speed ohmeter is fast

[kwplot34]

99 Fleetwood tioga ford E350, V10. Is it normal for the speed/o to read fast on motor homes. Ours compared to the GPS reads 5 MPH fast. At 70 MPH the GPS says 65MPH. The GPS is accurate, have had it for several years and compared it with our other 4 vehicles and they read the same MPH.

[kwplot34]

CaptainCal wrote:
99 Ford's use an electric speedometer. They can be reset by you to read accurate for tire size changes. Type in 99 e350 speedometer on {YOU TUBE}. It will give you instructions on how to. Get the value that your speedo is presently set at and start from there.

Thanks for the information

[CaptainCal]

99 Ford's use an electric speedometer. They can be reset by you to read accurate for tire size changes. Type in 99 e350 speedometer on {YOU TUBE}. It will give you instructions on how to. Get the value that your speedo is presently set at and start from there.

[kwplot34]

Matt_Colie wrote:
Nobody's speedo is right on, you have to look. Is the error constant or linear. Meaning is the error always 5 or is it half of what you see at 70 when you are at 35??
The constant error can be fix as above, more the pointer on the shaft. If it is linear, then call a Ford dealer. Manufactures often have different speedo pickup gears for this. When they build a transmission they don't know what the final drive will be and the driveline people don't know what tires will be on the assembled vehicle.

Matt

The faster you go, the greater the difference,

[Matt_Colie]

Nobody's speedo is right on, you have to look. Is the error constant or linear. Meaning is the error always 5 or is it half of what you see at 70 when you are at 35??
The constant error can be fix as above, more the pointer on the shaft. If it is linear, then call a Ford dealer. Manufactures often have different speedo pickup gears for this. When they build a transmission they don't know what the final drive will be and the driveline people don't know what tires will be on the assembled vehicle.

Matt

[ronfisherman]

On my Chevy Kodiak chassis the speedometer was reading off from GPS. The ScanGaugeII read correct for MPH to GPS. Removed gauge cluster from dash. Removed needle from step motor and positioned to more correct location. Speedometer now reads within 1 MPH of GPS.

[kwplot34]

Thanks for all of the reply's. The tires are the correct size, I might try a shop and have them check the calibration. It is not huge issue, just kind of annoying.

[tatest]

Federal Motor Vehicle Safety Standards allow some small error, and there will always be a chance of error with variation in tire diameter from brand to brand (even in the same nominal size) and changes with wear. The standards do not allow the speedometer to read slow enough for you to notice, so it will normally be calibrated to read slightly fast at some speeds.

My last truck read 3-5 mph fast at slow speeds, caught up with the GPS at about 65-70. My current truck (E-350) reads about 3 mph fast a slow speeds, 1-2 mph fast at 70 mph.

[crasster]

Cobra21 wrote:
If the tires are smaller than factory spec. it will read fast. Check if they
are the correct size?

X2 This absolutely can make a difference.

[tpi]

My E450 has always read about 2 MPH faster than GPS indicates. Quite typical.

[dicknellen]

My e-350 Winnie is 1 to 2 miles slower than my Garmin GPS. Have not done a MM check. Tires are the correct size. Dick

[TucsonJim]

Most cities have shops that will calibrate your speedometer. Just do a search for:

"Speedometer Calibration". Many options should pop up. I just did a search for my city of Tucson and had 1/2 dozen shops show up.

Jim

[WyoTraveler]

I think 3 to 5 is not uncommon.My MH is slightly fast. Not enough to measure. My PU is about 3 mph fast. Never saw one slower.

[enblethen]

Tires are not of correct size for speedo setting in computer. many tire shops have OBD unit to change.

[valhalla360]

I don't think it's a MH issue. We rent cars several times a year for work and 3-5mph faster than actual speed is pretty common (based on comparison to a couple of GPS that match each other). Sometimes, they match dead on.

Never see one show a lower speed...of course that may be a liability thing. The manufacturer doesn't want the blame if the speedo says 55mph and you get a ticket for doing 60mph.