Inertianinja

My 705 died, and i'm about to go get a 500.

If i can have the 500 reliably track my speed and course, I'd like to go without the speed/cadence sensor, for various reasons (dirt under the zip ties, unit getting knocked out of alignment, hitting the spokes, batteries running out, etc).
i plan to get a power meter in the future, which will handle cadence

does running GPS-only work for you?

Menel

Running GPS wouldn't report my cadence.

2 years, many thousands of miles, not hit a spoke, not come loose, interesting... Garmin includes an instruction manual with the device to help you install it, but I found it common sense.

Inertianinja

yes, i know, but the eventual power meter will. even so i don't feel like i need a cadence sensor that badly. i know what 80-100rpm feels like

ericm979

I use only the GPS. I was also using a powertap which provides speed info but it broke and I haven't finished fixing it.

Without a speed sensor the GPS speed is inaccurate at low speeds. I see it most when climbing up a wooded road. The speed display will vary quite a bit and sometimes the 500 thinks I have stopped and will pause. I dont' care about speed that much so it doesn't bother me. Other than that it works fine.

flaco

Works for me.

mwchandler21

I run the garmin w/o spd/cad censor on my older bike and it mostly works fine. Every once in a while it loses the signal and basically screws up the data on that ride, but it is pretty rare.

kissTheApex

This is the case when I use my Edge 500 on my commuter with an old Blackburn Delphi 5 and most of the time GPS speed is lower. As a consequence, GPS distance comes around 1 mile short on a 15 mile wooded route I like to ride from time to time.

LowCel 

I use a 705 and don't use a speed/cadence sensor. On one bike I have a Quarq crankset and the other bike I have a powertap so they both do cadence for me.

johnny99

Works for me most of the time, but accuracy goes down a lot in big cities or deep canyons where the GPS signal is erratic.

Bacciagalupe

I used mine without a sensor, but decided I'd like to see cadence so I'm going to switch. Seemed OK and came up with the same numbers as the old cyclometer that I left on while testing the 500.

You can always buy the sensor as an add-on, so I recommend you try it and see if it works for you.

ancker

I'm not calling you a liar, but how is this even possible? The GPS knows where your are at certain points in time. Given it knows where you started, where you've been, and where you stopped, how can it judge distance incorrectly?
If you rode 15 miles in an hour, umm, because you did, even if the GPS thought you were doing 13mph the whole time, the distance covered would still be 15mph. Does the Map show you a mile away from where you ended up?
I guess if the GPS resolution was only so often and it didn't catch that you did a few loops or that you doubled back or something it could be off by a bit, but Garmin's smart tracking is usually pretty good at that. Also, you can set the GPS data interval to 1-second with 2.80.0 on the 500.

(I have speed/cadence sensor with my Edge 500. Never used it without.)

StevenAkaProek

yea u can

but why would anyone not want use the cadence and speed sensor?

intence

Works great without the sensor. I have Edge as well, and have been too lazy to install the speed/candence sensor on my primary bike (switched bikes a few months ago). Except for cadence, I don't feel like i'm missing much, and by now you can tell when your cadence is roughly too high or too low. Overall it's nice to have, but the unit works great without it.

Shuke

I ride without the sensor. I trust GPS more than I trust myself to get the tire roll out distance correct and plus it's GPS, satellites > magnets. I don't need the cadence sensor unless I'm training indoors on a trainer. I know when to throw a gear or two and I know how to spin my legs. Having those numbers on the road is just replacing common sense with useless data.

ericm979

The words you quoted from me were not in my original post. Don't put words in my mouth.

I do not think the distance is significantly off when there's no speed sensor. The distances I have seen for regular rides have been in the ballpark.

mvnsnd

I use my 500 on two bikes. Only one has the cadence/speed sensor. No problems for me on the bike without the sensor.

LowCel 

The gps speed is accurate enough for me and I have a power meter on each bike that gives me my cadence. Why would I want to use the cadence / speed sensor?

Seanholio

It depends on the course followed. A straight line will be fine, but a twisty route will come up short. This is because the GPS measures your distance by playing a mathematical game of connect-the-dots, and in so doing, clips a lot of corners. I'm not sure that a mile out of 15 is within the expected margin for error. I would expect that the cyclocomputer was set incorrectly in that case.

Silvercivic27

Gps is not 3d, in other words, if you climb or descend, it's a longer distance than it looks on a 2d map. Maybe this accounts for the distance and speed differences? That's one of the reasons why I run the magnet.

outofshape

b.s.^

Silvercivic27

I dunno, maybe it is BS. I'm just offering a possible explanation. Seems like it would be pretty complicated to calculate for the distance changes with elevation. Does anybody know if The Edge software corrects for this?

somedood

GPS knows your altitude. It uses all 3 dimensions.

Silvercivic27

Then why does the unit have a barometer to measure altitude? Why does garmin connect offer altitude correction? If the GPS already provides the altitude data, I would think the unit would not need either of those things. I would think any of these factors would introduce error which is minimized by use of the wheel magnet when measuring distance and speed (provided the value you provide for circumference is actually accurate)

dbc

Using GPS only to capture some course data. Unless I'm lucky, it's better to flush the altitude data. Typically ride computerless so I don't miss the cadence data.

Alot will be determined by how the Garmin calculates the distance of the trip, but keep in mind the instantaneous speed readout has a limited accuracy. The position data only has an accuracy of a couple of meters. You can see how much variation is possible when you look at course data that travels over the same spot.

A standalone computer uses data that comes in generally faster than once a second, and is able to better record small deviations in your course, so I would say the GPS would consistently record lower trip distance. The average speed over the whole trip should be quite decent however.

Looigi

Pretty much the same reason it has wheel sensor. GPS position is noisy, and due to the geometry with satellites, altitude is even less precise and noisier. Let's say you're riding a 5% grade. That's only 5' of climb in 100' of riding. Normal GPS isn't accurate enough and is too noisy to make that determination, but it can be done with a barometric sensor.