Which HED wheels?

I think you need a few more variables to complete this equation:

- Time in last race with old gear
- Hours / distance cycled since last race

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https://www.strava.com/...tes/zachary_mckinney

There's nothing out there more than a tiny hair faster than your 2014 speed concept so don't look to spend money there. Latex tubes should save about 0.5s per km. GP5000s will save about that much again. You'll get a little bit out of the wheel change as well, though likely not more than 0.5s/km. These are all pretty certain. The aero suit is less certain. It could save a lot (say up to 2s/km) but it depends on the person / position and exactly what you were using before and what you are switching to. The helmet is also pretty uncertain. One of the Lazers (can't remember the name right this second but I've tested it) is very good, and dipping your head isn't always that costly even if there's a tail, so again it depends. You might not get anything there but you might get a bit. So let's take a total stab in the dark and say somewhere from 1.5-3s/km overall?

Thank you for asking this question. I have been doing a similar investigation for my circa 2014 BMC Time Machine TM01. It will be great to see where I am wrong and what others think.

- Save up to 5w total for tires, particularly if your bike has space to go from 23mm tires to 25mm. Disclaimer: I am unsure about the aero loss for 25mm. I have seen suggestions to use 23mm front and 25mm rear.
- Save 3w total for two latex tubes.
- Tire pressure might come down some, but not as much as you think. Use Silca's tire pressure calculator and choose the road surface you have at IM NZ.
- In some cases, sleeved trisuits can be a wash. It is important you have no wrinkles either way.
- Consenus seems to be that the Giro Aerohead helmet works for almost everyone. Let's say 5w for that versus what's probably a Lazer Tardis. Maybe more.
- I have not looked at wheels because I have deep dish wheels. Let's say 10w total if you get deep dish Zipp, Hed, Enve, Flo, or similar.
- Last thing for me was water bottles. I used to run a 750ml bottle on the downtube. I went to a BTA and 600ml bottle on the seat tube. Now, I am going to an aero bottle on the downtube, plus the BTA and a 600ml bottle behind the seat. (The bottle behind the seat is for spares.) I'm probably saving 3w.

In total, you could be looking at 25w. To me, that's an excellent result. You can key that into Best Bike Split to see exactly what gains you get.

Water bottle, tire and tube data on AeroCoach UK. https://www.aero-coach.co.uk/...es/aero-testing-data
Tire and tube data on Bicycle Rolling Resistance. https://www.bicyclerollingresistance.com/...prix-5000-comparison (There are other articles on GP 4000, GP 5000 and tubes.)
Silca tire pressure calculator. https://info.silca.cc/...-pressure-calculator

Fast ones? They were just an example, but going from aluminium shallow wheels (my training wheels) to proper race wheels. Probably the 60/90?

I reckon I’d take 3s per km but I also reckon it should be at least that and hopefully a bit more.

That’s 9 minutes over 180ks which is not too shabby when chasing a stupid kona slot!

I thought latex was supposed to be way better than butyl and a proper sleeved suit way better than an older style two piece. My suit is quite tight though, so not too many creases.

Also, I’ll shave my arms next time...

I seem to recall the Specialized Win Tunnel folks saying that shaving legs made a significant difference, the arms not so much.

Why are you assuming that wider tyres will be faster?
Given you've got a link in the post to Silca, I presume you're aware of the testing they and Tom A have done around rolling resistance and pressure on different surfaces?
As I see it, a 23mm tyre will only be faster than a 25mm tyre if your pressure is too high on the 23mm and you can't reduce it because of pinch puncture concerns. With respect to aerodynamic drag, a 23mm tyre will likely incur less drag on most wheels. So it becomes a question of comfort and rolling resistance. Wider is not universally better. Higher pressure is faster to a point, but that point occurs at relatively low pressures if the surface is poor. It's probably best to err on the low side since the rolling resistance increase is sudden and significant once that point is reached. However, simply assuming wider is faster may not be correct, depending on the other factors.

A solid rear disc wheel would be faster and more stable.

That's a good point. Thank you. Your post reminded me about Josh Poertner's Rule of 105: "that the rim must be at least 105% the width of the tire if you have any chance of re-capturing airflow from the tire and controlling it or smoothing it". So, 23mm might be the best choice in this case.

https://blog.silca.cc/...ure-and-aerodynamics

Also, to help others new to this (like me), a 10w saving works out to about 1 second per kilometer.

https://forum.slowtwitch.com/...e_power%3F_P6780189/