I'm putting 315/70/r17 raptor tires on my leveled 2018 f150. Looking it up, I read that my speed would be off by about 5 miles per hour at 65. I have been looking for a tuner for a while to help my 2.7 ecoboost and read that some tuners have speedometer calibration as well. Any suggestions on one that could be had for relatively cheap? I'm working on a budget.

 

"I'm putting 315/70/r17 raptor tires on my leveled 2018 f150" is working on a budget??

 

Online comments about correcting speed is worthless far as accurate speed is concerned. Your F150 has a GPS speed readout and there are lots of GPS options for finding out exactly what your speed is. Install your tires and check the speed via a GPS or one of the roadside speed radar trailers. Then worry about correction if needed.
I have had poor success with tuner speed corrections (SCT GTX and BDX) but FORScan has gotten me dead on to multiple sources. KM

 

I've had success with the banks data monster
I like their whole set up
Pedal monster and derringer
2015 platinum screw 3.5 EcoBoost

 

I got the wheels and tires used on Facebook marketplace for a great deal and installed the 65 dollar leveling kit myself. I just don’t want to go and buy a 400 dollar tuner and 150 dollar custom tune.

 

You can do the speedo recal using Forscan, a $35 OBD dongle, and pretty much any reasonably modern (say, <10 years old) Windows PC. Plus a zillion other things.

 

I'd like to see some schematics showing the speedometer readout is sourced from GPS. I'm pretty certain that's not allowed as there are places galore where you are GPS blinded by terrain or canopy. Speedometer has to work at all times.

Vehicles still use a sensor in the transmission to clock the speedometer. As tire and diff ratio adjustments are made by the mfg via code now rather than by varying the gear ratio of the sensor, we can now make very accurate corrections to the speedo readout. The days of getting the speedo 'close enough' are long gone.

 

Yes vehicles still use a sensor in the transmission to clock the speedometer. But now include a GPS unit in the vehicle motion recorder (black box), mandatory since I think 2014.
Maybe my own assumption but there is a digital speed display in the engineering mode that displays the vehicles GPS speed to .1 decimal places. Note I'm not referring to the digital speedometer display from the dash display choices. I do use independent GPS units, Garmin Nuvi, several handheld, phone and laptop GPS. The laptop GPS agrees to tenths of a MPH with the engineering mode speed, while the dash speedometer is a bit optimistic. I have driven over most of the USA and the only time my Nuvi GPS speed drops off is thru long tunnels, the handhelds and laptop GPS units I own are quite similar in signal strength and drop-outs.

I have used FORScan twice now to correct the speedometer for tire diameters. I'll use my own GPS and the engineering mode display which both times agreed, as true speed and corrected the speedometer to that. Program Via GPS KM

 

Stating you are doing some special **** at the start would have helped to clarify.

Many GPS devices that provide speed data have a 3-axis accelerometer that is used to improve accuracy when you can't lock more than 4 satellites, and it can also be used to infer position for a very short period when you can't lock 4. This gives that appearance that GPS is rarely lost, but topographical shading hasn't changed since GPS came out. Receivers are more sensitive and there are more satellites in the sky, but every time I take an interstate through the central Smokies, I will lose lock long enough for total abandonment of positional data for several short sections of every crossing. This is with running a high sensitivity, dedicated GPS receiver that I bought back when phone GPS antennas were total crap. I'm using a fairly new tablet now, but the dedicated receiver is still better.

 

Guess I take GPS use for granted as I have used them since early commercial release for wilderness travel. Very familiar with the uses and possible errors. The only place in the Smokies I had receiver problems was the south side by the Cherokee Reservation. Otherwise the Nuvi I used worked flawlessly except in long tunnels. Out west in CO/NM/AZ up to the Canadian border I had continuous good reading that matched my speedometer and a separate handheld used for altitude. I will agree a laptop with an external GPS puck is almost as good as a pro surveyor GPS (I have used one, my BIL's). I would not call it "special ****" as I've used them since the 1990"s.

Besides all that stuff, a GPS speed display is not hard to accomplish for anyone these days, on an open section of highway for a length of time to eliminate CEP problems. And cheaper, easier, more accurate, than someones anecdotal recommendation. Probably the easiest method of checking a speedometer's accuracy short of a speeding ticket. KM

PS: Just tried my 62st outside and within 5 minutes had good signal from 9 satellites, CEP of 8 feet. km