Dual master cylinders and balance bar VS tandem and portion value
woodsy144 - 10/12/19 at 08:41 AM
Hello, as subject suggests is there any advantage / disadvantage of one over the other. Based on space and weight I am thinking of designing a box
using the later, but want to fully understand the systems.
JonBowden - 10/12/19 at 10:14 AM
If you use dual master cylinders with a balance bar, you will be able to adjust the balance to get it just right but with a single split master
cylinder, you may need to play with the size of the wheel cylinders.
I believe that for IVA, you must either use a single split master cylinder or if you have dual ones, the adjusting mechanism must be welded up to
prevent adjustment.
JAG - 10/12/19 at 08:02 PM
I would suggest you choose a third option...
3) Tandem Master Cylinder and adjust the brake sizes to get the correct front:rear balance.
Proportioning valves are an unnecessary complication and a twin master cylinder and balance bar arrangement has to be welded in one setting for
IVA.
My car has M16 front calipers from a Cortina and the 8" drumbrake from a Ford Escort. I increased the drumbrake wheelcylinder size from 19.05 to
20.64 mm diameter to adjust the front:rear balance.
woodsy144 - 10/12/19 at 08:06 PM
In Au, we don't have to weld balance bar. Just make it so the driver can not adjust it, ie remove the adjustment knob and cable. (and reinstall
later.... Cough cough)
Oddified - 10/12/19 at 08:56 PM
The other way is use a dual master cylinder and then change pads front or back with differing coefficient of friction, works very well.
Ian
voucht - 11/12/19 at 06:52 AM
quote:
Originally posted by woodsy144
Hello, as subject suggests is there any advantage / disadvantage of one over the other. Based on space and weight I am thinking of designing a box
using the later, but want to fully understand the systems.
They are two different kinds of systems, and it have different purposes. It is a bit like comparing pears and apples.
On the first (balance bar), you just push more on one master-cylinder and less on the other one, and you chose how much you push on each one by
adjusting the balance bar. But you don't put any limitation on the brake circuit. Mechanically, it makes much more sense. It can be used to
finely adjust your front/rear brake balance permanently. But is will be the most expensive setup of the two.
The second one (proportioning valve) is a limitation on the pressure of the rear brakes. The force applied to the master cylinder is the same, there
is just a restriction on the "downstream". Do not forget that most of the proportioning valves do not limit the rear brake more than 57%,
and it might just not be enough anyway if your front/rear brake system has been poorly planned. Normally, this system is used only when one master
cylinder (tandem) must be used (road or racing regulations). For example on rally cars, in series where dual master cylinder setup is not allowed, it
is used to adjust the rear brake between dry road and wet road conditions. But it is not designed to be used to balance your front/rear permanently.
Plus it is more connections on your brake circuit, which is more chance of leaks, bubbles, bleeding issues, etc. But it will be the cheaper setup of
the two.
As said above, the first thing is to correctly design you brake system and chose the right size of front/rear callipers to get the best front/rear
brake balance possible.
If you need to adjust, and money is not the biggest issue, I would suggest that you go for the dual master cylinder + balance bar, as it is allowed in
your country.