than we actually are. Bigger tires will cause your speedometer to register a speed that is slower than your actual speed. ), erratic speedometer sometimes registers higher or lower than actual speed, then returns to normal, then to faster or lower than normal, for 10 to 30 seconds, the cable ends look good, fit into the speedo head and transmission Inspect and test the vehicle speed sensor which is down by the transmission near the passengers side CV axle. European law (ECE-R39) says speedometers cannot show speeds less than the actual speed, and they must never show more than the 110 per cent of actual speed plus 4 km/h. In other words, if it reads 50mph, you won’t be doing more than 50mph but it’s possible you might actually only be travelling at 40mph. What controls this meter reading. It combines this data to send the speed reading to the instrument cluster. Speedometer driven gears in the Turbo 400 and 700R4 have between 34 and 45 teeth. Mine is indicating 7 mph faster than actual speed. Answer (1 of 5): No, that’s not particularly true. In this particular case, let’s say that your speedometer was reading 55mph. Makes the car seem faster. Different colored gears have different teeth, fewer teeth will speed up the reading and more teeth will slow the speedometer reading. Actual MPH = (New Tire Diameter x Indicated MPH) / Old Tire Diameter. The speedometer is original but at some time or other the c4 transmission has been changed out. I'm curious how the time of day could affect a GPS speed reading. One disturbing side effect of this is that the speedometer goes drastically out of calibration, reading a much faster speed than actual. Currently I have no speedometer and despite the transmission shifting very well, it skips second gear consistently (no intermittent functioning). They flash a warning for you to slow down if your going faster than the posted speed limit. it should not be possible to inadvertently speed because of an incorrect speedometer reading. The indicated speed must not be more than 110 percent of the true speed plus 4 km/h at specified test speeds. A car speedometer measures speed: how fast the car is moving. Speedometers measure speed in miles per hour or kilometers per hour. Some gauges display both readings. Speedometers have been standard equipment in automobiles since 1910. And my outside temperature readout is also 3 degrees higher than it actually is. Speedometer driven gears in the Turbo 400 and 700R4 have between 34 and 45 teeth. It is common for Accords to read 3-5 mph faster than actual at highway speeds, but 10-15mph is pretty far off. This can vary with vehicle type, e.g. But that’s the key thing: your speedometer needs to be reading low. My vehicle is a 2004 Jeep Grand Cherokee Limited, with the 4.7L, V8, SOHC, 16V engine, and has the "All-The-Time 4WD" transmission. A useful speedometer calibration certificate will show a speedometer reading that is slower than the actual tested speed. If the speedometer reading is higher than the actual speed, the speedometer is fast. Odometer accuracy is no longer defined. Up-sizing, or installing a taller tire, will lead to a speedometer reading that is slower than your actual speed. I presently have an 18 tooth gear in the trans. Long time lurker, first time poster. It combines this data to send the speed reading to the instrument cluster. GPS, on the other hand, uses a purely mathematical technique to measure the speed of the vehicle and is therefore more accurate than a speedometer. The causes of a bad speedometer will typically be found in these four things: A typical VSS. This will affect the length of your warranty (it would run out faster). Posts like an L36: Joined: Thu May 29, 2008 7:52 pm 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. European law (ECE-R39) says speedometers cannot show speeds less than the actual speed, and they must never show more than the 110 per cent of actual speed plus 4 km/h. The Turbo 350, Powerglide, and GM four-speeds have driven gears that have anywhere from 17 to 25 teeth. ... At 50 I was about 1 mph faster than the speedo was reading. Page 1 of 2 1 2 Next > For example, bigger rims will make you go faster than what the speedometer is actually reading. Very satisfied with this purchase My BMW is 2-3 mph faster on the speedometer than it is in real life (GPS). The UK law is based on the EU standard, with some minor changes. The faster your drive, the more your speedometer reading will be off. As long as a car is maintained at factory specs, its speedometer should continue to register vehicle speed within this range. Tires physically wear down over time, … 48. 60/65. Tire size and speedometer accuracy are directly linked to each other. This is the ONLY gear that it has issues with (reverse and the rest of the gears are good). I remember reading a notation about it in the factory shop manual. Edited September 30, 2019 by dmfconsult (see edit history) Apr 27, 2013. Ever wonder how far off your speedometer is with your new bigger tires? The law for car speedometers in the UK. For example, if the speedo is 3 mph too fast, the number of miles on the odomenter would be accululating at that rate as well. Drove an 06 LTD FWD from July 08 to August 10, moved on to a 2011 Flex. Speedometer reading at least 10% faster than actual speed. BMW does not allow the dealer to "fix" it. Up-sizing, or installing a taller tire, will lead to a speedometer reading that is slower than your actual speed. Your odometer will read lower, too. I've repeated the tests using a dash cam with GPS speed so you can observe the actual speed and the actual speedometer reading and clearly see they are way way off. I sent the cluster off and had all of the motors repaired and calibrated with the correct tire size 265/70R17. The speedometer in my 1965 mustang indicates 10 -15 mph faster than I am actually going. 3 Answers. The law for car speedometers in the UK. That means at 70mph, any reading between 70 and 80 is within spec. To put it another way, if the speedometer says you are doing 20 MPH, you're actually going 19 MPH. Ever marked your GPS reading lesser speeds than the speedometer of your vehicle? I am seeing an issue on my 2005 Freestyle AWD with the Speedometer Showing Faster Then Actual Speed by 5 MPH. I think we have the same tranny and rear end ratio in our cars. 2. I think my car speedometer is consistently 5 km/hr faster than the actual speed. 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 may not actually be the case. This is why the speedometer on my '7 with 35s and 4.10s is correct with no speedo gear change. Got An Electronic Speedometer (1995-Up): Superlift’s TruSpeed Module . My 2003 Cadillac CTS 3.2 V-6 Speedometer is reading approximately 25 MPH over the actual speed. A speedo must never show less than the actual speed, and must never show more than 110% of actual speed + 6.25mph. 13. My current car now is spot on with gps reading. It'll gradually read from 8mph faster than actual speed, and as you increase speed it'll read almost to 20mph faster than actual speed. Answer (1 of 8): Your speedometer will show a slower speed, assuming the diameter of your tires is greater than the factory spec tires. It just so happens that going to 31" tires over stock tires disturbs your speedometer by 10%, so it reads 10% less than what your actual speed is. Since the European laws do now allow the speedometer to display lower than the actual vehicle speed, BMW intentionally bias the speedometer readings high to make sure they do not violate that law. The speedometer is reading lower than the actual speed. Also you read higher speed if your tires is smaller than stock tires. 7 mo ago. Showing 60 when actually going 57. In general I would say 99% of all cars out there read 1 or 2 or even more mph faster than actual. One of the biggest signs your speedometer sensor is not working properly is the speedometer will display inaccurate readings or the needle or digital numbers will not move at all on the speedometer display. Nov 12, 2007. GM was sued, and lost, for certain models which displayed under actual speed. By Josh16. Car manufacturers will normally calibrate their sp… 1 Answer. This is a known and documented issue with BMWs. On a previous vehicle my reading was about 2kph faster than actual which was close enough, I put on winter tires, same brand, same size. Fixed my issue which was the speedometer was reading lower than actual vehicle speed. 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. The Turbo 350, Powerglide, and GM four-speeds have driven gears that have anywhere from 17 to 25 teeth. This can also affect your odometer and speedometer as larger tires will have a larger circumference, causing you to travel a little bit further per each complete tire rotation. Not a big deal but I was wondering if this can be repaired easily or is it a Subaru dealer fix only? 70/75. Strange-Agent. What would cause this to happen? I replaced the speed sensor located in the transfer case and still no luck. They send a signal to the ECM which then sends out another signal to the speedometer. If the speedometer was never re-calibrated with the new tires, it will register a slower speed than you are travelling. VSS– A faulty speed sensor will often be accompanied by the P0500 (VSS circuit malfunction) trouble code. I have a 2004 Chevrolet Silverado 1500 4wd with the 4L60-e 4 speed transmission. I have a 2009 GMC Sierra SLT 1500 with an edge performance chip and 20" tires and my speedometer. I swapped the rear axle in my '93 RMW due to a bad pinion bearing. I think I can answer you. I proved this my comparing my Speedometer to the speed being displayed on my Garmin GPS. I read in a couple places that speedometers are typically going to read a faster speed than the real speed. Speedometer shows 2 MPH faster than actual speed Discussion in ' Gen 3 Prius Technical Discussion ' started by windmilljumper , Sep 29, 2009 . 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