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Discussion Starter · #1 ·
Hi All,
I am looking for a computer and wondering what options I might have other than the Garmin Edge series. The features I want are...

1. Speed/Cadence wireless from rear wheel
2. heart rate
3. calorie calculation based on heart rate
4. Ant+ compatibility
5. Ability to plot key data (HR, Cadence, Speed, power if I use it) on the map and the profile of the ride.
6. ability to move the head unit between 2 different bikes without having to redo the setup for power and wheel size.

I don't have a power meter yet, but plan to get the type that is built into the spindle on the peddles once those have been on the market for a little while.

Nice features to have would be ability to have maps and way points, not sure how much i would actually use either one of these though.

I have been looking at the Edge 800, but want to know otehr options

Thanks
 

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Garmin is the only game in town for a cycling computer with GPS. The Garmin Edge 500, 605/705 and 800 meet all of your criteria. If you relent on the GPS capability (number 5), you could look at the Joule cycling computers from Saris.

The only other option is to go with a smart phone and a GPS/cycling app. There is an ANT+ widget for the iPhone for example. Of course, this approach comes with its own set of pros and cons.
 

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From Interbike via DC Rainmaker's blog some future version of the Joule will include GPS:

In the case of the Joule, GPS is definitely on the radar…soon. In my discussions they understand that GPS absolutely has a place in training and racing today – even if it doesn’t directly provide a metric or measurement that’s key to measurement or performance. They noted that when they first started looking at GPS for the unit during initial design, it would have increased the size and cost too much. But now both size and cost are dramatically different. And GPS is on the radar for the next iteration.
 

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Know that "calorie calculation based on heart rate" is wildly unreliable, to the point of being worthless IMO.

If/when you get a powermeter, then you will know exactly how much work you output, and can estimate how many calories you burned to achieve it.

I say "estimate" because only about 20-25 % of calories burned go into actual work output.
 

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Discussion Starter · #6 ·
tom_h said:
Know that "calorie calculation based on heart rate" is wildly unreliable, to the point of being worthless IMO.

If/when you get a powermeter, then you will know exactly how much work you output, and can estimate how many calories you burned to achieve it.

I say "estimate" because only about 20-25 % of calories burned go into actual work output.
'I know exactly what you are saying, but calorie calculation based on heart rate is much more reliable than calorie calculation based on average speed which is what many computers do, even if they have built in heart rate.
 

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stubek said:
'I know exactly what you are saying, but calorie calculation based on heart rate is much more reliable than calorie calculation based on average speed which is what many computers do, even if they have built in heart rate.
Until high power levels heart rate varies linearly with power, with slope of the curve varying between individuals. Without knowing the slope you can't do anything, and just having an initial relationship doesn't help because the slope increases as your heart becomes more efficient.

Past a deflection point the relationship can become curvilinear farther complicating things.

Then you have heart rate drift. With cyclists being just 20-25% efficient a 200W effort results in 600W of waste heat after which your heart runs faster to move hot blood to cool spots.

My Polar cs200cad spits out garbage which is both ludicrously high (if you ride at a relatively constant pace and just look at the impact of drag + friction) and inconsistent.

If you want accurate calorie counts you need a power meter.
 

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Reliability

stubek said:
'I know exactly what you are saying, but calorie calculation based on heart rate is much more reliable than calorie calculation based on average speed which is what many computers do, even if they have built in heart rate.
Actually, not true. Or at least if it is true for a given individual, it likely won't be true for others. You could get a much more accurate number from speed and grade (with rider weight as an input) if companies were willing to use the correct algorithm but that would give a much lower calorie expenditure number, and who wants to do that?
 

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Kerry Irons said:
Actually, not true. Or at least if it is true for a given individual, it likely won't be true for others. You could get a much more accurate number from speed and grade (with rider weight as an input) if companies were willing to use the correct algorithm but that would give a much lower calorie expenditure number, and who wants to do that?
The iBike Sport does that math. I wouldn't use it for power, but perhaps it would work well enough to estimate calories.
 

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Interchangibility

ukbloke said:
The iBike Sport does that math. I wouldn't use it for power, but perhaps it would work well enough to estimate calories.
If it can do calories accurately, it can do power or the other way around. They are interchangible with a direct watt-hours to calories burned conversion.
 

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Kerry Irons said:
If it can do calories accurately, it can do power or the other way around. They are interchangible with a direct watt-hours to calories burned conversion.
I know what you mean. But for me the acceptable error bar on calories is large (eg. +/- 10-20%) whereas the acceptable error bar on power is small (eg. +/- 1-2%). Part of this is that the conversion from energy output to calorie input is a guess for any random individual. How efficient is your stomach? :)

Also one would just be looking for calorie information over an entire ride or set of rides, whereas for power I'm also interested in the instantaneous power output. My feeling with the iSport approach is that it averages out to a reasonable number, but that the instantaneous number is much less credible. When I ride with a PowerTap the second-to-second variation in power is very significant and consistent with what is happening in terms of effort and situation (or my perception as to what is happening).

Anyway, I train with power and don't train with calories - I let my stomach/brain make the decisions on eating and that seems to work for me.
 

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I think heart rate is a pretty useless metric for calories. At least if you're trying to correlate it to thinking there's a correlation between power and calories. I was curious about this slope and found that I can have a heart rate of 125-135 at 200 watts and a heart rate of 155-165 for 300 watts. Biggest factor was the cadence I used, higher cadence=higher HR. That's 20 bpm between the extremes for a HUGE difference in effort. I think using 35 calories/mile is a much better measure especially if you're trying to lose weight.
 
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