Road vs. Hybrid Studies and/or Raw Comparison Data?



jpwkeeper

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Jul 25, 2004
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DISCLAIMER: I know all the usual arguments of Road vs. Hybrid as to why Road bikes are faster. I'm not asking that here.

Do any of you know of any articles that talk about why Road bikes are faster than Hybrid bikes that include actual test data OR do any of you have any test data yourself? I'll take Mountain or City in place of Hybrid.

Here are the types of things I'm looking for:

1. Graphics/photos that show the riding position difference between a Hybrid and a Road bike with hands on the hoods or top bars.
2. Wind tunnel testing comparing the two.
3. Power Meter Data comparing the two in testing scenarios (so comparing speed to the power necessary to generate it).

For home grown data, does anyone have a test where they used identical measurements for a particular route over time where they used a repeatable measurement (such as Strava) that shows the same person in the same circumstances? Understanding that things change from day to day, it would need to be multiple data points on each bike on the same courses. Power meter data would be best, but obviously very few people are going to have power meters on their hybrids or city bikes.

Barring that, if you have multiple data points that can be viewed side-by-side between the two bikes as measured by the bike computer, that would be OK.

Also, if you have a well fitted road bike and hibrid, side pictures showing you on that one in each of the 3 positions (bar, hoods, drops) along with one on your hybrid in riding position would be useful as well.

I know that Velonews had a very interesting article on rolling resistance; I'm heading there later to check it out.

FYI, I'm only looking for comparisons. I don't want to start a debate or conjecture as to why, I'm only looking for the facts.

The reason I ask is that there are probably at least a few hundred discussions about why Road Bikes are faster, but almost nobody has ever tested it and put a Road and Hybrid head to head. Sadly, many people blame the gears on a road bike, despite the fact that at max sustainable speed most people are not even close to their max hybrid bike gearing (seriously, on a flat road if I'm on a 48x14 and spinning 90RPMs, I'm going plenty fast enough, but that's just not going to happen), which is kind of my whole point in that there is a lot of "common sense" and "It's obvious" type statements that really don't hold water out there.
 
Here:
1000
It's the science, and it always holds water. I doubt you're going to find any serious comparison test that's been done because there's nothing of interest to be revealed in such test, nothing that hasn't already been predicted by the equation above.
 
The Analytic Cycling website has an online calculator for the equation above which allows one to plug in numbers for each of the variables and see the results in terms of power and speed. They present a set of "baseline" inputs which is a good start point. The equation is missing a term for drivetrain and bearing friction rolling losses, but these are small anyway unless the bike is in bad condiion. You could always add say 1-2% power loss for these just to throw them into the mix. The hard part is having all the correct values of real-world parameters to plug in.

The fun part is that you can vary inputs and see results. If I keep everything the same except for frontal area, and can reduce my area say from 0.5 to 0.3 by getting into a good low aero tuck position, what kind of power reduction do I get at a given speed?

For looking at aero effects, it's easier to start with a flat road, theta (angle of the road) at zero. That way weight (Mg) plays a small roll, Cd and A are the drivers. Conversely, for slow-speed climbing, only the third term (weight and angle of the road) are really significant. That makes a really easy case, since you don't need any of those hard to measure things like aero drag requires.
 
Most people who ride hybrids (thankfully) don't give a ****.

Then there's that miniscule minority who seem to need data to validate their badly informed decisions post-hoc.
 
Quote: Originally Posted by alienator .

Here:





It's the science, and it always holds water. I doubt you're going to find any serious comparison test that's been done because there's nothing of interest to be revealed in such test, nothing that hasn't already been predicted by the equation above.

So how does Presented Aerodynamic Area differ between a hybrid and a road bike in the three different riding positions on average? Is there anywhere that it has been measured for the same rider among different bikes?

That's the real rub (why I talked about the photographs) is that it doesn't seem to me that riding position on a hybrid is that different than a road bike on the top bar or hoods, maybe just a few degrees of angle, yet road bikes are measurably faster with the same power output.
 
What is "a few degrees of angle?" It's probably 20+ degrees of angle from my hybrid to the hoods on my road bike. It that reduces the presented area by 20% (and I suspect it's more than that) that's a huge change in power output which translates to a huge increase in speed, doesn't it?

Brian in VA
 
Quote: Originally Posted by Brian in VA .
What is "a few degrees of angle?" It's probably 20+ degrees of angle from my hybrid to the hoods on my road bike. It that reduces the presented area by 20% (and I suspect it's more than that) that's a huge change in power output which translates to a huge increase in speed, doesn't it?

Brian in VA


Can you get someone to take a side photo of yourself on each bike and post them here?
 
I suppose I could. Can you give me a reason to do so? I already know I ride faster on a road bike and don't require proof.

Brian in VA
 
Actually there's little reason to do so. All that someone has to do is compare the geometry of hybrid bikes to road bikes. That should show that for a given top tube length, head tubes are taller on hybrid bikes. For a given head tube length, the top tube should be shorter on hybrid bikes.
 
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Quote: Originally Posted by Brian in VA .
I suppose I could. Can you give me a reason to do so? I already know I ride faster on a road bike and don't require proof.

Brian in VA


I'd like to see a visual comparison of the difference in riding positions between the two.
 
Quote: Originally Posted by Brian in VA .
I suppose I could. Can you give me a reason to do so? I already know I ride faster on a road bike and don't require proof.

Brian in VA


You misunderstand.
I'm not trying to prove something or make a point. I'm trying to learn something. Road bikes are faster; I'd like to know why. There are lots of discussions and opinions on the topic, but very little actual testing or comparisons of hard riding data. I'd love it if someone put a power meter on each one and rode the same course a few times and compared the data (especially power vs speed vs. heart rate), but nobody puts a power meter on a hybrid. The most compelling argument is that on a road bike you and the bike are both more aero. But by how much? In the drops, obviously a lot more, but how often do you ride in the drops? It doesn't seem like the position on a hybrid and the position on either the top bar or the hoods is that much different. There is nowhere that I can find that exists a graphic to show how different the two positions are (but I have seen one that shows the positional difference between the drops and hood, which is what gave me the idea). With photographs of you in riding position on the bikes, I can make one to show the difference. The equation Alien gave uses presented aerodynamic area. How do you measure that? How much does it reduce between a hybrid and a road bike? You say 20%, but that's a guess by your own admission. The analytical sites are really not much help with that. They give typical values but don't tell you what they mean. More to the point, I want to buy an entry level road bike and I'd like to get some idea of how much faster I will be on it. Obviously a road bike will be at least 10 pounds lighter, have less rolling resistance, have a stiffer frame for more efficient pedaling (lack of front suspension probably aids this as well), and may even enjoy an increase in power output from being in a more efficient position for generating said power. But the Aero advantage appear to be where the majority of the gains are found, and I can't for the life of me figure out how much of that I'll gain with the change. I have the math, but not the values for the variables of the equation.
 
Buy road bike. See how fast you go after buying road bike and call that speed A. A is the answer you're looking for.
 
Quote: Originally Posted by jpwkeeper .

I have the math, but not the values for the variables of the equation.
Well yes, knowing what to plug into the equations is always the challenge. You seem to be seeking a universal answer which applies to your specific case, and of course that doesn't exist. I suggest you break it down in pieces and try to evaluate each part separately.

First, weight. If you know you can save 10 lbs by changing to a road bike, that's a major savings up steep hills (where only the last term is important). If your current bike/body/gear weighs say 200 lbs, and you reduce that by 10 lbs, you'll be climbing steep hills 5% faster. That's a one minute savings on a 20 min low-speed climb.....a huge savings on your buddies, and reason enough to buy a road bike.

Second, rolling resistance. If you switch from tires with a Crr of .005 to fast race tires with a Crr of .003, how much does that reduce your power loss at your typical crusing speed on the flats? If your all-up weight is 200 lbs (mass 892 newtons) and you ride at say 7 m/sec (15.6 mph), you could save up to say 12.5 watts of power. That's a pretty big savings, again arguing for a road bike....assuming you don't need to ride on gravel or dirt roads, and don't mind replacing expensive tires when they wear out or cut through.

The aero part all depends on how you sit on the bike of course, how your hybrid fits you now and what kind of fit you'd have on a road bike. If you can reduce your frontal area by going from 0.5 down to a good aero figure of say 0.4 by getting lower on the bike, you've saved 20%. If you don't like this estimate, measure your specific shoulder height on your hybrid, then tuck down to simulate a road bike position down in the drops and check height again. Using that 20% guessimate for frontal area reduction, you'll reduce aero drag by 20%. Doing the arithmetic, I get about a 14 watt savings at the same 15.6 mph. At 10 meters/sec (22 mph), the savings is almost 3 times larger, about 40 watts. This explains why most of us non-racers riding solo are well tucked into the drops trying to go over 20 mph.

Again, a no-brainer choice for the road bike, assuming you can get comfortable riding a bike with a drop between the seat and bars, and how much you stay in the drops with elbows bent. If you can't or don't want a bike that puts you in that race position, then maybe the aero savings aren't for you.
 
Quote: Originally Posted by alienator .

Buy road bike. See how fast you go after buying road bike and call that speed A. A is the answer you're looking for.
Or rent one for the weekend.

dhk2, are you an engineer or something? Some questions are so trivial and the answers so obvious that nobody bothers.

Now on the other hand if you're comparing time trial bikes for a well financed pro race team, they're going to take these things to the wind tunnel and run tests. But nobody rides the prologue of the Tour de France on a Specialized Sirrus.

I guess while we're at it we could see how much drag the handlebar streamers add to an Electra Sugar Skulls.
 
Quote: Originally Posted by oldbobcat .
Or rent one for the weekend.

dhk2, are you an engineer or something? Some questions are so trivial and the answers so obvious that nobody bothers.

Now on the other hand if you're comparing time trial bikes for a well financed pro race team, they're going to take these things to the wind tunnel and run tests. But nobody rides the prologue of the Tour de France on a Specialized Sirrus.

I guess while we're at it we could see how much drag the handlebar streamers add to an Electra Sugar Skulls.


Well, ex-engineer, but no work experience with these kinds of calculations. The OP seemed interested in the equations and maybe even playing with the online AC calculator, but said he had no clue about what numbers to plug in, so I threw some out for consideration, just to get in the "ball park" of what to expect.

Agree renting a nice road bike for the weekend or longer is a great idea. Maybe he'll find that going 2 mph faster down in the drops on the 10 lb lighter road bike isn't really something he cares about. Or, maybe he'll come back on Monday with a check to buy the road bike.

Calculating the extra drag of streamers would be really tough, with all the fluttering. I'd advise anyone looking for real speed on their Sugar Skulls to leave them off, or just use for special events.
 
Do LBSes usually rent road bikes?

I think mine rents bikes but only like beach cruisers.
 
Yup, a great many do. If you can't find something to rent, take a one or two hour test ride.
 
I understand just fine, thanks. My 20% number was a swag (scientific wild ass guess) and I don't claim it has any numerical value. Neither will pictures of me sitting on both bikes since you'll have no way of measuring how large the area is that is presenting to the air in front from either of them.

If this is something you really feel strongly about doing, and getting a real, accurate, scientific answer you need to be the one setting up the pictures, and taking the measurements. I look forward to the results although this reminds me of the physicians who discovered that women drinking cranberry juice reduced the chance of urinary tract infections. The newspaper headline said, "Doctors discover what women have known for years."

Good luck!
Originally Posted by jpwkeeper .

You misunderstand.
 

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