Inaccurate speedo reading

pablordf · 07-04-2021, 06:30 PM

Most of these chinese enduro bikes come with a 21" front wheel but mine came with a 19" (and 17" rear) and I think that's why my speedometer reads a higher speed consistently.
Does anyone know if there is a specific speedo gearbox (where the speedo cable connects) for a 19" front wheel?

Bill Hilly · 07-04-2021, 06:44 PM

They are not cable operated. They have what I assume is a magnetic pick up . I seen on a Facebook sight that I was on were a guy bought a device to correct his reading, but I think it was fairly high. I was carrying my phone on mine to watch a GPS speed app, but now I just figure if the speed limit is 35 , I can run 38 ,or 40 on my Speedo . 45 GPS is about 50 on my SpeedO, and I usually run about 62,or 63 according to my SpeedO for a true 55mph.

ChillRider · 07-05-2021, 08:02 AM

If that was a mechanical speedo, getting a compatible one (right notching for the forks, right diameter for the front axle, correct type of core, matching your existing speedo cable's length and termination etc.) PLUS with the proper gear ratio may be next to impossible.

If however it already uses a magnetic pickup, there are bicycle speedos that can be adjusted to a specific wheel diameter. Most of them have sufficient wheel size and speed ranges to cover typical dual-sport setups and achievable speeds (I tested one up to 150 km/h with a drill, so plenty enough for a 200-250cc dual sport with < 20 HP).

Oldenslow · 07-05-2021, 09:34 AM

I own 3 motorcycles, 2 automobiles and a pickup truck. All of their speedometers read 3 to 5 mph faster than actual speed. While a precise speedo would be nice, they are apparently quite rare...

ChillRider · 07-05-2021, 09:49 AM

Well, there's a difference between the factory-built (positive) inaccuracy that all speedos need to have (it's illegal for them to show you less than your actual speed, so they all err on the side of caution, saving you speed tickets), and a systematic inaccuracy caused by installing wheels of different diameter, or by missing teeth in the speedo gears at any point (ask me how I know the latter

).

The main difference is that the latter also affects the odometer reading by whatever % you're off on the overall resulting gearing, while the former geneally affects only your indicated speed.

Wild Dog · 07-05-2021, 09:51 AM

99% of the cars and motorcycles that made for road use have inaccurate readings

That's why people use a GPS for actual speed reading instead of the speedo.. Speedos are liars, but they tells lies on the safe.

https://www.thecarexpert.co.uk/how-a...r-speedometer/

07-04-2021, 06:30 PM	#1
pablordf Join Date: May 2021 Posts: 5	Inaccurate speedo reading Most of these chinese enduro bikes come with a 21" front wheel but mine came with a 19" (and 17" rear) and I think that's why my speedometer reads a higher speed consistently. Does anyone know if there is a specific speedo gearbox (where the speedo cable connects) for a 19" front wheel?
	0

07-04-2021, 06:44 PM	#2
Bill Hilly Join Date: Feb 2021 Posts: 1,003	They are not cable operated. They have what I assume is a magnetic pick up . I seen on a Facebook sight that I was on were a guy bought a device to correct his reading, but I think it was fairly high. I was carrying my phone on mine to watch a GPS speed app, but now I just figure if the speed limit is 35 , I can run 38 ,or 40 on my Speedo . 45 GPS is about 50 on my SpeedO, and I usually run about 62,or 63 according to my SpeedO for a true 55mph.
	0

07-05-2021, 08:02 AM	#3
ChillRider Join Date: Jun 2020 Location: A small country with a funny name Posts: 164	If that was a mechanical speedo, getting a compatible one (right notching for the forks, right diameter for the front axle, correct type of core, matching your existing speedo cable's length and termination etc.) PLUS with the proper gear ratio may be next to impossible. If however it already uses a magnetic pickup, there are bicycle speedos that can be adjusted to a specific wheel diameter. Most of them have sufficient wheel size and speed ranges to cover typical dual-sport setups and achievable speeds (I tested one up to 150 km/h with a drill, so plenty enough for a 200-250cc dual sport with < 20 HP).
	1

07-05-2021, 09:34 AM	#4
Oldenslow Join Date: Mar 2020 Posts: 153	I own 3 motorcycles, 2 automobiles and a pickup truck. All of their speedometers read 3 to 5 mph faster than actual speed. While a precise speedo would be nice, they are apparently quite rare...
	1

07-05-2021, 09:49 AM	#5
ChillRider Join Date: Jun 2020 Location: A small country with a funny name Posts: 164	Well, there's a difference between the factory-built (positive) inaccuracy that all speedos need to have (it's illegal for them to show you less than your actual speed, so they all err on the side of caution, saving you speed tickets), and a systematic inaccuracy caused by installing wheels of different diameter, or by missing teeth in the speedo gears at any point (ask me how I know the latter ). The main difference is that the latter also affects the odometer reading by whatever % you're off on the overall resulting gearing, while the former geneally affects only your indicated speed.
	1

07-05-2021, 09:51 AM	#6
Wild Dog Join Date: Dec 2016 Location: Argentina Posts: 756	99% of the cars and motorcycles that made for road use have inaccurate readings That's why people use a GPS for actual speed reading instead of the speedo.. Speedos are liars, but they tells lies on the safe. https://www.thecarexpert.co.uk/how-a...r-speedometer/
	1