Episode 181 - Ironman’s New Bike Hydration Rules: What You Need to Know

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

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.

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Episode Transcription

Episode 181: Ironman’s New Bike Hydration Rules: What You Need to Know

Welcome to the Triathlon Nutrition Academy podcast. The show designed to serve you up evidence-based sports nutrition advice from the experts. Hi, I'm your host Taryn, Accredited Practicing Dietitian, Advanced Sports Dietitian and founder of Dietitian Approved. Listen as I break down the latest evidence to give you practical, easy-to-digest strategies to train hard, recover faster and perform at your best. You have so much potential, and I want to help you unlock that with the power of nutrition. Let's get into it.

[00:00:00] Taryn: Before we dive into today's episode, I just want to say a massive thank you and shoutout to the latest supporters of the TNA podcast. Thank you so much to Rob Stent, Beppo, Steve Duquette, Steve Dempsey, Robson, and Katie. Thank you all so much for supporting the show.

[00:00:18] Your input really helps to keep the podcast ad-free, but it is a huge beast to maintain. If you’d love to support the show as well, head to dietitianapproved.com/legend.

If you're racing an Ironman this season, you need to listen to this episode because the rules have changed, and your hydration setup may now be illegal. Yup, that's right—Ironman has introduced new race regulations, effective from 17 March 2025, that limit how much fluid you can carry on your bike and where you can store it.

[00:00:56] If you don't adjust your strategy for races after that date, you could be setting yourself up for disqualification on race day—which is the last thing you want after all that training.

[00:01:14] Don’t worry, I’ve got you covered. Today, I’ll give you the cliff notes of the massive 34-page rules document—because, let’s be honest, nobody has time to read that. I’ll break down exactly what the new rules mean for you, how to tweak your hydration strategy, and, of course, how to avoid penalties while staying properly hydrated and fueled for peak performance.

[00:01:37] If you want to dial in your bike nutrition with confidence, I’ve got a great resource that will make it super easy for you, and I’ll tell you about that at the end of the episode. So stick with me.

[00:02:11] All right, let’s clip in and get into it. Let me break down the new hydration rules coming from Ironman.

[00:02:31] There are three major changes. The first one is that any front-mounted hydration setup—so hydration setups between your arms, on your tri bars, or sitting above the cockpit on your handlebars—is capped at two litres (or 67.6 fluid ounces if you prefer that measurement).

[00:02:56] Your rear-mounted hydration, meaning things behind the saddle, is also limited to two litres (67.6 fluid ounces), but here, you can’t have more than two water bottles, and each bottle has a maximum capacity of one litre (33.8 fluid ounces).

[00:03:11] The third component of the new ruling is that any additional hydration systems inside the frame triangle—so between your legs and inside your bike frame—are not counted in this limit.

[00:03:31] The rules are effective from 17 March 2025. The first Ironman-branded event where these new rules come into play is the Ironman 70.3 Geelong on 23 March, which is this weekend.

[00:03:56] The penalty for exceeding the hydration limits and being overloaded is actually disqualification. We definitely want to avoid that.

[00:04:11] There is a method to the madness, and some legitimate reasons why the rules have changed—primarily for safety concerns. Overloaded hydration setups on the front end can affect your bike handling.

[00:04:27] Your bike won’t steer as well if there’s too much weight sitting over the cockpit. Steering will be negatively affected.

[00:04:32] The new rules were also put in place to standardize hydration setups across races. The World Triathlon actually changed their ruling back in January, so now we are on the same playing field across all events.

[00:04:56] It probably originated because Gustav Iden stuffed a water bottle down his suit on his way to setting an overall course record at Kona.

[00:05:00] There’s been speculation about whether he used the bottle to divert air around his torso, reduce drag, and improve aerodynamics. Of course, since a pro did it, copycats started doing the same—both pros and age groupers began adding bottles and even bladders down their suits.

[00:05:03] Because of that, we now have a new rule.

[00:05:07] So how does this impact you and your race strategy? We know the rules have changed, but the big question is: what does that mean for your race-day fueling?

[00:05:27] For many athletes, bike nutrition is already a challenge, and these new limits could make it even harder if you don’t have a plan.

[00:05:47] If you used to carry more than the new limits allow, you’ll need to reassess your entire hydration and fueling plan. You might become more reliant on aid stations than before.

[00:06:00] You’ll also need a plan for when to swap bottles out and how to strategically use aid stations.

[00:06:19] Knowing how often you’ll hit aid stations and planning your refills accordingly is crucial. You might consider taking an extra bottle at key points and swapping it out later to stay within the allowed limits.

[00:06:45] If you previously stacked hydration on the front and back of your bike, you may need to shift to an on-frame setup instead.

[00:07:00] Another mistake I foresee happening is that people may either underestimate or overestimate how much fluid they need.

[00:07:07] Some athletes might feel the need to max out their hydration capacity, while others who previously carried more will now have to adjust to carrying less.

[00:07:18] Whatever changes you make, practice them in training first—don’t try something new on race day.

[00:07:36] Keep in mind that more hydration means more weight on your bike. Theoretically, you could carry up to 10 litres, but do you really want or need to do that?

[00:08:00] You don’t want to slow down at every aid station for more bottles, but you also don’t want to overload your bike with unnecessary weight.

[00:08:20] Many athletes either under-fuel, fearing gut issues, or have no idea where to put everything.

[00:08:40] Others over-fuel, feeling bloated and sluggish when transitioning to the run.

[00:09:00] And some athletes go into a full Ironman or 70.3 event without a solid plan, relying solely on aid stations, which is a huge mistake.

[00:09:10] You’ve spent so much time training and invested so much money in this race—why wouldn’t you also fine-tune your nutrition to maximize performance?

[00:09:55] Now, to help you adapt to these rule changes and build a perfectly formulated training nutrition plan, I’ve put together a 60-minute Bike Fuel Masterclass.

[00:10:22] Inside, I cover my Triathlon Ride Fuel Guidelines—because fueling for a triathlon bike leg is very different from just cycling alone.

[00:10:42] I’ll help you understand how to create a personalized fueling strategy tailored to your needs.

[00:11:28] I’ll also go over the best sports nutrition products for cycling, what foods to consider, and how to avoid common mistakes.

[00:12:09] If you want to grab that, head to bikefuel.co, and you’ll get instant access for the next 60 days.

[00:12:30] That’s it for today! This was a quick summary of the new hydration rules so you don’t have to read the 34-page Ironman document - you’re welcome!

[00:12:50] If you found this helpful, send me a message with any questions and share it with a training buddy who’s racing an Ironman-branded event this year.

[00:13:00] Don’t forget to subscribe to the podcast so you can have me in your ear next week for your wind trainer ride or long run.

Now go out, fuel smart, ride strong, and I’ll catch you next week!

Thanks for joining me for this episode of the Triathlon Nutrition Academy podcast. I would love to hear from you. If you have any questions or want to share with me what you've learned, email me at [email protected]. You can also spread the word by leaving me a review and taking a screenshot of you listening to the show. Don't forget to tag me on social media, @dietitian.approved, so I can give you a shout out, too. If you want to learn more about what we do, head to dietitianapproved.com. And if you want to learn more about the Triathlon Nutrition Academy program, head to dietitianapproved.com/academy. Thanks for joining me and I look forward to helping you smashed in the fourth leg - nutrition!