I digest the list and I saw a request for information about the 4 pot Toyota
front brakes. It occured to me that i had never passed along what the effects
are for modifying both the front and rear brakes.
John Lye's came up with the idea for putting the 4 pot Toyota calipers on
Triumphs.
His mention of upgrading brakes came at the exact moment I was about to swap
out the rear brake cylinders (based on information from Grassroots Motorsports)
so I did both conversions and took a few measurements (real pain to do).
John wrote up an article (that may eventually get published) and portions of
that article have appeared in this forum. The article specifcally addesses the
front brake modifications and does not address the test results associated with
the rear brakes.
In summary I RECOMMEND UPGRADING THE FRONT AND REAR BRAKES AT THE SAME TIME!!
Front - replace with Toyota 4X4 calipers. For a TR6 this requires manufacturing
a custom brake tube and some trimming of the dust shield.
I'll post pictures on the web if there is any interest expressed.
Rear - replace the stock rear brake cylinders with 7/8 inch diameter cylinders.
This is a direct swap with no custom modifications.
Here is a summary of my results:
All tests performed with a newly rebuilt master cylinder, dot 5 brake fluid. A
proportional valve was installed on the rear brake lines but set to have no
effect (completely backed out). I had predicted that the 7/8 cylinder would
overpower the rear brakes, silly me!
Stock configuration with semi metalic pads, composite shoes (with finned
aluminum 240Z drums)
262 feet with a standard deviation of 19
6 data points, tossed out minimum and maximum
Toyota front calipers with semi metalic pads, composite shoes (with finned
aluminum 240Z drums)
243 feet with a standard deviation of 9
8 data points, tossed out minimum and maximum
7.8 percent improvement.
Toyota front calipers with semi metalic pads, composite shoes with a 7/8 inch
brake cylinder (with finned aluminum 240Z drums)
215 feet with a standard deviation of 9
9 data points, tossed out minimum and maximum
11.5 percent improvement.
Net result is that I saw an 18% reduction in braking distance due to conversion
of both front and rear brakes on a 1974 TR6 (your milage may vary).
NOTE THAT BRAKING DISTANCES DECREASE MORE DUE TO UPGRADING THE REAR BRAKE
CYLINDERS THAN BY MODIFYING THE FRONT CALIPERS!
Also note: Pedal travel was increased as the size of the calipers / cylinders
increased. Initially a little alarming but fine once you got use to it.
Hope this helps
Lee
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