Speedo Accuracy....Testing
11-05-2008, 10:42 PM
#1
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Speedo Accuracy....Testing
If you have an iPhone, download SpeedBox from the App store.
It's free and I've found it to be spot on, cross referenced to my eTech.
Things I do while on my road trip...
BTW mine is -3.5-4 mph off.
It's free and I've found it to be spot on, cross referenced to my eTech.
Things I do while on my road trip...
BTW mine is -3.5-4 mph off.
Last edited by MJones; 08-03-2010 at 12:31 PM.
11-06-2008, 01:03 AM
#6
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Thanks - I'll check that too. I like the pic for comparison with the eTech.
Not sure if I could drive with my knees, balance two devices on the dash and use my camera as effectively as you could, though. Laptop on the passenger seat for immediate posting to Rennlist?
Not sure if I could drive with my knees, balance two devices on the dash and use my camera as effectively as you could, though. Laptop on the passenger seat for immediate posting to Rennlist?
11-06-2008, 01:14 AM
#7
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My 06 is optimistic at most speeds by showing nearly 3 mph over actual.
Interestingly, the rear tail comes up at actual 75 mph,--and not INDICATED mph. Now THAT is a neat trick by Porsche.
Interestingly, the rear tail comes up at actual 75 mph,--and not INDICATED mph. Now THAT is a neat trick by Porsche.
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11-06-2008, 01:59 AM
#8
Rennlist Member
Cool Brian!
Have a great time on your trip and of course at Barber. Tell Hurley I'm glad he's a cat person.
Have a great time on your trip and of course at Barber. Tell Hurley I'm glad he's a cat person.
11-06-2008, 03:37 AM
#9
Nordschleife Master
These days there is no reason why a speedo should not be accurate.
11-06-2008, 10:59 AM
#10
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The actual speed can differ from the speedometer by up to 3% for tread wear. then depending on what brand of tires you have on the car there can be almost another percentage due to different diameters. Then there is air pressure. This changes the diameter of the tire as you drive.
So other than the +/-5% you may see due to tire diameters there is no reason speedos shouldn't be accurate.
So other than the +/-5% you may see due to tire diameters there is no reason speedos shouldn't be accurate.
11-06-2008, 12:14 PM
#11
Race Director
My 06 and 07 were 3mph slower than my GPS. My 09 is 1mph slower. I wonder what they changed? Every BMW I have ever had is 3mph slower than actual speed. This is something BMW does. All my American cars have been spot on. Weird!
11-06-2008, 01:41 PM
#12
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My 07 TT indicates 3 miles per hour faster than actual.
BTW, Speedalert is a free iPhone App for monitoring speed. I compared it (Speedalert on my iPhone 3g) to a handheld Garmin to the car--both GPS's agreed.
BTW, Speedalert is a free iPhone App for monitoring speed. I compared it (Speedalert on my iPhone 3g) to a handheld Garmin to the car--both GPS's agreed.
11-07-2008, 08:24 PM
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Based on passing quite a few portable radar units, my digital speedo appears to read 3 to 4 mph high. The analog speedo is nearly useless at any velocity.
11-07-2008, 09:38 PM
#15
Markers on the highway, a watch with a second hand, driving 60 mph as indicated by speedo .......... I'm cheap. So, why spend $$$$$ for something that could easily be checked out by everyday stuff and simple math?
