Last week I mentioned the "flat" profile shape of the Continental Mountain King 29 x 2.2 when mounted on the 35mm wide Salsa Gordo rim and how it may have affected the handling. As you can see in the pic above, there is a distinct difference when on the 35mm rim (left) and a 24mm wide rim (right) (larger image below). The shape of the contact patch changes, being shorter and wider on the wide rim. But the angles of the biting edges of the tread blocks also change. Both of these affect the handling characteristics of the tire. How largely depends on the conditions and riding style.

Where I noticed the flat profile most last week was on a fast doulbletrack descent  with deep loose gravel. The front end was skatey with poor directional control. I was able to ride through it but it was a cheek-clincher. I think the tire was floating across the surface of the gravel rather than cutting in as it could with a rounder shape and more open/aggressive tread profiles.

The much simplified  drawing above shows how a wide "tire" would be more prone to slide as the gravel rolls under it while a narrow tire can cut into the loose surface.

Now I need to mount the tires on narrow rims and go ride that same doubletrack... 

 Update: There is a good discussion about this on the mtbr.com 29er board