Re: [Amc-list] small disk brake

[Russell Neyhart <rtneyhart@xxxxxxxxxxxxx>]

Good Morning Tom,

I had the same question when I discovered that my Saturn LW300 (a.k.a. 
Opel/Vauxhall/Holden Vectra B Estate) had the same European disc brake 
setup as the SAAB 9-3 Turbos and 9-5 of a similar year. The calipers, 
pads, rear carriers and discs are the same, just the front carriers and 
rotors are changed from, say, a "regular" 9-5 to a 9-5 Aero. The smaller 
ones are 288mm while the larger ones are 308mm, not much more than the 
about 15mm difference between the 4 & 6 cyl. rotors you mentioned.

I thought this must be a matter of physics, but since I am no physicist 
and don't even play one on TV, I thought I'd ask a fellow I work with. 
Fortunately, he just so happens to have a doctorate in physics. Why he's 
working with us, I'll never know, but maybe we're a good bunch? Anyway, 
I asked him about this and his answer was that the principle is like 
when you move the force out from the center of rotation as with a 
teeter-totter or see-saw. The same amount of force farther out is more 
effective, so the same caliper clamping with the same amount of force 
farther from the center of rotation would have a greater ability to stop 
the vehicle.

I would guess there's a point where the extra unsprung weight of larger 
rotors, carriers, and larger wheels to stuff everything under would have 
a negative effect... but if 308mm (12-1/4" setup can stop a 9-5 Aero, I 
would guess a 10-1/4" setup could stop most of our AMCs OK!

Regards,

Russ

Tom Jennings wrote:
> 82 TSM sez that Spirit/Concord with 4 cyl putt putt has
> 10.27" rotors.  The six gets 10.88" rotors. Apparently same
> caliper. Such a small difference, why bother?
>
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