Isn't it a bit late to be thinking about this?

Whatever you have been doing in training to this point is what you should be doing.

Right. Don't overbike but don't ride a like a tourist either. Keep the best power output you can and still run off it. Then keep the best run pace without blowing up and walking.

But what is that? Only you know.

Have you been using HR as a metric in training? If not, a race might not be the place to start. If you have, what zones have you been using for training and how has that worked for you?

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Oui, mais pas de femme toute de suite (yes, but I am not ready for a woman straight away) -Stephen Roche's reply when asked whether he was okay after collapsing at the finish in the La Plagne stage of the 1987 Tour

If this is your first, my only advice is that the first half of the run should feel slow. It took me four times at the distance before I learned to pace correctly. If you know your zones I'd keep it in high z2 for the first half. Then if you're feeling good open it up on the back half. My best runs off the bike have been negative splits.

Here's a story of two races - how to do it and how not to do it. Once you start walking paces go straight down the toilet.

Yes I've been using heart rate monitor, max is about 180 so I'm hoping to keep it around 140 for the race ? Most of the oly races I've got away with 155-160 but that's only 25 miles on bike

With a 180 max HR, if it was me, I would look at doing about 135 bpm on the bike and 150 for the run. In your training, what hr have you been training at?

I hold about 10% higher HR on the run than the bike. For me that is about the same RPE. But that is my n=1, and I'm definitely not FOP.

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Oui, mais pas de femme toute de suite (yes, but I am not ready for a woman straight away) -Stephen Roche's reply when asked whether he was okay after collapsing at the finish in the La Plagne stage of the 1987 Tour

I feel like 135 -145 is best idea but i also have a hard time with my ego telling me I'm going too slow ? i guess I just need to trust the system and push it on the run if I have extra energy .

I am 52 years old and like to keep my heart rate around 177.

Jim you're telling me you can hold 177 for 6 hours ? That's outstanding, well done

When I was in my 20s, I would keep my heart rate at 187.

Thanks for the fun facts Jim but you're contributing nothing to my original post.

I don't know if I can physically can keep my heart rate this low. My threshold heart rate is about 185. If I jog faster than a 10:30 pace, I'll break 145. I try to stay low 160's and will let it drift into the 170's towards the end of a long run.

A lot of people suggest 80% of max heart rate which puts me about 145 , I can usually do 165 on my bike rides for couple hours but I'm worried about bonking on the 13.1 run. I'm def a better cyclist than runner so maybe I just ride my normal ride , and slow down the run pace .

Just showing that everyone is different.

This might sound unhelpful to your original post, too, but for me, my HR is *always* way higher during a race than training, esp. on bike -- i.e., I've done enough races to know that my heart rate targets for rides/runs isn't something that I'll hit during a race (for example, I might do a harder effort on the bike at 150ish, but I'll average 165+ on the bike during a race). For a variety of reasons, I'm sure, not the least is hopping on the bike after swimming.

During the bike, esp. in a longer race, I just try to bring it down once I get on the bike and then monitor during ride to try to keep it steady and or dropping a bit.