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The Iron Duke Resource Site |
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Welcome to my newly
redesigned Fiero 2M4 resource site. The original site recorded over
12000 visits, hopefully this one will also prove as useful.
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Brakes,
Brakes, Brakes !!!
Are
the stock 1984-1987 brakes really that bad?
I
know these are not lightweight cars and solid rotors are much more prone to
fade, back in 1975 GM learned a lesson from the Chevrolet Monza. The
1975 Monza offered a V8 option on what was essentially a Vega chassis.
The chassis improvements GM made resulted in a fine handling machine (the rear
suspension design is essentially what we now see on the Camaro/Firebird F-bodys)
with decent performance for 1975 (about the same level in the pecking order
that the Fiero GT was in 1985). However they had 13" wheels
borrowed from the Vega (although they were 6" wide) and solid rotor disk
brakes up front. One panic stop and your plastic wheel covers would
shrivel and fall off. In 1976 the brakes had new calipers and vented
rotors, they were a big improvement and the result was a car with very
good brakes (for 1976 that is).
The
difference here was that the Monza had tremendous brake fade recorded by all
of the car magazines, along with the aforementioned melted wheel covers,
the Fiero brakes faired well in magazine tests with minimal fade recorded by
Road&Track, Motor Trend and even Car and Driver which seemed to have a
vendetta against the Fiero, always giving a very negative overall tone to
their tests.
I
know this statement will cause all of you who have had problems to jump all
over me but I need to understand here. If they are properly maintained, and
the right pads are used, are the brakes that bad?
Brake
Facts:
1)
The mass of the brake rotor is the single biggest factor in street braking
performance. The more mass, the better heat sink, and for street driving
the rotors must serve this purpose. Extremely rapid cooling can result
in warped rotors, for example racing brakes stay hot for the duration of a
race and then cool down while sitting in the pits, street brakes may be called
upon for a panic stop, which heats the rotor very rapidly, followed by
acceleration to highway speed where the airflow cools the brakes quickly and
may keep them cool for hours before they are again called upon for another
extreme stop. This is abuse. Many people will argue that the objective
is to cool the rotors as quickly as possible, changing the kinetic energy of
motion into heat energy and then dissapating this energy into the air, thus
completely avoiding brake fade, however temperature cycling this rapid may
result in warps. Another argument is that large vented rotors cool
quickly and warps are the result of overheating, this actually supports my
argument since more massive vented rotors will act as a better heat sink and
the vents will cause more even cooling. Fiero rotors are not very massive,
stroke against Fiero.
2)
Vented rotors carry this heat away far more efficiently that solid rotors
since the vents tremendously increase the surface area in contact with the air
(the greater the surface area the more rapid the cooling). Some vented rotors
are directional and actually pump air from the centre to the edge when moving.
Wilwood uses straight vanes in their Fiero rotors since this increases the
surface area but allows for rotors to cool on their own without added airflow.
Second stroke against Fiero.
3)
Solid rotors and aluminum calipers result in low unsprung weight. The Opel
based Chevette suspension was not designed with heavy brake parts in mind.
The wheel bearings are marginal and should be checked regularly, even with the
stock brakes. The Grand Am brake upgrade adds a significant amount to
each wheel in the worst possible way, as unsprung weight. The larger
bore iron calipers and the vented rotors of the Grand Am brakes do however
make for a system which supplies far greater fade resistance. Perhaps
the unsprung weight was the reason GM chose not to use bigger brakes until it
had the new suspension in place in 1988? Upgrades such as the Wilwood
system replace the spindle to use larger sealed bearings, they also use
aluminum calipers and rotor caps which makes the weight penalty mostly
confined to the bigger rotors ( where it should be, see #1 above). Low
unsprung weight is a Fiero plus.
4)
David C. at
http://www.terranexus.com/fieroman/
has an interesting solution for early Fieros which combines the Wilwood
Dynalite II aluminum calipers with the late model (1996 to present) Cavalier
10.2" rotors. Better brakes for less cost than the full Ryane
package, less unsprung weight, and they will fit the factory 15" wheels
with slight modifications. (Check out the site). The only issue with
this type of modification is that correct sizing of master cylinder bores are
necessary to provide for the calipers in use.
I
love the look of the aluminum calipers on my Fiero, but their purpose is to
work, not to look good. I intend to modify my Fiero to the maximum my
budget will allow ( OK, so right now that would mean buying a K&N filter).
A good brake system rebuild with the quality parts will do until a properly
engineered system is available for a reasonable price.
Ira
Crummey
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