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Discussion Starter · #1 ·
i've been searching through the archives and i haven't found much specifically about the cadence sensor.

i'm planning to buy an edge 305 w/ heartrate (mix of mtn & road riding); i'm not sure about the utility of the cadence sensor. i'm not concerned with cadence, but i'm very interested in speed & distance & altitude.

from the previous postings, does the 305 ONLY use the info from the sensor when the satellite reception cuts out? therefore, if the gps never loses signal will it never pull info from the cadence sensor?

i ride in northern california and i want to set up the road & mountain bike so i collect the same information with the gps. although i've only found myself road riding where the gps will have a clear view of the sky, i'm not sure if i'd need to get a cadence sensor for the road bike too.
 

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dirt & beer said:
i've been searching through the archives and i haven't found much specifically about the cadence sensor.

i'm planning to buy an edge 305 w/ heartrate (mix of mtn & road riding); i'm not sure about the utility of the cadence sensor. i'm not concerned with cadence, but i'm very interested in speed & distance & altitude.

from the previous postings, does the 305 ONLY use the info from the sensor when the satellite reception cuts out? therefore, if the gps never loses signal will it never pull info from the cadence sensor?

i ride in northern california and i want to set up the road & mountain bike so i collect the same information with the gps. although i've only found myself road riding where the gps will have a clear view of the sky, i'm not sure if i'd need to get a cadence sensor for the road bike too.
I have the cadence sensor, but I haven't used it yet. In the areas I've been riding (southern California - no forest cover, but lots of canyons), I've never had any trouble with my 305 losing its signal. Even though I ride mountain much more, I'm planning on putting the cadence sensor on my road bike, where knowing cadence makes more sense, because it doesn't seem like I'm going to need it for recording speed.
 

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I've been humming and hawing on picking up the sensor too. I recently got a 305 and have been enjoying the additional info I get from it for training.

I have a habit of doing a few epic rides a year (50+ miles) and I can see great benefit to the HR monitoring. The speed part I think may be worth getting (for me)...my understanding it that it helps keep things that much more accurate by using both GPS and wheel data to give your distance.

I've never worked with Cadence before, but I think for some of my long rides (especially when I do something silly like riding 90 km on the road with my mtb), it may be worthwhile.
 

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dirt & beer said:
i've been searching through the archives and i haven't found much specifically about the cadence sensor.

i'm planning to buy an edge 305 w/ heartrate (mix of mtn & road riding); i'm not sure about the utility of the cadence sensor. i'm not concerned with cadence, but i'm very interested in speed & distance & altitude.

from the previous postings, does the 305 ONLY use the info from the sensor when the satellite reception cuts out? therefore, if the gps never loses signal will it never pull info from the cadence sensor?

i ride in northern california and i want to set up the road & mountain bike so i collect the same information with the gps. although i've only found myself road riding where the gps will have a clear view of the sky, i'm not sure if i'd need to get a cadence sensor for the road bike too.
I have a cadence sensor on my road bike and use it a lot. I've been trying to keep my cadence up on climbs. I'm not sure how useful it would be on a mountain bike.
 

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I have a 305 but never installed my cadence sensor.
I did a 30 mile ride in some steep canyons / lots of trees.
I rode with a group and one guy had the same setup with the cadence sensor.

When he showed 27 miles, mine showed 22 miles.
A very large difference.

training center fixes this so you will have a correct total
back at home, but on the trail you can get a large difference.
 

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Discussion Starter · #6 ·
hmmm, perhaps it makes the most sense to have the cadence/speed sensor on my mtn bike and go without on the road bike. i wouldn't mind avoiding the extra expense of the sensor, but at least it sounds like i'll only need it on the mtn bike.
 

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dirt & beer said:
hmmm, perhaps it makes the most sense to have the cadence/speed sensor on my mtn bike and go without on the road bike. i wouldn't mind avoiding the extra expense of the sensor, but at least it sounds like i'll only need it on the mtn bike.
In terms of using the cadence output, seems like the road makes more sense. But for making sure the distance is correct, use it either where you are going to get the worst satellite coverage (no advantage if you have good reception), or where it matters the most to you. I had originally planned on putting on the mountain bike, but so far I haven't had any problems with reception. If my readings were off by 5 miles, no doubt I would put it on my mountain bike!
 

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I've been riding with a GPS and Polar HRM / Computer for many years now and have a very large set of data where I can compare distance from the polar using a wheel sensor and the GPS. The GPS distance is often off by as much as 20%. It's always less than the actual distance. It's not a reception issue; I think it has to do with the way the GPS calculates distance as a series of line segments. I have rides where reception was a problem and those are off by even more, but I also have tons of rides where I never lost reception. When the trails get twisty the algorithm isn't nearly as accurate as a wheel sensor. The amount of error is very consistent for the same trail over many rides. It's also consistent between the eTrex I use to use and the 60csx I use now. Not surprisingly, the distances are always spot on between the GPS and Computer for road rides since they aren't twisty. This holds true even when the road rides are in areas with tree cover and for MTB rides in areas, such as Sedona, that don't have tree cover.
 

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MtbMacgyver said:
I've been riding with a GPS and Polar HRM / Computer for many years now and have a very large set of data where I can compare distance from the polar using a wheel sensor and the GPS. The GPS distance is often off by as much as 20%. It's always less than the actual distance. It's not a reception issue; I think it has to do with the way the GPS calculates distance as a series of line segments. I have rides where reception was a problem and those are off by even more, but I also have tons of rides where I never lost reception. When the trails get twisty the algorithm isn't nearly as accurate as a wheel sensor. The amount of error is very consistent for the same trail over many rides. It's also consistent between the eTrex I use to use and the 60csx I use now. Not surprisingly, the distances are always spot on between the GPS and Computer for road rides since they aren't twisty. This holds true even when the road rides are in areas with tree cover and for MTB rides in areas, such as Sedona, that don't have tree cover.
Interesting! For my first few rides with my Edge 305, I compared the Edge's distance with my cyclecomputer. They were virtually identical. All the rides since have shown basically the same distance I was getting with the cyclecomputer. Maybe the riding here in southern California just isn't so twisty as to cause a problem. I have noticed a couple of times when my track didn't follow the switchbacks of a trail, which I attributed to not recording the position frequently enough, but that is not the norm.
 

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Psycho Mike said:
I've been humming and hawing on picking up the sensor too.
"hemming and hawing - Collaborative International Dictionary of English v.0.48 :

Haw \Haw\, v. i.
To stop, in speaking, with a sound like haw; to speak with
interruption and hesitation.
[1913 Webster]

Cut it short; don't prose -- don't hum and haw.
--Chesterfield.
[1913 Webster]

hemming and hawing speaking hesitantly and inarticulately,
with numerous pauses and interjections.
[PJC]"

I just got my 305 today and will have the Cadence on two bikes for base & build training. I'll give my experiences in a few weeks.
 

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MtbMacgyver said:
I've been riding with a GPS and Polar HRM / Computer for many years now and have a very large set of data where I can compare distance from the polar using a wheel sensor and the GPS. The GPS distance is often off by as much as 20%. It's always less than the actual distance. It's not a reception issue; I think it has to do with the way the GPS calculates distance as a series of line segments. I have rides where reception was a problem and those are off by even more, but I also have tons of rides where I never lost reception. When the trails get twisty the algorithm isn't nearly as accurate as a wheel sensor. The amount of error is very consistent for the same trail over many rides. It's also consistent between the eTrex I use to use and the 60csx I use now. Not surprisingly, the distances are always spot on between the GPS and Computer for road rides since they aren't twisty. This holds true even when the road rides are in areas with tree cover and for MTB rides in areas, such as Sedona, that don't have tree cover.
The wheel sensor is accurate as it tracks the travel of your wheel with a precision of one wheel revolution (let's assume the wheel diameter setting is right and you're not doing excessive wheelies ;) ).

The GPS takes a datapoint say every 1 second (the Edge at its fastest, in adaptive mode it is usually slower), and so it doesn't 'see' the trail with all its small bounces up and down with the same resolution as the wheel sensor (in one second the wheel does a large amount of revolutions). The GPS then calculates distance by adding up the segment lengths between the datapoints - which will almost always be a smaller number than what the wheel sensor gives, the more so on more technical trails... some more data is discussed here.
 

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Discussion Starter · #13 ·
ElHombre said:
The wheel sensor is accurate as it tracks the travel of your wheel with a precision of one wheel revolution (let's assume the wheel diameter setting is right and you're not doing excessive wheelies ;) ).

The GPS takes a datapoint say every 1 second (the Edge at its fastest, in adaptive mode it is usually slower), and so it doesn't 'see' the trail with all its small bounces up and down with the same resolution as the wheel sensor (in one second the wheel does a large amount of revolutions). The GPS then calculates distance by adding up the segment lengths between the datapoints - which will almost always be a smaller number than what the wheel sensor gives, the more so on more technical trails... some more data is discussed here.
so the 305 (with no sensor) will lose some trail resolution due to its sampling rate, but i gather the info coming in from the cadence/speed/distance sensor does not overide the distance measured by the 305 anyway.

the 305 only takes info from the speed/distance sensor when gps signal is not available?
 

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dirt & beer said:
so the 305 (with no sensor) will lose some trail resolution due to its sampling rate, but i gather the info coming in from the cadence/speed/distance sensor does not overide the distance measured by the 305 anyway.

the 305 only takes info from the speed/distance sensor when gps signal is not available?
I don't think that's true because a friend that has the 305 said that when his bike was in the workstand and he spun the wheel, the 305 indicated speed and he was getting GPS signal.
 

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MikeDee said:
I don't think that's true because a friend that has the 305 said that when his bike was in the workstand and he spun the wheel, the 305 indicated speed and he was getting GPS signal.
Dirt and Beer is correct. The 305 will not register speed standing still or without a cadence/speed sensor when used on a trainer.

I ride both with and without the cadence sensor. The GPS begins picking up speed and distance data one or two minutes into a ride without the sensor. Otherwise it begins showing speed and distance immediately when I start. The cadence/speed sensor fills in GPS gaps.

Adios for now,
 

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GEOMAN said:
Dirt and Beer is correct. The 305 will not register speed standing still or without a cadence/speed sensor when used on a trainer.

I ride both with and without the cadence sensor. The GPS begins picking up speed and distance data one or two minutes into a ride without the sensor. Otherwise it begins showing speed and distance immediately when I start. The cadence/speed sensor fills in GPS gaps.

Adios for now,
But the question was which does the 305 default to, the wheel sensor or the GPS when computing speed and distance traveled.
 

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I have a 305, have not installed the cadence sensor yet. (installed the 305 Jan 1)

I have used the 305 with both my road and mountain bikes. (21 rides to date)

Both bikes also have computers with wheel sensors and the reading on both have been almost exactly the same as the 305 on all rides so far.
 

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I tracked a night ride this past tuesday and had a 1/2 mile hiccup that couldn't happen if the wheel sensor were to override the gps data. This may or may not have been caused by the HID light I was using, I dunnot these kinda things.
The hiccup: There is a straight line from one point to another point in my data. I was at one of those points, but not the other. I am thinking that based on this, the 305 missed and or incorrectly read location points and interpolated my route. Had this information been gathered via the wheel sensor it wouldn't have concluded I made this straight line or gone that distance...
No? Yes? I've had this machine for less than a week.
 
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