7/8" Master Cylinder and Rear Disc Brakes...

Suspension, including wheel, tire and brake.
User avatar
JLsKA
Posts: 42
Joined: 06 Feb 2012 00:56
Location: San Diego, CA

7/8" Master Cylinder and Rear Disc Brakes...

Postby JLsKA » 11 Apr 2014 10:04

I just bought a new 7/8" MC and will be running rear disc brakes.
I have read that the check valve for the rear bowl should be removed, for rear disc applications... Is this correct?

Thanks,
James

User avatar
bertvorgon
Supporter
Posts: 10028
Joined: 04 Aug 2003 20:45
Location: White Rock, B.C. Canada

Re: 7/8" Master Cylinder and Rear Disc Brakes...

Postby bertvorgon » 11 Apr 2014 10:52

Check valve...???? Elaborate.
"Racing makes heroin addiction look like a vague wish for something salty" - Peter Egan

Keith Law
1973 2Door Slalom/hill climb/road race / canyon carver /Giant Killer 510
1968 Vintage 3HP Mini Bike
1971 Vintage 13' BOLER trailer

User avatar
Great_Escape
Supporter
Posts: 63
Joined: 14 Jun 2013 21:18
Location: Soquel, Ca

Re: 7/8" Master Cylinder and Rear Disc Brakes...

Postby Great_Escape » 11 Apr 2014 14:42

JLsKA wrote:I just bought a new 7/8" MC and will be running rear disc brakes.
I have read that the check valve for the rear bowl should be removed, for rear disc applications... Is this correct?

Thanks,
James

Residual pressure valve that is built into cylinder? If you pull the brass seat out of the out of the master cylinder you will see a rubber one way valve and a spring that holds it in place. I've found the easiest way to take out the seat is to tap it then use a small machine screw to pull it out, remember not to damage it because it goes back in.

User avatar
JLsKA
Posts: 42
Joined: 06 Feb 2012 00:56
Location: San Diego, CA

Re: 7/8" Master Cylinder and Rear Disc Brakes...

Postby JLsKA » 11 Apr 2014 16:04

You mean those big brass seats that look like hex nuts aren't threaded? Seems wrong to have to drill it.
Is this what Baz @ Datsport is doing to his optional MC for rear disc?
I bought mine from Troy Ermish but he hasn't replied to my same question.

User avatar
Great_Escape
Supporter
Posts: 63
Joined: 14 Jun 2013 21:18
Location: Soquel, Ca

Re: 7/8" Master Cylinder and Rear Disc Brakes...

Postby Great_Escape » 12 Apr 2014 09:31

JLsKA wrote:You mean those big brass seats that look like hex nuts aren't threaded? Seems wrong to have to drill it.
Is this what Baz @ Datsport is doing to his optional MC for rear disc?
I bought mine from Troy Ermish but he hasn't replied to my same question.

I was referring to the brass seat that the brake line tubing sits against. In this picture it looks like the seats are aluminum. Sometimes the seat for the tubing has a slight press fit to it. That is where the machine screw comes into play. Sometimes they fall right out. Just remember not to mess up the taper as that is where your brake line seals.
Attachments
10.jpg
10.jpg (75.03 KiB) Viewed 1374 times

User avatar
bertvorgon
Supporter
Posts: 10028
Joined: 04 Aug 2003 20:45
Location: White Rock, B.C. Canada

Re: 7/8" Master Cylinder and Rear Disc Brakes...

Postby bertvorgon » 12 Apr 2014 09:59

Ah....RESIDUAL PRESSURE VALVE.

I can see taking the back one out, as it was for drum brakes, but, would it not be a bit of an issue to remove the front brake one?
If we want to minimize pad retraction, I thought we want a hair of residual pressure, to keep the pads out.

I'm just curious, so if you have any info from Baz, let us know.

I do whatever I can to minimize pad knock back and retraction. I even specified the seals in my front calipers.
"Racing makes heroin addiction look like a vague wish for something salty" - Peter Egan

Keith Law
1973 2Door Slalom/hill climb/road race / canyon carver /Giant Killer 510
1968 Vintage 3HP Mini Bike
1971 Vintage 13' BOLER trailer

User avatar
JLsKA
Posts: 42
Joined: 06 Feb 2012 00:56
Location: San Diego, CA

Re: 7/8" Master Cylinder and Rear Disc Brakes...

Postby JLsKA » 14 Apr 2014 12:58

Thanks, guys... I just heard back from Troy and he said the 7/8" MC he sold doesn't need any mods.
Hopefully, I won't have any problems.

datzenmike
Supporter
Posts: 5259
Joined: 24 May 2006 12:40
Location: Van. Isle.

Re: 7/8" Master Cylinder and Rear Disc Brakes...

Postby datzenmike » 14 Apr 2014 19:07

Disc residual valves are only a few pounds but drum are 8-12 pounds. (give or take) When I installed my 15/16" zx master it would have had a rear disc brake residual valve in it. I just put the rear drum residual valve from my 710 master in it. I wouldn't run without one, just get one from the front of any old master. It's only a couple of pounds to keep the pad rubbing the rotor to keep it clean.
"Nissan 'shit the bed' when they made these, plain and simple." McShagger510 on flattop SUs


Return to “Suspension”



Who is online

Users browsing this forum: datzenmike and 1 guest