RPMs @70mph?
Senior User
Joined: Apr 2005
Posts: 430
Likes: 0
From: s.e. Michigan
harold, I have reason to believe my speedo is now correct after upsizing rear tires 8% and 8% of a 36,000 warranty adds almost 3,000 miles to that warranty that would have been shorted by that amount if stock tires had been left on. I think that is significant. If you only find amusement with that then enjoy, but this forum is a good source of info and I have trouble swallowing two people have trucks that underread on their speedos, while stock.
Senior User
Joined: Feb 2004
Posts: 330
Likes: 0
From: arcata, ca
hey, i happen to think my van may not be accurately indicating speed, and i don't know if that translates to mileage also, but i do not have a gps to check it out and am not willing to trust the speed signs around here(don't think they are that accurate). a gps is a wish list item for me, somewhere past suspension and wheels. and the thought did run through my mind(s) that ford could stand to gain from over reporting mileage. all in all, we are here to get knowledge, and the indication of the gps readings is knowledge. so let's try to absorb, adapt, increase, (and have fun doing it
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Senior User
Joined: Sep 2004
Posts: 235
Likes: 0
From: S.W. Michigan
I just got a GPS a few weeks ago and I have also noticed that my speedo reads fast (about 1 mph fast at 70mph), but the intersting thing is that the odometer on my truck will lag the trip meter on the GPS by about 1%. My GPS (Garmin) is WAAS enabled and does measure changes in elevation.
For my odometer reading 565 miles the trip meter on the GPS read 571 miles. Mabe the GPS's are not that accurate and the stock odo's and speedo's are right on? It is hard to tell what is going on.
But yes 70 mph is just a tick over 2000 rpm for me with stock wheels and tires.
2100 ish rpm is 73.5 mph according to the gps.
For my odometer reading 565 miles the trip meter on the GPS read 571 miles. Mabe the GPS's are not that accurate and the stock odo's and speedo's are right on? It is hard to tell what is going on.
But yes 70 mph is just a tick over 2000 rpm for me with stock wheels and tires.
2100 ish rpm is 73.5 mph according to the gps.
Last edited by laredo7mma; Jun 30, 2005 at 05:42 PM.
Mountain Pass
Joined: Oct 2004
Posts: 186
Likes: 1
From: New Mexico
I'm comfortable with the GPS reading. I run about 2000 rpm at 70 on the speedometer as well, 6.0 PSD, 5 spd TS, 3.73 gears. The speedometer is off by about 3 to 3.5 mph at 70 or so, on the high side. Indicated speed is higher than actual. The GPS is good for about 3 meters, anywhere in the world. I also plan to upsize tires to 285's when I wear out the stock rubber. This should get the speed- o in line with reality, ar pretty close. BTW, I run 80 most everywhere here in NM and get about 15.5, or maybe 16 if I'm lucky, when empty. 10 to 11 when pulling 8,000 to 10,000 running the same 80 mph. My old F-150, 5.4, 3.73 would get about 16 running 80 empty. When pulling 7,000 or 8,000 pounds it dropped right on down to about 6. I think I'll keep the PSD!!!
More Turbo
Joined: Jan 2005
Posts: 589
Likes: 0
From: Mililani, Hawaii
I have checked the mileage on my GPS also. I have only done it mile by mile so I don't have an average but it seemed that for every .8 miles on the odometer, GPS read 1 mile. And yes with the 35's on Speedo reads 70-71 and GPS reads 75-76