IM time predictor from 70.3

Those that do a 5-5:50 HIM, double and add an hour is a higher percentage of their time than someone that does 7+ hour HIM.

Conditions and race course play into how accurate this estimate is.

My HIM times are 6:36-7:05, and my IM times have been 16:33, 16:23, 15:26, and 16:53

First 2 IMs were in more hilly terrain than my HIM and last IM I was injured.

I'll tell you next weekend...

I went from a 5:36 at my first HIM to a 13:45 the following year at my first IM...on the same course (Vineman, 70.3 then Full).  However, I wrecked a hamstring in a fall less than three weeks before the IM, which pretty much ruled out a representative run...which brings up the big caveat in a thread like this:  The prediction is obviously going to be based on "all things being equal."

For me, they haven't been (equal) so far in my first two IMs, but I'm hoping for a more optimal IM result next weekend.  Went 5:25 in my last HIM and I'm honestly looking for something between 11:45 and 12:15 based on training (which would pretty much fit the X2+1 formula).

I'm gonna get another crack at this in a month. I did IMMT 70.3 in 4:54. Will be interesting how I do at the full. Weather has a huge impact on me. In the heat on the run, I wither. Hoping it won't be super hot at the end of August that far north. Also, there was ZERO wind on the bike at the 70.3, which gave me an out of this world (for me) fast bike split.

I did do a 12:05 at Placid last year, but in my opinion, that is a much harder bike and run course than IMMT.

What I am getting at is that it can be too hard to compare these types of races to one another. Too many variables! There are few opportunities to race a half and a full on the same course.

course is the biggest difference, I have done it 2x First HIM was 6:38 I got a little dehydrated that day then went on to post a 13:31 at B2B

Second time I did a PR 5:42 at Kinetic HIM with no taper 6 weeks out then... a 13:55 at IMCDA you might think what happened ? actually nothing CDA was way harder as a matter of fact I would say between 90 minutes and 2 hours harder then B2B, My Marathon time was faster at CDA that just told me that you can't compare flat sea level course to freakin climbing the Canadian Rockies.

So conditions and course really make it difficult to predict 

Agreed, and even when you can do both on the same course, they are in different seasons, which usually equates to different fitness levels, comparatively speaking. Doing an HIM and IM in the same season most likely gets you in the same fitness level department.

From the numbers people are throwing out, a rough average does seem like 2XHIM +1hr however.

Last year I did Augusta in 6:05.  Followed 6 weeks later at IMFL with 13:19.  So pretty much right about in line.  Of course with a 17 min transition I might have thrown off the curve   Also took it pretty easy in FL.  Had a great day. 

This year looking to go sub 6 hr in Augusta and around 12:30 at IMFL.

enjoy,

Duane

got ya.....yes I divided first than subtracted...

So many factors to consider, but from what others have said, this seems like a decent "guideline" from which to START a prediction.

Just a few factors that would add/subtract, possibly with a significant impact on time would include terrain, temperature and fitness. As was also pointed out, 1 hour on a 10 hour IM vs 1 hour on a 16 hour IM is very different as a percentage of the time.

I did my first HIM, the very challenging Auburn Half on May 20, with 6k feet of climbing on the bike and about 1.5k of climbing on the run. The first 500-800 of my swim was horrible, but a learning experience that I will take to the Vineman next Saturday the 28th....my first Full. At Auburn, I did a 5:32 (lost about 6-8 minutes due to a wrong turn on the bike and then a dropped chain 3/4 mile from T2...had to run with my bike the final 3/4 mile!)....so this "baseline" of "x2+1 hour" would predict at 12 hour full....the terrain on the Vineman is hilly, but nothing like the 1/2 that I did....the temp should be comparable, but my fitness has continued to improve. I'm expecting sub 11 hours, with a 10:30 being my goal time....but, as I've been told, you just don't know how your body will react to a full until you've done it!

(Oh, I have installed a "chain catcher" so I'll never drop that damn chain again!!)

This is obviously very much a "rule of thumb." 

For me, my half PR is 5:23:26 and my IM time was 11:31:39.  So about double plus 45min.

I think the guideline also depends on who you are and your physiology.  My half iron PR is 4:35 and my iron PR is 9:32- set about a month apart- that is 2x + only 20 mins- but I am a kind of "one speed only" guy- i.e. i got about the same speed for a sprint as for an ironman (i.e. i am much better at ironman).  I have clients who are the exact opposite though- huge short distance power, but no endurance.  

But overall watching a lot of athletes racing halts and fills id vote for the 2x + 1 hour thing- but it only works if you compare comparable courses.

I think it's more just a fun numbers game than a guide.

That said, in July 2010, I was 5:44 at Musselman (double + 1 hour would be 12:28).  At IMFL in November 2010, I went 12:34.  Similar courses with similar weather conditions and consistent training between.