seedometers don't agree
#1
Registered User
Thread Starter
Join Date: May 2002
Location: phoenix,az
Posts: 203
Likes: 0
Received 0 Likes
on
0 Posts
seedometers don't agree
anybody else notice that the speedometers don't coralate with eachother. both duing acceleration and at a steady speed. I fist thought that maybe the dial could move as fast as the digital readout during acceleration but when cruising I noticed a differance of 2-4 mph. on top of that they would alternate as to which one was higher.
which do you think is more accurate, the dial or digital?
which do you think is more accurate, the dial or digital?
#2
Registered User
Join Date: Jul 2002
Location: Fort Lauderdale, FL
Posts: 223
Likes: 0
Received 0 Likes
on
0 Posts
Same issue with mine, seemed to be 2 miles difference, digital always reads slower in mine than the analog speedo, except at 0 MPH. I'm wondering if they're measuring differently?
#6
Registered User
Join Date: May 2002
Location: maryland
Posts: 2,572
Likes: 0
Received 0 Likes
on
0 Posts
The reason for this (I read an article about the subject in C&D a while back), is that by law the spedo has to be calibrated so that the actual speed is never faster than the indicated speed. I think this may be a liability issue so that if you get a ticket you can't say "well the spedo said I was doing 55mph but the car was really going 60mph so it's not my fault" In other words every speedo has a built in error so that you are always traveling slower than indicated. This is a built in error and can not excees a certain percentage of the total speed, so the error will be less at slower speeds (say 2 mph at 40), but bigger difference at higher speed (say 6 mph error at 120).
Now the digital computer is not governed by this law so it is probably more accurate.
Now the digital computer is not governed by this law so it is probably more accurate.
Trending Topics
#8
Registered User
Join Date: May 2002
Location: maryland
Posts: 2,572
Likes: 0
Received 0 Likes
on
0 Posts
Originally posted by SunsetZ
Wouldn't it be the other way around then. If the digital does not have to show =/ or faster than reality, then why is it reading slower than the needle?
Wouldn't it be the other way around then. If the digital does not have to show =/ or faster than reality, then why is it reading slower than the needle?
#11
Registered User
I would think the digital is more accurate since it has to calculate the MPG, miles to empty, etc. Someone will enventually test this with a radar gun I'm sure.
#13
Registered User
Join Date: Aug 2002
Location: Annapolis MD
Posts: 66
Likes: 0
Received 0 Likes
on
0 Posts
Originally posted by Z&Jet-Pilot
I'm sure some Z owner owns a handheld GPS unit that read out the car speed! That would be an easy way to check the accuracy of both speed indications.
I'm sure some Z owner owns a handheld GPS unit that read out the car speed! That would be an easy way to check the accuracy of both speed indications.
#15
Registered User
Join Date: Jun 2002
Location: Central Jersey
Posts: 242
Likes: 0
Received 0 Likes
on
0 Posts
Now that it was mentioned I remember reading about Miata owner's filing complaints years back. Apparently when the Miatas first came out, Mazda dialed the speedos to the highest percentage above the actual speed allowed by law to give the owners the feeling of driving faster! Apparently there is a small range in which manufacturers must calibrate speedos within. Anyone else remember this?
#16
Charter Member #13
Join Date: May 2002
Location: California
Posts: 745
Likes: 0
Received 0 Likes
on
0 Posts
I don't know what the big deal is here; on the analog speedo, one MPH is about a millimeter in needle movement. Mine is usually within a MPH of the digital readout. Even two MPH is pretty damn close!
#17
Originally posted by spf4000
You could always try to find one of those police radar trucks that display your speed as you zoom past them.
You could always try to find one of those police radar trucks that display your speed as you zoom past them.
#19
Banned
iTrader: (2)
SPEED
Feeling like typing, so........
Try this simple calculation: Time with a digital stopwatch, or a Timex IronMan, the time between mile markers (on all expressways), divide that number into 3600, walaha(SP?), the REAL speed. As an example, 48.6 seconds to cover a mile=74.07 MPH, not that I would EVER drive that fast
Doing the same over 10 miles is even more accurate.
Message being, NEVER trust factory calibrations!
As a side note, highway mile markers are a great way to verify a vehicles odometers. Most are off.
BTW, most speedo's errors are non-linier, the percentage of variance changes.
Try this simple calculation: Time with a digital stopwatch, or a Timex IronMan, the time between mile markers (on all expressways), divide that number into 3600, walaha(SP?), the REAL speed. As an example, 48.6 seconds to cover a mile=74.07 MPH, not that I would EVER drive that fast
Doing the same over 10 miles is even more accurate.
Message being, NEVER trust factory calibrations!
As a side note, highway mile markers are a great way to verify a vehicles odometers. Most are off.
BTW, most speedo's errors are non-linier, the percentage of variance changes.
Last edited by EnthuZ; 09-02-2002 at 03:46 PM.
#20
I have a GPS unit that connects to my laptop and I use it along with Street Atlas software on long trips. With the cruise set exactly on 90, I noticed that the GPS stated I was going 88. I have noticed a 2-3 MPH difference in 3 different cars.
-Plucky
-Plucky