I finally got fed up with straps and having read here how much people love their lock racks I bought one for my board transport needs. I love the simplicity and quickness of getting the board on and off, but they sure do whistle a lot, especially when I don't have a board on them. With a board the whistling is reduced, but it's still there.

Any advice on what I need to do to try and stop this? They are on Thule wing bar. I had to remove the middle rubber bit to get the lock rack installed. I then cut the rubber to fill the gaps on either side of the lock rack base, but I didn't bother trying to fill in "accessory slot" , or whatever it is called, directly under the lock rack base, because that seemed like a lot of effort.

I am wondering if that open slot in the bar is what is causing the whilsting, or is it simply the gap between the bar and the lock rack base and I should just get used to the whilstling and listen to my music at a louder volume?

Thanks Colas. It looks like I need to do some science!

I have whispbar racks and on those there is the mushroom rubber insert running the length of the racks, to install lockrack you simply remove side cover of roof rack and slide adapter in (push rubber strip down) on top of rubber strip ( do not remove or cut down rubber strip ) If there is wind noise you can insert rubber between lockrack and roof rack as I did on one of my cars.
You can get a universal adapter that clamps around roof rack instead of being in the slot if you're unable to push the rubber strip down.
good luck

I am going to try all of these suggestions starting from the easiest and report back.