Max,
let me suggest that "it depends".
A little googling reveals that diagonal-split systems are normally
found on front-wheel drive cars.
As to whether increasing the diameter of the rear cylinders will
increase or decrease rear-braking bias, I think that ultimately it
depends on how the two pistons in a tandem master cylinder system are
connected. I can imagine different scenarios where increasing the
diameter could have either effect.
However, consider this, if increasing the diameter of the slave
cylinder results in reduced braking, then the same effect (for drum
brakes) could be achieved merely by backing off the adjustment of the
rear brakes (since more fulid will be required to bring the brake
shoes into contact with the drums). This would appear to be a simpler
method.
SImon
On Tue, Feb 24, 2009 at 10:55 AM, Max Heim <max_heim@sbcglobal.net> wrote:
> on 2/24/09 10:11 AM, Simon Matthews at simon.d.matthews@gmail.com wrote:
>
>> Max,
>>
>> It's not quite so simple. This description of dual master cylinders
>> describes a balance bar used to ensure equal force is applied to each
>> cylinder:
>> http://www.hotrodheaven.com/tech/brakes/brakes3.htm
>> In this scenario, the balance bar would act to equalise the pressures
>> between front and rear. Also, are not some brake systems split
>> diagonally?
>
> Balance bars are used in race cars (which are invariably disc/disc). I was
> talking about tandem dual MCs as used in almost all production cars.
>
> While I have heard of diagonally-split systems in theory, I cannot think of
> a single real-world application. I am sure someone will speak up and
> enlighten me.
>
>>
>> This patent describes a tandem dual-master cylinder setup in which the
>> two circuits also have equal pressure:
>>
>> http://www.tpub.com/content/construction/14273/css/14273_248.htm
>
> I can't tell from this fragment how this applies to the argument, if at all.
>
> Anyway, I am not just arguing from a theoretical standpoint, here -- I am
> describing reported real world experiences with examples of applications.
> You can say what you want, but there seems to be a generally-held belief
> that using larger diameter rear wheel cylinders on tandem MC disc/drum brake
> systems has the effect of reducing rear wheel lock-up, particularly for
> vehicles with strong front weight bias.
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