Sunday, May 1, 2011

Brake Master Cylinder Update

I initially thought upgrading the 7/8"  brake master cylinder (BMC) is as simple as upgrading to the 15/16" master cylinder from the SG-L and XG-L models. Life is or should I say Nissan unfortunately did not make it so simple. Picture below of my stock master cylinder.

There are 4 brake lines emnating from the BMC. Now here is a picture of the 15/16" BMC as fitted to the SG-L and XG-L.

There only seems to be two lines emnating from the BMC. So reconfiguring the brake lines will mean I can fit the larger BMC? Not so simple. Picture below illustrates why.

Those two things in red rectangles are what Nissan calls proportioning valves. Consider the fact that N16 models with no ABS and rear drum brakes come with 7/8" BMC while the rear disk brake ABS equipped models come with the 15/16" BMC. Apparently the proportioning valves/residual pressure valves/rear brake pressure reducers are to prevent rear brake lockup. On ABS equipped N16s the dual proportioning valve connected to the ABS unit is doing this job. You can read more about from the G20 Forum here. A thorough study of the USDM B15 technical service manual confirms this. Picture below of the brake hydraulic circuit and technical drawing of the BMC.

Then can I just get a non-ABS Nabco 15/16" BMC with proportioning valves build-in from the US? Altimas are widely sold there with such a BMC. Unfortunately the USDM and left hand drive market BMCs have their lines going into/out of the BMC body in a mirror image (ie the other side). If I stand looking at the BMC on RHD models the lines are emnating from the left hand side. In LHD models it is on the right hand side.What about the UKDM N16. That's RHD right? As far asI know all the N16s sold there with 15/16" BMCs and rear disk brakes are equipped with ABS. Believe me I have extensively checked. What about Australia and New Zealand. Well no one in Oz or should I say the Oz Pulsar forum was able to help. Bummer! :(

So are there any Nabco RHD non-ABS 15/16" BMC with proportioning valves available from Japan or anywhere in this world? I have checked around and the answer is not yet found at this point. I am willing to pay up to 4 figures worse case as I want something new and not some used part from a half cut which may bring more grief. My sources tell me the 15/16" BMC from a Bluebird U13 is a direct bolt-on but good luck trying to find a new one. The U13 Bluebird is the same as the USDM Altima btw. I can get a 15/16" non-ABS BMC from Taiwan that is supposedly a bolt-on but the long term quality cannot be vouched. At this point I've just bout given up and just going to bolt-on my Wilwood front BBK and see what happens. Wish me luck!

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