Thule Aero Bars w/BMW OE Rack Feet

[CirrusSR22]

I got a BMW factory roof rack a couple years ago (link to pictures/info) and finally pulled the trigger on a nice Thule Ascent 1100 roof cargo box. Got a great deal on Craigslist

I was always wondering if the Thule box clamps would fit around the big chunky BMW loads bars. It turns out they barely do, at least not enough for me to be comfortable with the fit. My plan was to buy two 6061 square aluminum tubes (1" to 1.5" range) and make my own. But then in my frequent browsing in the REI Scratch and Dent section, I came across a pair of 47" Thule Aero Bars for $35. They are $125 normally! That's about what I was going to pay for raw, square aluminum tubes so I thought I'd try to make them work. From my browsing in the store I could tell the attachment system is similar to the BMW bars (also made by Thule I belive) but not the same. I thought I'd need to do some significant modification, maybe even take it to a machine shop for some light work, but it turns out they work great with just a tiny modification!

Here's the problem with the factory bars. The box just barely grabs the bar.


The slight modification involves grinding the steel threaded insert that slides in the load bar channel by just about 1mm.



You can see how it slides into the Aero bar channel.


Simply bolt it down tight and that's it!

[CirrusSR22]

The Aero bar does now sit fully on top of the hump in the BMW feet instead of the BMW bar which "straddles" the hump and sits flush with the main portion of the feet. I don't feel this is an issue though as the attachment is still solid as can be.

Another downside it that the tab on the threaded steel portion is now exposed because the channel in the aero bars are so much shallower than the BMW bars.

You can see how it sits on top of the hump in these three pictures.




Vs the BMW bar which sits lower and flush to the feet


Now the box clamps securely around the new bars!


Note: The 43" Thule Aero bars would be a better fit, but for $35 the 47" bars were too cheap to pass up. I might cut them shorter so they look better, or maybe keep them the way they are for use on a possible larger car in the future. Bars over 47" won't work without modification because you can't slide the feet close enough to mount properly on the car.
Here's the Thule Ascent 1100.

[CirrusSR22]

Bars compared:

[solan goose]

I saw your thread on the swap of BMW bars for the Thule aero bars. I think I am going to try this too. Have you had good luck? Anything fly off your roof lol. I hope not!