| T O P I C R E V I E W |
| Squaredancer |
Posted - 26 mai 2005 : 16:56:11
I have noticed that my speedometer reading differs from the readings that I get from my GPS Programs. It doesn't make much difference which program that I use, the difference seems to be about the same. The automobile speedometer reads about 3 MPH higher than the GPS data. I'm wondering which is more accurate, GPS or auto reading.
Bob |
| 8 L A T E S T R E P L I E S (Newest First) |
| Sam Ontario |
Posted - 27 juin 2005 : 17:13:25
quote:
Originally posted by Squaredancer
I drive a 96 Ford Crown Victoria.
I thought that the factory "calibrated" accuracy of a speedometer was supposed to be in the 1% range. That would mean that traveling at 60 MPH, my speedometer should be within .6 MPH of my actual speed. A difference of 5 MPH makes the accuracy only 8%.
"Calibrated" against new tires not against bald tires! You probably need new tires if you are running correct stock tires.
Sam |
| Sam Ontario |
Posted - 27 juin 2005 : 17:05:59
From
http://www.bigwheels.net/index.php?location=wheels&view_mode=car&action=&model=&model_vehicle=Crown%20Victoria
Your car has stock tire size 225/60-16. If your car has 4 tires of that size (most probably you have a smaller profile car tire) and you are 5mph off, then choose 225/65-16 to correct your speedo. If you are concern about your 90yrold passengers feeling (?) get 225/70-16 to quiet (mislead) her down.
Sam |
| Squaredancer |
Posted - 25 juin 2005 : 23:48:04
LOL....that happens all the time when I drive my 90 yr old parents to FL. How do you tell your mother to SHUT UP? Even if you did, do you think she'd listen?????? |
| Marvin Hlavac |
Posted - 25 juin 2005 : 23:45:55
Bob, when the lady at the passenger seat it telling you to slow down, now you can give her a good explanation that your speed is not really as high as it appears to be 
Marvin Hlavac - Toronto, Canada |
| Squaredancer |
Posted - 25 juin 2005 : 20:21:26
I drive a 96 Ford Crown Victoria.
I thought that the factory "calibrated" accuracy of a speedometer was supposed to be in the 1% range. That would mean that traveling at 60 MPH, my speedometer should be within .6 MPH of my actual speed. A difference of 5 MPH makes the accuracy only 8%. |
| mkat1970 |
Posted - 25 juin 2005 : 20:03:02
gps is definitely the accurate one. what kind of car do you have? i have an older BMW, and when i worked in the parts dept of a BMW dealer a few years ago, one tech showed me a bulletin they used to explain to customers about speedo readings. The bulletin stated that BMW speedos could be off as much as 5mph from the factory, in the direction of reading faster than the car is actually going. Couple this with the fact that i had used rear end put in my car (it needed it) that has different gearing than original, and I consistently am going 5mph slower than the posted limit (if my speedo reads 45, and the limit is 45, my gps has shown i'm going 39 or 40). the previous post about tire size is very relevant too, as i run into customers that want bigger wheels. if they aren't careful to maintain the overall tire&wheel diameter, within the 3% he mentioned, the speedo reading will be wrong. |
| Sam Ontario |
Posted - 27 mai 2005 : 15:08:36
GPS is more accurate. Apart from tire wear, your tire profile might have been offset by 3% or more. Say if your tire is 195/60/R15, you can increase your tire size to 195/65/R15.
Sam |
| Marvin Hlavac |
Posted - 26 mai 2005 : 17:47:19
It is easier for your GPS to be more accurate. The car speedometer is affected by tire wear, too. Speedometers are allowed by law to be off by 0 to +10%, meaning they can show up to 10% higher than real speed, but they are not allowed to show you that you are travelling at a lower speed.
Marvin Hlavac - Toronto, Canada |
- 
- 
