Did a bit of an aero test.

Two weeks ago, did a 100 mile time trial. Conditions were about 70 degrees at start, 95 at end. Winds about 10-15 mph, mostly headwinds on the first half of the out and back flat course. Used a Bianchi 928 SL with Ksryium wheels, Veloflex clinchers, and aerobars. Regular helmet and clothing. Time was 4:58, about 20.1 mph.

Yesterday, did the same course, almost exact same conditions, but on a Cervelo P2C, Zipp clincher disc and clincher 808, Veloflex clinchers, cowhorns and aerobars, and semi-aero LG Chrono helmet. Time was 4:39, about 21.4 mph. (Not saying these are great results, they just are what they are.)

The aerobars were set about the same height relative to saddle each time. The Bianchi has a 73 degree seat tube angle, but the Cervelo in the forward position is about 77-78.

The effort was similar, and if anything, I didn't go quite as hard on the Cervelo (I've done these kinds of things for years, so I have a pretty good idea of repeatability). The time trial bike is very clearly faster in those conditions. I think this test is very indicative of predicted results and anecdotal results of others. If not for the aerbars on the Bianchi, the spread would have been even higher, at least another .5 mph.

The Bianchi was a bit more comfortable, as the Cervelo seems to put more weight on the arms and shoulders. But, for that time period, at least, it was tolerable. For an hour, no problem whatsoever.

So, for all those inquiries about "how much time can I save with time trial bike," I think this is a good reference.

Did a bit of an aero test.

Two weeks ago, did a 100 mile time trial. Conditions were about 70 degrees at start, 95 at end. Winds about 10-15 mph, mostly headwinds on the first half of the out and back flat course. Used a Bianchi 928 SL with Ksryium wheels, Veloflex clinchers, and aerobars. Regular helmet and clothing. Time was 4:58, about 20.1 mph.

Yesterday, did the same course, almost exact same conditions, but on a Cervelo P2C, Zipp clincher disc and clincher 808, Veloflex clinchers, cowhorns and aerobars, and semi-aero LG Chrono helmet. Time was 4:39, about 21.4 mph. (Not saying these are great results, they just are what they are.)

The aerobars were set about the same height relative to saddle each time. The Bianchi has a 73 degree seat tube angle, but the Cervelo in the forward position is about 77-78.

The effort was similar, and if anything, I didn't go quite as hard on the Cervelo (I've done these kinds of things for years, so I have a pretty good idea of repeatability). The time trial bike is very clearly faster in those conditions. I think this test is very indicative of predicted results and anecdotal results of others. If not for the aerbars on the Bianchi, the spread would have been even higher, at least another .5 mph.

The Bianchi was a bit more comfortable, as the Cervelo seems to put more weight on the arms and shoulders. But, for that time period, at least, it was tolerable. For an hour, no problem whatsoever.

So, for all those inquiries about "how much time can I save with time trial bike," I think this is a good reference.


that's pretty good to the results anecdotally that I have gotten....I have a 26 mile loop that I ride frequently by my house, about a month ago I rode it two days apart in similar weather conditions. The first time I rode my TT bike, A QR with a 76 degree STA, no aero helmet, velocity deep v rims, I averaged 22.4 miles an hour, I'm sorry but I didn't write down the time, the second time I rode my Specialized Allez with Mavic Aksiums...same helmet, same percieved effort. I averaged 20.7 miles per hour the second time. I figure it's good for approximately a 1.5 to 2 mph increase. So your results appear similar. I think if I go with a disk and an aero helmet I might get an extra 0.5ish mph increase, but we'll see.:thumbsup:

Two weeks ago, did a 100 mile time trial. Conditions were about 70 degrees at start, 95 at end. Winds about 10-15 mph, mostly headwinds on the first half of the out and back flat course. Used a Bianchi 928 SL with Ksryium wheels, Veloflex clinchers, and aerobars. Regular helmet and clothing. Time was 4:58, about 20.1 mph.

Yesterday, did the same course, almost exact same conditions, but on a Cervelo P2C, Zipp clincher disc and clincher 808, Veloflex clinchers, cowhorns and aerobars, and semi-aero LG Chrono helmet. Time was 4:39, about 21.4 mph. (Not saying these are great results, they just are what they are.)

20 minutes over 100 miles means 2 minutes in a 10 mile time trial. Your aero equipment probably isn't worth that much, especially at that speed. The numbers you see repeatedly are more like 75% of that, but within reason you are close. The danger here is that without knowing your power numbers, much of the difference could have been due to your feeling better one day than the other.