So this past weekend I participated in a stage race that started with an 8.6 mi TT. I opted to use my Canyon Aeroad with Enve 5.6 disc wheels over a borrowed TT bike due to concerns with handling and generally being unfamiliar with a TT bike.
I averaged 300W over the duration of the out-and-back course for a time of 20:01. Interestingly a friend of mine with full TT rig and aero helmet held the same average power and his time was only 11s faster. He is a shorter individual and a sprinter with big calves. So I put my information in Best Bike Split and had to adjust CdA to 0.306 in order to get the estimated time to 20:01.
My understanding is 0.306 is a pretty low CdA on a road bike so I question how much of an advantage I would potentially get with going to a TT bike with similar wheels and helmet. If I assume 1.5 mph faster on a TT bike, my time would have been 18:58 with a theoretical CdA (via BBS) 0.255. 2 mph faster would yield a time of 18:37 and a CdA of 0.242.
I guess a few questions/observations are whether or not I held a good position on the road bike to compensate or perhaps my friend had a bad position on his TT bike and whether or not I would benefit greatly by getting a full TT bike (aero extentions out due to H11 cockpit). I’ve also heard of low CdA values in the 0.20-0.22 range so maybe there’s even a greater benefit?
CdA values in the 0.2-0.22 range are very low - you’re into the territory of pros or extremely keen amateurs who have spent time in the wind tunnel and a lot of effort to optimise every last detail of their position, equipment and kit. A more normal CdA for somebody who’s ticked off the low hanging fruit (had a professional fitting, aero helmet, race wheels, snug fitting suit, etc) but not gone further is more likely to be in the 0.25-0.3 range. So if your friend is towards the top of that and you’ve got a very aero road position then your results would be fairly similar. Could also be that you had other advantages e.g. better wheels, tires, handling, etc. Even a single turnaround point on an out and back course can be enough to make up quite a few seconds if you’ve got a good handler on a road bike vs a rider who doesn’t ride their TT bike on technical bends too much.
Other factor is length of event, a big advantage of the TT position is that by resting your elbows your upper body is supported skeletally instead of muscularly. I can hold a TT position comfortably a lot longer than I can hold an aggressive drops position. Doesn’t really factor into a 20 minute event, but the longer you go the more of an advantage the TT bike has. Particularly if it’s a triathlon and you have to run afterwards, in which case having tense/tired arms and shoulders from holding a drops position can really slow you down.
I think to gain a significant advantage over a short TT like this (compared to a good drops position on an aero road bike with good deep wheels - i.e. your setup) you need to not only have a TT bike but also spend a good amount of time riding it to nail the position and handling, and a good amount of effort optimising your setup. So if you do the occasional short TT it’s not worth the investment. And you could likely save quite a bit of time from your current setup for a lot less money than a new bike if you invested in an aero helmet, a skinsuit, aero shoe covers, maybe a rear disc (or borrow one).
Good point about the shorter duration. I tried hoods with flat forearms and managed that position for the first half before the turn around but my triceps started to burn like crazy afterwards. The aero bars would definitely help with that. We both had good skin suits but I stuck with a Kask Utopia and him with a teardrop helmet.
Ultimately it’s still a matter of cost/use. I plan on more stage races next year and want to use the off season to get used to a TT bike should I get one but yea, cost/speed is huge when I’m still out of GC on these races anyway haha.
You don’t say how big you are. In the UK TT scene there are guys who can achieve CdA values under 0.2, but they tend to be people who have done it for a long time, done a lot of testing and are small. I don’t think a Nate sized individual could ever get to a CdA of 0.2, basically due to the A component.
0.306 is pretty good on a road bike though. Last TT I did I put the file into Aerolab and ended up with a CdA of 0.36 (plus change). I wasn’t fast!
I’m guessing you did Millersburg. There is a huge amount to be gained from a properly fit TT bike. Especially for a flatish course, a road bike can’t compare.
I’m 5’7"/156 and @ 300 watts, I had an 18.27 with a BBS estimated CdA of .2341. (my visor fogged up, so I couldn’t see and had to keep moving my head and I bobbled my start). My estimated BBS CdA from my last 40k TT was estimated @ .2109. I ran a speed concept with 808 NSW front and super 9 rear, velotech speed suit and giro areohead.
Would never stand in the way of getting another bike! Plus TT bikes are fun in their own right, assuming you have roads nearby that are smooth and quiet enough to enjoy the speed without feeling you should be sitting up on the brakes the whole time. Something very satisfying about racing against the clock, plus TTTs are an absolute blast if there are any events near you and you can find a few willing club mates.
Yup that’s the one. I kept telling myself to just focus on the road race and survive the crit but deep down if I was able to get 20:01 on a road bike I know I could have been maybe top 10 for the TT with a proper bike.
Yea! The one I tried seemed really fun to just lock in and hold power. There used to be a Friday night TT at our local oval but that stopped this year and I’m not sure it will continue unfortunately.
