I've been using my Carradice on my newish touring bike. I've been feeling some odd kind of shimmy feelings, mainly in rhythm with my pedal stroke at medium cadences and occasionally at speed. Riding with front panniers as well the other day I could feel the sensation amplified by the extra weight at the front.
I've got the bag on a bagmen QR rack. Previously, I had used it strapped straight to the saddle and seatpost of another roadbike and never felt this. When the bag is loaded; grabbing the bike by the saddle and rocking it (as I imagine my pedalling does) you can clearly feel the bagman wobble side to side and feel this moving through the frame.
My question is; is this a symptom of having the bag set too far back or just an issue with the bagman racks?
I would say its centre of gravity is probably just behind the rear axle, vertically. The chainstays are plenty long, 44 or 45cm, it's just a very big frame (yes those are 700c wheels), and 63.5cm of 72 degree seat-tube puts the saddle a long way back. I could move the wheels about 1cm back in the dropouts, and I could bend the rack forward a bit, which would probably get the *centre of gravity* in front of the axle, but not the whole bag.
Would this actually fix anything or do I simply need a more rigid mounting solution? I think I want to tour with the carradice, a large berthoud and my super C front panniers, but if I can't cure this shimmy problem I guess I'll be joining the 4 panniers club