mk1-forum.net

Happy New Year!
Need some info from the experts!
I’m running completely new braking system to the Jem . Have an adjustable pressure valve to the rears (MS72 from minispares)
Question is…. Is the orientation important? Does the valve have to sit with the inlet rear facing?
Thanks in advance.
Ian

I would say that it wouldn't matter which way the INLET feed pipe was facing. It's still the inlet and the others are still the outlet - feed to the wheel cylinders.

I'm not sure that it would even matter if the inlet was vertical. But please correct me if my brain has been fuddled over the Xmas period!

It works purely on pressure - not inertia - so direction seems unimportant. Except that there may be a consideration of which way up best allows any trapped air to escape into (at least one of) the outlets so it can be bled out at the slave. For example, positioning with the inlet at bottom would leave a lot of trapped air around the 'thin' end of the piston which would be unlikely to flush out... and could later find its way into a pipe or cylinder. Even the original orientation - with the outlets flat - doesn't seem optimal for bleeding. Best orientation - to get all the air out - appears to be with one outlet at the top and one at bottom. But then that's not very practical for running the outlet pipes. (edit: And on further thought, even that orientation seems to leave air around the top half of the fat end of the piston. The geometry of the interior doesn't seem to allow any orientation where all air inevitably finds an exit above itself. Perhaps BMC tested and found that the flow of liquid was enough to drag out any air, even if it didn't have a direct upwards path to exit? (edit-again: Since it seems air could end up trapped somewhere in this limiter no matter which way up it is fitted, the least-bad place for it to be trapped would be after the valve - that way the pedal sponginess caused by the air will cease once the valve closes. This would suggest that fitting the valve inlet-at-bottom, or at least tilting the inlet downwards a bit, could in fact be the least-bad option. But, really, doing anything other than standard has to be classed 'experimental' - so less than ideal for brakes.))

I would advise whatever method you use for Valve location and then set up adjustment of the rear brake applied pressure .. just make sure your Rear Brakes" NEVER" lock up .

Thanks for all the replies. Excellent advice as usual.

Polarsilver wrote: ↑Wed Jan 01, 2025 9:25 pm I would advise whatever method you use for Valve location and then set up adjustment of the rear brake applied pressure .. just make sure your Rear Brakes" NEVER" lock up .

Ditto on this, had a dodgy moment in my youth when we over did the balance on a competition car - in a straight line as we thought... but not for long!!

learnt my lesson in the early days of Mini7 at Silverstone with plenty of run off area
Moral of the story is Never Ever prepare rear brake bias with the potential for rear brakes to lock up.

Adapting very famous words at this time of year. "Get the wheels to brake in line." Michael Cain's latest book is well worth a read. A great actor with so many film credits.