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Old 12-20-14, 04:23 PM   #1
Aznman
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Bulky Panniers and Bags Aerodynamics

Which one produces lesser friction?

#1 )http://www.frankrevelo.com/hiking/se...ke_rackbag.jpg

or #2 )http://ecx.images-amazon.com/images/...aL._SY300_.jpg

As you can see, both options are quite bulging. I do feel, however, that the first option is more aerodynamic. It would be completely blocked by my butt and back. On the other hand, side panniers are only partially blocked by my legs. I still need to make sure: has there been any experiment to show any aerodynamic differences?
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Old 12-20-14, 04:32 PM   #2
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The rack bag will produce lower drag than the panniers because it's mostly hiding behind your body.

But this shouldn't be a primary (or even secondary) concern for a commuter. Odds are you'll be doing most of your riding where air drag isn't that much of a factor (about 15mph). Air drag increases proportional the the square of (air) speed speed and therefore becomes much more important at higher speeds. As a commuter, I suspect that you'll notice any difference in air drag between the bags mainly when coasting down hills, where it might shave some speed, but not otherwise.

Focus on what you need and the amount of weight you stuff onto your ride and live with any difference in air drag.
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Old 12-20-14, 04:41 PM   #3
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My information is dated but years ago I asked a similar question.The research found that the use of panniers on the front wheel was best for aerodynamics and handling.I bought some Blackburn panniers for the F wheel and have been pleased with them.
With the two choices you have presented I would choose #1 also as your body will block most of the wind.If aerodynamics is important to you the use of a small bubble windscreen will help more than anything.
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Old 12-20-14, 04:46 PM   #4
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FB nailed it in post no. 2.
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Old 12-20-14, 04:50 PM   #5
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The rack bag will produce lower drag than the panniers because it's mostly hiding behind your body.

But this shouldn't be a primary (or even secondary) concern for a commuter. Odds are you'll be doing most of your riding where air drag isn't that much of a factor (about 15mph).

Focus on what you need and the amount of weight you stuff onto your ride and live with any difference in air drag.
And.....to provide other over-thinking opportunities to further complicate riding a bicycle:

Take into consideration that while the rack bag is behind the butt, the panniers are not pushing through clean air themselves. They ride behind pumping legs and a whirling crankset.

Focus on what you need and the amount of weight you stuff onto your ride and live with any difference in air drag.
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Old 12-20-14, 04:51 PM   #6
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Personally I wouldn't worry about it a lot.

Depending on how you have your bike, in the first photo, the seat and back would be mostly above the bag anyway, but your thighs still have some bulk to break the wind.

I'd get whatever is most convenient for whatever you're carrying. A few extra pockets are nice.
On the other hand, big open space is nice.

I carry two duffels that are bigger than that on my Cargo bike. They are a little awkward, and I'll probably do panniers sometime. But, I can put a full 50 pound bag of flour into each duffel bag.

The Duffel bags give you a central load. The panniers give you a low load. Each has its benefits.

As far as going faster...
Consider filling your bags with rocks at the top of a mountain and emptying them at the bottom.
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Old 12-20-14, 04:55 PM   #7
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I'd expect option 1 to be somewhat more aerodynamic for the reasons already given. But I have yet to really notice the supposed aero drag effect of panniers. On our group club rides I sometimes carry one, or sometimes two, empty panniers if I need to pick up some groceries and will be passing near a store toward the end of the ride. Can't say I've noticed any difference in my ability to keep up with others in the club on days with the pannier(s) vs. days without them. Even coasting down hill side by side with other riders any difference has been hard to observe - but we don't have all that many extended downhills without twists and turns that serve to limit speed. OTOH, I certainly notice the slowing effect once the pannier(s) are loaded with groceries and I have to climb the very modest grade between the store and my home.
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Old 12-20-14, 05:12 PM   #8
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The rack bag will produce lower drag than the panniers because it's mostly hiding behind your body.

But this shouldn't be a primary (or even secondary) concern for a commuter. Odds are you'll be doing most of your riding where air drag isn't that much of a factor (about 15mph). Air drag increases proportional the the square of (air) speed speed and therefore becomes much more important at higher speeds. As a commuter, I suspect that you'll notice any difference in air drag between the bags mainly when coasting down hills, where it might shave some speed, but not otherwise.

Focus on what you need and the amount of weight you stuff onto your ride and live with any difference in air drag.
Thanks for sharing your opinions guys. I actually have two sided panniers right now that came with my bicycle. Although my "average" speed is much lower, I believe that my statistical mode would be between 19 -21 mph. And yes, I have a feeling that I could go a bit faster still.

I would still keep the panniers when I buy the #1 bag, but I think it would be better if I keep them folded. I will use the side panniers only when I have a lot of groceries.
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Old 12-20-14, 07:28 PM   #9
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Thanks for sharing your opinions guys. I actually have two sided panniers right now that came with my bicycle. Although my "average" speed is much lower, I believe that my statistical mode would be between 19 -21 mph. And yes, I have a feeling that I could go a bit faster still.

I would still keep the panniers when I buy the #1 bag, but I think it would be better if I keep them folded. I will use the side panniers only when I have a lot of groceries.
What is statistical mode speed?
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Old 12-20-14, 07:31 PM   #10
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What is statistical mode speed?
Sounds like something a government bureaucrat would come up with, doesn't it?
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Old 12-20-14, 07:38 PM   #11
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None of the Above ... Buy These>> http://www.angletechcycles.com/asset...s/techwind.htm, they put the Older Tailwind aero panniers back in production.

I have an Older set . in storage.

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Old 12-20-14, 08:26 PM   #12
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What is statistical mode speed?
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Sounds like something a government bureaucrat would come up with, doesn't it?
Actually I was inaccurate myself. You know the mode of basic statistics right? It is not the average, but the most frequent number.
My "most frequent" high speed (on flat ground with no wind either way) while carrying some 20 pound objects in addition to my weight is about 21 mph. Sometimes I go faster, but I'm not sure if something is helping me out.
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Old 12-20-14, 08:34 PM   #13
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Is this for racing purposes? If so get rid of anything that could cause drag... If not and you actually need what's in the panniers, who cares? It is what it is...
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Old 12-21-14, 03:14 AM   #14
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Is this for racing purposes? If so get rid of anything that could cause drag... If not and you actually need what's in the panniers, who cares? It is what it is...
I would like to commute as quickly as reasonably possible. I bought my now 2 year old used bicycle at a very good price and I loved it. However, my feet sometimes kick the side panniers, no matter how I try to adjust it. This is why I am interested in making a top rack bag.
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Old 12-21-14, 08:39 AM   #15
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Actually I was inaccurate myself. You know the mode of basic statistics right? It is not the average, but the most frequent number.
My "most frequent" high speed (on flat ground with no wind either way) while carrying some 20 pound objects in addition to my weight is about 21 mph. Sometimes I go faster, but I'm not sure if something is helping me out.
OK. Haven't seen discussion of mode in bicycling "average speed" discussions before. So, that's not the mode of a trip but of the time you are moving faster than a certain speed during a trip?
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Old 12-21-14, 08:46 AM   #16
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None of the Above ... Buy These>> http://www.angletechcycles.com/asset...s/techwind.htm, they put the Older Tailwind aero panniers back in production.
A recumbent bike would complement these bags - for maximum aero benefit. Angletech sells those, too.
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Old 12-21-14, 09:31 AM   #17
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My commute is east-west 32 miles round trip. A 20mph head wind + 15-17mph speed equates to 35-37mph. so the 15 mph argument does not hold water. I notice a big difference on days with or without panniers or wind. I say if your concerned go with option 1. there can be a noticeable difference
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Old 12-21-14, 09:31 AM   #18
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I use the Topeak stuff, I usually use my basket with a backpack, it's tucked in behind me. When I need to load up, I add some Ortlieb panniers along with the basket:
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Old 12-21-14, 11:27 AM   #19
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None of the Above ... Buy These>> http://www.angletechcycles.com/asset...s/techwind.htm, they put the Older Tailwind aero panniers back in production.
Angletech...hey, I've been there. Very nice folks and big supporters of our ever improving cyling infrastructure here in town!
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Old 12-21-14, 03:11 PM   #20
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Paging @wphamilton

Being thoughtful about aero can save only maybe a few minutes an hour but that's notable amounts of time when amortized across a year. Starting from jeans and an open coat on a mountain bike and finishing with full kit, the difference is large. However the difference between one bag and another is probably small. I don't know why bents with fairings aren't more popular except for image, but if you really want to go fast on the level, that's the answer.

speaking of notable amounts of time amortized across a year, have you ever done the math on brushing your teeth? 2 minutes twice a day adds up to over a day per year, no joke. Two days if you only count waking hours.
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Old 12-21-14, 03:49 PM   #21
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I find the easiest option to be front panniers. Loading the rear rack raises your center of gravity, which makes handling more sluggish and difficult. And there's something about pushing the load in front that's easier than pulling the load in the rear.
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Old 12-21-14, 04:02 PM   #22
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I would like to commute as quickly as reasonably possible. I bought my now 2 year old used bicycle at a very good price and I loved it. However, my feet sometimes kick the side panniers, no matter how I try to adjust it. This is why I am interested in making a top rack bag.
I find kicking the panniers annoying too.

I'm not using panniers at the moment. Mainly backpacks and tying big stuff to the rack due to convenience, and as mentioned, big duffels for the cargo bike. And trailers for the big, heavy, and awkward.

When I had the panniers, I'd usually set them as far back as they would go, which then would sometimes be a problem since my bike never had enough rear support to keep them out of the spokes.

I think designs may have changed a bit since then... time for the next round of upgrades

I have my cleats set quite far forward. However, I'm now considering a more medial cleat position which would also help with all the stuff behind oneself.
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Old 12-21-14, 06:32 PM   #23
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I find the easiest option to be front panniers. Loading the rear rack raises your center of gravity, which makes handling more sluggish and difficult. And there's something about pushing the load in front that's easier than pulling the load in the rear.
Panniers modestly loaded hanging on a rear rack shouldn't negatively affect the COG.
A really heavy load is best split between front and rear.
Can you explain the science behind the pushing/pulling thing?
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Old 12-21-14, 07:07 PM   #24
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Paging @wphamilton

Being thoughtful about aero can save only maybe a few minutes an hour but that's notable amounts of time when amortized across a year. ...
Bags on top of the rack will have less drag in general, but that one shown in the original post appears to be somewhat larger volume than the panniers also shown so I wouldn't hazard a guess without testing.

Whether it's worth worrying about - of course it is! Even if we're not concerned with the cumulative time savings, faster - or easier - is a priori better. It's why we spend thousands on carbon fiber bikes and ever better components, why would the same ideas not be valid for cargo equipment?
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Old 12-21-14, 07:28 PM   #25
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None of the Above ... Buy These>> http://www.angletechcycles.com/asset...s/techwind.htm, they put the Older Tailwind aero panniers back in production.

I have an Older set . in storage.
I was about to mention those Tailwind panniers. Interesting link. It is amazing to me that they didn't catch on to a greater degree, given the vast amount of money people pay to get their bikes a tiny bit lighter, which has an even tinier effect on speed.

Reducing air drag with panniers seems like the obvious way to design them.
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