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Purpose of the tool is a gauge to facilitate adjusting the booster pushrod to ensure .020-.030 clearance to master cylinder piston.

A question on logic. I think this tool was adjusted incorrectly upon arrival -- or is it. Arrived with the center rod set .025 less than the legs. I think the rod should be that distance longer than the legs.

In my convoluted logic, to get the needed clearance you would want the center to be the length of the legs plus include the required clearance, not subtract it. You would then bring the booster screw up to the gauge. With it shorter, would it not be bringing the booster piece too far out and pushing against the cylinder piston when assembled--or is that not correct?

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Howard, could you be so kind to show it while in use or to add a (simple) freehand sketch to the picture?


[picture source:http://www.menshealth.de/health/stress/maenner-stark-im-raeumlichen-denken.108286.htm]

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Its used by placing one end of the tool against the master cylinder & running the center rod into the recess where the booster rod fits until it is seated. Remove the tool and place the opposite end against the booster pushrod and adjust the adapter on the pushrod end until it is the correct distance. That prevents too wide a gap between the two with possible loss of motion or too small a clearance and cylinder piston is pushed forward when no brakes are applied and covers the relief port.

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Howard, I found an article that reports on different master cylinders (at least for Chevy and Ford), depending on the kind of brake system. Deep bore cylinders for manual brakes and shallow bore cylinders for power brakes. Do you have the correct master cylinder?

Open this page and scroll down 40% to "Check Booster Pushrod Adjustment".

Gerd, I have the right cylinder. That is actually the company I bought the tool from

What I was questioning is the adjustment as it arrived. Did the assembler make a mistake when putting it together by making the rod shorter than the legs or am I upside down and backwards in the way I think it should work and there is something I am overlooking.

I have been known to screw things up by using faulty logic.

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So do I.

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Yes Howard, and what I was trying to say was that different cylinders need differently pre-adjusted gauges. So let me try it the other way around: do you have the correct gauge?

Preadjusted gauge ???? Its a gauge that has a thumb wheel and a threaded rod. Place the gauge against the MC and screw thumb wheel out until it just touches the piston where the power unit unit stem bottoms out.

Now remove gauge from mc and screw the thumb screw further out an additional .020 - .032 (or what ever clearence u want). Place it against the power unit and adjust power unit stem to just kiss the end of the threaded rod of the gauge.

HTere is nothing "pre-adjusted" abou t any more than a micromter is preadjusted to measure anyhting.

Wwhat is the thread pitch of the gauge????? It appears to be a 1/4 - 20 thread????? In that case EXACTLY ONE TURN of the thumb wheel would cause a .050" change in length.

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Howard, I believe that Keith nailed it. You and me are wrong pre-adjusted.

I'm not sure about that gauge. Look at the end of the POWER unit stem. Is it ROUNDED???? Look inside of the piston of the MC. Is it rounded too????? BUT THE GAUGE has a squared off end on the threaded rod.

Yes Howard, and what I was trying to say was that different cylinders need differently pre-adjusted gauges. So let me try it the other way around: do you have the correct gauge?

They only have the one gauge.

Now remove gauge from mc and screw the thumb screw further out an additional .020 - .032 (or what ever clearence u want). Place it against the power unit and adjust power unit stem to just kiss the end of the threaded rod of the gauge.

That's the point. You shouldn't have to change anything once the cylinder measurement is set. Screw it in to the cylinder depth and remove and place the opposite end against the booster. A properly adjusted gauge should be already there with correction built in or at the least, the two should be the same lengths so you could use a feeler gauge. By having a difference already in the tool or having to make a correction after it is set, it introduces a variable.

I'm not sure about that gauge. Look at the end of the POWER unit stem. Is it ROUNDED???? Look inside of the piston of the MC. Is it rounded too????? BUT THE GAUGE has a squared off end on the threaded rod.

Yes, I agree. I was very disappointed in the quality of the tool. It does go down into the recess but not at all what I was expecting or what the picture showed. Could have made my own. Won't be doing any more business with them. MPB has the same tool but they wanted $26 in shipping and handling for a 6 oz $25 tool.