Half Marathon PR (modern day): 1:22:25 (Sept '05) - few months before first ever half Iron. Lots of speedwork.
Half Marathon half Iron PR: 1:30:17 (June '06). Very little speedwork.
Averaging things out, although I don't race the half marathon all that much, I'd say I could pop off a consistent 1:24. Under if I did more speedwork.
I've now done 4 half Iron's. Each of them I've done in about 1:30-1:32 (MiamiMan: 1:31, Mooseman: 1:30, Musselman: 1:30, Devilman: 1:37). My pace in my last half Iron put me in this pace category, too, although the time was slower due to two Portohead breaks.
So my difference is roughly 8 to 10 minutes.
But... I'm am a huge proponent that your bike is the gatekeeper to being able to run to your ability. The stronger you are on the bike, and the better you can recover from extended exerted efforts, the better you will run. This is why intervals are very important on the bike. And you have to get your legs used to running off the bike.
