Clamps on the front wheel, so it fits any axle stylewidth and doesn't touch your frame. Arrives completely assembled in the the box, just install it on the roof. Bikes go in and out easy. The only limitation I've found is tire width. Your fat bike tire's probably not going to squeeze into it, anything up to that is good to go.
I have two of the Frontloaders for mine and my girls 29ers and absolutely love the no hardware installation right out of the box and ease of use. There are markings for the size of the bike tire for easy adjustment. The rack holds the bike very sturdy and I have no hesitation with it at all. My only desires are 1) wish it was just a tad bit shorter so that the trunk of my Audi A3 would open all the way (I'd say it opens about 80%) and 2) that the optional lock core would have gone through the red knob that is used to tighten the front clamp for the tire. As it is right now, the Frontloader has one lock core to go to the front of the rack to prevent someone from actually stealing the carrier from your roof rack and the second lock core is one an attached cable that you can wrap around your bike as theft deterrent for someone to steal your actual bike. If someone really wanted to and had the cable cutters, they would cut the cable and start to unwind the red knob to loosen the front clamp and off they go with your bike. So if there were a lock on the red knob to prevent it from turning, then it'd be near impossible to steal.
But otherwise, this is a fantastic rack... especially at the sale price!