These brakes may have been troublesome, but they sure did stop the car.
Anyone that read the comparison of the 3 69 luxury cars knows that the
Imperials stopping distance beat the others hands down.
John
Peter Engel wrote:
> Hi all,
>
> There is probably a reason that the 69 Imperial SM warns against cutting
> the brake rotors: warranty experience proved it to be a problem.
>
> I'd say that the rotors were designed to be just barely thick enough in
> the first place. Weight (mass, actually) in motion is kinetic energy
> and your brakes convert that kinetic energy into heat energy during a
> stop. More weight means more heat during stops. The same type of brake
> caliper is used on 67?-72 Dusters, Demons, Valiants, and Darts. So
> Chrysler continued to use the design for 3 addition model years. Why?
> Probably because those cars are much lighter and easier on the brake
> components.
>
> Cutting a rotor down to smooth the faces isn't inherently evil (unless
> done purely for profit) and won't make the part structurally unsound (so
> long as the machining isn't extreme). The problem is that a too-thin
> rotor will not be strong enough to withstand the heat it absorbs during
> a hard stop and it will warp. I'm betting that Chrysler initially
> allowed minor "cleaning up" of the rotors in 67 but immediatey had tons
> of warranty claims for pedal pulsation and other, similar, un-Imperial
> like, brake problems. They therefore made it a no no to machine the
> rotors at all.
>
> I'm also guessing that the caliper design limited the initial rotor
> thickness. With the fixed caliper, the pistons have to do all the
> "taking up" as the pads wear. You only allow a piston to move so far
> out of its bore before cocking is a problem so that was certainly a
> concern. And the dust seals can only extend so far before they won't
> seal reliably. So the engineers were walking a fine line: 1) pistons
> can only extend so far out of their bores, 2) pads have to be of a
> certain thickness for adequate service life, 3) calipers can only be so
> wide before interference with wheels or suspension components is a
> problem, 4) so rotors can, therefore, be only 0.875" thick (or whatever
> the original thickness was).
>
> With warranty claims piling up, Chrysler quickly canned the Budd system
> and went to the trouble-free sliding caliper design for 1970 Imperials.
>
> Pete in PA
>
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