i have read a lot of threads where unless i am mistaken some very "sturdy" fellows are riding what we call in the uk racing bikes...how can guys over 300lbs ride these bikes?..what tyres are they using and what psi?..or have i seen pix in the thread that are hybrids?
90s? serotta t-max, 09' planet x ti frame w/sram force, '10 Bianchi Volpe
i dunno what the other guys ride, but at 17.5 stone, my 25s are 120psi and my 28s are at least 110. mavic ksyrium elite wheels. they look spindly, but mavics are pretty burly.
there is a "fat guy on a light bike" thread/flame battle you might want to look at. light doesnt always mean weak, but it usually means expensive. the only reason my bike is approaching light, is because i get a pretty good hookup on the stuff. light weight was a byproduct, not a goal.
btw, 20lbs is pretty damn light and its reasonably inexpensive to purchase a bike these days, compared to 15 years ago, whe 20lbs would cost an arm and a leg, which by the way would have gotten you under clydesdale weight.
Currently, I'm 260 pounds, 6'3". I ride a Kuota Kharma. It's a full carbon fiber frame. Very comfortable and strong enough for me. I use it in races and on long centuries. My tires or (tyres) are 700x23 Michelin Pro3 Race pumped to 115-120 psi. Frame is fine and will be for anybody else, too.
Weak point for us big guys is always the wheels. My regular wheels are Mavic Open Pro (32-hole) with Ultegra hubs. I also have some Mavic Ksyrium Elites that I only use for special events (races or centuries). The Elites do seem to go out of true after 40-50 miles. I tighten 'em back up.
I've been riding this way since September, 2007. I started at 318 pounds.
I started riding a mountain bike at 329 pounds. After 5 months, I was down to 280 pounds. At that time I picked up a 2007 Schwinn Fastback. This is a traditional drop bar road bike with an aluminum frame, and a carbon fiber fork. The only thing that I have replaced on it in the 1300+ miles that I have put on it since then is the rear wheel. The cheap stock one was simply not up to the weight challenge. I am now around 255 pounds.
most road bike frames are pretty strong, it's the wheels that clydes have to worry about...
at 273lbs and 6 foot, i ride a specialized roubaix (aluminum frame, carbon seatstays and fork). the only problem i've had was with the oem wheelset (they werent strong enough for me and the roads i ride). i replaced them with mavic cxp33's (32 hole) on ultegra hubs. the tires i use are specialized roubaix pros sized at 23/25x700c (they are 25c, but have a 23c tread size) and i run them at ~125psi (the recommended maximum).