Proper engine RPM at 90kph HDJ81?

[83bj60]

Hey Folks... (I know, I know, hope I'm not wearing out my welcome)

With my 33" tires (Bridgestone Dueller AT 285/75/R16), which are about 4.5% larger than stock (which I can confirm from chronometer readings between two distance markers on the highway), the engine goes at about 2050RPM at 90 kph on the speedometer (about 95 actual).

Is this a normal reading? Am I going susbtantially faster or slower? I'm asking because I'm not too sure about the behaviour of my overdrive/tranny lock.

Thanks for your invaluable input, and for your understanding. I'll have quite a few other questions in the coming days and weeks

 

[Martin White]

Your tires are very close in size to mine, but my odo correction (using GPS and comparing odometer to GPS distances, done over thousands of km) is 9.012%, so I think you are understating your mileage which may partly explain your fuel economy concerns. In other words you are traveling nearly 5% further than you think. Also, I've found that the ODO and the speedo don't agree entirely. My speedo reads about 8% under (using GPS again to track speed).

 

[83bj60]

Your tires are very close in size to mine, but my odo correction (using GPS and comparing odometer to GPS distances, done over thousands of km) is 9.012%, so I think you are understating your mileage which may partly explain your fuel economy concerns. In other words you are traveling nearly 5% further than you think. Also, I've found that the ODO and the speedo don't agree entirely. My speedo reads about 8% under (using GPS again to track speed).

BINGO! I think you're right on the money. That's exactly what I'm thinking now after reading a previous post of yours:

Can you not kick the tranny down at all or is it just really difficult? Most of these trucks seem resistant to kick down, but they will go. I've found you need to be right near the floor at times to make it happen. Also, what is your fuel consumption? Are you using GPS for distance?

These two devices are traditionally NOT mechanically linked (speedo activated by a rotating magnet, odo connected to gears). I assumed wrongly that the odometer should be corrected exactly like the speedometer. More measuring is in order!

BUT, if your odo is 9% too slow and your speedo is 8% too slow, shouldn't mine be pretty close to each other as well? In any case, I'll take a 5% increase in economy and top speed rating rating any day

Thanks, I feel much better now (told you I was going gaga with my new truck!!!)

Tonight when everyone is asleep I'll upload some pictures taken when I first saw it back when it arrived at the importer last month. Now the weather is too miserable to take decent pictures.

Thanks again, keep it coming, I'm all ears

Chris

 

[wussyPup]

with 35" BFG MTs at approx 2300 RPM = 100 km/h on the speedometer = 116 km/h on the GPSr