Cav is on Strava!

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Hacienda71

Mancunian in self imposed exile in leafy Cheshire
How good is quite good? Curious, as to what sort of percentage error we are talking about and what ranges of rider and equipment were tested.

I don't think they were that scientific, I read two or three reviews of Strava where people had compared their power meter figures against Strava figures and found that on longer segments the results were pretty close. Today shows how way off it gets if it is windy or if you draft a vehicle. Nothing is going to compare to a power meter for accuracy. It's just the grand or so that makes them an issue for most of us.
 

Rob3rt

Man or Moose!
Location
Manchester
Personally, I am even sceptical of some of the actual power meter's ability to produce good power figures, not without reason, doesn't take much research to find lots of information about how unreliable many of them can be, they are most certainly not a fit and forget bit of kit. I am hoping to buy one in the near future (probably power2max or Quarq) and am currently doing a lot of reading and tbh, it almost seems like if you can't afford SRM you just buy anything else you can afford and then hope you get a good one, so what hope in hell does some algorithm have in getting it right if the equipment you would use to validate the algorithm is so sketchy.

Most pro's are running SRM PM's, the problems many people experience probably won't bother a pro, because their team will have a load of them and will have engineers to calibrate them and will get faults repaired quick sticks, but for a part timer, it seems you are not alone if you only have the PM on your bike 80% of the time of ownership.

I am aware I may be over egging some of the issues with PM's here, but they are definitely not on the same level of buy it, fit it, use it and blindly accept what it is telling you as you might hope!
 

jdtate101

Ex-Fatman
I've got a forerunner 110 as well as a 800, so I could record on both using a HR strap, but only power on the 800, it should give me a rough comparison of how strava calculates the power and how close they track. The only difference between the two files would be the lack of power, cadance and direct speed reading from the spoke magnet, but it should be close enough for this purpose.
 

Andrew_P

In between here and there
All you need to know about Strava calculations

Strava Calculated Power vs. Power Meter

We have seen that in most cases our watts number are very close to the numbers provided by a Powertap or SRM. Note that Strava calculated watts are not the watts produced at the crank but the watts produced by the rider-bike system, this will create a slight difference between the powermeter data and the Strava watts. Lack of good chain lubrication and low tire pressure can rob you of the watts you see on your Powertap or SRM. Other reasons watts can be inconsistent include strong winds and bad elevation data reported by the Garmin.
Our calculations are most accurate when climbing given accurate rider and bike weight.
 

jdtate101

Ex-Fatman
Probably because he signed himself up over the net just like we do. I'm sure once the Strava bods catch on they will do all they can to get him in the Pro's list. It would be quite a catch for them to have a cyclist of Cav's prowess posting rides regularly.
 

Hacienda71

Mancunian in self imposed exile in leafy Cheshire
Not all of the pro's around here log themselves as pro's.
 

VamP

Banned
Location
Cambs
They can only be as good as the underlying mapping which is often wrong. One flat run along the prom for me, has 3 10% hills on Strava, giving me an estimated power of, ridiculous, as I 'climb' them all at 20mph. So, pinch of salt, interesting in relative terms only when compared to previous logged rides.

Even there it's not reliable. Look at my logs for Box Hill over the last year. I have been meticulous with keeping my weight up to speed. The power figures are all over the place...

RankNameDateSpeedHRPowerVAMTime
1 Vam Polecat Sep 18, 2012 12.6mi/h 160bpm 285W 1014 7:25
1 Vam Polecat Oct 9, 2012 12.6mi/h 162bpm 259W 1014 7:25
3 Vam Polecat Nov 22, 2012 12.5mi/h 163bpm 308W 1010 7:27
4 Vam Polecat Dec 29, 2011 12.4mi/h 158bpm 304W 1001 7:31
5 Vam Polecat Oct 9, 2012 12.4mi/h 158bpm 258W 999 7:32
6 Vam Polecat Sep 18, 2012 12.3mi/h 158bpm 279W 994 7:34
7 Vam Polecat Sep 7, 2012 12.3mi/h 170bpm 284W 992 7:35
7 Vam Polecat Nov 22, 2012 12.3mi/h 163bpm 317W 992 7:35
9 Vam Polecat Aug 26, 2012 12.2mi/h 173bpm 263W 981 7:40
10 Vam Polecat Oct 9, 2012 12.1mi/h 159bpm 230W 977 7:42
11 Vam Polecat Nov 2, 2012 12.0mi/h 164bpm 262W 965 7:48
12 Vam Polecat Nov 7, 2012 11.9mi/h 159bpm 248W 963 7:49
13 Vam Polecat Oct 16, 2012 11.5mi/h 163bpm 222W 925 8:08
14 Vam Polecat Nov 22, 2012 11.5mi/h 159bpm 285W 923 8:09
15 Vam Polecat Dec 29, 2011 11.3mi/h 154bpm 267W 914 8:14
16 Vam Polecat Nov 22, 2012 11.2mi/h 156bpm 280W 899 8:22
17 Vam Polecat Aug 22, 2012 11.1mi/h 158bpm 212W 892 8:26
 
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