Bikes whistling on tow bar rack mount

[Dog Star]

I’ve been carrying my eMTBs on the back of estate cars (E class Merc, Alfa 159 SW) for years. No problem.

However on the back of my Merc SL they whistle like mad, roof up or down, 40mph upwards.

Anyone any ideas or had this? I can only think it’s something high up - the bars for example - as the car is pretty fat.

[egomeister]

On the estate the bikes will likely be sitting in a pocket of stiller air, whereas the SL it will probably see more turbulent air coming off the roofline. Not sure there's a great deal you can do except make sure the bikes are tucked in as close to the car as possible.

[Barchettaman]

Maybe remove the seatpost/saddle, and detach the handlebars from the fork steerer; zip tie them to the top tube, something like that. Anything to reduce the height of the bikes.

[Dog Star]

Hmmm. I’ll try taping a bag over the bars as a first step. Report back tomorrow

[Super Sonic]

Dog Star said:

Hmmm. I’ll try taping a bag over the bars as a first step. Report back tomorrow

Hope you like loud flappy bags!
FLAPPITYFLAPPITYFLAP!