I'm looking at replacing the brake levers on an older road bike and was wondering if the cable pull ratio for the old Dia Compe center pull brakes pictured below is compatible with new road brake lever like Tiagra or Cane Creek SCR-5. Also do these brake levers fit the old thinner drop bars seen on older bikes? I will eventually be replacing the brakes as well but was hoping I don't have to replace everything at once.
I've used Cane Creek levers with old MAFAC racers which are pretty similar. However, the MAFACs allow you to adjust the length of the cross cable which allows you to tune the brake force.
It's my understanding that all road caliper brakes use roughly the same cable pull so that all "standard" caliper levers are interchangeable. Where you need to be concerned about the cable pull is caliper vs V-brake levers. This question covers that difference.
As always Sheldon Browns site contains lot's of useful information for older bike technologies.