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Speedometer Question
- Thread starter Moparracer89
- Start date
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stationhollow
Plinker
no i dont think so. an atv is legal in most county areas and most have no speedometer.
if they stop you for any reason your speedometer will look functional anyway. just yell out your window every once and awhile and ask people how fast they are going. (funny but ive seen it done) probably would be better off to get it fixed though. good luck
if they stop you for any reason your speedometer will look functional anyway. just yell out your window every once and awhile and ask people how fast they are going. (funny but ive seen it done) probably would be better off to get it fixed though. good luck
Tactical Dave
Grandmaster
[ame]http://youtu.be/ZKtFIgmoqoI[/ame]
If you haven't got a speedometer why don't you use a GPS to see how fast you are going or even a smartphone with GPS, or better still fix your speedo, just sayin'
IndyBeerman
Was a real life Beerman.....
DING DING DING!!!
Winner Winner, Chicken Dinner!!
Ulysse Speedometer
It's a great andriod app that even features a Heads Up Display for the dash.
Great App, I've used it for a lobe time and it is very accurate.
https://play.google.com/store/apps/...wxLDEsImNvbS5iaW5hcnl0b3lzLnNwZWVkb21ldGVyIl0.
Indy_Guy_77
Grandmaster
- Apr 30, 2008
- 16,576
- 48
Our Garmin GPS is 2-3 mph slower than our Speedometer in our van...
I've not done anything with my phone.
Thing is: Without some kind of standard to measure each device against, how would one know which one is the correct one? Or the more correct one?
I mean, unless you have a RaceLogic GPS system like the car mags use, can the regular ol' navigation GPS units be completely trustworthy for speed measurement?
eldirector
Grandmaster
Speedomoters are not required by IC, but an odometer is (with a few exemptions) : Indiana Code 9-19-9
Since most are paired with the speedometer, this could be an issue.
Since most are paired with the speedometer, this could be an issue.
Thing is: Without some kind of standard to measure each device against, how would one know which one is the correct one? Or the more correct one?
Known distance divided by time equals speed. Just south of Franklin on US 31 is a speedometer check area. Five miles of accurately spaced mile markers. 60 miles per hour equals 60 seconds. If you complete a mile in less than 60 seconds, you are going faster than indicated. If it takes you longer than 60 seconds, you are going slower than indicated. Stopwatches are your friend. Know the distance between any two points and how long it takes to go between them and your basic grade school math will solve the issue for you.
That is..........assuming you passed grade school math.
Distance/Time works like ...well math. Honestly, as good as most modern gps is, I'd say your speedo is off if there is a difference between them. I've had up to 13 students, all with varying brands of gps units, in a university van and had no discrepancy between them and a 2 mph discrepancy with the speedo. But yeah, fix the speedo...
Indy_Guy_77
Grandmaster
- Apr 30, 2008
- 16,576
- 48
Yes, I'm quite aware of the speedometer check zone. Also quite familiar with how R = D/T.
Want to get into how unscientific a feller and a stopwatch is?
Part of my job is that I certify instruments against standards. I know how the process works. Thanks.
-J-
Accuracy shouldn't be too much at issue with any decent, even cheapo stopwatch, at least not at mph rates. Precision would be the wildcard. The stopwatch method is only as precise as the weakest link in the system; in this case that would be the human being tripping said watch. With practice, an individual should become more proficient and presumably more consistent.
It works, its accurate, its not so precise. The police still use it to issue tickets, so its apparently "close enough."
Ed: I just downloaded a Speedo app for my iPhone, gonna make a run to Indy in a few so I'll test it against my truck's digital speedo and Sportrac Pro gps. Data incoming
It works, its accurate, its not so precise. The police still use it to issue tickets, so its apparently "close enough."
Ed: I just downloaded a Speedo app for my iPhone, gonna make a run to Indy in a few so I'll test it against my truck's digital speedo and Sportrac Pro gps. Data incoming
Indy_Guy_77
Grandmaster
- Apr 30, 2008
- 16,576
- 48
Looking forward to the comparison!!!
If you can have a passenger take photos of the devices while in-transit, that'd be fantastic.
-J-
DocGlock86
Expert
Beat me to it. Had an older truck that the speedometer went out in it. Was quoted a few hundred dollars to fix it. The truck wasn't worth the cost. Just used my Tom Tom until I got me a newer vehicle. Probably wasn't completely accurate but it got me by.
No passenger to take photos, sorry.
The Sportrac Pro and iPhone app, called (appropriately enough) Speedometer, were in good agreement at all steady speeds ranging from 35 mph to 70 mph, with the iPhone seeming a little less responsive to variation(s). Both showed speeds of approximately 1.7mph greater than my vehicle speedometer.
Using mile markers as a fixed reference, my odometer reported slightly less distance traveled (0.10 mi standard) than the mile markers. This remained constant regardless of speed. Using the stopwatch and odometer method yielded calculated data that were (as close as I could collect, considering myself as the source of systemic error with the stopwatch) in good agreement with respect to each other, and approximately 1.5-1.9mph slower than both GPS readings, again at all speeds. Using the stopwatch and mile-marker methodolgy I calculated a rate(s) of speed in generally good agreement with the GPS unit(s).
This lead to three possible conclusions: 1) that the GPS units are inaccurate, 2) that my vehicle speedometer/odometer is inaccurate, or 3) that the tires on my vehicle are of incorrect size. Reasons for this could be: A) GPS technology inherently sucks, B) miscalibration of the speedometer/odometer, or C) tire size being larger than the size for which the speedometer/odometer is calibrated.
I reject the premise that GPS technology inherently sucks; and I verified that the tire sizes are correct as recommended per the manufacturer tag in the vehicle, and cross-referenced this with an online tire store as a secondary line of evidence.
Having donned my lab coat and slide rule appropriately, I lean toward the conclusion that miscalibration of the speedometer/odometer is the culprit. This conclusion is well supported due to; the tires being of verified correct size (and theoretically being of a slightly reduced diameter due to 20k wear, which should have the opposite effect of showing an increased speedometer reading and a greater number of miles traveled), the incongruity between the odometer data and the mile-markers, the additional incongruities of the speedometer not reporting the same speeds as the two GPS devices used, the general agreement of the stopwatch and mile-marker method as compared to the GPS data, and that the data from the two GPS devices being in good agreement with each other.
The good news is that due to the lower number of miles being recorded, my vehicle is retaining value longer.
The bad news is that any time I get paid mileage for work, while using my vehicle, I'm losing money. I am now also on record as being more of a geek than I ever wished to publicly admit.
The Sportrac Pro and iPhone app, called (appropriately enough) Speedometer, were in good agreement at all steady speeds ranging from 35 mph to 70 mph, with the iPhone seeming a little less responsive to variation(s). Both showed speeds of approximately 1.7mph greater than my vehicle speedometer.
Using mile markers as a fixed reference, my odometer reported slightly less distance traveled (0.10 mi standard) than the mile markers. This remained constant regardless of speed. Using the stopwatch and odometer method yielded calculated data that were (as close as I could collect, considering myself as the source of systemic error with the stopwatch) in good agreement with respect to each other, and approximately 1.5-1.9mph slower than both GPS readings, again at all speeds. Using the stopwatch and mile-marker methodolgy I calculated a rate(s) of speed in generally good agreement with the GPS unit(s).
This lead to three possible conclusions: 1) that the GPS units are inaccurate, 2) that my vehicle speedometer/odometer is inaccurate, or 3) that the tires on my vehicle are of incorrect size. Reasons for this could be: A) GPS technology inherently sucks, B) miscalibration of the speedometer/odometer, or C) tire size being larger than the size for which the speedometer/odometer is calibrated.
I reject the premise that GPS technology inherently sucks; and I verified that the tire sizes are correct as recommended per the manufacturer tag in the vehicle, and cross-referenced this with an online tire store as a secondary line of evidence.
Having donned my lab coat and slide rule appropriately, I lean toward the conclusion that miscalibration of the speedometer/odometer is the culprit. This conclusion is well supported due to; the tires being of verified correct size (and theoretically being of a slightly reduced diameter due to 20k wear, which should have the opposite effect of showing an increased speedometer reading and a greater number of miles traveled), the incongruity between the odometer data and the mile-markers, the additional incongruities of the speedometer not reporting the same speeds as the two GPS devices used, the general agreement of the stopwatch and mile-marker method as compared to the GPS data, and that the data from the two GPS devices being in good agreement with each other.
The good news is that due to the lower number of miles being recorded, my vehicle is retaining value longer.
The bad news is that any time I get paid mileage for work, while using my vehicle, I'm losing money. I am now also on record as being more of a geek than I ever wished to publicly admit.
Last edited:
remauto1187
Shooter
Good god! You would think with all the knowledge of using the equation to figure speed that there would be someone out there that would be more entertained on how to fix the speedometer...like me......
What is the year make and model. If its a GM and around 1998 or newer then theres a 90% chance that the Stepper motor that drives the needle is bad because the originals have been superceded by a more dependable version.
Here's a question for you! DOES THE ODOMETER STILL ADVANCE WHILE DRIVING? If so then your speed sensor is working and your problem is in your instrument cluster. If not then most likely your speed sensor (VSS) is bad.(most bolt onto tailshaft of tranny, some fords put them on the rear axle).
If your vehicle is so old that its speedo is cable driven then thats a totally different game.
What is the year make and model. If its a GM and around 1998 or newer then theres a 90% chance that the Stepper motor that drives the needle is bad because the originals have been superceded by a more dependable version.
Here's a question for you! DOES THE ODOMETER STILL ADVANCE WHILE DRIVING? If so then your speed sensor is working and your problem is in your instrument cluster. If not then most likely your speed sensor (VSS) is bad.(most bolt onto tailshaft of tranny, some fords put them on the rear axle).
If your vehicle is so old that its speedo is cable driven then thats a totally different game.
eldirector
Grandmaster
I remember reading, though it was a long while ago, that factory speedometers are purposely set to read high (display a higher rate than actual). I don't recall the reason, but assume liability.
Well, from Wiki:
Speedometer - Wikipedia, the free encyclopedia
All my vehicles read 3-5% higher than GPS recorded speeds (3 different Garmins and my iPhone). Even the rental cars I've driven read slightly higher than GPS speeds.
Actually, my TJ reads 10% LOWER right now. Larger tires, and I haven't installed the new speedometer gear yet. I just do the math in my head, or drive with traffic.
Well, from Wiki:
Speedometer - Wikipedia, the free encyclopedia
All my vehicles read 3-5% higher than GPS recorded speeds (3 different Garmins and my iPhone). Even the rental cars I've driven read slightly higher than GPS speeds.
Actually, my TJ reads 10% LOWER right now. Larger tires, and I haven't installed the new speedometer gear yet. I just do the math in my head, or drive with traffic.
