SuperCrew speedo correction
#16
06-19-2002 | 01:34 PM
Senior Member
Joined: Mar 2001
Posts: 509
Likes: 0
From: Corona, CA
Scratchin' my head on this one...
I swapped out wheels/tires last year. The stock tires were 275/60-17 (30" tall)...replaced with 285/60-18 (31.5" tall). To find out the difference in speedometer registration, I looked up the difference on some website and going from memory, the difference was a minus 4.7% (speedo registering slow).
To verify the math, I passed by one of those radar trailers that lets you know how fast you're going. My speedo said 70, and the radar trailer sign displayed 73.5...which coincides with the math calculations. However, my odometer is off even more...over 7% (under-registering mileage). I found this out on one of the highways that has mileage marker signs. In a 3-mile distance and doing some quick math...my odometer registered 8.0% slow. I thought: "whoa...I must be getting better fuel mileage than I thought". To confirm this, I used a Garmin GPS and drove about 35 miles around town and the difference was 7.4%. I can only surmise that even with the stock wheel/tire setup, my odometer was under-registering ~3%.
Has anyone else experienced slow odometer registration directly from the factory?
I swapped out wheels/tires last year. The stock tires were 275/60-17 (30" tall)...replaced with 285/60-18 (31.5" tall). To find out the difference in speedometer registration, I looked up the difference on some website and going from memory, the difference was a minus 4.7% (speedo registering slow).
To verify the math, I passed by one of those radar trailers that lets you know how fast you're going. My speedo said 70, and the radar trailer sign displayed 73.5...which coincides with the math calculations. However, my odometer is off even more...over 7% (under-registering mileage). I found this out on one of the highways that has mileage marker signs. In a 3-mile distance and doing some quick math...my odometer registered 8.0% slow. I thought: "whoa...I must be getting better fuel mileage than I thought". To confirm this, I used a Garmin GPS and drove about 35 miles around town and the difference was 7.4%. I can only surmise that even with the stock wheel/tire setup, my odometer was under-registering ~3%.
Has anyone else experienced slow odometer registration directly from the factory?
#17
06-19-2002 | 02:49 PM
Technical Article Contributor
Joined: Jun 2002
Posts: 10,511
Likes: 7
From: Under the flightpath of old ORD 22R
I have notice the speedo being off..
The electric speed sign going into O'Hare airport is for 35, when I drive 40 mph ( using the analog, I keep forgetting to try the odometer electric speed hack ) I get a 37 or 38 mph reading.
I took this to be the angle of the gun, deflection, and maybe the sign is not in the best repiar, until you just posted this.
Maybe you shoudl verify your electric sign reading against the odometer hack, just to rule out the analog viewing.
The odometer delta...I don't have any solid thing to check against this, unless you can use an acreage wheel to verify the DOT guys put the sign at the right place. In IL I would nto put it past them to have some of them be off <g>
sms
I took this to be the angle of the gun, deflection, and maybe the sign is not in the best repiar, until you just posted this.
Maybe you shoudl verify your electric sign reading against the odometer hack, just to rule out the analog viewing.
The odometer delta...I don't have any solid thing to check against this, unless you can use an acreage wheel to verify the DOT guys put the sign at the right place. In IL I would nto put it past them to have some of them be off <g>
sms
#20
06-20-2002 | 12:28 PM
Senior Member
Joined: Mar 2001
Posts: 509
Likes: 0
From: Corona, CA
Creole,
If you hold in the trip meter button in on a digital console, turn key to on position, continue to hold the trip meter button for another 4-6 seconds, the display will go into a test mode. You then release the button, then push again to cycle through the various read-outs. One of the readouts is MPH. What SSCULLY stated previously, you can then watch the MPH in numbers versus watching the speedometer needle.
If you hold in the trip meter button in on a digital console, turn key to on position, continue to hold the trip meter button for another 4-6 seconds, the display will go into a test mode. You then release the button, then push again to cycle through the various read-outs. One of the readouts is MPH. What SSCULLY stated previously, you can then watch the MPH in numbers versus watching the speedometer needle.
#21
06-20-2002 | 01:00 PM
Member
Joined: Apr 2002
Posts: 52
Likes: 0
From: Down South
#22
06-20-2002 | 01:42 PM
Senior Member
Joined: Mar 2001
Posts: 509
Likes: 0
From: Corona, CA
I don't believe "odometer" and "trip" are included because you already get that in normal mode.
and Yes, you can go into the test mode with the engine running...
Instead of stopping at the "ignition on" position, continue turning the key to start the engine with the trip meter depressed. After it's started, continue to hold the trip meter button in until you see all of the gauge needles sweep to their highest point and back...about 5 second hold time.
Here's some more info on it:
http://www.mustangworld.com/ourpics/News/99hec.htm
Have fun with it!
and Yes, you can go into the test mode with the engine running...
Instead of stopping at the "ignition on" position, continue turning the key to start the engine with the trip meter depressed. After it's started, continue to hold the trip meter button in until you see all of the gauge needles sweep to their highest point and back...about 5 second hold time.
Here's some more info on it:
http://www.mustangworld.com/ourpics/News/99hec.htm
Have fun with it!