Assuming it fits properly, does anybody have any idea of the time savings that can be expected over a half iron bike course from wearing a Fusion Speed Top as compared to a tight fitting tri top? In wetsuit legal races, can the Speed Top be worn under the wetsuit or does it impede upon shoulder rotation? Is the Speed Top comfortable to run in?
I don’t know much about the Fusion Speed Top, but the Castelli Stealth Top is similar and is made to be worn during the swim and bike and removed in T2. They claim 3:01 time savings in an Ironman at 23 mph…
Assuming it fits properly, does anybody have any idea of the time savings that can be expected over a half iron bike course from wearing a Fusion Speed Top as compared to a tight fitting tri top? In wetsuit legal races, can the Speed Top be worn under the wetsuit or does it impede upon shoulder rotation? Is the Speed Top comfortable to run in?
I have the top but have not raced it. Warning: it fits very small (I am 5’10.5ish 150-155lbs with a small upper body and went medium).
It could definitely be worn under the wetsuit. I would compare it to the Castelli Stealth top, which is not yet available for purchase. I see no reason to run in the top, that is not its purpose.
It is possible I will have some tunnel results from this top in the next 4-6 weeks.
I ve got the Fusion Speed Top, and yes it is very slimfitting and I wear an XL, and am 182cm with 86kilos. It is possible to wear it under the wetsuit, but it depends on how tight your wetsuits sits around the shoulders, I at least find no issue with it. I see the top more as a bike leg top to keep myself a little warmer if its a chilly bike leg. I m not able to comment on the time savings on it, as I m not the quickest fullstop. 
I would not recommend it to be worn whilst running, at least I find that I overheat to quickly in it. But again it comes down to ones own preference on it, as it is not uncomfortable to wear, and I did not notice that I was wearing a speed top. Just the overheating issue, was a bit of downer.
James, I will be very interested in your wind tunnel results.
Any news on wind tunnel results on the Fusion Speed top?
I will likely try it or the Castelli T1 stealth this season.
Anone have experience with both and can give a comparison? Can both be worn under a wetsuit?
I only do wetsuit legal races, so I would prefer a top to wear under the wetsuit.
I don’t have any wind tunnel data at this time. From what I have been told from those who have been to the tunnel in various outfits is that it depends a lot on the individual. There was a group that went out to the Velodrome in LA and they had mixed results on about a half dozen tops depending who was wearing what.
I can tell you the Fusion top is designed to be worn under the wetsuit and then discarded at T2. Try it, if you don’t like it I will be happy to return it for you at any time.
Chance Regina
so the thinking behind the product is to change your shirt in t2? Doesn’t that waste time? I suppose tossing on a singlet top is quick and probably more comfortable for the run though.
No idea about the time savings but i used it for th first time last weekend @ IM cabo. As expected we had a blistering hot bike portion, I drenched the shirt at every water station in water. It kept me cool through the bike leg. Furthermore no sun burn like last year. The shirt literlally pops off your body when opening the zipper in T2, so no time loss here. I grabbed my Tri Shirt (which also has a full zipper) and ran out of T2 in about 2 minutes…
Typically you would wear your TriTop under it. Then when you are in T2 it pulls right off. Maybe costs you 5 seconds. Jordan Rapp used it in Oceanside. Maybe he can comment on the amount of time it took to get off.
It’s really not designed to “change” in T2. I guess you could for a 140.6, but for 70.3 (or even 140.6), the goal is to just wear whatever you are going to wear for the run underneath.
In Oceanside, I had a one piece tri suit on underneath.
For St. George, I will also wear a one piece.
For Texas, I am tentatively planning on a two piece, and will very strongly consider a “swap” from the long sleeve only for the bike to a Fusion vent top for the run - http://www.fusionsportsusa.com/triathlon/competition/vent-pro-top I may just wear that vent top for the whole race. Need to test.
Also considering this - http://www.fusionsportsusa.com/triathlon/competition/triathlon-ice-top - with a cooler in T2 with the ice packs in it.
But as far as time to take it off, I wasn’t lightning quick in transition, but taking this top off had nothing to do with it. I would say it was even less than 5sec to take off the top. I’d say, at most, it probably took not more than 3 seconds. One-one-thousand-two-one-thousand-three-one-thousand.
Taking OFF clothes is pretty fast in almost every case. What you tend to want to avoid is putting ON clothes.