Unfortunately there is no way to access top tube from seat tube. And can't enter via fork either as discussed earlier. So only chance would be to insert thin liner through top tube to enclose the brake cable. Actual brake cable housing is not an option, the housing would not fit inside entry holes. So next step is identify some liner that is wide enough to fit the brake cable but thin enough to fit through the Klein cable entry holes.


But this comes back to my original question, was there supposed to be a cable liner installed for all Kleins like this with integrated brake cable? I just can't see how the road buzz could be avoided without some type of liner.