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Computers with Gradient function?(10 posts)

Computers with Gradient function?litesp
Mar 24, 2003 11:13 AM
1. How does the unit determine gradient?
2. Which models have you tried, cost?
3. What are the gradient functions (current, max, avg, etc.)?
4. Is the gradient reading responsive to gradient change?
5. Are the readings accurate (compared to publish gradient)?
6. Any recommendations?

Specialized Speed Zone Promapei boy
Mar 24, 2003 11:40 AM
My Specialized Speed Zone Pro does gradients. It does it by calculating altitude gained or lost along with distance traveled. It cost me $99 in 2001. It does not store or interpolate any gradient information. It simply tells you what the percentage gradient was during the previous twenty feet or so that you traveled. Because of this, the gradient readout is always several seconds out of date. I have never compared the computer's gradient readings to a topo map. As for accuracy, it must be said that, for every grade, the computer generally gives a steeper percentage reading when I'm ascending the hill than when I'm descending. The variance, however, is never anything over 2%. All told, despite the shortcomings, I like the Speed Zone Pro a lot. It is truly wonderful to know the steepness of the hill you're struggling up. Whenever I'm blowing by somebody on a hill (just kidding...), I never fail to shout out the percentage grade to them. Sometimes they appreciate it. Most of the time they do not.
Ciclosport 414 has it as wellirregardless
Mar 24, 2003 2:33 PM
works the same way and just as well as the Specialized Speedzone Pro. Current readings only, no averages. It's a little more expensive. The top of the line Ciclosport(s) may also have the incline function. As far as the gradient function goes, I'd call them a wash.

The Ciclosport 414 (it may have been replaced with a newer model recently) will also estimate your power based on your speed and altitude gain. Not very accurate on the flats because it ignores the wind and maybe other factors that are critical to power output, but it will give you some indication of your power on ascents.
Specialized Speed Zone Prolitesp
Mar 24, 2003 3:26 PM
Thanks for the feedback.

That's disappointing if the computer uses altitude changes with distance to calculate % gradient. I expect the readings to be grossly inaccurate (repeatably inaccurate?). I have a Nike "zero drift" Lance watch that can never even give repeatable relative altitude gain, not to mention absolute elevation. The "zero drift" technology seems to drift all over the freakin place for $200. I have a GPS device which gives repeatable but inaccurate elevation readings as well. Does anybody know how "instrument" or laboratory grade altimeters compensate for barometric variations?

I was hoping the computers use a special circuit or sensor such as this -

or this

or this

or this

Does anyone know if all the computers with gradient functions use the same principle as the Specialized Speed Zone Pro?

Very repeatableirregardless
Mar 24, 2003 4:11 PM
I have noticed that while altitude readings tend to be inaccurate over a long ride, or from day to day, for the short periods used to calculate incline, these computers tend to give the same readings time and time again. Both of these computers (speedzone pro and CM 414) repeatedly give me the same altitude gains on my routine hillclimbs, and also routinely give the same incline readings at each section of the ride. If all you want is a relatively instantaneous gradient reading, they're pretty consistent.
The Smart Levelmapei boy
Mar 24, 2003 4:12 PM
I dig that Smart Level. If you don't have a sloping top tube, why not just duct tape the thing at a spot where you can read it? How much could it possibly weigh? If you're looking for genuinely accurate readings, it seems like the way to go.
The Cheap Level4bykn
Mar 24, 2003 5:48 PM
Check this out, may not be too easy to read on the bike, but I've always thought it looked interesting
Available at:4bykn
Mar 24, 2003 5:50 PM
re: Computers with Gradient function?toomanybikes
Mar 24, 2003 1:07 PM
I use two instruments for this. First I have a Polar 710 which measures altitude and records the info which can then be downloaded. The s710 also measures in each exercise session the total feet (or metres) of altitude gain.

I also have a Timex Helix WRKS watch which among the 632 other functions measures altitude and rate of alt. change and stores the info for later review (not download). The plus side of this is that is also a very useful watch and waterproof.

The think I think is important with these is that they must re-calibrated often as BArometric pressure changes. I will say that the altitude readings, in my experience are pretty accurate, however, what they do more than measure absolute altitude is to measure and indicate relative alt. changes and to record that info.

Good luck.
I've used a few.Ian
Mar 24, 2003 6:34 PM
Mainly because I'm a bike junky and like to try different things. I have used the Specialized Speedzone Pro, Ciclosport CM414 and Ciclosport HAC 4.

They all use barometric pressure for altitude. To my knowledge, that is really the only way to measure altitude. Correct me if I am wrong?

The HAC 4 was my favorite, but mainly because it also had heart rate and allowed me to clean up my bars. It would show current grade and then at the end of the ride, I could check max grade and total elevation gained. I used it while training for a hilly century (Six Gap, 10,700 feet of climbing) and rode many of the same hills and routes over and over. It always seemed accurate on the same hills and routes. Now, the current elevation would not always be correct, it might vary plus or minus 100 feet per day, but that didn't effect the other readings.