New RP-171 Owners

From what you're saying I'd highly suggest that you still take your rig through a public scale once when loaded as you plan to travel, including cargo, gear, fuel, and humans. That will help you get your software calibrated if nothing else.

So far, I've done a fairly accurate tongue weight check against a credible tongue weight scale, and I've done a "cargo" weight check inside the vehicle where I knew the exact weight of the cargo. In both cases, the weight was within ±50 lbs. (cargo was within ±20.) I did learn that it's best to let it settle (the measurement is refined as it gets more measurements to generate an average,) and it's best to take a few measurements (there's usually at least one outlier from some unexpected force.)

And I've discovered it to be quite sensitive even to the slightest pressure, which is why settling time and multiple measurements help (and turning off the vehicle for many measurements.) My initial test was on level ground in a large church parking lot on a windy day. But I couldn't get consistent measurements because the wind was moving the tow vehicle enough to severely impact the measurements. It's important to note that many of the measurements work on a calibrated model of suspension travel for the tow vehicle, measured through the tow vehicles change in angle (read by the accelerometer,) due to additional weight added to the vehicle. So wind gusts that gently move the tow vehicle are interpreted as angle changes and can, depending on how soft or firm the suspension is, equate to significant changes in measured weight.

Here are some example measurements I took.

This is a measure of "cargo" weight after calibrating suspension travel. The "cargo" is myself, and I weighted 161 lbs. on the bathroom scale just before I stepped into the third row of my minivan to take this.

 

This is a pair tongue weight measurements done in succession. My Sherline tongue weight scale was measuring ~300 lbs. at the same time (the scale is purposefully hard to get precise measurements with, so it's hard to be certain.) NOTE: This was the best out of about 5 tests I did, and it was in that windy parking lot. But they were all between about 270 lbs and 340 lbs., with one outlier at almost 390 lbs. Note that my WDH weighs about 85 lbs. and the RP-171 dry tongue weight is specified at 250 lbs., but I never confirmed what its actual dry weight was without my hitch, so I don't have an accurate measure for my specific unit. Still, this all feels "in the ballpark" enough to build some confidence in the device.

After the tongue weight test, I tried out the WDH tuning feature and again, it got pretty close. Note that this was taken a day after purchasing the trailer where the dealer installed and set up the WDH. Judging from a tape measure test, the WDH seemed well set up, and this just seemed to confirm it.

Finally, I don't have any screenshots of the combined vehicle weight measurements that it's capable of because it requires you to accelerate at medium throttle to 15 mph on level ground. I never thought to get a screenshot once I'd slowed down to look at the result. Interestingly, the reason for a maximum 15 mph speed is to ensure you don't shift gears. The tool needs to eliminate any variable gear ratios and there are few to no automatic vehicles on the market that'll shift out of 1st under 15mph when you've got at least half throttle.

In any case, I performed a measurement on my tow vehicle with just me inside and no real cargo and got a little under 5000 lbs. which is about right for our 8 passenger minivan. Later, with a few more humans in the car, I hooked up the trailer (dry) and did the same test. I got a bit under 8000 lbs. (maybe 7800-8000 lbs. or so) which, assuming a 2500 lbs. dry weight (as stated on my sticker from Forest River,) and the addition of the almost 100 lbs. hitch and extra humans again, seems about right.

I didn't get to do more then one measurement for combined weight (one for the tow vehicle, and one for both.) And I really want to because I think a few more measurements would give me a lot more confidence if the numbers converged. And I haven't had a chance to put it on a scale before I do this test.

But again, this isn't a perfect evaluation, but it's enough to make me listen to the numbers it's giving, and given how darn simple and easy it is, made me feel like it was worth it's $100 price tag.

On mine, I added a few items that greatly increase effective ground clearance.