Brake system: Connecting Wilwood Residual Pressure Valve to Proportioning Valve

[jacrz]

Is there any reason I can't just thread the Wilwood residual pressure valve directly into the rear drum brake outlet on the Wilwood proportioning valve using a male-to-male fitting? It seems more efficient than running an extra segment of brake line with flare nuts between the PV and RPV.

 

[JeepGuy]

Is there any reason I can't just thread the Wilwood residual pressure valve directly into the rear drum brake outlet on the Wilwood proportioning valve using a male-to-male fitting? It seems more efficient than running an extra segment of brake line with flare nuts between the PV and RPV.



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Not a brake expert by any means, but I do tinker a bit. The only thing I can think of is maybe serviceability down the road??? I'm sure one of the usuals will chime in here.

 

[Apogee]

Does a 3/8-24 MIF X 3/8-24 MIF coupler fitting existing? I know that the female version of that is pretty standard, but I've never seen the male version myself. That said, you could probably modify a 3/8-24 MIF X 3/8-24 (-03) AN coupler, machining the AN end to be an inverted flare without too much effort or expense, but I tend to shy away from custom fittings if I can help it. I would personally mount the inverted flare fitting down under the vehicle along the frame rail and use it as a coupler, shortening and typically simplifying installation/removal of the main front to back hard line if I were fabricating new hard lines. ~ Tobin

 

[DirtDonk]

Just seems to me, intuitively, like the valve should go between the master cylinder and the proportioning valve. Not after it.
But I don’t have any information in that regard, or know that it has anything to do with anything.

 

[Apogee]

Just seems to me, intuitively, like the valve should go between the master cylinder and the proportioning valve. Not after it.
But I don’t have any information in that regard, or know that it has anything to do with anything.

Paul, historically you're not incorrect...the RPV's were installed in the outlet ports of most master cylinders for the drum brake circuits, but it doesn't really matter where it goes in the brake circuit from a functionality perspective. Maintaining residual pressure on the proportioning valve doesn't help or hurt anything, especially when we're only talking about 10 PSI or less, depending on the valve.

 

[DirtDonk]

Thanks for that information. Good to know.

 

[jamesroney]

Does a 3/8-24 MIF X 3/8-24 MIF coupler fitting existing? I know that the female version of that is pretty standard, but I've never seen the male version myself. That said, you could probably modify a 3/8-24 MIF X 3/8-24 (-03) AN coupler, machining the AN end to be an inverted flare without too much effort or expense, but I tend to shy away from custom fittings if I can help it. I would personally mount the inverted flare fitting down under the vehicle along the frame rail and use it as a coupler, shortening and typically simplifying installation/removal of the main front to back hard line if I were fabricating new hard lines. ~ Tobin

I think that the distribution block body is 3/16 inverted flare female, and the residual pressure valve is 1/8 NPT female. (27 TPI)

If you want to do it in one fitting, you would want 1/8 NPT male to 3/8-24 MIF. Machining the AN adapter is a great idea. The Wilwood 220-6956 "Caliper inlet fitting" would do it. Just need to reverse the cone on the AN end.

 

[ntsqd]

Like Apogee, I'm not a fan of custom fittings, but this one could be justifiable.

Same basic adapter, in SS: https://www.summitracing.com/parts/ear-ss981603erl or in steel: https://www.summitracing.com/parts/aer-fbm2511
Would still need to be modified to have the reverse the cone. Needs a lathe and a 90° countersink to do a good job of it, be careful about tool chatter. Downside to steel is that the modification will leave it bare metal where the mod is made, but the cost difference is substantial.

 

[jamesroney]

Like Apogee, I'm not a fan of custom fittings, but this one could be justifiable.

Same basic adapter, in SS: https://www.summitracing.com/parts/ear-ss981603erl or in steel: https://www.summitracing.com/parts/aer-fbm2511
Would still need to be modified to have the reverse the cone. Needs a lathe and a 90° countersink to do a good job of it, be careful about tool chatter. Downside to steel is that the modification will leave it bare metal where the mod is made, but the cost difference is substantial.

Good point on the material selection.

But if I were ACTUALLY going to do it, I'd probably source an SAE tube fitting, (not AN) like a Parker 48F-3-2 in brass, And I think I could counter sink it with a hand drill. It's small enough that a zero-flute 45 degree countersink would do the trick.

(and no...I really wouldn't do it. I also despise custom fittings. I'd replace the rear wheel cylinders with 3/4 bore, and install the correct master cylinder.)

 

[ntsqd]

Maybe you could do it with a hand drill. I'd get the coaxilality screwed up and have to start over with a new fitting......
Which is part of why I own a lathe.

Maybe I've missed the thread where the rest of the system is discussed? Rare to need an RPV unless the m/c is mounted low in the chassis or using disc/disc application with drums.

 

[jacrz]

Thanks all. I thought I had found a good male-to-male fitting and then received it and it doesn't fit. So I may be back to the approach of using a stainless line in between the PV and the RPV. The Wilwood folks seem to agree with Apogee that inserting the RPV after the PV and not in between the MC and PV, is ok/expected with their system. Their mounting system isn't set up too well to accommodate the RPV between the MC and PV in any event -- the lines are specifically designed to connect MC direct to PV.

 

[ntsqd]

Why do you think that you need the RPV at all?