|Originally posted by Will:|
... racers have no choice but to use custom braided stainless lines.
I wouldn't go quite that far. Since WW-II racers have depended on the aerospace industry for a lot of hardware, including PTFE/stainless hoses, but there are aircraft-spec hydraulic hoses suitable for race car brake use that incorporate rubber lining and non-metallic fiber reinforcement. So there are other choices available. I don't have applicable race experience, so I don't know the factors that go into the selection of PTFE/stainless hose over the rubber/non-metallic alternatives. However I suspect that superior properties at high temperatures and low expansion under pressure (and thus higher precision brake modulation) are major considerations.
[This message has been edited by Marvin McInnis (edited 07-15-2013).]