Which brake fluid?

["Mike Ross" <MIKEROSS@prodigy.net>]

Hi fellow Spit pilots,

I'v had to replace a rear brake cylinder and had refilled the empty system
w/ Castrol Dot 3 brake fluid before learning than some early Spits used
natural rubber seals.  The old brake fluid looked, smelled, and felt like
the Castrol Dot 3 (I didn't taste it though).

Does anyone know when Triumph began using a seal that would allow the use of
a Dot 3 or Dot 4 brake fluid?  My '68 Spit's Commission # is FD11675   L.

Thanks in advance for any information,

Mike