You folks are making me feel better as I go around shutting cabinet doors and drawers and closet doors. But then you did laugh at me when I complained about the street crew not getting the people hole covers on straight so that the yellow lines on the cover lined up with the yellow lines on the road.
A couple of points, car speedometer accuracy varies from car to car but changes as tires wear. I always used to check truck odometers on a 100 mile span on the NY Thruway but I caution you not to try it on I- 90 in Ohio, they seem to plant their mile markers wherever they get kicked out of the pickup truck. You don’t need to go 60 mph to check your speedometer, just set your cruise control where you want it and see how many seconds it takes between mile markers and divide into 3600 and that is your actual mph. For example 50 seconds = 72 mph.
Thanks for the kind words! It really is about elapsed times, but I always enter average speeds in my book that I started a little over 5 years, ago.
I don’t always run or bike the same course, so it allows me to compare. Once in while I’ll run an organized 5k and get a cool, but expensive T-shirt 
, but depending on the day, knee or hip pain can take the “fun” out of it. Bicycling doesn’t seem to bother my joints. 
CSA
From what I’m reading about them they’re basically mount and go, doesn’t have all the navigation features that you could spend $300 on but would do just fine for most users.
A few years back I had a new Mazda whose speedometer and odometer were off by +6%. After many hours of pursuing it with Mazda, i finally talked to an engineer at their USA engineering facility who confirmed that the company considers it normal to be within +/- 7%.
I’ve since learned Mazda isn’t alone with those tolerances.
That’s one way to make owners feel that they are getting better fuel economy.
That too!
CSA
It would be interesting to see what the Measure Distance tool in Google Maps reports, although you’ll have to put in a large number of intermediate points for a curvy route.
From all comparisons, my speedo and odo are dead-nuts accurate. However, the MPG calculation is always 5% optimistic. Last tank took 8.9 gal after going 518 miles for 58 MPG while the computer said 61 MPG.
I guess I am in the I don’t really care that much category. The speed limit tracking signs match my speedometer pretty well, my big concern would be speed limit, keeping myself less than 10 over.
I hate to break it to you conservatives out there, but this is an issue Ralph Nader talked about in “Unsafe at Any Speed”.
Referencing Ralph Nader as an expert on cars does not impress…
;-]
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If you wish to insult those who do not meet your political standards please do so on an appropriate forum.
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The handling problems of Corvairs was exacerbated by inflating all 4 tires to the usual 29psi instead of the factory recommended 18psi front-30psi rear. Yes. Ralph Nader is an automotive idiot.
And the Corvair had exactly the same type rear suspension design (independent swing axle) as the VW Beetle and early Mercedes Benz (and others). No criticism from Ralphy for those 2 carmakers.
Seems incredibly thin-skinned of you to consider that an insult.
Do study our current president, the reigning master of insults.
Actually, Nader had plenty of criticism for the Beetle. Just look it up.
Not thin skinned just pointing out that this is not a political forum. Oh. There you go again. My 4favorite POTUS in my lifetime are Truman, Eisenhower, JFK, and Regan. I wish we could return to the politics I grew up with when Democrats and Republicans could work together for the good of our nation and it’s citizens.
Interesting when the beetles swing axles did not kill a driver and 83 innocent spectators at LeMans in 1955 like the Mercedes 300SL.
I just took a trip around in the course in the Bonneville. I added it to the list.
Dodge Caravan: 27.3 miles
Grand Prix: 27.0 miles
Map My Ride GPS app: 27.5 miles
Bonneville: 27.0 miles
I guess with all things considered, the cars are pretty close to each other in odometer readings.
A Marathon is 26.21875 miles. I went 27. Good to know that I rode the distance faster than the world record Marathon runner! 
Oh, incidentally, I don’t know if it matters or not, I was sitting on my butt 
and able to accelerate to 26 mph on some downhill sections, whereas a runner 
can’t do that. LOL 
Close enough, right? 
I wish I could come up with a way to verify the distance. I have been reading up on how they set the distance for official Marathon races. It is interesting.
CSA
You should read the 1959 Popular Science mag provided in another thread. They had the testing information for 59 Fords, Chevys and Plymouths. Speedo accuracy was one thing tested. Don’t quote me but both Ford and Chev were off about 1 mph at 60 but plymouth was off more. The odometer read 106 after 100 miles. Might be a point of contention if a problem develops at 36,100 miles and the warranty ran out at 36,000. I never had a problem with my Buick since the covered it anyway slightly past the 50,000 mark on a 50K warranty, so maybe they figured the mileage wasn’t accurate anyway…