[TR] TR6 Clutch Master cylinder (.70 vs .75)

Randall tr3driver at ca.rr.com
Fri Dec 26 13:15:13 MST 2008


> I have read (somewhere?) that the earlier master cylinders 
> (,75) vs. later
> (.70) provide greater throw or ease of operation.

It's the other way around, a smaller diameter MC gives lower pedal force,
and more pedal travel for the same motion at the slave.

> Is this true and a viable reason to use a .75 in a 1970? 

If you have a .75, then switching to a .70 will reduce pedal effort by about
12%.  Whether that is worthwhile depends on your knee (and pocketbook).
Note that some folk have trouble with insufficient travel at the slave when
using a .70 MC; so the rest of the system needs to be in good shape.  You
might consider one of Ted S's braided lines at the same time, as it should
reduce lost motion due to the original plastic line swelling under pressure.

> I'd like to give my left knee all the consideration possible.

Research done by several people seems to indicate that many vendors are
selling the wrong, much too stiff, pressure plate for the TR6.  If your car
has one of these installed, then the only reasonable cure is to replace it
with the correct unit.  See for example
http://www.mntriumphs.org/Tech_Info/Clutch%20Folder/clutch.pdf
and
http://tinyurl.com/927hr2

IMO, replacing the stock steel bushings for the clutch shaft with the wider
brass ones from a TR3-4; plus adding zerks so they can be greased
occasionally; will also help with reducing pedal effort.  An occasional drop
of oil on all the pivot points wouldn't hurt either.

HTH
Randall


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