You see the bike race numbers mounted in a number of ways. In fact, I have seen them flapping around on very expensive, super aero bikes. Even the PRO’s will have them stuck on any which way.
If your bike has a round seat tube you can fashion the race number to mimic a more aerodynamic airfoil shape. However, my race bike already has an airfoil shape.
Here is how I like to mount my race number.
Take your race number and wrap it around the tube that you would like to display it on. Trim the lower edge as necessary.
Dry fitting the number to the bottom tube
Tape one side to the tube with electrical tape. This tape will be hidden inside the race number. You just want it to be flat.
Next, wrap the race number around the tube and tape the other side on the bottom of the tube.
Now, put a couple of strips of tape on both side of the number. This stream lines the race number and there will be zero flapping around.
The race number neatly installed on your race bike. Completely aero and professional looking.