Speed seems pretty inaccurate.

[TimBobCom]

I have a Slash 4X4 VXL OBA and I have added the basic telemetry sensors (motor temperature, voltage and rpm/speed) and I have also swapped out the stock pinion gear in my Slash with the 18T which was included in the box. I am still running the stock 54T spur gear.

In my Traxxas Link application I have made the necessary changes to my model settings, setting the pinion to 18 and the battery type to LiPo 2S. On the battery, I am using a 5200mAh, 7.4V, 2S LiPo (Floureon) which seems pretty decent to me, I am not planning on racing, I just bash around the yard and such.

Since swapping out the spur gear, my Traxxas Link application is showing a max speed of 45 MPH after making a couple passes up and down my street at top speed. I wanted verification, so I strapped an old iPhone 5c I had laying around to the battery bar and launched the SpeedPro app. After my runs, the SpeedPro app was showing a max speed of 39.6 MPH.

Now, both of these are respectable top speeds in my opinion, especially since I have done nothing to tune the suspension for high-speed runs, but I am just surprised by the discrepancy of nearly 6MPH.

[dr frankenstyle]

Unless you have the GPS Speed module, the app just calculates speed from the RPMs. It can't adjust for slight differences in tire size or other variables. You're phone was probably the more accurate reading. (sorry)

[TimBobCom]

Oh, I know the phone was more accurate, I am just shocked that the calculated speed is so far off.

When Traxxas advertises a vehicle as "60+ MPH" are they using their calculated value or a true GPS reading?

I'll do more testing later this week when my 19T pinion gear and 3S LiPo come in. According to the box and manual, that combo should give me 60+ MPH, I'm skeptical though, especially after seeing only 39.6 on the GPS with the 18T/2S combo.

[TimBobCom]

Okay, after another test run yesterday (this time on 3S LiPo) I am seeing 76 in the Traxxas Link app, and 50 on the GPS I strapped into the Slash.

What could account for such a HUGE discrepancy? Surely I am not just spinning my tires that much, the math has to be off somewhere to be off my almost 50%.

[Panamon Creel]

Fine tuning of the indicated vs. actual speed can be done via the drive ratio value in the app. However just one short spin of your tires can cause a huge difference between the Link Max. speed and actual speed.

[IanRose]

Unrelated to gps, what surface are you running? I've always been curious about traxxas top speed claims, they must be on something really smooth. Not that 50 or 39 is even slow.

[TimBobCom]

I've been running on the street in front of my house. My tires are really starting to show wear from the pavement. It's a poured concrete slab construction street, smooth rounded curbs.

[DieselPro]

If you look through the manual you will see the speeds attainable and what it takes to get you there. It's more than just gearing you'll need 3s power.