I have a nice road bike with 7005 Easton aluminium frame and carbon fork. The ride was always pretty harsh, so I changed saddle to Brooks, changed aluminium handlebar to a carbon one with gel padding under bar tape. It improved comfort a lot. I had my bike fitted at LBS when I bought it and fitted again in a year.

Despite of that I still cannot get rid of pain in my forearms after the ride. I cannot say that I lean to much on my hands while riding. Basically, I can let my hands go without changing my position and strain in my back, so I assume that it fitted just right.

This weekend I went to an LBS and tried Trek Pilot 5.0, carbon frame bike. The ride is as harsh as on my bike. My coworker has an old 10 speed steel bike, and ride on it is very soft and nice, no vibrations.

What can I do? Change the frame to a steel one? Fatter tyres (I can only use 25)? Anything else?

Whenever I've had forearm pain I've found it to be from either bars that are too wide or bars that are too low combined with road buzz. What tires do you use?

Conti GatorSkin 700x23.

They give a fairly smooth ride for a 23mm tire and I doubt that 2mm will make that much of a difference.

FWIW I can tell a huge difference in my aluminum and steel frames as far a road buzz and vibration, so much that I don't ride the aluminum frame at all. The steel is much more comfortable for me.