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The Best Hydration Setup for an Ironman
Learn why two bottles behind the saddle along with and aero drink bottle mount between the aerobars is the best combination of convenience and aerodynamics for HIM and IM racing.
Member Question from Focker
"What is the fastest hydration set-up on a bike when looking at weight vs aero vs time loss at the aid station? Last IM I rode with an aero bottle and one nutrition bottle on the frame. I would stop at each aid station and fill my aero bottle which added up to eight stops for the aid stations. I averaged in the low 23 mph so by the time I slowed down, got in traffic, rode to the end of the aid station (where the water is), grabbed a bottle, filled the aero bottle and threw the empty water bottle away, got back into traffic, got back up to speed - I would lose a lot of distance to the riders who did not stop.
Would it be better to ride with a rear hydration system and carry two full water bottles with an addition to the aero bottle and frame cage bottle then I only have to stop every 3rd or 4th aid station? Does the weight and the aero of the extra rear bottles affect your speed more or less then stopping at an aid station?"
Answer by Dean Phillips
Lead Fitter FitWerx2
For IM racing, I recommend the two bottles behind the saddle in addition to the aero drink bottle mounted between your aerobars. I’ve found this setup to be the best combination of convenience and aerodynamics for HIM and IM racing. It’ll allow you to refill the aero drink bottle easily with the rear mounted bottles, and when you get to an aid station you’ll simply drop the empty bottle(s) and grab a full bottle(s) without stopping.
The aero drink bottle makes it convenient to drink, and when drinking isn’t convenient triathletes tend to not drink enough. The aerodynamic penalty is minimal with a front mounted aero drink bottle, and in some studies it’s proven to be more aerodynamic than no bottle. Even if an aerobar mounted system had an aerodynamic drag cost, that cost is far outweighed by the penalty of not drinking enough and suffering on the run. This is definitely an area of convenience and best race nutrition strategies trump aerodynamics. Mounting a water bottle cage horizontally between your aerobars so it rests between your arms is an alternative setup that’s proven both aerodynamic and convenient for many triathletes as well.
The behind-the-saddle hydration system should be mounted where it’s sheltered and convenient to reach. For best aerodynamics, mount the rear hydration system so the middles of the bottles are approximately the same height as the back of the saddle. This provides great shelter where the tops won’t be sticking up in the wind above your lower back and they’re also easy to reach with your hands.
If it’s going to be more convenient to have a 3rd water bottle on the frame, then by all means use one. The aero penalty is similar to the aerobar mounted systems – little to none. The aero-shaped bottles for the downtube are nice, but you can’t swap them out at aid stations so they have little value in long course triathlons.
Don’t be concerned about the weight of the extra water bottles. Every pound of extra weight on the bike only costs you about 10-20 seconds in your typical IM bike leg depending on the course. Stopping at aid stations or not drinking enough water will cost you many times that penalty, so go with what’s convenient and you’ll be thankful on the run.
Ontherun's road bike setup:
User aarondavidson's triathlon bike setup:
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