[Vwdiesel] Was: brake bleeding hell on a VW bug-Drum brake overheating

[Tony and Lillie]

I understand that. But, the original comment I posted was that if the 
brakesa re adjusted too tightly, they will drag to the point of heating and 
nearly locking up. However, in a big rig, as the brakes heat up, they loose 
their effectiveness, to the point of completely being innefective.

I just don't understand why one vehicle's brakes gets tighter while the 
other looses effectiveness. However, I've experienced both (thankfully only 
once on a big rig!), so I know it's a fact.

BTW, that was a good explination.

Tony

----- Original Message ----- 
hell on a VW bug question


If you look at a material like metal, when it expands it generally
does so in a uniform manner. Think of a balloon being blown up. If you
have a dot on the surface, no matter where it is it will get bigger.
The same thing with a hole drilled in metal - it will get bigger as
the metal expands. The same thing for the inside of a brake drum - it
will expand as the metal expands. Everything expands in all
directions, but the net effect is an outward expansion at all points.

If you don't believe me you can do some research on it. When I first
encountered such a thing I was very unsure which would happen -
expanding inward or outward. I finally managed to find the math that
showed very conclusively that everything expanded. But in essence you
can just imagine a balloon. Even if you draw a circle and then blow it
up the whole thing will expand, even though the line of the circle
itself is getting thicker.

Erik