Hi Guys,
 
As part of the Volvo & Nissan R31 disc brake conversions I am doing I will be mounting the M/C from a 120y on the firewall and I have a question about the Pressure Differential Valve.
 
Will I be able to just plumb the M/C into the valve or will I need to remove it altogether?  What potential issues if any could result if it was to stay?
 
It will be a great deal easier if it were to stay and I would also like to keep the brake fail warning circuit as well.
 
Failing that is there another type of pressure valve you can plumb in that will trigger if the pressure in the brake system drops?
 
Cheers
 
Matt

Hi matt,
 
I've just bought an item of ebay that a mate of mine is running in his mustang that has disc's front and rear. Only thing u would have to do is make a new plug on your exisiting loom for the brake fail light to come on.
 
http://www.ebay.com.au/itm/290634856372?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

That's a good idea but was leaning towards this due to the adjustability factor.  http://www.ebay.com/itm/Wilwood-260-11179-Adjustable-Combination-Proportioning-Valve-3-8-24-IF-/260887416580?pt=Motors_Car_Truck_Parts_Accessories&hash=item3cbe1a0f04&vxp=mtr#ht_1771wt_1270
 
If I kept mine and just plumbed everything through it, would there be any issues?
 
Cheers,
 
Matt

mate that looks like a better unit than mine..think ill sell mine soon.
 
If you run the standard valve you'll have pressure problems for the rear. Meaning you wont have enough.

Cool, makes sense.
 
It never ends.  You do one thing then that leads you to doing another and another and another ...............
 
Cheers,
 
Matt

It's never ending, you never really finish as there is always something to do.
 

Matt75

Will I be able to just plumb the M/C into the valve or will I need to remove it altogether?  What potential issues if any could result if it was to stay?

It will be a great deal easier if it were to stay and I would also like to keep the brake fail warning circuit as well.
 

Matt, the pressure differential valve (original) and the proportioning valve (ebay link) are two different things altogether. If you plumb in the pressure differential valve it will not affect anything and will keep the brake fail light as required for RWC. The ebay link is for a proportioning valve which changes the amount of fluid flow to the rear brakes (brake bias). Hope that helps. Best way is to calculate the sizes of pistons in calipers and match the master cylinder accordingly. Think Paul Dunstan made a spreadsheet covering this. 
 
Craig.

Thanks Craig,
 
That explains things nicely.  I will be running a 120Y M/C (17.46mm) so it should be pretty close to match the brakes I have.
 
The wilwood proportioning valve I choose as it'll do the job of the differential valve (to alert me to brake failure, though I think I'll work it out pretty quick) as well as giving me some adjustability of rear bias.
 
Thanks for your reply.
 
Matt