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Speedometer accuracy - when I set my Cruise to a certain speed, the speedo doesn't match - any others??

lmadsen

Member
When I set my cruise to a certain speed my speedometer does not show the same. My speedometer shows faster than set speed. Is this common and which one should I believe is correct? They are not that different but curious about what others see. Thanks
 
I've noticed that the speed shown on the speedo varies a bit (1mph up and/down) from the cruise set speed depending on road, weather conditions, etc.
I have also found that my speedo runs consistently 1mph higher than actual speed (according to Google and my wife pacing me in the car)...
 
I have also found that my speedo runs consistently 1mph higher than actual speed (according to Google and my wife pacing me in the car)...
Mines the same, reads about 2kph higher than actual, same deal with the cruise as well, it'll fluctuate 1-2kph.
 
There is really not much sense in trying to get the speedometer exactly on perfect. Every time you put a different rear tire on it will change again. Even a good bit of tire wear can make it go one or two mph off. The speedometer may be electronic, but tire diameter still affects it. Tire pressure can affect it too.

Even the front tire size can affect the speedometer, since there are speed reading disks attached to both front wheels which the nanny uses to compare to see if a tire lifted or one is sliding. I'm not sure if the speedometer is getting the speed reading off only one wheel, but it is probably the average of all three. Trying to adjust all that would be a waste of time which would soon be inaccurate again. If it within is 3 or 4 MPH, that is close enough. Even State laws allow enforcement vehicles to be +3 or -3 off the actual speed in Florida.
 
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I noticed something similar on my Honda Ridgeline recently.
The Cruise Control setting showed 55 mph, but the speedometer was showing 56 mph.
 
Speedometer accuracy has been an ongoing discussion issue here since Oct. 2009, the furthest back a search for speedometer accuracy goes. I've read that changing tires can improve the accuracy.

Another issue that has been discussed frequently is the accuracy of the clock. I believe the clock issue has been corrected since the clock on my 2022 is always correct. My previous rides were always off by 2 or 3 minutes.
 
Every speedometer on every vehicle I have owned since the 1960's has error. GPS and cellphone apps just give us the ability to view that error more precisely. Some of the variable are: tire size, tire pressure, load on the machine, wind resistance, and the calibration of the sensor (on modern equipment). Not only is the indicated speed in error, but an equivalent error will be observed in the odometer reading. For example, GPS speed (on flat open ground) is 60 mph, indicated speed is 62 mph, for a 3% error. For an actual distance of 100 miles, your odometer will read 103.3 miles. (p.s.: that's why the Iron Butt Association doesn't go my speedometer/odometer readings.)

Know the error, and go with it. If the reading is off by a couple of mph, that's a problem that doesn't need fixing.
 
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When I use the Waze app, the Spyder seems to be a pretty consistent 1 mph higher than what the Waze tells me I am really doing. But I am not sure what others here are referring to as the indicated cruise control speed. If that speed is indicated on the screen of my 2021 RT I never noticed it. I just use the cruise control switch to activate the cruise control based upon the speed I see on the digital speedometer. Taking account of the typical 1 mph variation, I usually set it, for example when the speedo shows 61 if I want to actually be going 60.
 
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