Garming showing wrong speed

philinmerthyr

Über Member
My Garmin 500 has started giving me incorrect speeds with the cadence and speed sensor. The GPS is ok so I've just turned the sensor off but I can't now use it on the turbo.

I've changed the battery. Anyone else had this problem? How can I solve it?
 

bpsmith

Veteran
My Garmin 500 has started giving me incorrect speeds with the cadence and speed sensor. The GPS is ok so I've just turned the sensor off but I can't now use it on the turbo.

I've changed the battery. Anyone else had this problem? How can I solve it?
Have you set the wheel size correctly? Or not at all maybe? It should auto calibrate, but may not have completed properly and now set wrong.

The correct settings are online for most tyre sizes.
 
OP
philinmerthyr

philinmerthyr

Über Member
The wheel is set correctly. It has worked for months but is giving wrong readings from this week. I thought it may be the battery but it's the same after I changed it.
 

jarlrmai

Veteran
How wrong are the readings? Mile out or near, too high or too low, does it do it all the time or just every so often?
 
OP
philinmerthyr

philinmerthyr

Über Member
It's about half the speed. Starting my ride this morning it was showing 7.5mph when I switched to GPS I was doing 14 mph.

Seems to be all the time. I was killing myself to get 8mph on the turbo yesterday
 
Last edited:

jarlrmai

Veteran
Sounds like the sensor intermittently missing the magnet, have you checked the distance between sensor and magnet?
 
OP
philinmerthyr

philinmerthyr

Über Member
Just checked it again and the magnet was ok. I rechecked the settings and the wheel size seems to have switched to auto. I've changed it to manual and put the recommended wheel size in and it looks like it's sorted. I'll go for a ride or get on the turbo tomorrow to check.
 
Location
Pontefract
They do fail after time, as do the H.R.M. I seem to get two years for a Sp/Cad sensor and about 18 months for the HRM, my current Sp/Cad, I can pick up the cad on my 705 but not on my Rider 20, and no speed on either.
 
Have you set the wheel size correctly? Or not at all maybe? It should auto calibrate, but may not have completed properly and now set wrong.

The correct settings are online for most tyre sizes.

IIRC correctly the auto calibration needs a signal form the GPS

No movement there is no gps change and no calibration

As above, set for wheel size
 
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