Very stiff, it shared many characteristics with the Cervelo R3... one of the best climbing bikes I've ever ridden and the wheels are sublime. Sent in 7 body measurements for the build and ended up with a 55cm... I normally ride a 58cm but, although I had to have the seat-post right out, it was spot on, comfortable and super nimble..... came in at a very svelte 7.5 kg without pedals.