Teams & Riders Froome Talk Only

[SlowFeet]

Re:

Froome's chainrings are not that oval, so 6% adjustment seems believable for a dual-sided stages? i.e. 3% for each crank arm.

That's not how the correction would work. If it were 3% for one-crank-arm Stages it would still be 3% for two-crank-arm Stages. For the one-arm they are multiplying it by 2 already...and multiplying a 3% error by 2 is still a 3% error.

 

[gazr99]

Re:

If you ignore their caveat, you get the same figure the experts calculated, which lines up perfectly well with the performances of everybody else in terms of watts/kg and time lost.

In other words, their Osymetric chainrings do not cause their power meters to overstimate power output by as much as 6%, and they definitely don't give you 6% extra power for free either (I've found some references, including by Ferrari, to Richie Porte having reverted to normal chainrings, which he wouldn't have done if they actually worked like that).

Which means they're telling the truth.

Exactly, I think the reason more people don't use them is something to do with the chain coming off? Wiggins had them and there was a debate about them in 2012

 

[jmdirt]

So SKY publish data, and the reaction on here? "They're lying". how predictable ...

The thing is they publish data and the very first line is a caveat "oh btw, because of the chainrings he uses, he needs 6% less power for the same speed, so drop 6% of the power meter and you get the following readings yada yada yada...".

I mean come on ! Wouldn't all riders be using the same chainrings if it gave 6% bonus !

The powerdata loses all value with this caveat, it becomes unreadable unless one can conclusively demonstrate the effect of the chainring, and it leads to a simple question than : if this chainring is potentially magical, and furthermore if its level of magicality depends on the style of pedalling you have meaning all riders aren't equal regarding its uses, shouldn't it be banned ?

This is basically the only even remotely conclusive element one can get from this published "data"....

I don't trust Sky any more than I trust any of the teams, but I don't think that this data release is "crap". My understanding is that Rotor rings ('unround' rings like O-Symetric) read about 5% high on a power meter. Its not that they get a bonus like you have interpreted it. Kerison doesn't use the 6% in his calculation though: "Again that’s just the power meter and does not include the 6 per cent adjustment (for O-symmetric).” so its not a caveat.

 

[Benotti69]

Re: Re:

If you ignore their caveat, you get the same figure the experts calculated, which lines up perfectly well with the performances of everybody else in terms of watts/kg and time lost.

In other words, their Osymetric chainrings do not cause their power meters to overstimate power output by as much as 6%, and they definitely don't give you 6% extra power for free either (I've found some references, including by Ferrari, to Richie Porte having reverted to normal chainrings, which he wouldn't have done if they actually worked like that).

Which means they're telling the truth.

Exactly, I think the reason more people don't use them is something to do with the chain coming off? Wiggins had them and there was a debate about them in 2012

If Osymetric rings worked, dont y'all think that Wiggins who had used them in 2012 would've used them in a controlled environment like an indoor track to use the 'gains' for his hour record? He didn't. Standard round ring.

 

[ScienceIsCool]

So SKY publish data, and the reaction on here? "They're lying". how predictable ...

The thing is they publish data and the very first line is a caveat "oh btw, because of the chainrings he uses, he needs 6% less power for the same speed, so drop 6% of the power meter and you get the following readings yada yada yada...".

I mean come on ! Wouldn't all riders be using the same chainrings if it gave 6% bonus !

The powerdata loses all value with this caveat, it becomes unreadable unless one can conclusively demonstrate the effect of the chainring, and it leads to a simple question than : if this chainring is potentially magical, and furthermore if its level of magicality depends on the style of pedalling you have meaning all riders aren't equal regarding its uses, shouldn't it be banned ?

This is basically the only even remotely conclusive element one can get from this published "data"....

From a technical perspective, I think that the argument is not that oval chainrings give a 6% advantage. Rather, it's something that presents itself as measurement error.

Power is normally measured as P = T x w where P is power, T is torque, and w is rotational speed (cadence). To calculate power you need to measure torque and speed. Notice that these are both time based measurements. If you measure each of them once per second you'll get less than one sample per pedal stroke. This would be okay if torque and cadence were constant like you would see in a freely spinning motor. But on a bike, both cadence and torque change dramatically throughout the pedal stroke. So sampling rate is one source of error.

The second problem is that you need to measure torque and cadence at the same moment. However, cadence must be sampled over a time interval - there's no good way in this setup to measure instantaneous cadence. So now you must sample at large enough time intervals to get an accurate reading of cadence. But both those values are changing! So there's another source of error. In this case the error is larger for ovalized chainrings because the torque and speed are changing even faster than for round ones.

Then there are lots of tertiary effects such as impulse loading (rapid changes in torque) that might not be measured correctly with a strain gauge type of torque meter. It's likely that impulse loads happen more frequently with ovalized chainrings. Etc, etc, etc.

So when you go to add up all your errors, you can see that some of them will be variable. That gives you a range that the true value is different from what is measured. Let's say +/-3%. However, some of the errors will be biased in one direction only and cause a difference of maybe 2 to 4% but never a negative value.

What Sky is saying is that ovalized chainrings cause a biased error that is roughly 6%. I can see, as I've shown above, that there will probably be some bias in the measurement. But 6%!? I think that might be a load of horsesh!t because it's enormous. I think they're taking a valid bit of science and wildly inflating the numbers.

John Swanson

 

[ScienceIsCool]

Re:

Stages themselves tell you to adjust for readings for oval chainrings. Kerrison isn't lying. I'm not sure what exact rings Froome uses, but I see no reason to not believe it, when Stages confirm it anyway?

"Due to the changes in velocity non-round chain rings produce through the course of an 'event' you will see that your power will be skewed higher than with a round ring, which has a constant velocity throughout each event. Through our own testing, and using a hub-based meter as a control, we conclude that there will be a 4-5% increase on the readings from a Stages Power meter when used with a non-round chain rings. We recommend that our customers take this into account when changing from round to non-round chain rings, as they may need to adjust their functional threshold power accordingly. "

I'm betting that Stages did a quick and dirty test without taking time to really understand and measure the difference between rings. The fact they claim that round rings are at constant velocity is laughable. I have no doubt that there is a difference between rings, but 5%!? Unless you've built the absolute worst power meter there's no way.

John Swanson

 

[carton]

What Sky is saying is that ovalized chainrings cause a biased error that is roughly 6%. I can see, as I've shown above, that there will probably be some bias in the measurement. But 6%!? I think that might be a load of horsesh!t because it's enormous. I think they're taking a valid bit of science and wildly inflating the numbers.

Yeah, exaggeration is the dumbest spin technique. It actually weakens your argument. I'm guessing there's probably a 95% that the error is below 6%, so they talk themselves into going with 6% because it's in the range and they think it looks better, when it actually looks worse. If you use 3% it's roughly 6W/kg. Great, but not alien, fairly in line with the estimated 6.09. Much better than a number that's just too low.

 

[veji11]

So SKY publish data, and the reaction on here? "They're lying". how predictable ...

The thing is they publish data and the very first line is a caveat "oh btw, because of the chainrings he uses, he needs 6% less power for the same speed, so drop 6% of the power meter and you get the following readings yada yada yada...".

I mean come on ! Wouldn't all riders be using the same chainrings if it gave 6% bonus !

The powerdata loses all value with this caveat, it becomes unreadable unless one can conclusively demonstrate the effect of the chainring, and it leads to a simple question than : if this chainring is potentially magical, and furthermore if its level of magicality depends on the style of pedalling you have meaning all riders aren't equal regarding its uses, shouldn't it be banned ?

This is basically the only even remotely conclusive element one can get from this published "data"....

From a technical perspective, I think that the argument is not that oval chainrings give a 6% advantage. Rather, it's something that presents itself as measurement error.

Power is normally measured as P = T x w where P is power, T is torque, and w is rotational speed (cadence). To calculate power you need to measure torque and speed. Notice that these are both time based measurements. If you measure each of them once per second you'll get less than one sample per pedal stroke. This would be okay if torque and cadence were constant like you would see in a freely spinning motor. But on a bike, both cadence and torque change dramatically throughout the pedal stroke. So sampling rate is one source of error.

The second problem is that you need to measure torque and cadence at the same moment. However, cadence must be sampled over a time interval - there's no good way in this setup to measure instantaneous cadence. So now you must sample at large enough time intervals to get an accurate reading of cadence. But both those values are changing! So there's another source of error. In this case the error is larger for ovalized chainrings because the torque and speed are changing even faster than for round ones.

Then there are lots of tertiary effects such as impulse loading (rapid changes in torque) that might not be measured correctly with a strain gauge type of torque meter. It's likely that impulse loads happen more frequently with ovalized chainrings. Etc, etc, etc.

So when you go to add up all your errors, you can see that some of them will be variable. That gives you a range that the true value is different from what is measured. Let's say +/-3%. However, some of the errors will be biased in one direction only and cause a difference of maybe 2 to 4% but never a negative value.

What Sky is saying is that ovalized chainrings cause a biased error that is roughly 6%. I can see, as I've shown above, that there will probably be some bias in the measurement. But 6%!? I think that might be a load of horsesh!t because it's enormous. I think they're taking a valid bit of science and wildly inflating the numbers.

John Swanson

Yes sorry I was wrong in what I wrote, the key point was more that that 6% number seemed pulled out of thin air and if indeed the measurement difference is 4% instead of 6, well it does change the data significantly.

 

[goggalor]

He reported that he was 66kg in 2013. In 2015, he is 67.5 kg? Not taking his competition as seriously this year?

Bulking up a bit for the long time trials.




Oh.

 

[jmdirt]

In this thread, is the assumption that Froome (Sky) is the only one doping in the TdF this year?

 

[Benotti69]

Adam Yates (SRM) 5.84 w/kg, lost 2:04 to Froome......................just sayin

 

[pastronef]

Re:

In this thread, is the assumption that Froome (Sky) is the only one doping in the TdF this year?

carefull with this kind of posts on here.
anyway that´s the Froome thread so people talk just about him

 

[BYOP88]

Re:

In this thread, is the assumption that Froome (Sky) is the only one doping in the TdF this year?

I can't speak for anyone else but, I wouldn't put my hand in the fire for any of them. But Sky get more heat in the clinic/twitter because they have #magicalchains and #Marginalgains etc etc.

 

[veji11]

Re:

In this thread, is the assumption that Froome (Sky) is the only one doping in the TdF this year?

No, but that his having some significant advantages wherever they came from would be very significant to the final outcome, rather than what a Gallopin or a Mollema do.

 

[carton]

Re:

In this thread, is the assumption that Froome (Sky) is the only one doping in the TdF this year?

I think it's more he's winning so he's the only one worth going after.

Also he pretends to be a good guy (calling for testing, checking the boxes, releasing data) so he must be a hypocrite.

Also magic pillows. Everyone hates Sky's pillows.

 

[46&twoWheels]

He reported that he was 66kg in 2013. In 2015, he is 67.5 kg? Not taking his competition as seriously this year?

Bulking up a bit for the long time trials.




Oh.

his second heart/pumping engine might account for these few kilos more
Which is also one of the few ways you can dope by increasing your weight!!

 

[Benotti69]

Re:

In this thread, is the assumption that Froome (Sky) is the only one doping in the TdF this year?

this is the 'Froome talk only' thread. Did you not understand that?

There is a Wiggins thread about his magical transformation from Grupetto to Podium

There is the Sky thread for all things sky.

There is now a Geraint thread to discuss his recent transformation.

etc

etc

Sky so giving to the clinic......

 

[Benotti69]

Kerrison talks about high margin of errors to be drawn from the data! Wow, what have Sky being doing with all these numbers and looking for gains for the last 5+ years. One would almost draw the conclusion that they are scrabbling around in the dark...........

I mean Froome has been a Sky rider for how long now, 5 years, and Kerrison says they were surprised that his heart rate remained at a constant 160BPM on Ventoux in 2013! I mean what are Sky doing if not constantly measuring the riders information loo ing for where the gains work and how to improve on those gains? That was 2 years ago, and what have they done to find out why Froome's heart rate remained constant? Zilch it would appear.

Smoke and mirrors,,,,,,,

 

[sometriguy]

If there really is an error of 6% and sky has known about it for years, wouldn't they have calibrated their power meters for the riders using the oval rings?

 

[Benotti69]

Re:

If there really is an error of 6% and sky has known about it for years, wouldn't they have calibrated their power meters for the riders using the oval rings?

Ssshhhhhh, don't start introducing logic to the discussion and make sky look like amateurs........

 

[jmdirt]

Re: Re:

In this thread, is the assumption that Froome (Sky) is the only one doping in the TdF this year?

this is the 'Froome talk only' thread. Did you not understand that?

There is a Wiggins thread about his magical transformation from Grupetto to Podium

There is the Sky thread for all things sky.

There is now a Geraint thread to discuss his recent transformation.

etc

etc

Sky so giving to the clinic......

Not only do I understand it, I started my post with it.

 

[samhocking]

Why would Kerrison add the 6% adjustment caveat to skew the data in his favour when he is the one that can manipulate the data easily anyway. I mean, i'm pretty sure the Sky accountant can show him how to do it in MS Excel or even Google Search?

 

[70kmph]

Natty brah man, cleans with bread and water...

 

[Netserk]

Re:

Why would Kerrison add the 6% adjustment caveat to skew the data in his favour when he is the one that can manipulate the data easily anyway. I mean, i'm pretty sure the Sky accountant can show him how to do it in MS Excel or even Google Search?

Have you heard about the 'hacks'? What do you think will happen if people find out that it is manipulated numbers that Sky release?

 

[Benotti69]

Re: Re:

In this thread, is the assumption that Froome (Sky) is the only one doping in the TdF this year?

this is the 'Froome talk only' thread. Did you not understand that?

There is a Wiggins thread about his magical transformation from Grupetto to Podium

There is the Sky thread for all things sky.

There is now a Geraint thread to discuss his recent transformation.

etc

etc

Sky so giving to the clinic......

Not only do I understand it, I started my post with it.

Should posters ignore the top 'dawg' at the TdF and dicuss what we already know about Contadors doping, Piti or even BMC....they have their own threads. Feel free to engage in debate int he respective threads.

Big difference between Froome and other riders in top 5 or even 10 is no one, i repeat no one, thought he would get near the podium of a GT let alone win 1.