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jim beam wrote:

> Dave and Trudy wrote:

<snip>

>> Just one question...If disks are so much better, why do the large
>> trucks and tour buses still use drums on all axles? I know there are
>> some exceptions but most use drums. I hadn't really considered this
>> until your above comments...
>>
>> Dave D
>>
> very few of the modern tour buses use drums these days, or at least, not
> on the front.
>
> the main reason drums are still used on large trucks, especially big
> rigs, is because of the air brake thing. unlike cars and lighter
> vehicles, they're "fail safe" which means their "natural" position is
> full on as opposed to off like a car. strong springs inside the drums
> press the shoes real hard against the drum, and the air system actuates
> against the springs to hold the shoes off the drum so the vehicle can
> roll. if the braking system fails, the brakes come on, and the 30+ ton
> cargo comes to a halt. hopefully. "fail safe" is much more complicated
> to implement on disk brakes, but real simple inside a drum. plus imo, a
> lot of domestic truck manufacturers are not exactly innovative pioneers
> in the engineering department - the quality of the chrome plating seems
> to get more attention from what i can see.

Plus interstate buses and 18-wheelers are seldom bought on the strength
of some advertising campaign (as opposed to passenger vehicles), IMHO
anyway.

Sparky Spartacus wrote:

> Plus interstate buses and 18-wheelers are seldom bought on the strength
> of some advertising campaign (as opposed to passenger vehicles), IMHO
> anyway.

sure they are! durability, low maintenance costs, that kinda thing.
makes the beancounters that buy the fleet truck purchases feel all warm
inside.