Power Meter Deal Thread

Questions about purchasing bicycles and parts

Re: Power Meter Deal Thread

Postby J Quinton » Wed Aug 21, 2013 1:06 pm

Ugh, I really wish they would all (i.e. not just Brim) stop misusing the word "efficiency".

No on-bike power meter can measure efficiency, since no power meter can measure an individual's metabolic rate.


No, but there must be some way of incorporating your metabolic rate once you know it, yeah?


As per this website:
http://www.bmi-calculator.net
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by BNA » Wed Aug 21, 2013 5:36 pm

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Re: Power Meter Deal Thread

Postby Alex Simmons/RST » Wed Aug 21, 2013 5:36 pm

J Quinton wrote:
Ugh, I really wish they would all (i.e. not just Brim) stop misusing the word "efficiency".

No on-bike power meter can measure efficiency, since no power meter can measure an individual's metabolic rate.


No, but there must be some way of incorporating your metabolic rate once you know it, yeah?


As per this website:
http://www.bmi-calculator.net

That website calculator is only providing an estimate of your body's daily energy demand required to keep you alive (basal metabolic rate). That does not work out how much extra energy you expend to perform activities, and the point being, that one's efficiency determines how much metabolic energy production is required for each joule of mechanical work done.

The only way to know your metabolic rate (i.e. how much energy you are expending) is via gas exhange analysis (you have to measure O2 utilisation and expired CO2). That's only practical in a laboratory. Even then it's not perfect since we can really only assume contribution from aerobic energy production pathways for such calculations which is why typically such tests are perfomed at aerobic power levels only.

When on a bike, you are roughly 20-24% efficient, meaning that only about one in every four to five joules you metabolise actually gets to the cranks to propel the bike forward, the rest is given off mostly as waste heat. But we are all different, you might be 24% efficient and I might be only 19% efficient (that's a pretty normal range for trained cyclists).

IOW if we both pedalled at 200W for an hour, we'd do the same amount of mechanical work: 200W x 3600 seconds = 720kJ, however the amount of energy we each metabolise during that hour would be very different.

The rider with 24% efficiency will metabolise 720/0.24 = 3,000kJ to do the 720kJ of mechanical work, but the rider with only 19% efficiency metabolises 720/0.19 = 3,790kJ, or 790kJ more, in order to do the same amount of mechanical work.

So, unless you know what your individual gross mechanical efficiency level is (which as I said before, requires laboratory testing to ascertain), then calculating how much you metabolise, even with a power meter to precisely quantify mechanical work done, is prone to sizeable error. Without a power meter, well it'd be nothing more that wild guesstimates.
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Re: Power Meter Deal Thread

Postby joomz » Sun Aug 25, 2013 4:49 am

Might have been mentioned already, but 99 bikes are giving a $150 voucher with a Garmin vector order. Makes it effectively $1350. Pretty good?
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Re: Power Meter Deal Thread

Postby J Quinton » Mon Aug 26, 2013 8:30 pm

joomz wrote:Might have been mentioned already, but 99 bikes are giving a $150 voucher with a Garmin vector order. Makes it effectively $1350. Pretty good?



It's good if you use Look pedals, I guess. These haven't been totally road tested yet. Depends on how you see $1350.

I'd say if you cannot wait and have look cleats/pedals, then yes go for it.
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Re: Power Meter Deal Thread

Postby Slvr32gtr » Wed Aug 28, 2013 10:36 am

Im going to be ordering the Power2max Rotor 3D crankset from Bikecycle in NZ next week, so will report back on how it all goes.
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Re: Power Meter Deal Thread

Postby J Quinton » Fri Aug 30, 2013 1:27 pm

Slvr32gtr wrote:Im going to be ordering the Power2max Rotor 3D crankset from Bikecycle in NZ next week, so will report back on how it all goes.



Look forward to it.

Meanwhile here's a round up by DC Rainmaker:

http://www.dcrainmaker.com/2013/08/euro ... undup.html
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Re: Power Meter Deal Thread

Postby jcjordan » Fri Aug 30, 2013 7:15 pm

Slvr32gtr wrote:Im going to be ordering the Power2max Rotor 3D crankset from Bikecycle in NZ next week, so will report back on how it all goes.

If your experience is anything like mine you will be very happy.

Some of the best customer service I have ever received

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Re: Power Meter Deal Thread

Postby Slvr32gtr » Mon Sep 02, 2013 8:33 am

jcjordan wrote:If your experience is anything like mine you will be very happy.

Some of the best customer service I have ever received


Great to hear!! I rang them a week or so ago to get some info on availability etc of the cranks and they were really helpful.

Im putting the order in on Wednesday, cant wait to get them through!
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Re: Power Meter Deal Thread

Postby Le Mong » Fri Sep 06, 2013 7:04 am

For anyone interested im selling my powertap as I kitted the new bike with a Quarq. PM for details.
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Re: Power Meter Deal Thread

Postby Slvr32gtr » Wed Sep 11, 2013 10:44 am

My power2max power meter cranks arrived today!! 4 business days from ordering so pretty happy with that!

Will be installing them tonight and trying them out tomorrow with any luck.
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Re: Power Meter Deal Thread

Postby Arlberg » Thu Sep 12, 2013 9:04 pm

I've had my Stages for just over a week now, and so far it has performed flawlessly. Very simple to install, as well as easy to move between bikes.
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Re: Power Meter Deal Thread

Postby J Quinton » Tue Sep 17, 2013 1:21 pm

Arlberg wrote:I've had my Stages for just over a week now, and so far it has performed flawlessly. Very simple to install, as well as easy to move between bikes.


I often wonder about the durability of the crank arm based power meter.

You don't want to be removing and installing a crank arm every other week, do you?

Unless you're willing to replace the nut housing once a year or so?
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Re: Power Meter Deal Thread

Postby jcjordan » Tue Sep 17, 2013 1:36 pm

J Quinton wrote:
Arlberg wrote:I've had my Stages for just over a week now, and so far it has performed flawlessly. Very simple to install, as well as easy to move between bikes.


I often wonder about the durability of the crank arm based power meter.

You don't want to be removing and installing a crank arm every other week, do you?

Unless you're willing to replace the nut housing once a year or so?

I have been moving my P2M between bike 2-3 times a week for over 18 months with no problems so far

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Re: Power Meter Deal Thread

Postby Ross » Thu Sep 19, 2013 4:36 am

Power2Max drops power meter prices nearly 20%, adds Praxis Works for chain rings

http://www.dcrainmaker.com/2013/09/powe ... raxis.html
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Re: Power Meter Deal Thread

Postby Slvr32gtr » Thu Sep 19, 2013 9:39 am

Ross wrote:Power2Max drops power meter prices nearly 20%, adds Praxis Works for chain rings

http://www.dcrainmaker.com/2013/09/powe ... raxis.html


It says at the bottom of the article that the pricing shift will only be coming to the North American market.
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Re: Power Meter Deal Thread

Postby Ross » Thu Sep 19, 2013 10:35 am

Just send to a freight forwarder
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Re: Power Meter Deal Thread

Postby Xplora » Thu Sep 19, 2013 11:34 pm

Very interesting. I was stickybeaking at the 3DF earlier this week. Ended up with a used Quarq today, ultimately won't make a big difference. Can still get the Rotor OCP3 rings onto it. This should be a good incentive to avoid Quarq now. BIG reason.
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Re: Power Meter Deal Thread

Postby doggatas » Fri Sep 20, 2013 12:25 pm

I have had a powertap in the past and broken torque tubes just outside the warranty period. Torque Tube replacement is roughly 75 % of the new price of powertap, plus you have to send the hub/wheel to get it fixed. At least you do get another year warranty, I believe this is because the hub is basically rebuilt with new components.

I now have an SRM 9000 as I couldn't justify the large repair cost of the powertap relative to the new purchase price.

I am yet to fault it and it has been ridden in some pretty horrific conditions. The SRM is paired with an Edge 510. I purchased the SRM from Alex.

A contributing factor for me in getting the SRM was that I wanted it to match the 9000 groupset, I know the crank arms are from the 7800 era but I couldn't get my head around have a SRAM crank. I see now (2nd Gen DA 9000) have the shaded arms to match the 9000 colour scheme.
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Re: Power Meter Deal Thread

Postby J Quinton » Fri Sep 20, 2013 1:50 pm

Pushy's should be delivering pre-ordered Vector's today according to their website.

http://www.pushys.com.au/catalogsearch/result/?q=vector

Anyone ordered one?
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Re: Power Meter Deal Thread

Postby Ross » Fri Sep 20, 2013 3:52 pm

J Quinton wrote:Pushy's should be delivering pre-ordered Vector's today according to their website.

http://www.pushys.com.au/catalogsearch/result/?q=vector

Anyone ordered one?


A guy I know has had a set for a week or so now, not sure where he bought them from.
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Re: Power Meter Deal Thread

Postby Xplora » Fri Sep 20, 2013 4:36 pm

I saw the Vector's in stock at Park Bikes in SOP Homebush. It's happening.
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Re: Power Meter Deal Thread

Postby Ross » Mon Sep 23, 2013 8:37 am

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Re: Power Meter Deal Thread

Postby Xplora » Mon Sep 23, 2013 12:55 pm

Squeeeeeeeeeee
Quarq arrived today. Now, if I could only get it installed to USE lol
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Re: Power Meter Deal Thread

Postby Le Mong » Mon Sep 23, 2013 5:57 pm

Quarq + Praxis + Tarmac = Win

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Now to learn how to use it, tossing up the idea of getting coached to get the most out of it if anyone has any suggestions for someone in Newcastle or Sydney.
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Re: Power Meter Deal Thread

Postby Alex Simmons/RST » Tue Sep 24, 2013 6:58 am

Le Mong wrote:Quarq + Praxis + Tarmac = Win

Now to learn how to use it, tossing up the idea of getting coached to get the most out of it if anyone has any suggestions for someone in Newcastle or Sydney.

We work with riders all over the world, including riders in Newcastle and Sydney. I'm based in Sydney personally.
Drop me a line or see links below.
[email protected]
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