Speed Theory

02/03/2026

Ironman NZ week is upon us, as usually happens this time of year. Thus it is time to look at the weather forecast.
I have good news and bad news.
The good is that the chance of rain is rated very low.
The bad is that the ride will take longer, however this is course related, not conditions.
The bike course change is going to cost ~7-15mins (the penalty escalates with slower pace). We've already seen proof of this with the 70.3 course.
The conditions are a little faster than 2025 ~80s for the 5hr and below athletes, 2-3mins for 6hrs and above.
The wind will be mostly in your face on the return leg, but everyone should be used to that by now and it's not particularly strong.
Note that it will be quite chilly at the beginning of the ride (13-15deg depending on your swim pace) so dress accordingly.

The conditions for the run are promising - not too hot, a bit of wind off the lake and some cloud cover.

As of today, the lake level is extremely similar to last year and the outflow is a little higher, so the swim conditions should be the same - the low early wind will mean smooth water.

Image courtesy of suncalc.org showing that there could be some sunstrike for faster swimmers on the final leg to the swim exit.

PS. If you're doing the 70.3 the numbers above will be roughly half, aside from the start temperature at a balmy 10deg.

16/01/2026

The Loan Market Oceanside Tauranga Half & Fulton Hogan Mount Festival is upon us once again. Which makes it a good time to look at the weather forecast.

And it's actually quite nice. No rain is forecast and the temperatures will be fairly mild.

The swim will mostly be in slack tide conditions for the age groups (incoming tide for the Pro/Open field) which should make the drag along the beach a little less soul destroying.

The wind directions are not particularly favourable - you'll feel a bit of a crosswind outbound on the bike the first time, which will switch to a more direct headwind on the second lap. However - this should mean a fast ride back to T2. And the wind speed is forecast to be low, so it shouldn't be too sapping riding into it.

Overall the riding conditions are slightly faster than last year: 20-40s depending on the speed you're going. This is thanks to marginally lower air density and the lower wind speed.

Once on to the run the temperature will rise of course, make sure you make the most of the opportunity to hydrate with the tailwind home on the bike to prepare for the run.

All the best to everyone racing

02/11/2025

Reminder for Auckland based athletes - the Twilight swim run series kicks off tomorrow - Tues 4th Nov - at Pt England Reserve.
Races for everyone - check out - https://twilight.co.nz

It would be great to see strong support for a resumption of grassroots racing in Central Auckland (we all know how rare that has become).
Twilight Swim Run Series

The 2025 Twilight Swim Run Series

30/03/2025

Just back from the Taipei Bike Show, didn't get much of a chance to look around but GCN did come along for a chat about my latest road race bar

We're back on the show floor at the Taipei Cycle Show for Day 2, bringing you even more of the coolest and most innovative cycling tech from around the world...

03/03/2025

Ever dreamed about having a 25m lap pool at home, living in beautiful Cambridge, NZ?

Here is your opportunity!

We will be sad to leave our amazing pool, warm house and lovely neighbours and would love if a fellow triathlete were to take up the reigns.

Share with fellow swimmers and talk to Rebecca if you have any questions.

Our mission is be your premium service orientated Real Estate choice. Achieving the best outcome for your situation is our drive and focus. Our vision is to optimise results for our clients; challenging existing market models and adopting a mix of techniques, new and proven.

27/02/2025

IMNZ Weather Analysis
Long story short - the slowest conditions since 2016.
With that out of the way, there are some positives:
- Drizzle is forecast for the start of the day, but will clear early
- Temperatures for the run should be fairly comfortable
- Outflow on the lake is fairly low so there shouldn't be much current

The flipside to some of those points:
- If you are susceptible to the cold you should plan to wear a bit more on the bike
- For the 70.3 you'll likely have a bit of sunstrike on the return leg of the swim

The factors that will make it slow are:
- Relatively high air pressure (colder than normal is the main factor here)
- Headwind all the way home on the bike (close to the worst orientation for speed)

The image shows red as headwinds and blue as tail. It's not flash for the return leg and the wind will increase through the day. In the early part of the day it will be more of a crosswind, moving to the west through the day.

What typically happens in conditions like this is a large chunk of the field gets overexcited in the tailwind on the way out, then suffers progressively more on each subsequent leg. So please mind your pacing.

All the best to all the athletes in both races.

08/12/2024

Time to look at the long range forecast for 70.3 WC. It's pretty good, unless you're a man that melts in the rain.

Modelling the Taupo 70.3 World Championships course with weather data

11/11/2024

In further evidence that I should engage the Marketing department in producing content. It turns out that I posted a version of the video with no voiceover. It may make more sense now

An overview of the Profile Design HSC250

10/11/2024

I'm rather pleased to finally be able to share a new product that I've been testing for a while. It always feels like a long wait from my job concluding (conception and development) to having actual product in the market.

The genesis of this idea was wanting to improve the options for carrying high carb fluid mixes in Tri. To explain further I have both written a post, which gives some background on the concept: https://www.speedtheory.co.nz/blog/post/137280/profile-design-hsc250/

And made a video. Which makes it clear that I should stick to thinking of new products, but hopefully it's informative. https://youtu.be/wOOi9KAWpcQ

RRP is $150 (NZD), get in touch if you'd like one.

31/07/2024

All set for nearly 4 hrs of watching top level triathlon. Children have been briefed on acceptable topics of conversation (none, apart from the race as I want them to be engaged) and M&M bribes (for silence) procured. About to tell them they can stay up if they want to watch the mens race.

Go Kiwis!!

07/07/2024

First serious competition use of my newest aerobar design at a race in France.