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Brake Pressure Reducing Valves
Mark Allanson - 7/4/03 at 05:17 PM

I was checking a Y reg Fiesta today and found these two barrelly things dangling from the master cylinder.They are pressure reducing valves, and cost between £20 and £35 from Ford.

Has anyone tried these in a Locost, or know the theory behind them - they look too easy to be true....

Mark Rescued attachment brake1.jpg
Rescued attachment brake1.jpg

theconrodkid - 7/4/03 at 06:12 PM

look at bob,s site ,there is a pic of a fiat uno valve,that is adjustable,the fiesta ones are decel valves and not adjustabubble.

Dick Axtell - 7/4/03 at 06:30 PM

quote:
Originally posted by Mark Allanson...dangling from the master cylinder.They are pressure reducing valves,..Has anyone tried these in a Locost, or know the theory behind them

Mark, this type of PCR valve is non-adjustable. The "switch" point (i.e. when the valve starts functioning) is determined by the internal bias spring. I intend using one, in conjunction with standard Cortina fronts & 8 inch rear drums. The vehicle layout will be fairly close to the book version.

I can mail you a pdf file of the internal guts of the valve, if you wish (3.27Mb).

CairB - 7/4/03 at 07:10 PM

Mark,
I've used a similar one (pressure control relief - PCR valve) off a Mondeo. It passed SVA ok on my pinto Indy with std Sierra drums and discs. The adjustable ones may give more brake tuning later though. On the Mondeo the two valves had different male thread sizes, I think to stop the circuits being crossed accidentally, The one with the smaller thread fitted the Sierra m/cyl, so don't forget to get the larger nipple if you go this route.

Cheers,

Colin

[Edited on 7/4/03 by CairB]

Mark Allanson - 7/4/03 at 09:02 PM

Are they
1, standard thread, for instance a sierra master cylinder?
2, will they only work in one plane ie vertically downwards?
3, how do you determine the best one to suit a locost?
4, is Glen Miller still missing?

Mark

Dick Axtell - 8/4/03 at 11:13 AM

quote:
Originally posted by Mark Allanson
Are they
1, standard thread, for instance a sierra master cylinder?
2, will they only work in one plane ie vertically downwards?
3, how do you determine the best one to suit a locost?

Mornin' Mark,
1: M10x1 standard port thread,
2: Vertical position helps bleeding,
3: Valve suitability determined by Lucas in-house computer analytical tool.

Dick

westdown - 8/4/03 at 11:53 AM

Does any one know where the uno bias valve is fitted on the car?


Dave

bob - 8/4/03 at 12:16 PM

Dave

Its sort of under back seat and near back axle

redeye - 23/4/03 at 10:33 AM

is it difficult to get to

im planning on going to the local scrappies this weekend to get the m/c and servo of something like a fiat uno

i wwas thinkin because of the whole weight thing the uno should be ideal plus the servo is quite compact

what do u reckon?

westdown - 23/4/03 at 12:01 PM

The uno valves are easy to get to, left hand side forward of the rear wheel. Strange thing is they work the opposite way to which you might think. To reduce the flow you need to pull the operating rod out not push in. Suggest you take the valve mounting as well looks as if it may be useful. As for the master cylinder ive no idear.
Dave

Fast Westie - 24/4/03 at 08:01 AM

quote:
i wwas thinkin because of the whole weight thing the uno should be ideal plus the servo is quite compact

You don't want a servo