What is the time savings with a firecrest on an ironman course?
According to Zipp’s data -
808 (old) front + super 9 disc = 104s saved over 40km
808 (fc) front + super 9 disc = 113s over 40km
(9s / 40km)
= 40s over IM 180km faster.
808 (old) wheelset = 81s saved over 40km
808 (fc) wheelset = 96s saved over 40km
(15s / 40 km)
= 1m07 over IM 180km faster.
It depends on wind conditions and how fast you are and what bike your riding. I think the more aero your frame is, the more it fares the wheels and reduced the impact of disc vs deep rear. Disc probably helps the most the more turbulence you have, as it smooths the air somewhat before it reaches the trailing edge.
My own anecdotal evidence at least, not owning a disc, when comparing my race times at disc. legal races vs. my time at Kona, tells me that the difference in the real world, is minimal at best. At low yaw, the old 808 or 404 front is still pretty fast. There was some article recently showing that the amount of time spend at yaw angles over 5 degrees was actually lower than previously estimated, and therefore the time savings data from wheel mfg’s is less than is seen in the real world. However, in an IM< which is slower, you might see more savings.
I know BBS doesn’t give much “weight” to a disc vs. a deep wheel unless its high yaw.
Those quoted Zipp numbers are one possibility, but something this close will also depend on tire choice, how windy your IM is, and your speed on race day. The old 808 with a 20mm supersonic on it is VERY fast at low yaw. If you don’t want to use a 20 mm tire, then the pendulum swings back more in favor of the 808 fc. If it’s going to be really windy, the 808 fc will definitely be faster (and easier to handle). I could see the older 808 being faster than the 808 fc under the right conditions. YMMV.
Those quoted Zipp numbers are one possibility, but something this close will also depend on tire choice, how windy your IM is, and your speed on race day. The old 808 with a 20mm supersonic on it is VERY fast at low yaw. If you don’t want to use a 20 mm tire, then the pendulum swings back more in favor of the 808 fc. If it’s going to be really windy, the 808 fc will definitely be faster (and easier to handle). I could see the older 808 being faster than the 808 fc under the right conditions. YMMV.
The FC performs pretty smokin fast with the 20mm on it as well.