Found something quite interesting about braking systems on Minis (and most probably on all cars) yesterday. When changing your braking system, so changing from drums to discs, for example, the bore of the brake cylinder changes, so in my case I have upgraded from front drums to 7.9″ discs & 4 pot callipers which have a larger wheel cylinder bore than my original set up.
Now, if you imagine trying to blow really hard through a straw, your cheeks will puff out and you will go red and look silly. However, if you blow really hard through the centre of a toilet roll, you won’t puff out as much, and you wont go so red.
Going by this, if you can imagine at the end of the brake pipe you have a cylinder with a certain size bore pipe, which is different to the brake pipe. If the front cylinder bore size is larger (or smaller – or infact different) to the rear, then you will begin to experience problems where one or the other is better, make sense?
In my case, at the moment I have incredibly good rear brakes and nothing up the front at all. This is because my rear wheel cylinders have a smaller bore than the ones up front. By changing to larger rear wheel cylinders, it should overcome this problem and I will again have equal braking power. However, I’ve heard that matching the bore of wheel cylinders can become a bit of an art, so here comes the ultimate way of getting superior brakes…
Fully adjustable brake bias valves (as the name suggests) are able to increase or decrease the amount of braking power can go through a certain brake pipe. Since I have a front & rear split (common on 1975 Mini’s on based in the UK) I will be putting one of those jobbies on my rear system, having the ability limit the braking power to my rear system. Of course, it will help if I also increase the bore of my rear wheel cylinders as well, and try at least to get them matched as well as I can, before fitting the bias valve.
[...] With regards to my post a few weeks back about my brakes and the bias to the rear wheels [...]