I don't have much to offer since I have the exact same issue. I am more interested in seeing others' responses to this, especially part 2.

I always assumed it was the bike which killed my run time in the 2 1/2s I've completed. I'm by no means an accomplished distance cyclist and so I expended too much energy on the bike leg to be able to even come close to the race pace I trained at. I'm not sure what your biking background is. So this season I was also planning on doing more bricks to work on the leg adjustment from bike to run as well as just improving my bike efficiency, mainly by teaching myself to ride at a higher cadence and to throw in more long rides. I am not doing another 1/2 until next year (my A race this year is olympic), but I have already gotten out and ridden a 40 mile ride and plan to keep building on it since I'm only in base1 of my training plan. I figure that my A oly race this year is really more like a B race on my 3 year plan to build to my first IM (hopefully in a decent time).

What jumps out at me is what you didn't talk about: The bike. What is your bike effort and pace like before you started your run? If you can run low 8's at the 13.1mile distance - just the run - but slow down to 9's and 10's per mile once off the bike, I would look at whether you are pushing too much on the bike. You can only go as so hard and still have some left for the run. Next, I would look at your cadence. If you are holding a decent pace but mashing at 50-70rpms, you are blowing out the legs before the run. Possibly consider spinning at a higher cadence. Finally, you may need more bricks (as you noted). Not just more, but better. I think bricks tear you up more than build you up, so be judicious with them. I wouldn't recommend more than one bike-to-run brick per week, and then 5k tops at race pace.

For a half: I would probably do 4-6 13.1 mile runs at race pace up to one week out from the half. I would treat those runs as discrete workouts as if I were only training for a half marathon. For example, the Saturday run would be 13.1 or so at race pace. For bricks, I do 100k bikes followed by 5k track runs, typically on a Sunday. Then take about 48 hours off. Which would give you the most benefit: Bricks or Long Run? I'd say bricks. You've been doing the long runs and it turns out it doesn't transfer to the race. Look into brick workouts specifically for Half IM. But ideally you would do both, possibly on alternate weekends. One weekend the key workout is the brick; the next is the long run. The key to a brick is to simulate - I think - the first 5k on the run. This is completely anecdotal from my experience, but the first 5k in long course is a killer. After the legs flush out the lactic acid in the quads from the bike, the hammies take over and it feels more like a normal run. So tear it up on the training ride (40-50 miles) then focus for 5k on the run.

A SLOW run split could be from a swim/ bike pace that was more appropriate for Olympic distance or from poor hydration/ nutrition, but you said you BONKED. That's a serious depletion of energy stores or hydration.

I believe we SLOW DOWN from moderate fatigue, but we BONK from seriously low fluid/ nutritional stores.

My bike pace this past weekend was an average of 20.3 MPH at somewhere between 88-93 rpm. I was conciously trying not to push the bike too hard knowing the run was coming up, but it is possible I overdid it. My training bike rides were generally averaging somewhere around 20.5 and that included all the stop/starts which tend to lower your arerage a few tenths. All in all, I didn't try to mash the bike. I did drink way too much of the gulf of mexico on swim and did have a bit of an upset stomach. It may have impacted my food intake, but I think this time I got the hydration right (or at least better). In my first half my nutrition plan went out the window since I was riding rolling hills that I was not used to and consequently I didn't drink/eat like I wanted do. At about mile 12 of that race I had to actually stop for 5 minutes or so I was so wrecked and when I did start back up, I couldn't run for more than about 15 seconds. It may not have been a true bonk, but I think it was close.

So back on the bike question, if I'm riding 20.5 MPH on a long training ride (60+ miles), doesn't that seem like I should be in the same range for a race or should I be conciously trying to back off another half MPH or so?

Braden

+1 to jedi master RV. What is gained on the bike, for many, is often lost on the run. Also, I'd consider doing at least one if not two overdistance runs in training...15 to 18 miles at your training pace.

Another item to consider is whether you were using a tri bike or an adapted road bike, the more upright position on a road bike uses more of the hip abductors which are needed for the run. you then start the run on musles which are already tired hence slower times.
The steeper position on a tribike helps your "running" mustles come off the bike fresher and you should be able to hold a faster run pace.

If your stomach was feeling a little off, I'd suspect you didn't absorb as many calories as you normally would. You may have put the correct amount of calories in, but a good portion of it remained in the gut.

RV on the nose.

I disagree that 18 mile runs are necessary for good HIM performance. 14-15 should do the trick. I mean why would you go further than that? You don't do 30 mile runs for marathons...

As RV said, bike pacing is KEY. Once you know what you SHOULD do on the bike, you can then tailor your nutrition to that effort level. Most people can get by with 250 cal./hour on the bike during a HIM, no matter their size. You just aren't out there long enough for nutrition to be a huge impact unless you seriously UNDER or OVER do it.

Liquid calories are always easier than solids.

One other thing--HIM race rehearsal should be in your training plan. Do one about 3 weeks out from a race. You don't need to swim--it's fairly short. You bike 56 miles AT RACE PACE and then run 5-6 miles, also at race pace. This will tell you a LOT about what you should be able to do under race conditions. Since this is a fairly stressful session, make sure and take the day after it off.

What is your bike training? Whereas I said I wouldn't necessarily do >14 mile long runs, you can and probably SHOULD do overdistance long rides, maximum 4 hours is all you should need.

A good cyclist should be able to get pretty close to their open half mary time in a HIM, so if you blow up on the run, odds are you either aren't that strong on the bike or you just went WAY too hard, as others have said.

From a power perspective, I find I run well in a HIM if my bike effort is around 80-85% of FTP (Functional Threshold Power), which is like about the same % of your LTHR if you don't train with power. Thing is, it's pretty easy to ride for 2.5-3 hours HARDER than that if you don't have to run afterwards, which is why I guess a lot of folks try and ride that hard and then think their run won't suffer. 2 words: IT WILL.

Hi guys - I had problems on the run too on a just completed 1/2 IM. Rather than hijack this thread have started a separate one at http://www.trifuel.com/forum/13034/bad-cramps. Any help appreciated!