8 replies to this topic

[Chappb]

Good afternoon!
I'm aware the Yellow tag master cylinder pipe connections are well documented on here. But from what I've seen, they are all assuming that it is getting piped into the bulkhead limiter valve.
I'm ditching this valve and going to fit a brake bias valve into the rear line instead.
But ultimately what i'm asking is are the connections to the front/rear the same in regards that the top port on the M/C goes to the front brakes and the bottom port goes to the rear brakes?

Cheers!

[KTS]

yes

[ac427]

Is the output pressure from both the top and bottom ports the same with this type of master cylinder?

Edited by ac427, 05 May 2022 - 11:11 PM.

[Spider]

Is the output pressure from both the top and bottom ports the same with this type of master cylinder?

No.

The bore in these is stepped with the smaller bore at the top. This will make a higher pressure and so that's why that port is connected to the Front Brakes.

[Icey]

I'm ditching this valve and going to fit a brake bias valve into the rear line instead.

And to expand on Spiders post above, because the MC is stepped bore you don't need a bias valve. You can balance the system by fitting correctly sized rear pistons.

Calver covers this but does state that he uses a valve. I don't, but then I don't want to adjust the bias for different driving requirements, as long as the rears aren't locking up I'm happy.


 

[ac427]

 

I'm ditching this valve and going to fit a brake bias valve into the rear line instead.

And to expand on Spiders post above, because the MC is stepped bore you don't need a bias valve. You can balance the system by fitting correctly sized rear pistons.

Calver covers this but does state that he uses a valve. I don't, but then I don't want to adjust the bias for different driving requirements, as long as the rears aren't locking up I'm happy.


 

 

 

I've just seen that i have the dreaded FAM PDWA unit !!

 

Is there a table or some way of calculating the rear brake cylinder bore required on Mini's, particularly if the front drums have been swapped to discs?

Edited by ac427, 06 May 2022 - 04:24 PM.

[Spider]

Is there a table or some way of calculating the rear brake cylinder bore required on Mini's, particularly if the front drums have been swapped to discs?

 

There's a few tables floating around, which I have doubts on.

I think the most reliable info here is from the Factory Manuals.

In general, Discs need a higher hydraulic pressure to work than Drums, so when there's a Disc / Drum mix on a car, you can be sure the Rear Wheel Cylinder Sizes will be smaller than the Drum / Drum combination.

 

[ac427]

 

Is there a table or some way of calculating the rear brake cylinder bore required on Mini's, particularly if the front drums have been swapped to discs?

 

There's a few tables floating around, which I have doubts on.

I think the most reliable info here is from the Factory Manuals.

In general, Discs need a higher hydraulic pressure to work than Drums, so when there's a Disc / Drum mix on a car, you can be sure the Rear Wheel Cylinder Sizes will be smaller than the Drum / Drum combination.

 

 

Thanks very much Spider. I have the Haynes manual but where can i get factory manuals?

[Ethel]

There are more factors than the hydraulics.

 

The yellow band master was only ever fitted with the FAM7821. You could certainly get working brakes without it, but the reason the factory used it is doubtless because it won't limit the rear braking effort if the front fails.

 

If you really want to get rid of it (I don't think the case has been made,) fit an inertia valve. It will have the same failsafe (but not the rear circuit fluid loss protection) perform better under varied condition (because it senses actual braking effort) and allow you to fine tune the brake bias by just adjusting its fitting angle.