Carbon bar to stem question

[Andrepaul]

I just bought an Easton EC90 Equipe carbon road bar and a FSA OS-115 stem and just noticed that the bar states to only use stems with a two-bolt face mounting. The stem I bought has a 4 bolt pattern. Should I not use this combo or just go with my setup? I haven't yet installed either component onto my bike yet. Any suggestions?

[artmichalek]

Two and four bolt stems distribute the clamping force across the bars differently. With a two bolt stem, the clamping force is concentrated at the center of the face plate and tapers off towards the edges. So the bars see a smoother transition in internal stresses at the edge of the stem. A four bolt stem applies the clamping force right out at the edge, so that transition is a lot sharper. If it were me, I would listen to the manufacturer. If you use a four bolt stem with those bars you won't have much of a warranty claim when they shatter during a sprint.