With the exception of Clark's housing and some '80's MTB housing, all brake cable housing is and was 5mm OD.
Normal ferrules bring the diameter up to 6mm but many older derailers and brakes accepted the housing without the ferrule caps.
Corrosion inside cable guides can make them tight. Wiggle a threaded bolt through them and the corrosion should easily clear out.
David Snyder Auburn, CA usa
Mark Cutrufelli wrote:
>
> Using modern brake cable housing (prelubed, not jagwire) works ok on my 83
> Masi but getting it through the cable guides on the TT is a tight fit. Was
> old Campy brake cable housing 4.5 mm diameter? ( I think jagwire makes
> both
> 5 mm and 4.5mm Diam.). Will 4.5 MM be the stuff to get to solve the
> problem?
>
>
> With the modern derailler cable housing (jagwire) all works ok but you
> have
> to omit the ferrules because they won't fit ( like in the rear Rally
> derailler) They sell 4.5 mm diameter with I think smaller ferrules. Wil
> thi
> solve the problem?
>
> I prefer to stick with prelubed cable if possible- just seems cleaner.