Message text written by "Power British Performance Parts, Inc."
>Actually, the center bore that fits over the axle nut is the same for both
drums, and
there is no problem with drums locating on center for either combination.
The
difference is in the shank of the wheel stud. While both cars take the
same 7/16 - 20
lug/stud, the shank on the solid axle cars is stepped to about 9/16 at the
hub and the
holes in the drum for the studs are correspondingly larger. With that in
mind, if you
were to install a TR-4 drum onto a TR-6, the drum would locate properly on
the hub's
center, but you'd have axial shift about the extra clearance in the stud
holes. In
this situation, the only positive location for the drum would be the
retaining
screws. True, friction between the drum, hub, and wheel would and should
probably
keep it from shifting. But if it doesn't, the drum may slip, especially in
a panic
stop the forces involved are quite high. If the drum does slip, all the
panic-braking
force would be transmitted throught the locating screws and the they might
shear under
such stresses. This could result in potential damage to the drum or hub.
Of course, you could run the combo without the screws, and just allow the
drum to
shift on the clearance around the stud holes, but I sure wouldn't want to
take any
chances like that with my brakes.
<
The sole purpose of the screw is to keep the drum in place until the wheel
is secured tot he hub. The screw is made of low grade steel and would
deform straight away if subjected to the braking torques involved. Then,
as you say, the drum shift shifts back and forth through the 1/8 in of free
play between the stud and the hole in the drum the impact would stress the
two components involved and could lead to failure as you pointed out,
Brian.
However, one could locate some steel tubing that is 7/16 ID and 9/16 OD and
cut washers that are slightly shorter than the thickness of the brake drum
and remove the clearance problem. In theory.
But then if this were a big problem someone would be selling them.
Dave
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