Listen to the Triathlon Nutrition Academy Podcast 🎧

Ironman’s New Bike Hydration Rules: What You Need to Know

Mar 28, 2025

If you're racing an Ironman this season and you don’t want to be disqualified, I’m sharing some crucial information you need to know. As of 17th of March, the Ironman rules have changed which means that your current hydration set up may now be illegal.

Ironman has introduced new race regulations that limit how much fluid you can carry and trust me, you don't want to be caught off guard by these changes.

Nobody has time to read the massive 34-page document outlining the new guidelines so today I’m breaking down exactly what the new rules mean for you. I’m sharing ways to tweak your hydration strategy and how to avoid penalties while still staying properly hydrated and fueled for peak performance.

Why the New Hydration Rules?

The new limits on how much and where you can carry fluids on your bike are grounded in safety concerns. Excess weight, especially up front, can mess with your bike handling. So, by standardising hydration setups, Ironman aims to promote fair play and improve rider safety.

It might also have something to do with Gustav Iden stuffing a water bottle down his suit on his way to setting an overall course record at Kona. This raised questions around whether he used the bottle to divert air around his torso to reduce drag and improve aerodynamics. The problem is, because a pro did that, copycats started adding bottles and even bladders down their suits, adding to the safety concerns.

Here are the three main updates you need to know:

1. Front Mounted Hydration: Your tri bars or handlebar setups can carry a maximum of two litres (67.6 fluid ounces). This is a cap, not necessarily a goal.

Important to note: The fluid carrying capacity of the vessel or water bottle is what matters - it's not how much volume you put into it. For example, if you have a 1 litre bottle and you only fill it up to 500 mils, it doesn't matter. It’s still counted as 1 litre.

2. Rear Mounted Hydration: Similarly, you can have two litres at the back, but you mustn't exceed two bottles, each capped at one litre.

3. Frame Triangle Storage: Any fluid stored inside the bike frame or between your legs doesn't count towards this limit. This is where you can get innovative to cater to your unique hydration needs.

The Impact on Your Race Strategy

For any triathlete, these changes present a challenge, especially if you’re accustomed to carrying more fluid. Here’s how you can navigate the new landscape:

Plan Your Aid Station Strategy: Prepare to depend more on aid stations. Plan your stops meticulously to swap bottles smartly, making sure you meet your hydration needs without exceeding new limits.
Reassess Your Kit: Consider on-frame setups to balance weight distribution and compliance with the new rules. Modern TT bikes often feature integrated hydration reservoirs, which can be a game-changer.
Tweak Your Hydration Needs: As you adjust your fluid intake plan, practice in training sessions to avoid surprises on race day. Never try something new on race day.

There is so much to consider when it comes to your bike nutrition, particularly the logistics of how to carry everything you need for your hydration and fuel. The most important thing is to be prepared. Have a solid strategy and get everything optimised so that you can fuel smart, ride strong and set yourself up for a killer run.

My number one tip is to incorporate these new rules into your training sessions now, not next season or next race. Figure out the most efficient ways to swap bottles, adjust to aid station schedules and maybe even explore integrated frame reservoirs. Believe me, the way you distribute weight on your bike can make a world of difference.

Ironman’s New Bike Hydration Rules: What You Need to Know

Why the New Hydration Rules?

The Impact on Your Race Strategy

Other articles you may be interested in:

Join the Dietitian Approved Crew!

Stay connected with news and updates!