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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.
Ira Crummey

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