My current setup is OEM crossbars, OEM bike trays, and a Thule fairing. I put the driver's side bike tray on 'backwards' ie the lock is not facing you but the curves of the trays go in the same direction. I added the fairing (38") because initially there was a fair amount of wind noise and whistling at freeway speeds. Granted, I have a sunroof. Anyway, now with the fairing on there is certainly less noise, and more consistent droning as opposed to buffeting, whistling, dynamic sounds (which makes sense, aerodynamically) but it's still not quiet by any means. It also rattles a bit under crosswind, as the fairing is straight and the roof/glass is curved. The fairing also sits ON the glass, for better or worse.

I'm curious about the impacts on gas mileage and sound in various configurations.

I'm going to do a few tests:
- compare rack with bike trays facing forward and fairing on at 60mph or so, with;
- bike trays facing forward, no fairing, with;
- bike trays reversed, no fairing;

The reason I want to explore this is that the bike trays I use cant UP like a very shallow S curve. These are the OEM ones, with the downtube gripper. So air may be catching under there unnecessarily. It's frankly an odd choice in the design, and I've never seen it in any other mfr.'s product. So, I'm curious what would happen if I flipped the trays (bikes mounted backwards, which is aesthetically untoward, but who cares when you're driving). I also want to test fairing on/off. Granted I haven't sealed those channels in the crossbars yet with rubber, but I'd probably put duct tape down for the test, just to cover the holes up. You have to cut the rubber gasketing to fit the space remaining in between bike trays, so I have held off doing so. So I need to seal that opening with tape to minimize the 'blow over glass rim' effect. Very scientific description.

That would give me a better sense of sound AND mileage impact.
So, I'll post back here after I run the tests. I'll try to do each configuration for about 2-3 days.

 

Just curious if you have any results to share yet. I'm interested to find out what you observed.

 

I was just preparing this, actually! Hang tight...

 

So, the answer is, in the immortal words of Leo (Albert Finney) in Miller's Crossing, 'clear as mud.'

The fairing only fits if the bike trays face forward, both left and right. This is because the design of the tray mounting for this particular model OEM tray, puts the tray way forward of the crossbar. So, the front of the tray has this unusual sweep upwards like a really lazy Cooper S logo (heh) that happens to mean that the fairing can fit UNDER it. You still have to sort of pinch the fairing mounting arms to fit inboard of the very large mounting plates of the trays themselves. But basically, to use two racks, and a fairing, you have to have the left most (driver's side) facing forward, when it is otherwise intended to face backward. I say this because the lock and twisting mechanism on the downtube clamp is one sided, not dual-sided, so to reach it on that side of the car you'd have to have the tray reversed to make it visible to you.

Each of these tests was conducted over a full tank of gas with very consistent driving, a combination of bumper to bumper traffic and freeway speeds, typical here in Northern California, which generally pushes mileage down. This is an S model R60 with manual transmission, and I'm not a lightfoot, but not super aggressive either. So while the mileage values are what they are, the key to these tests is that the mileage has been very consistent on this car so far, so the relative changes in mileage might have told us something, below. Prior to installing the roof rack, I was getting 25.8-26.3mpg. Young engine, under 2000 miles.

Test 1: bike trays facing forward and fairing on at 60mph or so:
23.8mpg. Wind noise audible, but slightly dulled. Slight tapping, depending on wind direction and speed, from the fairing wobbling it's wings, ie dipping harmonics from side to side as if pivoting on center axis (tap to the drivers side, tap to the passenger side, repeat) which could be solved by moderately pre-stressing the fairing with a heat gun in an arc so that both ends of it want to dip downward a hair, rather than remain flat at the bottom edge (which is silly, right, when every car these days has a sloped roof);

Test 2: bike trays facing forward, no fairing:
23.7mpg. wind noise heard, at higher speeds (say above 70mph) and depending on wind direction, sound increases, but is consistent.

Test 3: bike trays reversed, no fairing;
23.6mpg. Similar audible results to the above test. Wind noise, increases with speed. Very consistent. Not noticeably different.

A fourth test was done, with trays facing per mfrs directions (like Test 01) but, as stated above, without the fairing as the back of the drivers side tray blocks the fairing mounting point. In this instance, same mpg and slight whistling can be heard at higher speed and with certain wind direction.

So, the .3 mpg difference between configurations is well within tolerance range, so these are effectively the same mileage, though it is interesting to note that mileage went down about 3mpg consistently with the roof rack. My rear hitch MINIs prior (two of them, both with minidomore hitches) had negligible mileage impact when carrying a bike rack.

It's interesting that the fairing didn't change mileage, as that's one of the common assumptions about fairings streamlining the airflow. So while it did appear to modestly reduce air noise, it didn't improve mileage.

The decision then came down to function. The fairing use drives the orientation of the trays necessarily. However, as I began to use the trays with two bikes, I found that having the driver's side tray facing forward, thereby obscuring access to the lock/twist mechanism of the downtube clamp, was problematic. I think on a standard MINI it wouldn't be as much of an issue, but on the Countryman, you're already reaching pretty high (and I stand in the door wells, being 5'-8") and this makes for some awkward reaching to try and get at that clamp from the back like that. This was especially onerous when I was transporting two old restoration bikes, which due to the steel frames and old components, were very heavy.

On the basis of that, I'm left with:


So, current configuration is trays installed as recommended by mfr ie. one goes forward, the other goes backwards, and no fairing. I'm not sure if this will be my permanent config, though, because the designer in me is rattled by the asymmetry, and the fairing WAS a bit quieter.

 

There's a twin of my CMS (sans stripes) in my neighborhood that I've seen with both trays oriented with the sweep facing forward. So I'm not the only one that questioned what orientation to use...

 

Slightly off topic, but did you have to modify the thule fairing to fit the oem base? I read another thread that they had to, I don't want to buy the fairing if I need to modify it and may look into inno or Yakima if that's the case. Thanks in advance!