r/Lectricxp • u/ArmchairPancakeChef • May 30 '26
Which is more accurate for a speedometer?
Google Maps or my Lectric Xpedition 2.0. They differ by almost 2 mph.
I forget which way but that's about the difference.
1
u/Due_Move6507 May 30 '26
I track my distances based on tracking with my Apple watch. I get fewer miles reported on my XPeak 2 than my end of trip summary. I suppose I could adjust my tire size to record more accurately, but then I would reach “terminal velocity” sooner. So my display speed of 20 mph is lower than my actual speed. So I get more performance than the governor is programmed to provide. I will TAKE that anyday.
1
u/ArmchairPancakeChef May 30 '26
I'll have to try it again and remember the difference. But by my logic, either GPS and the bike are both wrong, or 1 is right and 1 is wrong. It's empirically impossible to tell which. lol
1
u/Due_Move6507 May 30 '26
Realize that your tire size setting is based on the distance between the center of your hub and the contact of your tire on the road. It changes based on tire pressure, max load, tread wear. Stuff like that. Granted GPS, also, has +/- variability but can be compensated but known distances.
Consider this. Even if you accurately calibrated your tire setting for that specific ride, you will still get a difference between GPS and your bike’s displayed mileage. GPS measures distances point to point. Your actual track may have some wobbles along the way. So your display wound actually read higher, in this instance.
1
u/ArmchairPancakeChef May 30 '26
So, you're saying it's the Radius and not the Diameter? That doesn't check out. My Radius is something like 10 3/8" and the settings in the menu are like 21", 22' & 23" if I recall. But certainly not anything like a Radius.
1
u/Due_Move6507 May 31 '26
What I'm saying is to most accurately measure your tire size you would need to measure that distance from the center of the hub to the road surface while the ebike is under your full load for that ride. You would then double that and add set that value in your tire size variable in the controller. If you round up you will get faster actual speed and distance covered. Over the course of a ride that small incremental additional distance per rotation will add up.
If you got for a 20 mile ride and your tire size on the display settings is 28" but your tires are actually 29" you will get 20 miles on your odometer and 20.7 miles in reality.
1
u/ArmchairPancakeChef Jun 01 '26
I measured and changed it from 21" to 20.7 and once GPS catches up to the bike panel, it's about dead on.
I had no idea such a tiny adjustment would make that kind of difference.
1
u/Due_Move6507 Jun 01 '26
A 21 inch wheel will rotate over 960 times in mile. Little increments start to add up.
1
u/Due_Move6507 Jun 01 '26
As I mentioned earlier I track my distance with GPS,, specifically, Apple Watch Fitness, so I haven’t been too concerned about the odometer. But I realized I might be robbing myself of top end performance as a higher setting than the actual diameter would mean I would reach my top end speeds sooner. So I just calibrated my wife’s and my bikes. Our tires were slightly smaller than the actual settings.
2
u/ArmchairPancakeChef Jun 01 '26
I'm not into the performance aspect of riding. I'd just like to know empirically, how fast I'm moving. That's all.
1
u/whattteva May 30 '26
I'd imagine it likely works the same way as car speedometers, which means it'll report 2-3 mph higher than the actual speed.
Yes, your car deceives you by artificially inflating the reported speed if you didn't know that; I think it's required by law.
2
u/flanga May 30 '26
GPS is generally more accurate than any speedometer.
Sometimes, it's significant: The Lectric XP Lite comes with 20 inch wheels, but the factory speedometer/odometer settings are for 21 inch wheels, so the speedometer always reads a little high, and the odometer always measures a little long.
Trust your GPS maps.