I faced this problem in the Lubbock 1/2IM recently, and as I am considering getting a power measurement tool, I was wondering how you handle temperature differences.
In my training prior to Lubbock, I have been experiencing temperatures in the very high 90’s just like I expected in Lubbock. I had a very tight HR range for the bike since I had trained for so long in similar heat, I knew exactly what I could handle. When race day came, it was cool, windy and cloudy, and about 15 degrees cooler than I had anticipated. I was forced to rely solely on RPE for pacing.
Doesn’t your power output also depend largely on temperature just like HR? If I could maintain 225 watts for 56 miles and still have a good run in 80 degree heat, It stands to reason that If the temperature climbed to 95 degrees, then I could sustain much less than 225 watts over the course. In the end, you would have to rely solely on RPE just as I recently had to in Lubbock.
By training with power you will learn your body’s response in terms of sustainable power under different conditions. My 1/2 this spring was projected at 230W avg based on training. Race day came and was in the 90s, or about 15 degrees hotter than the hottest day to that point. I adjusted my power target downward to 210-220 and had the race of my life. As you noted, though, ppower is only one metric for helping your pacing. It is very powerful, but cannot be your sole method of pacing. One of the biggest plusses to riding with power is to monitor your power over hills and rolling terrain. Instead of seriously spiking power as most riders do, even when trying not to, you can limit the wattage spike to your own zones. For instance I limited any wattage spikes on hills in that 1/2 IM to 325, or LT wattage. I think power fulfills the promise that hr training/racing has never been fully able to do.
Well, that’s where the PT system gets a bit more expensive. If you want a race specific wheel you’ll have to get another hub. You can lace it up to any 28 or 32 spoke race rim you’d like. Graber/CycleOps offer the hub factory laced to a Zipp 404 or 303 rim if you’d like. Price is about $600 or so, but I don’t remember specifically. If you want a disc with the PT your only option is something like the CH aero cover. I think ExcelSports still offers those. Personally, The advantage of racing with power metrics outweighs the difference between the 404 rim and a disk, especially over distance. Racing with power is not as useful at short sprint distances since you are racing in the red anyway.