How Fast are Triathletes as Bike Racers?

Chris Lieto aside, I wasn't sure how fast some of the pros were in a bike race setting (Lieto is fast).  Here's a cool thing Macca did.  Macca was invited with 8 other athletes to experience the prologue on the Tour of California course before the pro mens field left 10 minutes later.

"My race start was set for 12:58pm. I headed over to the start 10 minutes before my scheduled departure and drank in the atmosphere. It was huge. The place was pumping. Once up on the starters house I got my countdown and took off.

The course went 400 meters down before taking a hard left turn and then another 200 meters before another hard left. After these two turns, it was all a false flat to the finish line.

my legs were screaming for a while after and my lungs were sore from breathing

I roared out of the blocks as hard as I could, and before I knew it I was turning a hard left. I accelerated out of the saddle again and then took the next left. It was here I saw the huge crowd and thought, WOW. I was pushing a relatively nice cadence of about 95rpm and sitting in my 53:15 gears. I felt great and rode the bike as hard as I could. Like the guys said, I really started to taste the lactic acid about 2 minutes into the effort and was at maximum effort.

I simply could not push the bike any harder, even if I had tried. I came around the turn with about 200 meters to go and really enjoyed the buzz. I was in pain but it was a nice pain. I did not have the fast twitch fibers to get any more speed out of myself, and this really limited the ability of myself to go any faster.
I stopped the clock at 4:24, which was cool. I was content but definitely not as fast as I have been when I was a short course boy. I really got the buzz but my legs were screaming for a while after and my lungs were sore from breathing in so hard to capture the air needed to feed my muscles.

The overall race winning time was 3:52, so it is amazing how quickly these guys can ride their bikes. Fabio Cancelara who won the day, rode 8 seconds quicker than the rest of the field. He was amazing to see.
I really enjoyed the experience and had a great time. These boys really earn their money, and I have to say that the sport of cycling is cool. Everything about the day was awesome. I loved it. I had a great weekend in Northern California and will enjoy watching the rest of the Tour of California on TV.
I am now off to Valyermo and a clinic with bike fitting guru Dan Empheild to look at my bike position and take part in an accreditation course to add to my knowledge about bike position. It will be really interesting".

Macca would have finished around 123rd place (out of 132) - but I bet if each rider had to ride each stage as a TT followed by a 10k or longer, he'd do a little better.