Reality of a hilly course

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Reality of a hilly course

Postby akabruno » December 26th, 2013, 2:24 pm

Hello all. I present my dilemma:

I am preparing for Oceanside 70.3, followed by Escape from Alcatraz. Both of these races have some significant climbing. Oceanside in particular is creating an issue for me in choosing a wheelset. Most of the course is rolling/flat/downhill, but in roughly the middle are some butt kicker climbs. The majority of the approximately 2000' of climbing is in the middle of the course. I have raced it before on borrowed Zipp 404 tubulars and loved the light weight on the climbs, but hated having to work so hard on the flats compared to those on discs. I have decided to bite the bullet for a disc rear wheel and I fully buy off on aerodynamics trumping weight, but I'm not sure if dragging the Flo's nearly 1300 gram weight up those climbs will be justified by the aero gains on the rest of the course. In contrast, I'm looking at a used Zipp sub-9. The weight is dropped off to 980 (weighed), but it is tubular, not clincher.

I'm hoping for some real world hilly course comparitive descriptions between the Flo Disc and other, much lighter but also much more expensive discs. I get that if I was looking at flat courses, my issue would probably be moot. Bottom line, I guess is if the Flo Disc weight penalty is realistically too much, or not that big of a deal on the a course like Oceanside. And as for Alcatraz, that course is short at a little over 18 miles, but it is either climbing or descending. The flats are too few to discuss. Thoughts?

For what it is worth, I'm 190 pounds and I'm riding a 2011 Speed Concept. Whichever disc I get, I will likely run a 404 tubular front, since I have access to one.

Thanks in advance for any input.
akabruno
 
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Joined: December 22nd, 2013, 7:24 pm

Re: Reality of a hilly course

Postby Chris Thornham » December 27th, 2013, 10:31 am

This is a good question. I took the time to run a model for you. If you are interested I ran the model using Analytic Cycling's Calculator that can be found here http://www.analyticcycling.com/ForcesLessWeight_Page.html.

I'll start with my assumptions.

- Effective Frontal Area, Drag Coefficient and Air Density Values were set at 0.5, 0.5 and 1.226 respectively.
- You weigh 190lbs, and I'll assume your bike, shoes, helmet, water, gear etc weights 30lbs. Making your total weight 220lbs or 100kg.
- The Coefficient of Rolling Resistance will be 0.004 for an asphalt road.
- The majority of your climbing seems to take place over about 13 miles from mile 23 to 36. Let's assume that you climb at 2% over these 13 miles totaling 1374 feet of climbing. The total gain of the entire course is 1608 feet, so I think I'm being quite generous by assuming 1374 feet are being done in 13 miles. This equates to 20921.5 meters.
- The difference in weight between a Zipp Disc and a FLO DISC is 280 grams. This means you and a Zipp Wheel weigh 100kg and you and a FLO DISC weight 100.28kg
- Let's assume that aerodynamically the Zipp Disc and the FLO DISC are equal.
- Finally we will assume your power output is 250 watts.

If we run the model using those assumptions, here are the results.

Benefit From Less Weight
This Much Less Weight 0.28 kg
Over This Distance 20921.5 meters
On Hill of Slope 0.02 Decimal
Faster by 3.55 s
Ahead by 27.21 m
Frontal Area 0.5 m^2
Coefficient Wind Drag 0.5 Dimensionless
Air Density 1.226 kg/m^3
Weight Rider & Bike 100 kg
Rolling Coefficient 0.004 Dimensionless
Power 250 watts

So... the FLO DISC will cost you 3.55 seconds at Oceanside 70.3 BUT... what about going downhill? The heavier weight on the downhill will actually help you since it will give you additional momentum. The general rule of thumb states that you gain about 1/4 of your time back on the down hill. So 3.55/4 = 0.8875. Then adjusting for the time we gained back...

Your total time loss using a FLO DISC is as follows... 3.55s - 0.89s = 2.66 seconds.

In all honesty, the weight difference between the discs makes a very very small difference.

I hope this helps,
Chris Thornham
FLO Cycling: http://www.flocycling.com
FLO Blog: http://bit.ly/b3Zlpq | Twitter: http://bit.ly/bOQ08x | Facebook: http://bit.ly/d8KDhI
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Re: Reality of a hilly course

Postby akabruno » December 27th, 2013, 11:38 am

Thanks you. That does help immensely. I'm no Engineer, but I (and I think many other Triathletes) am a nut for some data to help me understand all the subtleties of racing. I posted my question with the hope of real world commentary from people who had ridden your disc wheel, and some other lighter but pricier disc wheel on the same race course. I hoped for some insight to how it "felt" to ride the heavier wheel. I'm interested in the perceived difference in effort - if any - that was needed to deal with the climbs. I never expected to hear from Flo with such specific information. That was a cool surprise.

Thanks again for the data. I think your assumptions were fair in assessing the data that was part of the calculation. However, in my experience, weight on a climb translates into a "feeling", that itself translates into the perception of more effort. Ultimately that translates into how well I can run, which is ultimately where my thoughts are going.

Your answer gives me the sense that the weight won't be an issue - on paper. Now, I'd love to hear from someone who can give perception and actual performance data to coincide with the calculation.

Thanks again. This is good stuff for everybody.
akabruno
 
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Joined: December 22nd, 2013, 7:24 pm

Re: Reality of a hilly course

Postby Chris Thornham » December 27th, 2013, 6:30 pm

You can definitely feel weight on a climb but we are talking about 280 grams here which is very very small. A lot of people look at a number like 280 and think that must be a lot of weight because 280 is a big number. But you have to remember the unit you are using. 280 grams is about half of a pound. I don't know about you, but there is no way that I could "feel" 2.66 seconds over 13 miles of climbing. If you are going to feel weight on a climb, I'm guessing you would need much more weight than 280 grams.
Chris Thornham
FLO Cycling: http://www.flocycling.com
FLO Blog: http://bit.ly/b3Zlpq | Twitter: http://bit.ly/bOQ08x | Facebook: http://bit.ly/d8KDhI
Chris Thornham
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Re: Reality of a hilly course

Postby steepcreeker » January 29th, 2014, 9:01 pm

Plus you need to factor in flatting a tire if it happens. A tube is much lighter than a tubular and trying to change a tubular in the field during a race? Yeah disaster. Pros use tubular cause they're a little less likely to flat and they "feel" better. Plus they actully need to shave a few second. (Also they get those 4k wheelsets for free).For age groupers they're just a pain in the ass and expensive. Also those carbon zips are fragile and you'll need to change brake pads if you switch between hoops and your race wheels. You can train more with the Flo and not worry about breaking it. Never mind the cost. Weight in wheels is a red Herring. Especially if your a bigger rider. What's important is the right stiffness side to side and ride flex. I demoed "light" wheels with low spoke counts and they drove me nuts rubbing the brakes on corners and when I'd lean into them. Just get flo's and save cash for those new power pedals from Garmin .
steepcreeker
 
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Re: Reality of a hilly course

Postby Chris Thornham » January 30th, 2014, 9:51 am

akabruno wrote:Hello all. I present my dilemma:

I am preparing for Oceanside 70.3, followed by Escape from Alcatraz. Both of these races have some significant climbing. Oceanside in particular is creating an issue for me in choosing a wheelset. Most of the course is rolling/flat/downhill, but in roughly the middle are some butt kicker climbs. The majority of the approximately 2000' of climbing is in the middle of the course. I have raced it before on borrowed Zipp 404 tubulars and loved the light weight on the climbs, but hated having to work so hard on the flats compared to those on discs. I have decided to bite the bullet for a disc rear wheel and I fully buy off on aerodynamics trumping weight, but I'm not sure if dragging the Flo's nearly 1300 gram weight up those climbs will be justified by the aero gains on the rest of the course. In contrast, I'm looking at a used Zipp sub-9. The weight is dropped off to 980 (weighed), but it is tubular, not clincher.

I'm hoping for some real world hilly course comparitive descriptions between the Flo Disc and other, much lighter but also much more expensive discs. I get that if I was looking at flat courses, my issue would probably be moot. Bottom line, I guess is if the Flo Disc weight penalty is realistically too much, or not that big of a deal on the a course like Oceanside. And as for Alcatraz, that course is short at a little over 18 miles, but it is either climbing or descending. The flats are too few to discuss. Thoughts?

For what it is worth, I'm 190 pounds and I'm riding a 2011 Speed Concept. Whichever disc I get, I will likely run a 404 tubular front, since I have access to one.

Thanks in advance for any input.


Your question inspired me to write the following blog article. You might find it interesting.

http://flocycling.blogspot.com/2014/01/flo-cycling-great-debate-aero-vs-weight.html

Take care,
Chris Thornham
FLO Cycling: http://www.flocycling.com
FLO Blog: http://bit.ly/b3Zlpq | Twitter: http://bit.ly/bOQ08x | Facebook: http://bit.ly/d8KDhI
Chris Thornham
Site Admin
 
Posts: 581
Joined: March 2nd, 2012, 3:35 pm
Location: Las Vegas, Nevada


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