Great to find a web site devoted to Chinese carbon fiber frames with knowledgeable members. I'm new to riding anything carbon fiber as I've been a steel guy for like forever. I normally ride a 56/57 cm road frame with a 56 cm top tube and a 10 cm stem. So now I'm wondering if a 17.5 will fit better than a 19 29er frame. I recently fell into a new job where I ride the Mickelson Trail (a rails-to-trails conversion) here in the Black Hills of South Dakota. The job requires me to ride various sections of the trail 5 days/week to ensure trail users are safe, following trail rules/etiquette and pay the trail user fees. So I get anywhere from 130 to 150 miles riding in/week. I have been riding a cyclocross bike, but for the amount of time I'm on the bike, the riding position is a little too race oriented. I've been riding on 32 mm knobbies but a wider tire would add greater comfort. So a slightly more upright position and wider tires as well as a considerably lighter bike is what I'm shooting for. I've been looking at zgr9's frame: http://www.ebay.com/itm/Full-Carbon-Matt-29er-Mountain-Bike-Frame-19-BSA-Fork-Seatpost-Headset-Hanger-/171398898441?pt=US_Bicycles_Frames&hash=item27e82ba309
with a solid fork which looks like it would weigh in around 17lbs. So I'm open for suggestions from you all as to whether a 17.7 or a 19 would be the better fit. And BTW, feel free to come up to SD and ride the Mickelson Trail. Its been identified as one of the best!