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Old 07-27-09, 09:55 AM   #1
johnknappcc
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Handlebar Bags, Aerodynamics, and Weight Distribution

I have a Topeak Tourguide (the medium size) handlebar bag on order. It is 10.5 inches wide and 8.5 inches high.

I've never used a handlebar bag before (I would be using it for centuries, double centuries, etc, no real touring). Will this have a significant effect on aerodynamics? Will this potentially lower my speed or make riding more difficult? I generally like to keep a quick pace on centuries.

Also, will handling be (significantly) altered with an extra 2-3 pounds hanging off my drop bars?

I will probably only be storing some bars, gels, misc food, my cellphone, and a small camera, maybe a wind breaker. I use a bento box for nutrition right now (the kind that mounts to stem & frame), but it always sags, and isn't big enough for my cellphone.

The bag has gotten good reviews, do any BF members have any experience with it?
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Old 07-27-09, 10:48 AM   #2
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it won't affect your speed.

handling might be a little weird/different but you will get used to it quickly. i did a four day/300 mile tour a couple of weeks ago and used a large lone peak handlebar bag and a medium seat bag with home built mount. the weight of the bag might make riding no hands a little tougher and the front end gets more floppy but with the bag i could ride no-hands. once the bars start turning there no going back


Last edited by zzzwillzzz; 07-27-09 at 04:08 PM. Reason: forgot to add pic, duh
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Old 07-27-09, 03:46 PM   #3
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You mean this one?



Looks to me like due to aerodynamics, this thing will slow you down at speeds over, I dunno, 15 mph perhaps. In the long run it may be worth it though, if you can access whatever you need without stopping.

I don't think weight will have much effect on speed or handling unless you really load it up.

Something like the Topeak Dynapack might be a bit more aerodynamic, but I'm a little bit skeptical unless someone has actually tested it out. And again, to get anything out of it you'd have to stop, which may kill more time than you get back from the more aero design.
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Old 07-27-09, 04:09 PM   #4
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if you're riding with a group just stay in the draft and it won't matter whether or not you have a handlebar bag
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Old 07-27-09, 04:27 PM   #5
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if you're riding with a group just stay in the draft and it won't matter whether or not you have a handlebar bag
I think the term is "wheelsucker".

A bag you can access while moving or without dismounting is a big help.


I'm guessing behind the seat is more aerodynamic... but then again....
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Old 07-27-09, 06:21 PM   #6
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Wind tunnel testing has shown handlebar bags do not add drag in most situations. Drag is mostly a result of frontal area, and the bag does not actually add to frontal area in most cases. The bag does appear to add drag in quartering headwind scenarios, because it does add frontal area. It's a small amount, however, and is still less than is added by a similar size seat bag under most situations. Somewhat counter intuitive, but the saddle bag sticks out to the sides, adding frontal area, while the handlebar bag sits in front of the rider, so doesn't add to the total frontal area.

Unfortunately, the bag probably will affect handling. Most bikes aren't designed for a front load and get a little twitchy and/or "floppy" when a bag is added. This is exacerbated by attaching the bag directly to the bars rather than having most of the weight supported by a rack. I do know people who don't mind it, however. Hopefully you'll be one of them!
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Old 07-27-09, 07:25 PM   #7
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Wind tunnel testing has shown handlebar bags do not add drag in most situations....
Fascinating. Do you have a link to the tests / results?
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Old 07-27-09, 08:10 PM   #8
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Wind tunnel testing has shown handlebar bags do not add drag in most situations. Drag is mostly a result of frontal area, and the bag does not actually add to frontal area in most cases. The bag does appear to add drag in quartering headwind scenarios, because it does add frontal area. It's a small amount, however, and is still less than is added by a similar size seat bag under most situations. Somewhat counter intuitive, but the saddle bag sticks out to the sides, adding frontal area, while the handlebar bag sits in front of the rider, so doesn't add to the total frontal area.
Speak for yourself. My Carradice is virtually exactly the same width as my hips and thighs, I blame my mother.
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Old 07-27-09, 08:23 PM   #9
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Unfortunately, the bag probably will affect handling. Most bikes aren't designed for a front load and get a little twitchy and/or "floppy" when a bag is added. This is exacerbated by attaching the bag directly to the bars rather than having most of the weight supported by a rack. I do know people who don't mind it, however. Hopefully you'll be one of them!
+1!!!! If your bike was not designed for a handlebar bag it can have a very detrimental effect on handling. That doesn't mean it will, but it definitely can! 2-3lb probably won't be a big deal but if you start throwing a load of stuff in there I'd do some experimenting before you go blasting down a curvy mountain road.
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Old 07-27-09, 09:26 PM   #10
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it won't affect your speed.

handling might be a little weird/different but you will get used to it quickly. i did a four day/300 mile tour a couple of weeks ago and used a large lone peak handlebar bag and a medium seat bag with home built mount. the weight of the bag might make riding no hands a little tougher and the front end gets more floppy but with the bag i could ride no-hands. once the bars start turning there no going back

Is that the DX or the regular Tourguide? I used a box (of approximate size) to check clearance, and that seems much larger. Gorgeous bike BTW.

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You mean this one?



Looks to me like due to aerodynamics, this thing will slow you down at speeds over, I dunno, 15 mph perhaps. In the long run it may be worth it though, if you can access whatever you need without stopping.

I don't think weight will have much effect on speed or handling unless you really load it up.

Something like the Topeak Dynapack might be a bit more aerodynamic, but I'm a little bit skeptical unless someone has actually tested it out. And again, to get anything out of it you'd have to stop, which may kill more time than you get back from the more aero design.
Yep that's the one, and yes the main reason would be ease of access. I've seen cute baby deers, to a strange mannequin threesome get-together outside a cafe (it's Chicago afterall). I would love to pull out the camera and flash a pic quickly, while riding

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if you're riding with a group just stay in the draft and it won't matter whether or not you have a handlebar bag
That won't really work, a lot of my rides are solo-ish, and I'm usually passing people on the trails/roads.

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I think the term is "wheelsucker".

A bag you can access while moving or without dismounting is a big help.

I'm guessing behind the seat is more aerodynamic... but then again....
That's intense, and pretty cool. Not a big fan of MTB's but well done my friend.

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Wind tunnel testing has shown handlebar bags do not add drag in most situations. Drag is mostly a result of frontal area, and the bag does not actually add to frontal area in most cases. The bag does appear to add drag in quartering headwind scenarios, because it does add frontal area. It's a small amount, however, and is still less than is added by a similar size seat bag under most situations. Somewhat counter intuitive, but the saddle bag sticks out to the sides, adding frontal area, while the handlebar bag sits in front of the rider, so doesn't add to the total frontal area.

Unfortunately, the bag probably will affect handling. Most bikes aren't designed for a front load and get a little twitchy and/or "floppy" when a bag is added. This is exacerbated by attaching the bag directly to the bars rather than having most of the weight supported by a rack. I do know people who don't mind it, however. Hopefully you'll be one of them!
I'm thinking along those same lines, since my body will probably produce more drag than the bag. I can always add a front rack later, the bike is a touring bike (1986 Schwinn Voyageur) with a modernized wheelset and drivetrain. I'm assuming if any bike could do, a long wheelbase, more relaxed geometry touring frame could. Edit, I'm using two cages/bottles currently not the one in the pic:



Thanks for the tips!
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Old 07-27-09, 09:37 PM   #11
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That's intense, and pretty cool. Not a big fan of MTB's but well done my friend.
Oh heck thats not me, its John Nobile who knows a little about covering long distances efficiently.
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Old 07-28-09, 12:50 AM   #12
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Is that the DX or the regular Tourguide?
neither, its a lone peak alta, the h-100. the h-75 is the same without the front pocket. it even worked with the sti levers and cables, i just installed new cables and housing before the trip and set them up on the longer side to give them more room to route around the bag. it wasn't great but it worked fine.

the bag is great for taking pictures, the lone peak has mesh pockets on the side and i just left my camera in there with the strap hanging out. i would put my hand through the strap so i wouldn't drop the camera and pull it out to shoot photos. the hard part with the handlebar bag is not being able to ride no-handed (and i can do no-hand trackstand) and i took my on my photos while riding. see my flickr account for some photos of my trip from l.a. to mammoth lakes ca

http://www.flickr.com/photos/73142394@N00/

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Old 08-02-09, 11:58 AM   #13
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Not to bump my own thread, but I finally got to use my Tourguide on a hilly/windy metric this weekend. I don't think there was any added wind resistance because of it. Most of the time the speed was 20+ mph, 32+ mph on the downhill.

Also, the handling was fine, a little tricky to go no-handed, but otherwise no adverse effects otherwise.
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Old 08-12-09, 10:24 PM   #14
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I actually run exactly this bag on my Audax bike (custom Hab Ti), and used it in PBP 2007 and continue to do so. I agree with most of the above comments - probably limited aero impact at Audax speeds. For me, handling is not a problem - one's internal gyroscope tends to adjust to the marginal change in handling characteristics associated with what is a fairly small bag. And its a great bag - nice size, lots of compartments etc.
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Old 04-04-11, 08:14 AM   #15
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Is it possible that using a handlebar bag can make you MORE aerodynamic than not having one?

I participated in a local cyclosportif race last weekend in France. It was only 140km (85 miles), so I decided that I'd do another 80-100km (50-60 miles) after the event was over before taking the train home again. I therefore used a small handlebar bag to carry extra food and clothes.

I was riding in fair-sized groups most of the day doing about 32-35 kph on the flat (20 mph). When we got to the downhills (i.e., speeds of 50-70 kph / 30-45 mph) I found that I could pull out and pass everyone quite easily and was quickly at the front of the group. A few times I even got a gap and started to pull away from the group. I've done many other 'sportif rides like this, and I'm normally struggling to keep up with the straight-line speed of others on the downhills. I've generally attributed this to the fact that my handlebars are not particularly low and I don't weigh that much (about 68kg / 150lbs). The only thing different about this ride was the addition of the 'bar bag. My theory is that the bag was deflecting the wind and not allowing it to get to my body (my torso & thighs probably act much more like a sail than does the bag).

The bag I was using is a Vaude Road II model; pretty small at 24cm wide and 17cm high (10x7 inches), mounted on a standard road bike (2007 Trek Madone) with drop handlebars. The effects of the bag on the handling of a bike like this were mentioned above; I didn't have much weight in the bag and felt no difference in the handling compared to when riding without it, and I went down some pretty serious descents with zero problems. I didn't see anyone else on the ride using such a bag; I think everyone thought I was a bit weird for doing so, one guy asked me if I'm in training for Paris-Brest-Paris, which I'm not; but I think people were quite jealous when they saw me easily grabbing snacks from the bag and putting my jacket and arm warmers in there as the morning warmed up from 12 to 22 degrees C (55 to 75 F).

I haven't been able to come up with any other explanation for the difference in my descending speed relative to others in the groups I was in compared to what I normally experience, but the difference was quite dramatic (from previously struggling to keep up to easily sailing past everyone). Does anyone have any info / experience that would confirm my theory that my 'bar bag was making me more aerodynamic?

I wasn't sure whether I should resurrect this old thread, but it is on the same topic that I wanted to write about, so it seemed to make sense.
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Old 04-04-11, 09:29 AM   #16
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Originally Posted by Bacciagalupe View Post
You mean this one?



Looks to me like due to aerodynamics, this thing will slow you down at speeds over, I dunno, 15 mph perhaps. In the long run it may be worth it though, if you can access whatever you need without stopping.

I don't think weight will have much effect on speed or handling unless you really load it up.

Something like the Topeak Dynapack might be a bit more aerodynamic, but I'm a little bit skeptical unless someone has actually tested it out. And again, to get anything out of it you'd have to stop, which may kill more time than you get back from the more aero design.
Someone HAS actually tested it. Some time back, Bicycle Quarterly went to a wind tunnel at UW and tested a bunch of stuff. Turns out that large, boxy 'bar bags actually IMPROVE aerodynamics, as do fenders (if done properly, and most available fenders are too short to do properly). Don't recall which issue it was, but the title was something along the lines of "Real-world Aerodynamics".

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Old 04-04-11, 10:10 AM   #17
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Handlebar bags don't add to your frontal area so they don't have a negative effect except in "quartering" winds that come at you from an angle. As Homeyba says, don't load it very heavy.
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Old 04-04-11, 10:37 AM   #18
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Is it possible that using a handlebar bag can make you MORE aerodynamic than not having one?
Theoretically yes, if it acts like a fairing.

But it could also go the other way, if it has lots of protuberances that create more drag than whatever is behind the bag. Or, it might make you more aero, but the advantage may be too small to notice.

Aerodynamics is an extremely tricky business. Tests may not even tell the whole story; e.g. if they only tested headwinds rather than a variety of cross-winds, the results could vary from the real world.

So, I'd doubt that you descended faster than a group on one particular day strictly because of a handlebar bag. You'd certainly need more than one descent on one day to really draw a conclusion like that.
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Old 04-04-11, 11:43 AM   #19
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If you loaded the h-bar bag with rocks, it might make you descend faster.
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