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Old August 10th 2004, 06:04
Jeza Jeza is offline
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Join Date: Sep 2002
Location: Wellington, New Zealand
Posts: 108
Quote:
Originally Posted by Wally
There is one thing that doesn't seem to add up with Shad's calculations though:
Using his front/rear bias ratio calculation, a bigger front cup diameter in your m/c, would yield a more rear biased set-up!?
To stay with the title of this thread: 'that doesn't seem right'

I can't figure this out yet as to why or what I am missing here...?
It a leverage thing, if you increase the diameter of the slave cylinder in relation to the mc you increase the power to the brake. Increasing the MC diameter will increase the hardness of the pedal but not the power to the brake. Jeff Hibbard has a section in his book Baja Bugs and Buggies that explains it well without getting too technical. The most common example is those that increase the size of the slave cylinder in the rear drums / fit T3 drums to increase the braking.

Quote:
Originally Posted by Wally
BTW, I'am running now the N/A 944 rear disks on my square (has stock 42mm front cup caliper diameter), which would give a F/R ratio of 1,36.
It brakes great, but feels just not as powerfull as my former 1303 with the stock 40mm front cup caliper diameter disk and rear 944 N/A, which gave a 1,23 F/R ratio, but that 1.23 ratio may be on the edge in wet conditions.
Because of the square dē, a little variation in diameter gives quite a different result in the ratio!

All this leads me to believe that between 1.30 and 1.35 should be about 'right'.
What you have now is probably a very good ratio for a rear engined car.

I also ran my beetle with the stock fronts and 944 rears (stock mc) and it brake quite unusually being so rear biased. I imagine you would get away with this most of the time, but my main concern is the differing way they would react when pushed, ie the rears would remain very cool and responsive while the fronts would get very hot and possibly fade (non vented rotor and small pad area in comparison to the rear).

The 944 brakes with the 944 MC gives a ratio of 1.41, which I reckon will probably work quite nicely.

Cheers
Jeremy

PS have you done brake performance comparisons or is it just a feel thing when you mention your 1303's powerful brakes?
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