If placing conventional round bottles on the down tube or seat tube is not considered very aerodynamic, then why do I see many of the pros race with bottles there instead of, or in addition to, bottles behind the seat (zip-tied, XLAB, etc.)? Thanks in advance
According to some test protocols, bottles on the DT and ST have been shown to act a little like a fairing. Bottles behind the seat, especially when there are two beside each other, high up and far away from the rider’s back, disturb the air as it reattaches after leaving the rider and can create a fair amount of drag.
I couldn’t be bothered finding sources. They are fairly common. If you are interested, search functions are your friend.
Bottle on the downtube is a great place for an advertisement logo too.
I did some searching with mixed results - generally studies by manufacturers of this product or that stating that their product was more aerodynamic. I figured the best use of my time was to utilize the experience of the folks on ST. Thanks
Very true…
Convenience might be one reason. Improving aerodynamics is not. In our wind tunnel testing, adding a bottle to any bike’s down tube (or seat tube) added drag in various amounts, typically between 25 and 50 grams. At common race speeds that’s around 2 to 5 Watts.
One report with data on bottles is here on Slowtwitch:
http://www.slowtwitch.com/Tech/Cervelo_P4_in_the_Tunnel_1929.html
Compare the drag of the same bike in the different plots to see the effect of adding a bottle.
Another source (same wind tunnel data) is on Lava:
http://lavamagazine.com/gear/free-speed-cervelos-tips-on-aerodynamic-hydration/#axzz1pwDAmciV
This one includes numbers for bottles in front of the rider, behind the rider, and on the frame in various places.
Hope this helps,
This is perfect. I really appreciate it.
Looking at the results of these studies it appears the answer to “why the pros race with bottles on the down tube or seat tube” is likely convenience and/or advertising.
Looks like the optimal set-up for me would be a bottle between the aero bars and one tight behind the seat (provided it convenient).
Thanks again
If you have to put a bottle on the frame, the downtube is faster than the seattube.
Thanks Mike. I figure I will practice with different set-ups to see which work best. One thing that was clear from what I’ve read is that if access is not easy, than it is not an effective set-up - regardless of drag.
Not always true. The Speed Bottle for the Speed Concept is designed to go on the seat tube.
I know the bottle gets bolted there but that bottle typically fits in the junction of the DT ST pretty well. You could make a cage that bolts to the DT and have the exact same shape
I’m sure you could, but my thought on that particular bottle was based off of this:
http://forum.slowtwitch.com/cgi-bin/gforum.cgi?post=3247581#3247581
.
Convenience might be one reason. Improving aerodynamics is not. In our wind tunnel testing, adding a bottle to any bike’s down tube (or seat tube) added drag in various amounts, typically between 25 and 50 grams. At common race speeds that’s around 2 to 5 Watts.
These MIT kid’s tests contradict your statement:
http://www.examiner.com/cycling-in-allentown/wanna-get-more-aero
round bottles on round seat tubes are faster according to these guys. I’m always curious about how to get the most speed out of my comparatively low end equipment.
round bottles on round seat tubes are faster according to these guys.
its just not universally true, or perhaps even true at all. that article doesn’t talk about what yaw angles are being considered for instance.
Cobb also has a test result where two bottles was faster than 1, and faster than none at all. That also isn’t universally true.
its hard to know for sure what is best!
Hi corneliused,
Thanks for the link. I think that article is from a few years ago.
Here’s the issue: “On a round-tubed frame,…”
Cheers,
Convenience might be one reason. Improving aerodynamics is not. In our wind tunnel testing, adding a bottle to any bike’s down tube (or seat tube) added drag in various amounts, typically between 25 and 50 grams. At common race speeds that’s around 2 to 5 Watts.
These MIT kid’s tests contradict your statement:
http://www.examiner.com/.../wanna-get-more-aero
round bottles on round seat tubes are faster according to these guys. I’m always curious about how to get the most speed out of my comparatively low end equipment.
Here is my theory as a barely-average Age Grouper.
Convenience = Speed (for me).
If I haveto fumble with a bottle on my bars then I am either:
A) more likely to crash or
B)more likely to spend time out of “Aero” to get a drink.
C) Or not get a drink at all.
I use a PD Aero Drink (with the STRAW!!! GASP).
On my Speed Concept I have a PD Razor bottle on the seat tube. This bottle is also kind of a PITA to stick back in the cage (at least vs a standard round bottle and cage)
When I use that bottle then I can’t put a bottle on the down tube.
curious:
how is it your find grabbing a bottle that is in front of your face tricky. I assume that grabbing one from between your moving legs is something you have mastered, probably without looking.
now, given that for longer races, you have to refill the pd aerodrink, how is that not tricky?
curious:
how is it your find grabbing a bottle that is in front of your face tricky. I assume that grabbing one from between your moving legs is something you have mastered, probably without looking.
now, given that for longer races, you have to refill the pd aerodrink, how is that not tricky?
Good question. I have actually wondered how people are able to grab the bottle from in front of their face and drink it without issue.
Maybe (probably) I need to work on my handling skills.
In a long race I try to drink every 15 minutes. Much easier for me to move my face a little and place my mouth over a straw than to pull the bottle out of the cage and get a drink.
And refilling is usually done near an aid station when the pace is a little slower and people are on the lookout.
Also - My bars are ski bends with the tips angled inwards to relieve some shoulder issues. It make it hard to get the bottle in/out easily.
some peoples cockpits definitely make it hard to use the front bottle at all
but I swear, it is not complicated. you just take a hand, grab the bottle, pull it out, drink from it.
you can do this drunk, and you don’t have to slow your pace, or get out of aero to do it!
Why not upgrade to the Torhans aero bottle and get the best of both worlds with a straw in your face and decreased drag compared to the profile bottle? Lots less splashing too.