I have just performed an upgrade of brake levers on my Plug Racer, from the original cross-style levers (top mounted, possibly Promax 239A models) to Cane Creek 200TT bar end levers, connecting them to the original Tektro R538 brake calipers. The change of handlebar position entailed the installation of new cabling and housing also.
The response I get when braking has changed significantly post-upgrade, with a very spongey action. Having done a bit of research into why this might be, it would appear to be an excess of mechanical advantage in the braking system (as discussed by Sheldon here and here), a result of the new levers being of a short-pull type, and the original calipers requiring a long pull.
I haven't been able to confirm the 'pull' characteristics of the components in question however (the 200TT manual just says "200TT brake levers are compatible with caliper brakes", and instructions for the R538s are not available from Tektro), so before I go and look for a compatible set of brake calipers, is there anything else that might cause spongey action in the braking system?