by Jim Morrison

If you are having a problem with your Tiger’s clutch not fully disengaging, one potential solution is the installation of a clutch master cylinder with a 0.750-inch bore to replace the stock unit (having a bore of 0.625-inches). This will provide greater movement of the clutch arm for the same pedal movement. As the volume of hydraulic fluid displaced (for the same pedal movement) is a function of the square of the bore diameter, the increase in bore will result in a 44% increase in clutch arm movement.

But all this does not come without a trade off: clutch pedal effort is also increased by 44%. I have made this change to my car with good results, previously having had some trouble with a dragging clutch. The pedal effort is high but not unbearable (with a 2200 lb. performance pressure plate). The larger bore clutch master cylinder can be purchased through a Sunbeam parts supplier. Be sure to specify a bore size larger than 0.625″. 0.700″ and 0.750″ are the next two popular sizes.

Comments (2)

I rebuilt a TR4 .75 clutch m/c and replaced the original 5/8 m/c in my Tiger with good results. I’ll get used to the heavy pedal. Your article is right on.

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