Power2Max in accelerometer based cadence so no magnets. SRM needs to keep sending the last signal since it only knows about cadence when the switch passes the magnet so 30rpm with a single switch is 2 seconds to determine if it is slow or stopped. I think SRM is 3 seconds without a cadence trip for it to go to 0. On a road bike going hard then coasting suddenly has a tail of the last reading.
The accelerometer should be able to detect 0 power cadence within the 1 second ANT+ broadcast.

You are right, it should.

Stages uses the same type of cadence sensor and it is lousy in situations where you let off the pressure.

I have heard Stages combines the accelerometer readings with looking for power pulses (similar to power tap indirect cadence) to smooth out false readings from bumpy roads. If he power is really 0 then cadence is not so important at least from a power meter perspective. I suspect that power2max may be doing something similar. Quarq (new ones) and Garmin vector use the same accelerometer cadence detection so it would be interesting to see what they come up with.
If it is just the cadence at 0 watts then a cadence/speed pickup would solve it. Null data is more of an issue if it there is force and rotation so you miss real data.
I am playing with a power2max on the trainer so can see if rotation with no power registers.

Without getting into the details, if you are getting 0 RPM readings sometime during your time trial on the track, then your average cadence data isn't reliable. And Time Trials are where a power meter is the most useful on the track. Speed, power, cadence data from mass start races isn't scrutinized nearly as much as data from TTs.

There are several instances where floating is a viable technique (i.e. kilo or team pursuit).

In short, this sucks.

Maybe a dedicated cadence sensor will work. But, most wireless PMs get their cadence from the power meter unit.

Eh, if you have a separate speed sensor you can work out cadence. Doesn't seem like a call breaker, just not ideal.

These customers don't pay $1500-3500USD in order to have to still calculate their cadence based on average speed :D

The data should be there, period. Having 0rpm show up when you are on a track bike doing an effort means that something is wrong with the system, period.

This is like your expensive car registering 0 kph/mph when you are coasting downhill :D Something is wrong!

It's not that the Cadence is always Zero when power is Zero... It's just that in situations where pressure is realeased cadence can mis-read. Sometimes it dips sometimes it spikes. its a little annoying- but generally speaking the averages are accurate.

Maybe It doesn't bother me- because honestly I see almost no need to know cadence of efforts beyond just generally being in the ranges that I prefer.. It just doesn't factor in to effort analysis for me at all.

On another note, eurosport also make a docu about François Pervis trips to Japan. In this case it's both available in english subbed version and original french version.

French version :
English version :

Im still not sure how important it really is. I can still see cadence for when it matters (when Im on the gas) but when I swing up on our extremely tight steep corners, I am off the gas briefly (1s) and it seems to drop to zero for power and cadence. Here are 2 examples from last night

pursuit drill without swing, so similar to motor pacing (the dip in speed was just a miss on the magnet):

http://i787.photobucket.com/albums/y...ps6ba6b7cc.jpg


Race simulation (so swinging up)

http://i787.photobucket.com/albums/y...psf0d012c4.jpg

I'm a data nut.

In the examples you have above, you are looking at sections that are several minutes long. So, your averages are fine. But, let's say you are looking at a 1:10 kilo effort where there is a long float for several seconds after the standing start.

When you analyze the file, you can section off intervals in several different ways:
- 0 to 125M
- 0 to 250M
- 250M to 500M
- 500M to 750M
- 750M to 1,000M
- 0 to 500M
- 500m to 1,000M

Also, let's say you are looking at yourself in a Team Pursuit. You float on the pedals A LOT when you are in a team pursuit. So, your average cadence for whatever splits you section off will be skewed lower with the zeros in there.

The purpose of buying a power meter is to get data for analysis. Period. If your data drops off, then the tool isn't serving its purpose as expected.

Analyzing the data is the #1 reason you buy a power meter. Based on the analysis, you adjust to improve. No analysis, no opportunity to improve.

Also, if the drop offs are just a few readings, then maybe you can manually interpolate those using the software. Basically look at the cadences at the ticks before and after the drop off and put the average in.

Example:

121RPM
122RPM
121RPM
120RPM
0RPM
122RPM
120RPM

Will become

121RPM
122RPM
121RPM
120RPM
121RPM
122RPM
120RPM

I would be really surprised if most of this wasn't from the head unit.
I get occasionally erratic cadence data- but this seems to be more than that.

Carletons fix is all it takes to even it out and takes just a second in Golden Cheetah- and in my experience it rarely happens when it matters. Never a problem during the actual effort

I would get in touch with them to see if there might be a firmware fix for this type of issue. The cadence is going to have some filtering/smoothing to try to weed out stray results and come up with a reasonable value. Stages took a couple of updates to get things right and I suspect getting the fixed gear firmware stabilized might take a couple of iterations here too. Garmin is also doing some smoothing on the readings to avoid spikes.

Figuring averages out isnt a problem, and the only time I care about cadence data is looking for high/low points to decide if the gearing was the right choice. The actual average doesn't mean TOO much since the pace of the race/attacks/lack-there-of could bring that up or down.

I think Ill send them an email and see what they say. For me its not a deal breaker, but I also want it to be as accurate as possible as often as possible.


Ill try and get a standing start data point this weekend if I can, just to see how long it takes to kick in. I came into it expecting the 2 rotations or whatever most PMs don't get though. Id go outside and do it tomorrow but...its cold :)

thank you!

Ok, so here is the best proof that something is funky with the PM. This was a last man standing race (4 guys spread out, you are out if you are passed, standing start). Think of it like a Kilo that you don't know when the end is lol


http://i787.photobucket.com/albums/y...ps72f05752.jpg


This is the only time I have seen it THIS bad, all other data only shows the odd drop here and there. Anyway I have 3 race nights worth of data Ill send over to see whats up to the manufacturer. I dont think its hardware related, rather firmware.

I agree.

If you want, I would think you could get a refund if you bought it new.

Im hoping I can keep it :) but yes, there is a 2 year warranty. Its a new version of the product so Im willing to work with them.

Remember that a 2 year warranty may not be the same as your return for full refund window.

Returning for a full refund may be 30 or 60 days. The 2 year warranty means that they will fix something and return it to you or give you a replacement if it's is defective.

On a related note:

I'm a strong believer that Cadence is King on the track. Cadence and Speed are much more important than power (in my not-so-humble opinion).

I believe that you can train effectively as a track enduro using Cadence, Speed, and Heart Rate data.

For endurance events, HR data can be just as good as Power data.

A Garmin 500 (or whatever the equivaltent is these days) is probably sufficient. I use a SRM Powercontrol 7 with separate speed, cadence, and HR sensors. I don't have PM cranks anymore. I chose the PC7 because it can record ever 0.5s (double what normal head units do). HR isn't important to me as a sprinter (it's always pegged at max), but to an enduro, I can be very useful.

Thats true, and Ill be reaching out soon to make sure of it.

While I agree the cadence is the most important data, what I get now is still sufficient. While the averages for the whole race are a little low due to the zeros, I still get the highs and lows of certain points in the race. Overlay that with power, and I can see what cadence I was at when it mattered. Did I feel under/over geared? Well I only hit X rpm in the attacks and final sprint, so looks like I was/wasn't and just being a cry baby. That said, at FCV we were limited to 88in (and I only cheated by 2in.. :P )

My garmin is a little tired now and its possible the issue might be there. But I have a PT wheel for the road and have never had any of this.

@gtrob
did you ever confirm that the Data Collection on the G500 is set to include "zeros" and that it is recording every second and not on "Smart Record"?
this all looks like what happens when those are set wrong

Carleton- I know you have said this before, but can you expand on how you would create or modify a program based on cadence and speed alone?
while i have had very good success in a season with no data other than top speed and time- recorded with a stopwatch and cheap speedo that cost less than $50 total. That is simply recording progress. And times are Condition dependent.
Using Power allows you to record output on race days and then create training situations based on the output for a specific duration.. Its like knowing your 1-rep Squat Max and then doing rep-schemes based on a percentage of that number. all the while you know the relation between training output and race day output and you can know that if output in training is raising- so is race day... its like using a "1-rep-max calculator".. "if i can do this set of intervals at X-watts then my 1-off effort is likely X+Ywatts

how would you change a days training based on cadence data?

When I was watching John Coffee with his young athletes at his gym, it was enlightening...and seemed familiar to what I have been doing.

Coffee watched every rep that these athletes (19, 20ish) did. Clean & Jerk, Snatch, Box Snatch, Box Jerk, etc... He'd say, "OK, add 5 more lbs." "OK, take off 10." "Do one more set", etc... they never missed a rep (that I saw).

They didn't come into the day saying, "I'm going to snatch X lbs today for Y reps and Z sets" It was all based on his feel. That feel came from decades of him coaching, lifting, and watching. I assume that he watched the speed and confidence they had in each rep to know how well they "owned" the weight and he'd adjust accordingly.

With track, especially sprinting, we should train to cadence ranges, not power. Basically, for say a flying 200M, ride the biggest gear that you can max out at 140rpm with. If you are touching 145-150rpm, then the gear is too small. If you aren't touching 135rpm, then the gear is too big.

You'll see your progression as your gear choices go up (and your speed).

When we squat, we squat the same reps at around the same speed and we measure progress by how much weight we can move at those reps at that speed, right? Same concept. Just like when you are doing your working sets and you are moving it really fast off the ground...time to add a few more lbs. And if you are struggling and moving the weight slowly, then maybe you should go down a few lbs to complete the set(s).

So, to apply this to pursuit training, you'd have to find both a target heart rate range AND target cadence range and pick the gear that keeps you in both of those ranges.

I don't know much about enduro TT training, but that's how endurance runners train. They don't train by power meters (there are no power meter running shoes) they train by heart rate and (you guessed it) cadence :D