Zipp 900 Disc with 23mm tyre OR Zipp 808 FC with 25mm?

Equipment
1

Hi Y’all,

I’m currently training for Ironman Cairns (fairly flat) in 28 weeks. My race wheel options are Zipp 900 disc with 23mm, or the matching Zipp 808 Firecrest with a 25mm (either option would be with Vittoria Corsa tyres).

As the Zipp 900 is quite narrow, I don’t think the 25mm will work/fit that well, so got me thinking - will the drop in rolling resistance of the 25mm tire on a 808 outweight the aero benefits of a disc??

For reference, I will be running the Zipp 808 with 25mm at the front.

Edit - wheels are tubulars.

Any thoughts or advice appreciated.

Cheers,

2

The disc is going to be faster than the 808 by a pretty significant margin. I would be surprised if the difference between a 23 and 25 outweighed the aero advantage, but I’m just speculating.