 Speedometer Speed Adjustment ?, Speedometer Speed Adjustment ? |
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| Ken Mikos |
 May 2 2021, 07:31 PM
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#1
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Newbie  Group: Members Posts: 28 Joined: 20-February 14 From: Pgh Member No.: 17,024 Region Association: None  |
How do i adjust the speedometer, reading about 20mph to fast. Thanks in advance for any replies. Ken
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| robkammer |
May 5 2021, 06:54 PM
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#2
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Member Group: Members Posts: 179 Joined: 7-January 21 From: Vermilion Ohio Member No.: 25,049 Region Association: North East States |
During my second drive of my new 74 I noticed that the speedo is off by 5mph at 60 compared to the Waze gps reading. Waze says 60 and the speedo says 65. Skinny standard spec tires, no knowledge of any gearing changes. The car seems mostly stock.
I'm ok with it but what could be the source of this discrepency? |
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| Superhawk996 |
May 6 2021, 06:42 AM
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#3
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914 Guru Group: Members Posts: 5,993 Joined: 25-August 18 From: Woods of N. Idaho Member No.: 22,428 Region Association: Galt's Gulch 
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QUOTE(robkammer @ May 5 2021, 08:54 PM)  Waze says 60 and the speedo says 65. Skinny standard spec tires, no knowledge of any gearing changes. The car seems mostly stock. I'm ok with it but what could be the source of this discrepency? Waze or other GPS based speed app's are often 1-2 mph different from speedo even on modern vehicles running OEM tires. Modern vehicle electronic speedo is much more accurate than 914 analog, cable and gear driven speedo so not surprised by higher variance to 914. 5mph is a bit high but not outrageous. 1) Tire have OD (Revoltuitons per mile) variability based on manufacturing, load, inflation pressures, and even running speed itself. 2) GPS has location accuracy/resolution is limited and is not perfect either, that can affect speed calculations. https://www.gps.gov/systems/gps/performance/accuracy/ For highly accurate positional and speed accuracy you need a GPS base station and a differential GPS arrangment. https://www.nj.gov/dep/gis/faqgps.html#:~:t...n%20the%20field https://en.wikipedia.org/wiki/Differential_GPS |
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Posts in this topic
Ken Mikos Speedometer Speed Adjustment ? May 2 2021, 07:31 PM
TheCabinetmaker What wheels and tires? It makes a difference. May 2 2021, 08:15 PM
Ken Mikos It’s not the tires. Had the Speedometer in for O... May 3 2021, 07:32 AM BENBRO02 You would probably need to take it apart and chang... May 3 2021, 08:12 AM Shivers
It’s not the tires. Had the Speedometer in for ... May 3 2021, 08:30 AM brant unless you have the correct ratio gears... not so... May 3 2021, 08:45 AM Dave_Darling The speedo works by spinning a magnet inside of an... May 3 2021, 10:36 PM Ken Mikos Thanks for all the replies, looks like I’m sendi... May 4 2021, 07:09 AM robkammer During my second drive of my new 74 I noticed that... May 5 2021, 06:53 PM brant
During my second drive of my new 74 I noticed tha... May 6 2021, 06:24 AM mepstein Even modern cars aren’t usually gps accurate. May 6 2021, 06:32 AM Jamie
Even modern cars aren’t usually gps accurate.
... May 6 2021, 07:23 AM |
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