[Amc-list] Grand Unified Brake List

["Swygert, Francis G MSgt 436 CES/CECM" <Francis.Swygert3@xxxxxxxxxxxx>]

TomJ wrote:
There are four different combo valves. Many truisms I've heard
here are not necessarily true:

* Front disc/rear drums, the rears always need/get proportioning. WRONG!
* Front disc/rear drums, front always gets metering. WRONG!
-------------

Enlighten me some more here! The second statement I've found to be true
-- only a few years used a metering valve. It's more of a nicety than a
necessity. Even if the rear brakes start to engage a split second before
the fronts, that's not likely to cause any problems as the rears will
still be far from locking up. I've never heard of a metering valve used
without a proportioning valves, though it's possible to do so with
aftermarket parts. I don't think any US factory car has ever had a
metering valve that wasn't part of a combo valve, but I could be wrong. 

I've yet to find a COMBINATION VALVE that doesn't have rear
proportioning built into it -- at least in an AMC. The TSM may not state
the valve has it, just that it's a combination valve. The TSMs don't
spell out things that are considered general knowledge, often just
detailing a feature the first year or two it's used then glossing over
it every other year. 

Some disc brake systems have a standard distribution block with a brake
light switch only (after 1965, 65 and earlier don't have a brake light
to switch!). Those had one of two brake balancing devices: 65-67 used
non-servo rear brakes to reduce rear brake power, 68-70 used a separate
proportioning valve in the rear brake line just in front of the rear
axle. The 65-67 cars are probably the ones you're referring to as having
no proportioning valve -- that's a fact! But there is still a
*balancing*, if not a *proportioning*, device used. Stating that no
proportioning valve is needed/used is a misrepresentation since
*something* was used to balance braking action. 

You have to remember that most current AMC enthusiasts don't know much
about pre 68 cars like you and I, and don't really care much about
"Rambler era" cars. The majority are late 60s/early 70s fans. The older
cars are just "interesting". Performance and parts availability are the
driving factors, as well as styling. I put the 63-64 Classic/Ambo right
up there with the Javelin as a "timeless" design, but others don't
agree. Even the Hornet is close -- though I wonder how much of that is
just familiarity since it was used so long.  

-----------------------
Disc brakes: basically there's K-H which are fine but rotors
are expensive. There's the funny little 4cyl Bendix rotor,
the low-drag caliper [and drum?] then the big single piston
Bendix. That's the one everyone wants for swaps. Simple!
-----------------------

Almost. 
65-70 -- four piston Bendix 
71-74 -- Kelsey Hayes 2.75" piston calipers
75-76 (all), 75-78 Matador -- Bendix 3.1" piston calipers
77-78 (except Matador) -- big bearing Bendix 2.6" piston calipers (used
same bearings as big Bendix)
79-81 -- small bearing Bendix 2.6" piston calipers
82-83 (and through 88 Eagle/Jeep) -- GM 2.6" piston calipers 
The "small bearings" are typical for all six cylinder drum brake AMCs,
the "big bearings" were used with V-8s. All K-H and 3.1" Bendix disk
brakes use the big bearings, six or V-8. I did a little spindle research
over the weekend and discovered that. All AMCs used only two bearing
sizes. I think Andrew Hay pointed that out some time ago. 

79-83 are the sought after brakes, with 82-83 considered the best
because they are a low drag design. The big bearings make the 77-78 2.6"
rotors more expensive, and the fact that they were only used two years.
The rotor interchanges on all 79-83 models. A few people prefer the big
Bendix brakes because the rotor is thicker -- it has more cooling
capacity. Worth the extra dough for the rotors on a road racer, not
important for a street or drag car. It takes some hard driving to heat
up the thinner rotor (0.88" compared to 1.125"... check the books on
those numbers though, might be a bit less than 1.125"... 79-83 only,
some earlier ones are different, 73 are all 0.94"-1.00")

The factory 77-78 2.6" calipers reportedly had a phenolic piston, but
rebuilds use steel. I've never seen an original caliper that hasn't been
rebuilt -- probably because the phenolic piston supposedly started
leaking after a few years use. I doubt an original caliper exists on a
car that was driven much! 

I've never seen four piston Bendix brakes on a six cylinder car from the
factory, probably seen as a waste, could have been a V-8 only option. 

Part numbers, incidentally, don't help a thing when identifying parts
interchangeability! Numbers seemed to change for no apparent reason for
parts that I know look identical. Maybe a new casting die was made or
the material the part was made from changed, who knows? There's no way
to find out now!


Tom knows I'm not trying to be argumentative -- we had a little
discussion about these "debates" off-line. Just wanted everyone else to
know! 
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