Board logo

blanking master cylinder ports
hughpinder - 26/2/09 at 08:45 AM

Sorry if this has been asked before - couldn't find it anywhere. My dual circuit master cylinder has 2 ports per circuit - is it ok to only use one per circuit and put a suitable set screw inthe other port (for the rear circuit, as I only want to buy/set up one pressure balancer, not 2!

Thanks
Hugh

Mr Whippy - 26/2/09 at 08:47 AM

yes and you could use the spare port for a brake light switch

02GF74 - 26/2/09 at 08:50 AM

quote:
Originally posted by hughpinder
it ok to only use one per circuit and put a suitable set screw inthe other port


I don't think so.

The seal is made by the cone shape on the pipe or bleed nipple.

Either use
1. a socket screw (aka grub screw) that you have filed down to a point to block off the port
2. a bleed nipple, solder up the hole to be extra safe - usng plumbers solder
3. a short lenght of copper pipe solderued up as above

with option 1, you need to ensure the cone angle on the screw is greater than that in the orifice - I did this on a mountain bike caliper using a drill press, file and marker pen to show the sealing area when lightly done up. (think I posted about it on here).

hughpinder - 26/2/09 at 08:57 AM

Wow - thanks for the quick replies.
I'll probably do as Mr Whippy suggests

Cheers
Hugh

Mr Whippy - 26/2/09 at 09:06 AM

Convention is - front piston is either for both front wheels with the back piston for both back wheels

but this can lead to skids if the front brakes fail as it’s like a handbrake turn especially so if its raining

or you can connect each piston to a front wheel and its diagonally opposite rear wheel which will make the car much more stable if a circuit fails

Dusty - 26/2/09 at 10:34 AM

quote:
as I only want to buy/set up one pressure balancer
Latest draft IVA 3.2 doesn't like mechanical valves. Automatic proportioning valves that are load sensing or gravity/inertia sensing are permitted. Mechanicaly adjustable valves which allow alteration of brake balance must not be fitted.
Even a bias bar on twin cylinders must be set and then rendered permanently non adjustable by welding the adjusting nuts to the bar and destroying the bar thread with a weld bead.

hughpinder - 26/2/09 at 12:07 PM

Hmmm
Are the 'automatic' valves like the little in line things you see on production cars? How do they work - its just that I guess the brake line pressure in a 7 wil be lower than in a production car, so I'm not sure they will work if they just reduce the pressure available to the back wheels.
I am aware of the diagonal split used on production cars, but thought it could be tricky to do if you are using adjustable proportioning valves, as you would have to have 2, one in each rear line, and I bet it's tricky to adjust them both exactly the same.
I think I'll have to use the old brain a bit more ....

Thanks
Hugh

[Edited on 26/2/09 by hughpinder]

britishtrident - 26/2/09 at 12:52 PM

Essentially it boils down to don't fit anything that can't be twiddled without spending at least half an hour removing a locking device first.

It isn't how the device works that they are worried about but the temptation to twiddle factor --- nothing will put you through a hedge tail first faster than the rear brakes locking prematurely.

rusty nuts - 26/2/09 at 07:30 PM

Hugh , go to your local motor factors and ask if they have any of the correct bungs in stock. Sometimes get them with new master cylinders, they are made for the job .A brake light switch may be OK ( VW type Beetle switch would be ideal ) DO NOT use any other means to bung them up!!