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Posted by Clint Dixon on Thursday, July 31, 2008 at 13:24:47 :
In Reply to: call me crazy BUT ! posted by copey on Thursday, July 31, 2008 at 09:30:03 :
The front shoe is naturally self energizing. The rear shoe is not. This is due to the direction of rotation of the drum in relation to the fixed anchor ends of the shoes and the effect the rotation has on the floating non anchored ends.
Gordon Maney will remember this a n a l o g y: It is kind of like a little kid riding forward down a hill in his little red wagon. If he throws the tongue forward it will dig into the ground and stop the wagon real quick. If he then tries to ride down the hill backwards, and throws the tongue rearward, it will just kind of drag along and not create much friction to slow him down. The anchor end of the wagon tongue is the wagon itself. The floating end is the handle.
The front brake shoe naturally has a better mechanical advantage than the rear (because of the direction of drum rotation and the location of anchor points below the axis of rotation). The front shoe acts like the tongue on a little red wagon that is traveling down a hill forward. The rear shoe acts like the tongue on a wagon that is traveling down a hill backwards.
The most efficient braking systems have both the front and rear shoes equally sharing the same amount of work. Since the front shoe naturally has more mechanical advantage, some breaking systems make up for this (somewhat) by applying longer linings to the rear shoe in order to create more surface contact area. The WDX-WM300, style of brakes, makes up for this difference in mechanical advantage by applying greater hydraulic force to the rear shoe. This was accomplished by designing a wheel cylinder with a larger bore to the rear.
You can physically put the wheel cylinders in wrong with the large bore to the front, but this will not be of any advantage because now the front shoe will be doing a LOT more of the work and the rear shoe a LOT less. No advantage is gained.
Junior
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