Tri Talk HomepageTri Talk EventsTri Talk ForumsBlogsTri Talk TrainingTri TradeTriPlayerWikiTeam Tri Talk
Speed vs Power
Goto page Previous  1, 2
 
Post new topic   Reply to topic    TriTalk.co.uk Forum Index -> Gear
View previous topic :: View next topic  
Author Message
JaRok2300




Joined: 01 May 2014
Posts: 388
Location: Worcester, UK

PostPosted: Mon Sep 03, 2018 9:37 am    Post subject: Reply with quote

I downloaded the tcx file from Garmin connect desktop site to my laptop then uploaded to BBS from there.
Back to top
View user's profile Send private message
jibberjim




Joined: 15 Aug 2008
Posts: 8332
Location: Kingston

PostPosted: Tue Sep 04, 2018 9:24 am    Post subject: Reply with quote

Have you actually validated the power from your power meter - as a 0.18 CdA is way too low without a lot of "traffic" to help you, which I guess their could have been.
_________________
Jibbering Sports Stuff
Back to top
View user's profile Send private message Send e-mail Visit poster's website
stenard




Joined: 04 Sep 2013
Posts: 1821

PostPosted: Tue Sep 04, 2018 10:22 am    Post subject: Reply with quote

jibberjim wrote:
Have you actually validated the power from your power meter - as a 0.18 CdA is way too low without a lot of "traffic" to help you, which I guess their could have been.


I kind of said the same thing, but then his initial post of "20.4mph from 217W" seems to imply a really high cda, given I was able to obtain 36.4km/h off 213W.

Hence my assumption another metric input into BBS is wrong, as the only way it can logically assume such a low cda is if something else would imply going way faster (relatively). It would appear not to be power, from the above, so then you get into CRR, drivechain efficiency, weight, or some kind of weather data anomaly in the system on that particular day.
_________________
My blog: https://stenardstuff.wordpress.com/
Random stuff and race reports
Back to top
View user's profile Send private message
Doca




Joined: 27 Feb 2014
Posts: 222

PostPosted: Tue Sep 04, 2018 10:54 am    Post subject: Reply with quote

I don't think the relays course yielded a good power to speed ratio. The surface is not the best, it was windy and you had to slow down a lot for one of the turns (wet & sharp).
Back to top
View user's profile Send private message
stenard




Joined: 04 Sep 2013
Posts: 1821

PostPosted: Tue Sep 04, 2018 11:27 am    Post subject: Reply with quote

That could be a factor, but the Southport data I included on the first page (36.0km/h for 193W) had four dead turns, that were stupidly tight and meant you almost had to come to a complete stop. Not sure if the relays had more, but it shows that a small number of very sharp turns doesn't impact the BBS analysis that much.

Dampness could hamper I suppose. The algorithms might presume you can carry more speed around a corner than is possible in the wet. But my understanding of the aero analyser is that it should be able to infer that zero power was being produced at the point of breaking, and recognise that a subsequent period was acceleration out of a turn.
_________________
My blog: https://stenardstuff.wordpress.com/
Random stuff and race reports
Back to top
View user's profile Send private message
JaRok2300




Joined: 01 May 2014
Posts: 388
Location: Worcester, UK

PostPosted: Tue Sep 04, 2018 1:14 pm    Post subject: Reply with quote

jibberjim wrote:
Have you actually validated the power from your power meter - as a 0.18 CdA is way too low without a lot of "traffic" to help you, which I guess their could have been.


I'm fairly confident of the power data. I ran the P2M in tandem with a Powertap wheel not long ago and they tracked pretty well. It's also felt about right compared to similar efforts in training. Given how far out I think that Cda figure is I don't think I was cruising round at 100W and couldn't do 300W for 30mins if my life depended on it.

The course was dry in the afternoon, other than a couple of small patches near transition but they were so small I don't think they impacted cornering speed. I don't profess to be the last of the late brakers but having ridden motorbikes and push bikes most of my life I don't think I give much away through corners. The only time I ever get anywhere near a KOM are technical descents!

I'll try running it again to see if anything changes. Ultimately this is all just curiosity as I'm not in any kind of position where this will impact my results as I'm very much BoP.
Back to top
View user's profile Send private message
JaRok2300




Joined: 01 May 2014
Posts: 388
Location: Worcester, UK

PostPosted: Wed Sep 05, 2018 7:28 am    Post subject: Reply with quote

I re-ran it in BBS last night
This time I use the tif file rather than tcx from Garmin and for terrain I selected "Mixed/Populated" compared to "Ground Level" the first time.

O yaw came out at 0.245 which looks more realistic, although probably a bit lower than I really am. On such a narrow track there is a fair bit of "drafting" when passing (honest, I did pass one or two, even at that speed!) or being passed but I never sat behind anyone at the same speed.
Back to top
View user's profile Send private message
tuckandgo




Joined: 03 Sep 2012
Posts: 421

PostPosted: Fri Sep 07, 2018 7:33 am    Post subject: Reply with quote

This weight issue on a flat course is a red herring.

The fastest guy I know on a bike on the flat (and he is VERY fast) is about 80kg.

(up hills they are slightly skinnier.)

As to the actual OP question I find it varies so much between course, road surface and 'pack density' (there is no doubt you get a drag in a race even if not technically 'drafting') as to be almost meaningless.
Back to top
View user's profile Send private message
Jorgan




Joined: 12 Nov 2007
Posts: 17607
Location: alles was ich bin, alles was ich war

PostPosted: Fri Sep 07, 2018 9:57 am    Post subject: Reply with quote

tuckandgo wrote:
This weight issue on a flat course is a red herring.


In this particular instance yes; but for Triathlon as a whole it is highly pertinent. Your CdA or NP don't mean squat if your swim & run are compromised...but that's a whole other discussion Smile
_________________
26 Years since it all began....
Back to top
View user's profile Send private message
Buzz_




Joined: 19 May 2007
Posts: 384

PostPosted: Fri Sep 07, 2018 10:15 am    Post subject: Reply with quote

Jorgan wrote:
tuckandgo wrote:
This weight issue on a flat course is a red herring.
In this particular instance yes; but for Triathlon as a whole it is highly pertinent. Your CdA or NP don't mean squat if your swim & run are compromised...but that's a whole other discussion Smile

Given some of the body shapes getting out of the water ahead of me I'm not sure weight is a huge determining factor in the swim. And this conversation seems to be suggesting that body weight is impacting CdA and therefore cycling speed. Maybe not weight specifically, but broad shoulders creating a large frontal area. Not sure how much weight loss could improve this though?
Back to top
View user's profile Send private message
Jorgan




Joined: 12 Nov 2007
Posts: 17607
Location: alles was ich bin, alles was ich war

PostPosted: Fri Sep 07, 2018 11:58 am    Post subject: Reply with quote

Buzz_ wrote:

Given some of the body shapes getting out of the water ahead of me I'm not sure weight is a huge determining factor in the swim.


Are we talking about a 60 min or 90+ min swim here? The only 'big' people who've gotten out onto the bike before me are generally ladies who are very good swimmers, but have more body fat (buoyancy) rather than muscle; they generally aren't 15+ stone either.
_________________
26 Years since it all began....
Back to top
View user's profile Send private message
Buzz_




Joined: 19 May 2007
Posts: 384

PostPosted: Fri Sep 07, 2018 12:14 pm    Post subject: Reply with quote

Jorgan wrote:
Are we talking about a 60 min or 90+ min swim here? The only 'big' people who've gotten out onto the bike before me are generally ladies who are very good swimmers, but have more body fat (buoyancy) rather than muscle; they generally aren't 15+ stone either.

I'm talking 12min and 26min because I don't do the silly distances that you do at the speed that you do them. Yes, at the pointy end most look fit and lean, and as the distance increases I can imagine that is even more the case, but mid-pack size and shape are incredibly diverse.
Back to top
View user's profile Send private message
Jorgan




Joined: 12 Nov 2007
Posts: 17607
Location: alles was ich bin, alles was ich war

PostPosted: Fri Sep 07, 2018 12:45 pm    Post subject: Reply with quote

Buzz_ wrote:
Jorgan wrote:
Are we talking about a 60 min or 90+ min swim here? The only 'big' people who've gotten out onto the bike before me are generally ladies who are very good swimmers, but have more body fat (buoyancy) rather than muscle; they generally aren't 15+ stone either.

I'm talking 12min and 26min because I don't do the silly distances that you do at the speed that you do them. Yes, at the pointy end most look fit and lean, and as the distance increases I can imagine that is even more the case, but mid-pack size and shape are incredibly diverse.


But doesn't that prove the point, about weight impacting performance. The only 'unit' I can remember doing really well as a Pro was Torbjorn Sindballe, for example.
_________________
26 Years since it all began....
Back to top
View user's profile Send private message
hammerer
Site Admin



Joined: 19 Nov 2007
Posts: 16574
Location: Right Next Door To Hell

PostPosted: Fri Sep 07, 2018 1:48 pm    Post subject: Reply with quote

Jorgan wrote:
Buzz_ wrote:
Jorgan wrote:
Are we talking about a 60 min or 90+ min swim here? The only 'big' people who've gotten out onto the bike before me are generally ladies who are very good swimmers, but have more body fat (buoyancy) rather than muscle; they generally aren't 15+ stone either.

I'm talking 12min and 26min because I don't do the silly distances that you do at the speed that you do them. Yes, at the pointy end most look fit and lean, and as the distance increases I can imagine that is even more the case, but mid-pack size and shape are incredibly diverse.


But doesn't that prove the point, about weight impacting performance. The only 'unit' I can remember doing really well as a Pro was Torbjorn Sindballe, for example.


and Ain-Alar Juhanson although that depends on your definition of really well
_________________
Blog
Back to top
View user's profile Send private message
chickenboy




Joined: 06 Jul 2005
Posts: 1653

PostPosted: Fri Sep 07, 2018 4:21 pm    Post subject: Reply with quote

Hey Jase,

take what you like from my stats, BUT
Bike course conditions for IM copenhagen last year and this year were pretty similar.

i raced 2017 on my trusty old cannondale slice with aero lid, no disc, but 808 firecrest wheelset: Avg power 220: 21.4mph, 82kg's

2018: new cervelo p3, super 9 disc, same aero lid, lower stack, 808 front
avg power 217: 22.3mph, 82kg's
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    TriTalk.co.uk Forum Index -> Gear All times are GMT
Goto page Previous  1, 2
Page 2 of 2
  Share
 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum





Home | About TT | Privacy Policy | Terms and Conditions | Advertising | Contact TT
Copyright ©2003-2015 TriTalk®.co.uk. All rights reserved.