RE: [ST] Brake fluid

["Mike Bostock" <mike@xxxxxxxxxxxxxx>]

In your message regarding RE: [ST] Brake fluid dated Sat, 23 Nov 2002 13:57:05
- -0800, Brad Turner said that ...

>BT-  Mike,
>BT-  
>BT-  I hope you mean "DOT 5.1" not "DOT 5". DOT 3,4 and 5.1 are gylcol based
>BT-  fluids whereas DOT 5 is a silicone based fluid and is does not mix with the
>BT-  glycol based fluids. Not only are the fluids chemically incompatible but
>BT-  sometime the seals used in the brake system (master cylinder and calipers )
>BT-  are not compatible and can be attacked by the silicone based fluids. You can
>BT-  convert a brake system to DOT 5 if you make sure the seals are compatible
>BT-  with silicone fluid then and disassemble everything and clean out the glycol
>BT-  fluid and reassemble using silicone fluid.

Thanks Brad and the rest of you I guess I'll stick with DOT 4 (seems I got a
bum steer from a local garage).

The Triumph OM recommends Mobil - is there any significant difference between
brands?

>BT-  All-in-all a royal pain in the ass IMO. I think you'd be better off keeping
>BT-  the stock system as is and just bleeding it more frequently. My favorite
>BT-  gylcol based fluids for my street bikes is the Motul 5.1 fluid it has a
>BT-  really good boiling point (185°c/365°F) and bleeds nicely. Also something
>BT-  that makes bleeding brakes trivial is the installation of speedbleeder
>BT-  valves on the calipers (http://www.speedbleeder.com/).

My neighbour used to be a mechanic - at which time he did some research into
brake fluid degradation and says that the fluid at the caliper end can degrade
quite quickly due to heating up and that the fluid circulates very little in
the brake system (even on the school buses he was testing).  Thus testing at
the reservoir doesn't reveal the state of the fluid at the caliper end.  It
therefore makes sense to bleed through from time to time AFAICS to purge the
degraded fluid out of the system.  Anything that would make this easier would
seem sensible.




- -- 
Mike Bostock
http://www.toothfairy.co.uk/
Wales & SW ST Riders
http://www.sprint-st.org/

'99 Red ST

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