road/crit bike vs tt bike

it really depends.

aero wheels will buy you time, but then you can put them on a road bike.

integrated aero bars instead of drops definately cut down on frontal area.

a time trial frame will not buy you all that much because of the "aero" tubing etc, the question is whether it can get you into a realy low aero position that you cant otherwise get on your road bike.

in my experience, going from time trialling on a road bike with spoked wheels to a dedicated tt bike with aero bars, aero wheels, very low riding position (flat back, chris boardman style), the difference can be 2-3mph.

it really is the package of aerodynamic aids that matters, not one individual thing. there is however some order to the benefits you can get, probably in this order:

tri bars
lower position
aero wheels
aero helmet
integrated bars
aerodynamic frame design

9606 said:

How many miles/hr will a tricked out tt bike get you over a good road/crit bike with clipon aero bars?
Assume 24 mph for the base speed of the road bike. Assume 170# rider. Assume same course. Assume same power output. Yes, I know analyticalcycling.com can probably give a good answer - only after my steep learning curve. I am just looking for a reasonable estimate, by someone who has more skill at ac.com, of from being in the industry.
Thanks

Read an article off the www.cervelo.com web site that basically said over a 40k course you can pick up roughly 6 mins with a good rider aero profile, 2 mins with a good set of time trial wheels and 1 min with an aero frame.

Hi, the main differences between a dedicated tt machine and a regular road bike will be the use of narrow and air foil shaped down tubes and front fork and head tube, possibly (with the more expensive ones) rear and or front wheel integrated into the frame somewhat. Also cableing will be hidden on the front. An aero shaped handlebar usually comes standard with tt bikes but can be had on a regular road bike as well. A good tt frame will take about 1 minute off a 40 k TT, or even more.

Aero wheels will take about a 1:30 off a rider at just over 40 kph (hed tri spoke front or similar + disc rear) vs conventional round 32 spoke box section wheels. Good deep aero wheels include Corima, Zipp, Hed, Campagnolo Bora.

A good aero helmet will take a little under a minute off.

Adjustments to riding position and being able to constantly hold that position for the entire race (of course you should stretch sometimes) will yield gigantic improvements. Being properly able to roll the hips over into a flat back tt position (while riding on aerobars) can cut considerable amounts of time off a 40 k TT, even if using standard cowhorn bars. Adjustments to the seat height, seat fore/aft position, frame sizing, crank length, or distance to handlebars through use of lower/longer/shorter stem can yield fair increases in power and comfort, and thus speed. For me I've discovered a longer reach with a longer stem allows me to get a full breath of air when down low, and has already increased by training speeds about 0.5-1 km-hr. I'm thinking about trying 185 mm cranks now.

-Bikeguy

A TT frame alone will save you ~45-55 seconds in a 40K TT (flat, no wind) at the speeds you're talking about. Everything else (wheels, helmet, skinsuit, etc.) can be used with a road frame. The other frame consideration, as noted by robkit, is the position it allows you to get into. That could be huge (e.g., several minutes), depending on how aero your position is on your road bike. BTW, don't forget about the time savings of riding with a PM. I consider that to be equal to or greater than the benefits of a TT frame, depending on the course (grades) and conditions (wind).