Snoopy and ManxDavid are making sense to me. As mine works I'm going to do nothing 

Same

I have discs all round and run 2psi rvp's the peddle feel much better with them fitted

Davydoff,

Are your RPV fitted to the rear as well as front . What psi

Ta
Paul

Goes completely against everything I was taught when I apprenticed and what I was taught while I worked as pit crew for a team about 25 years ago, but I'm always happy to acknowledge I could be wrong (especially as my memory is so terrible lol) so just had a quick chat with a friend still in motorsport engineering. They confirmed RPV's are used in both, though less important on disk and usually use considerably lower PSI on disk as a result.

10psi most common for drum, 2-4psi for disks.

That confirms it for me, and marries up with what I'm reading on every supplier site I've been looking at for them - e.g. from McGill Motorsport:

"These residual pressure valves retain a minimum brake line pressure to help eliminate excessive pedal travel in both disc and drum brake systems. The 10 PSI valve is used in drum brake applications where the valve is used to compensate for return spring tension and to maintain wheel cylinder sealing inside the drums."

Which matches what I thought I remembered as correct.

I'll strip down the new m/c when it's here and see if they have any fitted inside, if not I'll bung 10psi in-line ones in. I'd rather have original style ones as they're such a neat solution but if they can't be got, they can't be got. Also going to test one of the least-damaged RPV's I've got just to confirm the sort of pressure it runs at!

Got my RPV from McGills

thought I would let the thread run a bit before I mentioned that I have always thought disk residual valve pressure was generally 2 psi. Don`t remember where I picked this up from. I have come across mention a number of times that folk experience poor sealing with "female" brake pipe end to valve seat.  Carbuilder solutions have a photo of an "adaptor" that sits between the pipe end and the valve seat. This may help sealing. (M10 x 1.5... I think).

most vehicle master cylinders retain a pressure if you crack a bleed nipple and fluid momentarily squirts out as it does there is already an rpv action inside the master cylinder.. The relationship in size of the master cylinder pistons and volumes  to the fluid required by the wheel cylinders and callipers gets overlooked as we just bolt on different parts.

I have come across mention a number of times that folk experience poor sealing with "female" brake pipe end to valve seat.  Carbuilder solutions have a photo of an "adaptor" that sits between the pipe end and the valve seat. This may help sealing. (M10 x 1.5... I think).

Biggest issue I found is that here in the UK, we generally use M10x1.5 threads but anything found on the net / USA / China is of a different pitch thread and they do not seal. To compound matters, the ones coming in from Europe seem to be a mix of M10 and other. Some RPV`s are also very deep seated inside, so again, watch that the fittings match - I don`t think anyone could have made it any more complicated to join two bits of threaded pipe together.

Last pair and only pair I have fitted were for buggysteve and I used bulkhead adaptors as the have a long male section where they secure into the panel so stripped them bare and had loads of thread to screw in.

I have come across mention a number of times that folk experience poor sealing with "female" brake pipe end to valve seat.  Carbuilder solutions have a photo of an "adaptor" that sits between the pipe end and the valve seat. This may help sealing. (M10 x 1.5... I think).

Biggest issue I found is that here in the UK, we generally use M10x1.5 threads but anything found on the net / USA / China is of a different pitch thread and they do not seal. To compound matters, the ones coming in from Europe seem to be a mix of M10 and other. Some RPV`s are also very deep seated inside, so again, watch that the fittings match - I don`t think anyone could have made it any more complicated to join two bits of threaded pipe together.

LOL a pet hate of mine - mixing metric and imperial sizes in a project. Absolutely HATE it. I've had to already on this build as the clutch MC is 7/16AF thread, slave is M10 x 1.25

Standard Beetle brake fittings are all M10 x 1 so I've now got three different fittings, which is seriously screwing with my OCD!

The relationship in size of the master cylinder pistons and volumes  to the fluid required by the wheel cylinders and callipers gets overlooked as we just bolt on different parts.

I'm completely anal on this - just doing the hydraulic clutch I've built the entire system in CAD to work out throws, mechanical and fluid advantages etc. Probably why it takes me so long to get anything done lol.

Still, 2 weeks down and the scratch built pedal set are almost complete, just waiting for paint to dry before assembly!

just doing the hydraulic clutch I've built the entire system in CAD to work out throws, mechanical and fluid advantages etc.

Really hoping to see a seperate write up on this one . . . .  Please !!   

just doing the hydraulic clutch I've built the entire system in CAD to work out throws, mechanical and fluid advantages etc.

Really hoping to see a seperate write up on this one . . . .  Please !!   

I'll see what I can do if I find some time next week!

I have come across mention a number of times that folk experience poor sealing with "female" brake pipe end to valve seat.  Carbuilder solutions have a photo of an "adaptor" that sits between the pipe end and the valve seat. This may help sealing. (M10 x 1.5... I think).

Biggest issue I found is that here in the UK, we generally use M10x1.5 threads but anything found on the net / USA / China is of a different pitch thread and they do not seal. To compound matters, the ones coming in from Europe seem to be a mix of M10 and other. Some RPV`s are also very deep seated inside, so again, watch that the fittings match - I don`t think anyone could have made it any more complicated to join two bits of threaded pipe together.

LOL a pet hate of mine - mixing metric and imperial sizes in a project. Absolutely HATE it. I've had to already on this build as the clutch MC is 7/16AF thread, slave is M10 x 1.25

Standard Beetle brake fittings are all M10 x 1 so I've now got three different fittings, which is seriously screwing with my OCD!

How would you feel using my toolbox..... mixture of ancient imperial and metric spanners..