I signed up a while back for Ironman Mont Tremblant in 2015.  Here is the official FAQ.

What do I need to do to seriously think about finishing.

Race day: 2015-08-16

Timing:

1. Swim start: in the water between 6:42 and 6:45 (you enter the water by age/sex group).
2. Swim cutoff: 9:20.
3. Bike cutoff: 17:30.
4. Run cutoff: “midnight.” (I need to finish by 11:42pm, 17 hours after my start, to be considered an official finisher.)

Thoughts on speed. Obviously, I need to get faster, but maybe not too much:

1. 2.4 mile swim. This is 4,224 yards, or 169 25-yard laps in my pool. If I can get to a speed of 30 seconds per lap, that puts me at an hour and 15 minutes for the swim, getting me out of the water at 8:00. I feel like this is doable, but it’s the most aggressive speed-up I need.  I will feel pretty good about my level of fitness for the cycling and run if I can achieve this. I’m budgeting 1.5 hours for the swim just in case. (6:45 – 8:15)
2. Let’s say the transition takes 20 minutes (8:35)
3. 112 mile bike.  It turns out that, to walk the marathon at 4mph (which I feel would be a good plan), it would take roughly 6 hours 40 minutes. Thus, I need to start the marathon by 17:00. Adding in transition time, I need to be done the bike by 16:40, which means I have roughly 8 hours to do the bike.  That means I need to bike at 14 miles per hour, which seems doable. I probably need to train at something like 15 or 16 mph to account for things like stopping for food or the bathroom. (16:40)
4. Transition 2  (17:00)
5. 26.2 mile run. (23:40)

Another key thing seems to be to practice transitions — if I can shave off 20 minutes there, that would help a lot with having some spare time for eating, etc.

Since I don’t have a ton of time for long runs/bike rides, I think I probably should start by using interval training to boost my fitness so that I can hit these speeds, or above. (For example: 30 second laps in the pool for a 40 minute workout, biking at 18 mph for an 45 minutes, running 3 miles in 21 minutes.)