Brucey wrote:TT bikes are faster for sure, but mainly because you sit on them differently, as per the photos I posted upthread. The bike itself accounts for roughly 10% of the total aero drag. If you are doing (say) 25mph and you get rid of the drag of the bike entirely you won't go 2mph faster.
cheers
Long ago, when road racing, I did TTs as a sort of training for breakaways and getting-back-on solo riding at speed. I did the TTs on my road bike, since that would be what I was road racing.
A lad I knew was selling his rather swish TT bike for very little (£150) despite it being made of exotic Columbus tubing with Campag Record gubbins. It did have a small front wheel, though, to get the front end lower and thus the rider lower. I put aero bars on it and did a few TTs on that, just for fun. I was slower than on the road bike.
This was confusing at first, since I was definitely in a more aero position. Sadly, it didn't suit my physique, which is of the not-so-supple type. I couldn't get the power out as I could on the road bike.
So I might have benefited from aero wheels on the road bike. A few lads tried putting in a rear disc wheel but did no better (on their road bike). Many complained of the racket they made. The also tended to weight a ton, so only a flat course was going to see any improvement at all ... assuming a gust of side wind didn't deposit you on the verge or under the wheels of a passing lorry.
Some TTers did have low profile frames with disc wheels and those queer helmets. They sometimes went fast but we roadies always enjoyed the ones who went slow, despite all their gear.
These days I don't give a toss about my average speed or anything other than the cycling .... which does include trying to drop the others up the hills and winning the sprint for the village sign. But that's just olde pharts having fun and doesn't require a technology-based marginal gain, especially one of 40 seconds over an hour at 25mph.
Cugel
“Practical men who believe themselves to be quite exempt from any intellectual influence are usually the slaves of some defunct economist”.
John Maynard Keynes