I’ve a torpedo BTA and a single bottle BTS.
I don’t need any more nutrition while on course but I’m wondering what the consensus is on if adding an xlab aero TT bottle to the down tube reduces or adds drag. It obviously adds weight so I’m leaning against using it.
I’ve noticed many bike manufacturers fill a small space now between the downtube and seat tube so the “hole†is no longer has a triangular shape. Would the aero TT bottle from xlab do the same?


Xlab claims its aero bottle is 51-64 seconds faster than round bottle (for IM distance) but I’m fairly sure that is still slower/adds more drag than nothing.
While I’ve not tested aero bottles on the pictured bike I have tested them on several bikes over the years.
There are certain bikes that an aero bottle seems to help with, or at least not hurt.
If you’re getting help it means you are usually on the smallest of sizes. XS & S. If it’s neutral then often it’s at most a Med. Sometimes on the SM & M it’s a time saver at the very lowest yaw angles and a loss of time at the larger yaw angles.
I can not recall a L or XL frame where any bottle, round or aero helped.
Some bikes seem to be designed with a certain BTA/nutrition refillable storage solution where it’s helpful or neutral. At least 50% of the time I see these things add to the grams of drag.
Using myself I knew a round bottle on the downtube on my former Scott was costing me ~2w at -10 yaw. I could live with that especially since I could run that + a BTA for a 70.3 + use a small bottle BTS as my flat kit. The BTS was neutral across the yaw spectrum, well at least at 0, -7.5 and -10.
I suspect, although haven’t tested it the newest plasma, that adding something where you propose is not your fastest option. Although my aero eyeball could be wrong.
Bottom line:
if you’re not testing it you’re guessing about it
Without getting into specifics, the bike that you’ve pictured has something very different than an aero bottle. These are bespoke boxes that fully blend into the frame on all edges, effectively turning the BB area downtube and seattube into one wind-facing piece. In almost every circumstance, having one long narrow beam will be more efficient than having two beams. Taken to extremes, if you were to cover the entire front triangle of a bike with a flat surface, there is little reason to think (at zero yaw) this would be less efficient. BUT filling that space indiscriminately will yield indiscriminate results.
Taken to extremes, if you were to cover the entire front triangle of a bike with a flat surface, there is little reason to think (at zero yaw) this would be less efficient. BUT filling that space indiscriminately will yield indiscriminate results.
You mean like a Trimble? IIRC they didn’t fair (see what I did there) that well at yaw angles.
