> When I purchased my Spitfire this past October I changed all the
> fluids and
> rebuilt the MCs and the clutch slave unit. The manuals, caps, spec sheets,
> etc. all say to use DOT 3. The majority (if not all)
> listers/owners say use
> DOT 4 (which I did) because of the "melting" affect DOT 3 has on
> the natural
> rubber seals Triumph used.
>
> Over the years I've never rebuilt any hydraulic components on my
> 3A, except a
> leaky wheel cylinder about 10 years ago. Occasionally I have
> topped off the
> reservoir with fluid, I'm sure I've used DOT 3 for many years
> with no adverse
> (noticeable) affects. It's not a daily driver, maybe 2K a year.
>
> Were there changes along the way in the rubber used in the
> earlier models, or
> was all the rubber used over the years "natural," and why? Is DOT 3 in any
> year/model an accident waiting to happen? TIA
Dave, the problem is not DOT 3 vs DOT 4/5/5.1. Those standards simply do
not address compatibility with British brake seals. As long as you use
Castrol fluid (or DOT 5), you should be fine.
The British seals did change composition at some point, although I'm not
sure when. The Girling seals available in the 70s for my TR3A would
definitely fail rapidly if used with American brake fluids. But, I haven't
heard of this happening to anyone for a long time, so I'm pretty sure that
they switched to a different material sometime in the 80s. But even running
American fluid with incompatible seals, I never had a drastic failure, only
constant leaks. Keep an eye out for leaks (a stripe running down a tire for
example), and for the fluid in the MC to turn dark, you should be fine.
BTW, After switching to DOT 5 I'll never willingly use anything else, guess
that puts me in the minority <g> Compatibility with natural rubber seals is
only one of the reasons ...
Randall
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