Curious what you guys have found is the difference in your full ironman average bike speed vs half ironman bike speed. Obviously course and conditions would affect this, but given the same course and conditions, what is about the norm?
I found a large difference in mine last season, albeit different courses with completely different terrain.
IM Santa Rosa- 18.5 mph- this was a rolling/ hilly course. Racing in mid Zone 2
IM Indian wells- 21.1mph- this was a pretty flat course. Racing in low Zone 3
Probably 10-15 extra watts (NP) between a half and a full… not idea what that translate into for speed (are people still looking at speed while racing ?!?)
That is tough to answer as I have not done races where there is a 70.3 and full IM that I have raced. The power difference is easy to note but to understand the speed differential would require doing a 70.3 and full on the same course. One could likely use BBB to estimate the speed difference.
IM 70.3 Elsinore 39.6 kph (24.6mph) 240w (400m elevation)
IM Hamburg 36 kph (22.4mph) 220w (650m elevation but windy)
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I personally feel that power is better as a comparison than speed. It is a little more relevant if the IM and HIM happen to be on the same course. Courses are different and things like hills, wind, road surface quality, turns, temperature, etc. can change speed on any given day. I tend to aim for around 70% power in an IM and 82% in a HIM. I do have an example of the same course at Mont Tremblant: 2:18 for a half and 4:51 for a full are my best times and around those power %’s above. My best ever HIM bike was around 2:09 on a flat and fast course - on an IM equivalent I figure I’d be in the 4:30-4:35 range.
The same course thing is a good way to compare. For me it’s weird because I’m a diesel and my HIM and IM watts aren’t that much different. OTOH, if I’m “racing” either, I sometimes get a big split because I’ll go harder on a HIM and easier on an IM for tactical purposes.
I’m guessing 2mph is typical though, irrespective of power, race dynamic, drafting due to race start format logistics, number of competitors, etc.
When I want to estimate something like this I use the equation speedA/speedB = (powerA/powerB)^(1/2.7) … should get you close, all else being equal. To answer your question directly I typically go ~24mph on a fast half and ~23mph on a fast full.