What’s the available volume inside a bike frame? Seems that would make for a pretty aero water store. Just the huge downtube on some of these carbon bikes would probably be big enough.
Hence the reason Spesh made an in-bike bladder for the older Shiv tri model. Despite the space, the actual implementation was less than ideal and plenty of people ditched the great concept and went with BTA, frame or rear saddle bottles.
Let’s ignore their worse solution on the following Shiv tri 
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100% agree….we all know that most drag resistance comes from the body, not the bike. We also know that smoothing out wrinkles in a skinsuit makes a measurable difference. Putting straps across your shoulders would therefore seem to be a big net loss in aero.
An abomination that should have been killed in concept……
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For short races, I’m quite sure bottles are faster. But for longer races, it depends a lot on the circumstances. You should have enough water (with something to spare) to get you from one aid station to the next. And the longer the race, the more important hydration gets.
Another factor is terrain: it is much easier to drink from a hose when things get super bumpy than having to handle bottles.
A third factor is that perhaps you might be able to skip aid stations with a bladder pack. I had to look up what volume 50 oz are, turns out it is almost 1,5 liters. That’s on the small end. You can get 2- and 3-liter bladders. (Hint: you don’t need to fill a 3 liter bladder all the way!)
Lastly, bladder packs and small backpacks are also useful to store things like spare inner tubes, pumps, gels, chews and all that jazz.
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To add to that, some bikes (by the likes of Specialized and BMC) also offer a hidden storage compartment in the downtube. That’s excellent, and more bikes should include that by default.
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Yeah, it’s funny to look back at the criticism S got back in 2015 when they first introduced in-frame storage on the Stumpy. Slowly spread on their bikes and now seen on several genres and more brands. It’s a fantastic solution and does deserve more widespread use.
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Yes, especially in bikes with bulkier downtubes (e. g. for aero purposes). Everybody should have a spare inner tube, a pump and a multitool with them when they ride outdoors. Yet it hadn’t occurred to manufacturers earlier to create cargo space?!? I’m glad none of my bikes have any internal cargo space, because if one did, I’d want it on all of my bikes 
Ditto for pockets/openings/holes for bladders. I have started out life as a mountain biker, so my bottle handling skills are not great. I can do everything just fine, but as soon as you add bunch riding or so to the mix, it gets complicated for me. Having a bladder is not just nicer, it is definitely also more aero.
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If only there were some way to test that.
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The UCI had Banned camelbags under the kit in time trials under the kit because of aero advantages.
So it seems to be More aero using a camelbag
Wow!
I didn’t expect to get this much response from this subject, we have a nice little chat going on here.
Being an Ex-Ironman (full distance) athlete with a background in road racing I am always looking for any advantage I can get.
In my experience with gravel racing the pack is nothing similar to a road pack/group. I find that we are always constantly getting strung out and surging due to the pack being unorganized because of a choppy section, super steep hill etc. This has me always finding myself covering some type of gap until I’m back at the front taking a pull so I really want to be as aero/light as possible.
It is funny @mcneese.chad that you guys are talking about bento/swat box in bikes. I specifically set out looking for bikes that did not have these features a few months ago. I did not want the bike being manipulated around a large hole causing unneeded tube size/shape’s and adding more “compliance”.
I ultimately came down to three bike choices, Specialized Crux, Scott Addict Gravel and the Ridley Kanzo Fast. I went with the Ridley solely on the basis that it is the most “aerodynamic” shape right now with a very aggressive geometry. I built it up to be as light as possible also to help me get over the jabs.
The camelbak under the jersey is interesting, I think I am going to try this without bottles on the bike. My position with an evade should put eye flow right on top of the hump and IMO the best situation in terms of aero. This is assuming I tuck the straw in and I manipulate the number plate to flow properly around the headtube
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Can we add some complexity to this whole mess by adding in the option of a hydration reservoir in a half-frame bag? I have put in for Unbound XL and am contemplating this vs. on my back for comfort, maybe aero gains?
Also, don’t say aero doesn’t matter over longer rides - it matters more!
- It was mentioned loosely above:
I do think that solution is worth a look and can be done to aero and comfort benefits if done well.
Edit to add: Discussion from here a while back.
Hi @teddygram! I’m going to share my data but you should be advised that the frame makes a difference and there is no other gravel bike that has a frame like mine. So, really, you should get out and test this yourself.
It’s always more aero to have the pack on my bike. Water bottles on the frame are really slow for some reason.
A couple of warnings. First, what you do with the drinking tube is very important. If you have a long drinking tube with a typical end valve & you leave it exposed to the wind (either just dangling down or looped out into exposed wind) then you are probably just as well off using water bottles on the frame. Keep the drinking tube close to your body…move it more to the center line of your chest and higher on your chest to reduce it’s impact on your aerodynamics…that’s what I’ve found. Second, what you do with straps is important. Don’t leave them flapping in the wind. Tape them up. If you can hide that behind your armpits, even better.
All my data was taken using a camelbak hydrobak. So keep that in mind.
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