Rough Country Speedometer Calibrator

Lol

 

I have the Hypertech module and discovered last month that it only corrects the speed up to a point, once you input a calibration factor that is equal to 1.10 or higher the speedometer will stop working and a bunch of christmas lights will come on. Also after you go higher than 1.05 it really doesn't make a difference anymore so you can get about 5% increase and quite a bit more decrease as I have been able to go as low as 0.80 where the speed readout is over 10mph lower than a GPS reading.

Also if you follow the instructions and plug in your tire size, gears, original size the formula is way off. I talked with tech support and they told me to just keep playing with tire size until I get a calibration factor that matches a GPS measurement. This is definitely not ideal as its basically trial and error where you have to keep flashing the module until you get it right.

I have 255/85R16 tires with 4.88 gears and I can get dead on to have the speed readout match a GPS, on my winter tires sized 265/75R16 it is not possible as there is not enough adjustment headroom. All this module does is take in the voltage reading from the speed sensor and adjust it with a calibration factor, it makes a difference on the speedometer and your odometer but not the cruise control as that module gets its own speed reading. So when you set your cruise control it will give you a different speed than what your speedometer shows.

 

I just installed the Rough Country version to correct the speedometer readings after installing 285/75r16's. To my pleasant surprise, my speedometer is accurate again. Matches GPS readings on my phone and I tested it against 3 different radar speed signs. Installation was a breeze as well. Pretty sweet! Glad I stumbled upon this shortly after getting the tires installed. No longer need to worry about driving 3 mph slower according to my gauge. I did a quick test of the ODO readings and it appears to be accurate as well. I'll do a better test soon just to make sure.

 

Have you confirmed the odometer was also corrected? I get 50/50 responses to this question so I keep asking people who have done it.

 

This is a good question and my early tests, for shorter trips, showed it to be fairly accurate. The challenge is GPS will always be different compared to the on-board odometer. I think when I tested last, it was off by a fraction of a mile after a 9 mile trip. I'll try it again tomorrow to confirm.

 

Ok, tested on an 8 mile trip this morning. Odometer/Trip meter showed 8.0 miles, GPS showed 8.16 miles. I think that's close enough and I'd assume with the stock setup, my 33's would probably have the discrepancy more than a fraction of a mile. Agreed?

 

Man it's hard to say?

With 32.8" tires you are traveling ~7.2% further than what the odometer displays because it thinks you are on 30.6" tires.

If it the programmer had not corrected the odometer, your GPS it would have read 8.57 instead of 8.16, but it appears the programmer did correct the odometer to some extent. I think a longer mileage test would yield more accuracy, but also the current error is exactly 2%...so maybe that's as perfect as it needs to be or can be.

 

Agreed with your logic. I’ll take this over nothing at all. At least it gets it more near to stock accuracy. My main concern was for speed-correcting so that I’m not going faster than I think I am. I’m sure you can fiddle with the numbers on the brains but at least it looks like it is indeed correcting (or attempting) the odometer as well. I have a manual transmission 3rd Gen just to add a little extra detail.

 

For sure man. I edited my earlier post and noted the odo error is exactly 2% Maybe that's as close as it can get?

The ultimate test to see what the odo is doing...change the tire diameter in the programmer by 2% and do the same distance test again the same way...if the programmer is correcting the odo, then both the odo and GPS would eventually match each other with diameter input changes if it the programmer is changing the odo. Or change it to the extreme to make these results more obvious knowing the speedo is no longer accurate. I totally get if you don't care to do this...just an idea!

Your trans gears and/or diff gears do not come into play because the sensors read wheel speed.

 

Your understanding of how the programmer is correcting the odo sounds accurate to me. You can literally put in any value you want to the new tires (both in inches and metric) to continue to skew the values that show up on your instrument cluster. If I had the time (or cared for better accuracy), I'd definitely tweak it. I know others have done this as well but could only get it to a certain margin of error before going the other direction. I do feel that with my current/recommended settings, the speed is very close to accurate compared to my phone's GPS as well radar speed limit signs. My main concern was not to get pulled over because I couldn't do the math some day while driving. I have two young kids and they have made my brain mush.

With all that said, maybe this is enough for you to pull the trigger and buy one? I think Rough Country has a 30-day money back thing (though you'll probably have to pay for shipping back). Although, even if it is slightly inaccurate compared to stock, it's still much better than running without it if you're running bigger tires.

 

Yes sir! I totally get it.

My only problem is that:
A. I don't even have the truck yet...build date coming soon...ish..or something like that according to my salesman.
B. These don't work on the 2021 as something was changed in the connection points. I already asked Hypertech and they input the request to expand product to 2021 "when possible". Ha

 

Ah... yes. All makes sense. I'm sure you've figured it out by now but the Hypertech and Rough Country are identical and use the same software to program. I hope they come through with an updated version for you! I would think they would.

 

Just ordered BFG KO2 265/75/16 will my speedo be off with only going up in size a little? I understand my MPG might go down but hopefully my speedo won't be off.

 

It will be off a bit. Not as much as 285/75r16s. Basically, anything other than stock tire sizes will be off.

 

Dang ok, the only reason I ordered the bigger size is because (1) the 265/70/16 are out of stock in my area and (2) they are $60-$70 more per tire.

 

You might luck out. Many members have reported the stock speedo reading too high and after adding an inch taller tire, they say it became more accurate. Let us know!

 

Just installed this on my 2021 OR. The software does have 2022 as an option in case you were wondering. There is also a "GPS" option, but I just plugged in my current tire size (285/70/17 KO2) and took the truck for a test drive.

Before the install, truck was indicating 3-4MPH slower than GPS. It's almost completely accurate now. I'm getting matching numbers on GPS and dash 99.5% of the time. There were a few times where the truck read faster by 1mph for a brief moment, but GPS data does fluctuate and tire wear has to be considered. Tweaking the tire size numbers by a few points will probably make it even more accurate. I'll report back with what I find.

Extras: It actually fixed my cruise control numbers (see pic). And I'm pretty sure my shift points have been affected. I'll have to do a longer drive, but initial impression is that this is no placebo. The truck wasn't holding on to gears and shifting when it was supposed to. Very happy with the purchase so far.

 

I went up to the same size and it's slightly off. For me, going 55 MPH reads as 54 MPH and going 80 MPH reads as 78 MPH. It's not horribly off but enough for me to be an annoyance. I'll be trying out the RC speedo calibration tool tomorrow.

 

Would you please give some more details about how you ran the USB cable down to the floorboard? I want to be able to adjust the settings after I install it too and don't want to have to disassemble the entire dash every time.

 

Ask someone you know who lives in the United States to buy it for you and then mail it to you. Simple. I did that for years with things like exhausts and fuel mapping tuner things for motorcycles. CA doesn't allow anything fun or useful because they are in the business of stealing tax dollars to save the whales. Like the $658 trillion dollar high speed Choo Choo to nowhere that they have been doing construction on for ten years (and will never be done). I'm so glad I left and moved back to the USA.