Brake question...

Bassman/NZ

Bassman/NZ

Well-known member
Is a dual master cylinder with a 1" bore and about 1 1/4" stroke going to work with my 39 front brakes and 47 pickup rears?
Thanks, Marty.
 
I would say it should .I used a MK 2 zepher on this set up once and it didnt because the bore size of the MC was 5/8 .So the displacment was not matched .You need at least the size of the stock 39 MC .
 
The bore of the original 39 MC is 1-1/16", or 1/16" larger than the dual MC. This will work, but will require slightly more pedal travel to push same amount of fluid, but pedal will be a little easier to push. You do need to confirm that the pushrod stroke (resulting from full available pedal travel, including about 3/8" for free travel at pedal and 1/16" at pushrod) is equal to or exceeds the full stroke of the MC. See my recent other post regarding dual MC's. Also, IF the new MC has no built-in residual pressure valves, will need to use external 10lb valves as near to the MC as possible. I am aware of ONE MC # that has built-in valves for 4-whl drum brakes, but there may be others; someone may know...

You don't say what year/model your vehicle is, but space above the dual MC
can be an issue/problem, as well as toward the rear of where the original MC
was located... Need access for the typically larger "lid" so have to cut a bigger
hole usually...
 
Thanks Richard. Its an AV8, space is not a problem. The m/c is Australian Holden, I will have to check whether it has the residual pressure valves. Here in NZ it's a legal requirement to have dual m/c on a new build.
 
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