After a few seasons of TTs and hearing numerous times how adding clip on TT bars to road bikes typically adds a few km/h, I thought I would give them a shot.
Strange outcome however.
On a closed road 10 mile TT, I ended up beating my previous best by a mere 1 second.
Weather with TT Bars:
Weather impact 2.6%
42% into a Headwind @ 12.8-13.4km/h
Temp - 20.4c
Weather without TT Bars:
Weather impact 2.6%
49% into a Headwind @ 13.7-15km/h
Temp - 20.9c
Now I wasnt expecting miracles, but either TT bars aint all they are cracked up to be, Id set them up completely wrong (used a guide on British Cycling & advice from the guy who does my bike fits) or my aero hoods position is dialled in really well.
You need more time riding this setup and make small adjustments so that the position works in your favor. I wouldn’t expect any mayor differences over 25-30 mins without investing a lot of time optimizing your setup to the last mm.
So IMO, they increase … your time spent optimizing your position on the bike quite a bit.
Being more aerodynamic (lower CdA) is about improving the combination of slipperiness (drag coefficient, Cd) and reducing the area (A).
Aero bars typically, but not always, reduce your Cd by putting your arms online with your torso and reduces your area by bringing your head lower. But if your position without the aero bars is already very low, then bolt on aero bars may bring you up enough to increase your area and counteract the effect of bringing your arms in.
Try getting pictures of you from the side and front in both setups to visually compare areas. If you get video footage walking around you, there’s a website to estimate your CdA 20 second Video to CFD (Aero Drag) test is HERE!.
Also, every time you move your head, hands, or arms the airflow can detach and take a while (seconds) to attach again. You’re slower during that time. So try to keep a steady position and if you take position breaks it’s better to make them a bit longer and less frequent.
Makes sense to me that there might not be much in it between the clip ons and aero hoods position if your hoods position is good and you can hold it well for the duration of your event. The TT bars come into their own when trying to hold that position over much longer distances where they make a way bigger difference to postural fatigue and continued ability to put out power late in the event. You’ll probably see the gap between the two increase if you ride the clip ons a lot and get really comfortable in them (and inadvertently stop training your aero hoods position as much in the process), but I don’t think it’s weird that a good aero-hoods position yields functionally the same CdA as an average clip-ons position.
(I’m no TT specialist and I can’t hold aero hoods for 30 mins myself, but I do train various aero positions including aero hoods, puppy paws, and clip-ons for ultra-endurance racing - in that world I’d say all three aero positions are fairly comparable so it’s just about what’s sustainable to hold for the longest and when it’s most effective to use each of them.)
I forget what the numbers were when I did it but I put a lot of it down to being able to shift whilst staying aero and the braking position was more aero too.
I get that, I just did not expect even a good aerohood position to be almost equal to an OK aerobar setup. I’ll take it as a compliment I guess
This is probably true, however I wont be spending anymore time setting them up. Only a few TT’s left this season (most of which im tied into a roadbike cat) and Ive got a Felt IAx im building up for next season so that will be getting all the attention. Atleast it highlights the importance of minor tweaks.
I dont remember taking any breaks and did find them quite comfortable with my more steady HR I think showing that. It certainly felt higher than my aerohoods position though so it could be that counter effect you mention
