Garmin Edge 200 accuracy problem

[Matthew_T]

For a short time I am using both my old wheel sensor speedo and my new Garmin. However, when riding, I find that there is a serious speed different between the two.
My old speedo is saying at some parts that I am up to 5mph above what my Garmin says. However, they both say that I am doing the same distance.

What annoyed me most is that today i was heading down a fast downhill section and wanted to get over 40mph. I managed this with my speedo which said 40.6 but the Garmin said I only did 39.8.

Also when I am stopped, the Garmin seems to get excited and imagine that I am moving whan I am not. I have set it to auto pause when I go below 0.5mph but the speed jumps about and I can hear beeping constantly.

These are only minor issues but what is more accurate, a wheel sensor or a GPS?

 

[snorri]

Oh Matthew-T, you worry some of us you know.
Speeding downhill at 40 mph with your eyes darting from one screen to another and getting annoyed , just take a little care young man.

 

[Crackle]

Wheel sensor for instantaneous accuracy, a GPS lags

 

[defy-one]

I would say the Garmin is closer to actual speed.
Did you calibrate your sensor correctly
Maybe get a car to travel with you at 40mph ... Look at both speedos and chat with the driver to confirm he is doing 40mph and take the time to have a drink of water :joking

 

[Matthew_T]

Oh Matthew-T, you worry some of us you know.
Speeding downhill at 40 mph with your eyes darting from one screen to another and getting annoyed , just take a little care young man.

It was a momentary glance. No traffic infront, none behind, occassional car passed opposite direction, long straight downhill with relatively good visibility.
https://maps.google.co.uk/maps?q=ab...id=Yz8SxqLox2gbmUF8mZ17Sw&cbp=12,25.56,,0,6.4
It comes from being relaxed. I was able to concentrate well with nothing else on my mind (I was keeping an eye on the junctions in the distance though.

 

[robgul]

I would say the Garmin is closer to actual speed.
Did you calibrate your sensor correctly
Maybe get a car to travel with you at 40mph ... Look at both speedos and chat with the driver to confirm he is doing 40mph and take the time to have a drink of water :joking

Forget it with making a comparison with a car - they invariably over-read by about 5 - 7%.

Obviously the wheel/tyre calibration has be precise for the ordinary speedo to be accurate.

I too have a Garmin 200 + a Bontrager wired speedo on one of my bikes - yes, on fast downhills there is a very slight lag on speed display with the Garmin (more so if there's a tree canopy) ... but all-in-all over distance the records for both gadgets are within a gnat's crotchet of each other. Have to say I would rely on the Garmin over the Bontrager for overall stats.

Rob

 

[redcard]

Do you have both devices on the bars, on opposite sides?

If so, it's the curvature of the earth that's causing the discrepancy. If you're riding in Wales (a left-sided country) then you need to peddle slightly faster with your right leg. If you cross into England (right-sided) then go faster with your left.

 

[Cush]

and as the Scots dont know if they are left or right and you go over the Border you are in a right cleft stick!!

 

[smokeysmoo]

If you remove your "old wheel sensor speedo" and only use the Garmin you will find it's accuracy increases to perfect levels

 

[Peteaud]

Do you have both devices on the bars, on opposite sides?

If so, it's the curvature of the earth that's causing the discrepancy. If you're riding in Wales (a left-sided country) then you need to peddle slightly faster with your right leg. If you cross into England (right-sided) then go faster with your left.

But you can balance that by only shaving one leg, and causing the airflow to create a venturi effect. This works well near roadworks due to the metal in the signs being magnetic and altering the air density.

 

[redcard]

Riding over dog shoot with just the front wheel also evens things out.

 

[Matthew_T]

Do you have both devices on the bars, on opposite sides?

If so, it's the curvature of the earth that's causing the discrepancy. If you're riding in Wales (a left-sided country) then you need to peddle slightly faster with your right leg. If you cross into England (right-sided) then go faster with your left.

The garmin is on the stem and the speedo is on the right of the stem on the handlebars between the stem and bar tape.

 

[defy-one]

The garmin is on the stem and the speedo is on the right of the stem on the handlebars between the stem and bar tape.

well .... THERE is your problem!!!

 

[smokeysmoo]

well .... THERE is your problem!!!

He clearly needs throw money at the problem and fit one of THESE

or save money and refer to my above post #9 to solve the problem for free

 

[HLaB]

Even at best GPS is only accurate to +/- 3m or so, so your gps can think you are travelling 6m/s or so when you are actually standing still. The default measuring for the edge is data averaging; I'm going to try setting it to 1sec recording to see what it does?