# Front Wheel Speed Sensor - Utilize Data gathered from the Kart

How or What are the points that can be analysed from the data gathered from a Front Wheel Speed Sensor?
Is there any guidance video or documentation on it?

Before the Mychron 5, wheel speed sensors were more common. With the built in GPS you can now easily get your MPH. I think most were looking at/for wheel lock up or slip. Unless you’re doing a deep dive on data analysis or don’t have a Mychron 5 wheel speed sensors probably aren’t necessary.

If you REALLY want to geek out, there’s some talk about speed sensors in this topic. GPS has it’s merits, but wheel speed still has a place, depending how deep you want to go.

Hi Morgan,

Interesting thread on gps. I would venture to say the accuracy is within inches relative to data points taken within a few seconds in either direction. The government intentionally makes gps slightly inaccurate, otherwise it would always be within inches. The inaccuracy they impose is accurate relative to other readings within a few minutes. So you may notice some slight inaccuracies from one run to the next. But data points within a single run should be perfectly accurate. Bottom line, all this will really screw up is if you try to overlay your run over a google map image. If you are simply looking at data it is perfectly accurate for your run. If it was even close to being meters off the data would be 100% useless and would not be represented by smooth curves.

Putting a wheel speed sensor on the front can get you some better info on vehicle speed than your GPS, but you’ll need to write a math channel first. You need one math channel calculating corner radius, and a second one that calculates the vehicle’s speed at the centerline while accounting for the changing radius of the corners on the track. This is because your measured wheel speed will always go higher when the sensor is on the outside and lower when the sensor is on the inside of the turn.

With your corrected centerline vehicle speed math channel you can either lay the RPM trace directly over the top to see wheel spin, or you can create a math channel that takes the corrected vehicle speed and divides it by (RPM / 1000). This outputs a number that is constant under zero slip, decreases during wheel spin, and increases during under rotation.

That hasn’t been in use since 2007 says https://www.gps.gov/systems/gps/modernization/sa/

I am referring to how the signal can be intentionally degraded. I know its published that it no longer is degraded but the whole point of it was national security so i really doubt its still not degraded. The system is very accurate so something is being done to make it as much as 25’ off. The important takeaway is that the data points are very accurate relative to each other but the entire data set or session from one day might be several meters off from another day.

I disagree, it may be dependent on location or system but certainly with the mychron 5 i’ve had the privilege to work with top drivers in X30 or Rotax and there is no way they are 3ft different in raceline from lap to lap.

Given the choice I’d prefer a ebox with with g sensors and wheel speed sensors. Ricky Flynn Motorsport (one of the top teams in Europe) still use out of production PI dataloggers (that never had GPS, and I have no idea how he gets them) and Tonykart use their Dakton datalogger which has never had GPS.

@Stealth
It depends on what you are trying to find. You can use two wheel speed sensors, one on back and one on the front, to determine if your rear wheels are slipping more then they should be (you should be aiming for about 8% to get optimum acceleration or braking grip) or you can use rear wheel speed vs engine speed to determine clutch slip. Alternatively if you are running shifter you could have two front wheel speed sensors to determine braking performance across the front.

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I’m an ex Pi employee who keeps Ricky Flynns X-Kart systems running.

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Awesome @Tony_Kent. Are you using PI Toolbox?

@NikG I do personally, but Ricky prefers the older Club Expert Windows.

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I can verify from personal experience that this practice was still in use after 2007. In 2013 I was working for a battery company that serviced Telephone Offices and Cellular Phone Sites. We went everywhere from Corn Fields in the middle of nowhere, to High-rise buildings as well as Military Installations. In the case of free-standing sites, we would use provided GPS coordinates to navigate to the sites. Entering those coordinates into our Garmin-Navi it would get us really close and then we could use Google Maps’ Satellite view to find our path to the site where official roads did not exist. In the case of Military Installations, GPS would get us to the gate, however once on Base, the GPS was useless. Most of the time it was off by as much as 1/10 of a Mile. Google Maps was also useless, as the maps were blurred out for the base. We would have to use traditional Road Maps and try to work out where the coordinates fell. Even then it would take as much as an Hour or more to locate some of the sites.

Having grown up on several Military Bases, I am dead certain this is for National Security reasons. Otherwise any idiot with a drone and some explosives could send it on a GPS autopilot course and do some serious damage. How they deflect the signal is somewhat of a mystery to me. Either at the source or some kind of Jamming Signal at the site.

That being said, I do NOT believe this practice is used outside of High Security Areas. At least from my experience and I have used it across half of the United States. Most GPS inaccuracies are a result of too few satellites in line-of-sight of the reader. Whether it be topography, structures or RF interference (i.e. High Voltage Power Lines), they can all reduce GPS accuracy. In fact, most automotive GPS’ are augmented with secondary systems for dense urban areas where tall buildings can block the GPS signal. In those cases, there will be street corner transmitters to supplement the lack of signal. BTW those same transmitters also send out traffic data. Other than connecting to the internet, a standalone GPS would have no way of receiving traffic data.