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Reply to "brakes"

Gary: Most of the speedsters over here have later-model (think Super-beetle), dual circuit (front/rear) Brazilian master cylinders which are almost adequate for a Speedster, but typically need a little help. While a proportioning valve can be used, they are big (because of the housing and the knob) and, quite frankly, are not really needed on a Speedster unless you're racing it and may be changing brake pad/shoe compositions often and have a need to compensate for differing stopping coefficients caused by differing pads (or differing driver's tastes in multi-driver racing scenarios, like LeMans or Rolex long distance races).

So..... After you've adjusted the rear brake shoe adjusters and found that they were pretty much adjusted correctly in the first place and still you're getting far too much braking on the front and not enough on the rear, then get a 10 lb. residual valve and have a good brake shop install it anywhere along the length of the rear brake line BEFORE it gets to the "T" at the rear. It can go on at the master cylinder or anywhere along the line going to the rear (I like it about half way back, because it's easy to get at the brake liine and the seat hides the valve.

Get one of these: http://www.wilwood.com/MasterCylinders/MasterCylinderValves.aspx

Scroll down to the red, 10 lb. residual valve.

CB Performance has them, too, at higher prices.

BTW: ALL new cars with disk front and drum rear braking systems have these valves in their circuits. Some master cylinders even have them built in (like Honda).

Oh - I almost forgot.....WHY do you need this valve??

Because there are two pistons within your master cylinder (separate front and rear circuits) and they're both about equal in the amount of fluid that they move in a pedal stroke (and they were probably designed with drum brakes in mind). When you mix disk and drum brakes, even on different circuits connected to the same pedal stroke, you cause an imbalance in braking because disk brakes need to move far less than drum brakes and, therefore, need less fluid to actuate them. When you step on the pedal, the fronts engage first because, being disks, they need less pedal travel to engage so the rears are sort-of floating back there and not doing much. As you're about to run into the rear of that big SUV in front of you, you push much harder on the pedal but even that doesn't move much more fluid because the front circuit is pressing back and not allowing the pedal to move enough to engage the rear drums - your front brakes are doing all the work and your rear brakes are sitting there laughing as you hit the SUV.

The redisual valve keeps 10 pounds of pressure in the rear circuit, thereby keeping the shoes almost, but not quite, engaged. When you step on the pedal, both circuits move the same amount of fluid (not really, but close enough for this discussion) and then engage both the front and rear circuits at roughly the same time and with the same amount of force. Bingo! Both ends brake the car.

Hope this helps.

Gordon
The Speedstah Guy from Beaufort

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