Largest Misconception in cycling- wheel weight matters!
12-28-14, 01:57 PM
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12-28-14, 02:02 PM
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Let me see if I can simplify the problem we are discussing. We can assume the energy (Watts) it takes to ride a bike is made up of just rolling resistance and wind resistance with all else being equal between when riding a bike with two sets of wheels, one heaver aero and one lighter non-aero.
The problem is determining how much rim weight (rolling resistance) vs. wind drag (wind resistance) is causing the rider to expend the most number of watts.
Those that think a lighter wheel is better for climbing and accelerating believe the wind resistance on a spinning wheel moving forward is minimal compared to the weight of the rim when rolling resistance in increased either by accelerating or by the going uphill (increasing the slope).
Those that believe aero rims are better believe the wind resistance at these slower speeds still cause more drag on non-aero wheels then the added weight of the aero rim in the same conditions.
For a heavier aero wheel to feel easier to accelerate on than a lighter wheel, it has to provide an aero advantage greater then the increased drag in rolling resistance caused by the additional weight of the wheels.
I know if you ride into a 10 MPH wind and with a 10 MPH wind it makes a huge difference. We all know that. but how much of that difference is caused by just the wheels. Experts have estimated wheels are approximately 15-20% of overall drag of a person riding a bike due to the rotational speed of the wheels and drag on the fastest moving part on the bike. So if you reduce the drag by 3 percent and up the weight of the wheels by an amount of weight that does not increasing rolling resistance by 3% the heaver wheel will feel lighter when accelerating. The heavier wheel will actually feel lighter, faster and takes fewer watts to ride. This is the reason people have claimed an aero wheel will spin up faster then a non-aero wheel. It goes against common sense since and most always argue for the lighter wheel. The articles I posted try to measure and qualify the difference using different tests.
The problem is determining how much rim weight (rolling resistance) vs. wind drag (wind resistance) is causing the rider to expend the most number of watts.
Those that think a lighter wheel is better for climbing and accelerating believe the wind resistance on a spinning wheel moving forward is minimal compared to the weight of the rim when rolling resistance in increased either by accelerating or by the going uphill (increasing the slope).
Those that believe aero rims are better believe the wind resistance at these slower speeds still cause more drag on non-aero wheels then the added weight of the aero rim in the same conditions.
For a heavier aero wheel to feel easier to accelerate on than a lighter wheel, it has to provide an aero advantage greater then the increased drag in rolling resistance caused by the additional weight of the wheels.
I know if you ride into a 10 MPH wind and with a 10 MPH wind it makes a huge difference. We all know that. but how much of that difference is caused by just the wheels. Experts have estimated wheels are approximately 15-20% of overall drag of a person riding a bike due to the rotational speed of the wheels and drag on the fastest moving part on the bike. So if you reduce the drag by 3 percent and up the weight of the wheels by an amount of weight that does not increasing rolling resistance by 3% the heaver wheel will feel lighter when accelerating. The heavier wheel will actually feel lighter, faster and takes fewer watts to ride. This is the reason people have claimed an aero wheel will spin up faster then a non-aero wheel. It goes against common sense since and most always argue for the lighter wheel. The articles I posted try to measure and qualify the difference using different tests.
12-28-14, 02:06 PM
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Hey everybody,
Here's a few things to consider in this discussion: Gravity and the resulting acceleration therefrom is the thing that takes our energy when we're pedaling like mad or just cruising. Conservation of energy pretty much says that a body at rest tends to stay at rest and a body in motion tends to stay in motion. It requires energy to change those states and, obviously, the more mass an object has the more energy is required to change that state. These Newtonian physical laws are inescapable unless we're very, very far away from the planet or dead, which of course cancels out the enjoyment of a bicycle ride of any kind.
So, once you accelerate to whatever speed you want to ride, you want to stay at that speed at all costs, especially if you're riding an individual time trial or Tri. There's where all the aero comes in real handy and the extra weight can actually help you. When you're full tilt boogie against the clock, aero saves you precious grams of energy reserves for the final kick. You're trying to stay at as fast a constant speed as you can. It's just the rider, the bike and the wind...and what you had for breakfast. The extra mass of the aero wheels helps a bit to keep you at your chosen speed and the aero helps a lot to cut that wind resistance. Just hope you don't that strong cross-wind that could potentially take you off the bike. Ever watch the TDF individual or team time trial? Aerodynamic poetry in motion for sure!! It's all about aero, conservation of energy and 100ths of seconds!
Head out on the road in the peloton or by yourself and you have a whole different ride. Same physics apply, but the needs in applying those physics are very different. As pointed out by others, one needs to be able to accelerate quickly and, sometimes often, especially for that final sprint to the line. Less mass is better for the same conservation of energy reasons. You use less energy accelerating less mass. Then when the road turns up, gravity really takes over. The steeper the climb, the harder you have to work because gravity is trying to make you fall back down the hill. I don't need the vector math to explain that or what you know will happen when you go over the top and start to descend. Cross winds are your enemy and your enemy takes you out with cross sectional area. Cross winds can be almost as bad going up, although not as deadly. If you're going up a mountain and you climb say 1200 m in less than 10 km, wouldn't you want to be as light as possible to maximize your energy use? Add to that the fact that you will be repeating that "little" climb 3 or 5 more times before the end of the ride and you have everyone in the group wanting to be first over the top.
Competitive cyclists want to maximize everything for the race. Do you see TDF, Vuelta, Giro riders riding aero anywhere but the time trials? No, because you need stability, agility, comfort, response and strength for all other race conditions. Imagine being in a tight group at 30mph+ and you're feeling it with your aero wheels. Suddenly gusty cross winds come up, you get pushed to your left or right and take out whatever part of the group is right behind you. How about the cobbles or other really rough road? You won't get far on those incredibly stiff wheels. They'll break or you'll break and your done.
As others have said, drafting is the way to conserve energy in the group. Aero is the way to go if you're racing the clock. Otherwise, it's all about the coolness factor and how much money you spent or saved.
Anyway, it's sunny and mild in L.A., so I think I'll go ride!!!
Cheers!
Here's a few things to consider in this discussion: Gravity and the resulting acceleration therefrom is the thing that takes our energy when we're pedaling like mad or just cruising. Conservation of energy pretty much says that a body at rest tends to stay at rest and a body in motion tends to stay in motion. It requires energy to change those states and, obviously, the more mass an object has the more energy is required to change that state. These Newtonian physical laws are inescapable unless we're very, very far away from the planet or dead, which of course cancels out the enjoyment of a bicycle ride of any kind.
So, once you accelerate to whatever speed you want to ride, you want to stay at that speed at all costs, especially if you're riding an individual time trial or Tri. There's where all the aero comes in real handy and the extra weight can actually help you. When you're full tilt boogie against the clock, aero saves you precious grams of energy reserves for the final kick. You're trying to stay at as fast a constant speed as you can. It's just the rider, the bike and the wind...and what you had for breakfast. The extra mass of the aero wheels helps a bit to keep you at your chosen speed and the aero helps a lot to cut that wind resistance. Just hope you don't that strong cross-wind that could potentially take you off the bike. Ever watch the TDF individual or team time trial? Aerodynamic poetry in motion for sure!! It's all about aero, conservation of energy and 100ths of seconds!
Head out on the road in the peloton or by yourself and you have a whole different ride. Same physics apply, but the needs in applying those physics are very different. As pointed out by others, one needs to be able to accelerate quickly and, sometimes often, especially for that final sprint to the line. Less mass is better for the same conservation of energy reasons. You use less energy accelerating less mass. Then when the road turns up, gravity really takes over. The steeper the climb, the harder you have to work because gravity is trying to make you fall back down the hill. I don't need the vector math to explain that or what you know will happen when you go over the top and start to descend. Cross winds are your enemy and your enemy takes you out with cross sectional area. Cross winds can be almost as bad going up, although not as deadly. If you're going up a mountain and you climb say 1200 m in less than 10 km, wouldn't you want to be as light as possible to maximize your energy use? Add to that the fact that you will be repeating that "little" climb 3 or 5 more times before the end of the ride and you have everyone in the group wanting to be first over the top.
Competitive cyclists want to maximize everything for the race. Do you see TDF, Vuelta, Giro riders riding aero anywhere but the time trials? No, because you need stability, agility, comfort, response and strength for all other race conditions. Imagine being in a tight group at 30mph+ and you're feeling it with your aero wheels. Suddenly gusty cross winds come up, you get pushed to your left or right and take out whatever part of the group is right behind you. How about the cobbles or other really rough road? You won't get far on those incredibly stiff wheels. They'll break or you'll break and your done.
As others have said, drafting is the way to conserve energy in the group. Aero is the way to go if you're racing the clock. Otherwise, it's all about the coolness factor and how much money you spent or saved.
Anyway, it's sunny and mild in L.A., so I think I'll go ride!!!
Cheers!
12-28-14, 02:08 PM
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I don't understand why in this thread there is an assumed side of weight verses Aero in wheels. I feel strongly that you don't need to have one at the cost of the other. My current wheels are carbon Clinchers 23wide X 50 deep U-shaped rims that weighed 1530G. They are extremely aero and it is very noticeable how well I roll at high speeds (>25MPH). But yet the spin up very fast with being 1530G wheel set. While not the Lightest wheels made, or the most aero they feel great both ways. Some wont like it that they are farsports, but I have about 4500 miles on them and they are great wheels with no problems.
You can Have your cake and eat it too with great light aero wheels.
You can Have your cake and eat it too with great light aero wheels.
12-28-14, 02:10 PM
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Try running with a 1lb parachute tied to your back... Then run with a 10lbs backpack. It is much easier to accelerate with the weight then the parachute.
12-28-14, 02:30 PM
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It's all still physics. There's drag coefficients, frictional forces of the rubber on the road, gravity, friction in bearings, power loss in crank/ frame flex, etc. You want to know what works best? You experiment for yourself, as most of us do, or we can suck up all the tech that the professional bicycle community invests serious money investigating and experimenting with. If aero wheels were better for anything but TT riding, don't you think the pros would using them to win the millions in prize money and sponsorship dollars if they provided better performance?
12-28-14, 02:35 PM
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+1
I should add that frequent accelerations are a huge factor when drafting.
I totally agree that aero wheels are overall faster than non-aero when riding solo - the numbers I've seen for my own rides over the last 4 years seem to support that. I generally ride on a flatter route so ideal for aero wheels.
However in a situation where drafting is present and the rider knows how to take advantage of it (group ride, race), the drafting aspect is significantly more important than wheel aerodynamics. It's most important to have the draft, a distant second or third or whatever to have aero wheels. In these situations having equipment that enables a rider to draft more effectively is key. This might include a shorter front end (motorpace bicycles use small wheels and backward/negative-rake forks to bring the rider closer to the moto), rider position (Specialized found a significant decrease in drag while drafting in the drops compared to the hoods, for the n=1 sample they did), distance to rider in front (closer is better although the benefits are measurable even when relatively far away), number of riders in front of you (more riders = more draft, ideally with at least one rider drafting behind you), and even self drafting (on shorter tracks a rider doing laps will set up his own wind current and end up "drafting himself").
I should add that frequent accelerations are a huge factor when drafting.
I totally agree that aero wheels are overall faster than non-aero when riding solo - the numbers I've seen for my own rides over the last 4 years seem to support that. I generally ride on a flatter route so ideal for aero wheels.
However in a situation where drafting is present and the rider knows how to take advantage of it (group ride, race), the drafting aspect is significantly more important than wheel aerodynamics. It's most important to have the draft, a distant second or third or whatever to have aero wheels. In these situations having equipment that enables a rider to draft more effectively is key. This might include a shorter front end (motorpace bicycles use small wheels and backward/negative-rake forks to bring the rider closer to the moto), rider position (Specialized found a significant decrease in drag while drafting in the drops compared to the hoods, for the n=1 sample they did), distance to rider in front (closer is better although the benefits are measurable even when relatively far away), number of riders in front of you (more riders = more draft, ideally with at least one rider drafting behind you), and even self drafting (on shorter tracks a rider doing laps will set up his own wind current and end up "drafting himself").
A 500g ideal hoop rolling at 50 km/hr (13.8888 m/sec, 31+ mph) has 96.45 Joules of energy. At 52 km/hr (14.44444 m/sec), it has 104.32 Joules of energy.
To accelerate 500g of real-world rotating wheel weight from 50 to 52 km/hr in one second thus takes under 9W.
I'd say you get a bigger benefit from aero wheels, even when drafting. If you gain 10W from aero wheels, that more than offsets the power needed to accelerate 500g of added wheel weight from 50 to 52 km/hr in one second.
To accelerate that same wheel weight from 30 to 32 km/hr in one second takes under 4W.
12-28-14, 02:39 PM
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It's all still physics. There's drag coefficients, frictional forces of the rubber on the road, gravity, friction in bearings, power loss in crank/ frame flex, etc. You want to know what works best? You experiment for yourself, as most of us do, or we can suck up all the tech that the professional bicycle community invests serious money investigating and experimenting with. If aero wheels were better for anything but TT riding, don't you think the pros would using them to win the millions in prize money and sponsorship dollars if they provided better performance?
12-28-14, 02:40 PM
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Actually they do. Many run Zipp 202 and 303 wheels which are still Aero style wheels on the highest of climbs during the Tour de France.
https://cache.boston.com/multimedia/s...2010b/bs27.jpg
https://cache.boston.com/multimedia/s...2010b/bs27.jpg
12-28-14, 02:41 PM
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Competitive cyclists want to maximize everything for the race. Do you see TDF, Vuelta, Giro riders riding aero anywhere but the time trials? No, because you need stability, agility, comfort, response and strength for all other race conditions. Imagine being in a tight group at 30mph+ and you're feeling it with your aero wheels. Suddenly gusty cross winds come up, you get pushed to your left or right and take out whatever part of the group is right behind you. How about the cobbles or other really rough road? You won't get far on those incredibly stiff wheels. They'll break or you'll break and your done.
12-28-14, 02:43 PM
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Looks like lots of Aero wheels with the pros on these climbs. https://www.caltriplecrown.com/images/ToC07Balcolm.jpg
12-28-14, 02:44 PM
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Yes, other than hilltop finishes, the competitive riders are doing everything they can to be as aero as possible. Have a look at what Cavendish rides on a flat stage: aero helmet, deep profile wheels, skinsuit, aero bike. There are no compromises, everything is optimized for aero as the bike weight is essentially fixed at the minimum. Cancellara also rides deep profile wheels at Paris Roubaix: ...
Whoda thunk?
12-28-14, 02:47 PM
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Reducing rotating weight at the expense of wind resistance... That is the key. Which has more value. Just the weight alone is not enough to make the decision.
12-28-14, 02:51 PM
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Looks like lots of Aero wheels with the pros on these climbs. https://www.caltriplecrown.com/images/ToC07Balcolm.jpg
12-28-14, 02:53 PM
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12-28-14, 02:57 PM
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Because 10W of aero saves you MORE power ALL THE TIME than it costs to accelerate 500g of extra rotating wheel weight - you don't even need to get to consider the fact that the energy used to accelerate the wheel is conserved as kinetic energy that will help you maintain speed when you're coasting...
And out in the real world, the weight difference is nowhere near 500g for more aero wheels.
12-28-14, 02:57 PM
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Total weight of bike and body is what affects speed going up climbs. Sure you may have some benefit of aero going up a climb if you have a crossing tailwind butt keep in mind that the power output required to climb is directly related to pitch of the climb and the amount of weight being pulled up the climb - lighter weight equals less power required unless your name is Jensie....
12-28-14, 03:01 PM
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And who here thinks pros never ride underweight bikes per UCI rules anyway.
So they do in fact have to pay the weight penalty for the more aero wheels that they chose to ride - many of them chose such wheels even in hilly races.
So they do in fact have to pay the weight penalty for the more aero wheels that they chose to ride - many of them chose such wheels even in hilly races.
12-28-14, 03:15 PM
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Actually, 30-50mm wheels are standard peloton issue, even for climbing stages and sprinters. The top climbers are fast enough to warrant aero wheels, and due to the 6.8kg limit, there's no weight penalty, only inertia.
Sprinters again see exaggerated aero benefits because of the high top speed.
None of this applies to recreational cyclists, especially climbers who are too slow to really see aero benefits.
Sprinters again see exaggerated aero benefits because of the high top speed.
None of this applies to recreational cyclists, especially climbers who are too slow to really see aero benefits.
12-28-14, 03:25 PM
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10W of aero power savings trumps 500g of rotating weight savings - easily.
Because 10W of aero saves you MORE power ALL THE TIME than it costs to accelerate 500g of extra rotating wheel weight - you don't even need to get to consider the fact that the energy used to accelerate the wheel is conserved as kinetic energy that will help you maintain speed when you're coasting...
And out in the real world, the weight difference is nowhere near 500g for more aero wheels.
Because 10W of aero saves you MORE power ALL THE TIME than it costs to accelerate 500g of extra rotating wheel weight - you don't even need to get to consider the fact that the energy used to accelerate the wheel is conserved as kinetic energy that will help you maintain speed when you're coasting...
And out in the real world, the weight difference is nowhere near 500g for more aero wheels.
12-28-14, 04:03 PM
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12-28-14, 04:55 PM
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Sounds about right for the limits of bike acceleration - and a 30 to 55 kph acceleration is HUGE. It doesn't happen that often, even in a race. (Unless you're at the back of the cat 5 pack in a technical crit with about 10 90-degree turns per lap. And even then it still doesn't happen often because you soon get dropped and the accelerations stop. Ask me how I know...)
And it's still just 9W, or less than the power a good aero wheel will save you continuously.
