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Joe K · 03-25-2023, 07:51 PM

The limitation of the Model A in braking is NOT the mechanical system. You get the identical system duplicated in hydraulic when you do the conversion.

Rather the limitation on braking for the Model A is found FIRST in the "square inches" of rubber contacting the road. This doesn't usually change without upgrading to later Ford wheels/Tires. SECOND limitation is the original design of the pressed steel brake drums and their tendency to "fade" as the drums wear thin.

By WWII most of the original Model A brake drums were worn out. Ford themselves knew of the "sensitivity" of the pressed steel drums and for a very short time at the end of the Model A production Ford went with a cast iron drum on a pressed steel center, EXACTLY the same system used in the later 32 up Fords. And this includes the transition to hydraulic brakes after 1939. Model A late model "sandwich" drums are still very much in demand for the show circuit.

Aftermarket cast iron drums in the "hole" pattern (give good ventilation) were also available in the late 30s through the 50s. Until Mel Gross, these were the desired find at automotive flea markets.

Many have done the "change over" to hydraulic brakes using the 39 up setup. They don't fit exactly on the Model A axles, but "shim kits" are available. Without compensation somehow, the later brakes/drums are entirely too "strong" for the lighter Model A car. There are some advantages not the least of which is the cast iron drum. The earlier backing plates still require you to manually adjust. Later post WWII hydraulic backing plates have the advantage of "self adjusting." Clings had/has a good system and actually reverse engineered and "fine tuned" the 39-47 brakes. Nkaminar above describes another change aimed at fine tuning the mechanical brakes of the Model A (and describes PERFECTLY the error in design built into the Model A brakes - an error which can be corrected in adjustment or swapping the levers.)

He brings back memory of my working with my Dad to adjust the brakes the first time by driving the car on a gravel driveway and noting from the skid marks which wheel skids first. Dad had limited knowledge of the car "tilting forward" on braking, but the skid on the driveway tells all.

Really, the BEST thing you can do for Model A brakes is to retain the mechanical system. Buy the "widest" tires that fit your model year rims AND do Mel Gross' cast iron drums.

Widest tire - For a while Firestone tires were the widest available for the 28-29 Model year rims with a stated 5.25/5.75 inches. Some users then noted that the wheels were SO wide that when you take a tight curve the wheels rub against the fender supports (and spall off the inner edge of the tire.) These tires/width may not be available now

Good luck however you go with this.

Joe K

03-25-2023, 07:51 PM	#7
Joe K Senior Member Join Date: Jul 2010 Location: Cow Hampshire Posts: 4,188	Re: Brake drums The limitation of the Model A in braking is NOT the mechanical system. You get the identical system duplicated in hydraulic when you do the conversion. Rather the limitation on braking for the Model A is found FIRST in the "square inches" of rubber contacting the road. This doesn't usually change without upgrading to later Ford wheels/Tires. SECOND limitation is the original design of the pressed steel brake drums and their tendency to "fade" as the drums wear thin. By WWII most of the original Model A brake drums were worn out. Ford themselves knew of the "sensitivity" of the pressed steel drums and for a very short time at the end of the Model A production Ford went with a cast iron drum on a pressed steel center, EXACTLY the same system used in the later 32 up Fords. And this includes the transition to hydraulic brakes after 1939. Model A late model "sandwich" drums are still very much in demand for the show circuit. Aftermarket cast iron drums in the "hole" pattern (give good ventilation) were also available in the late 30s through the 50s. Until Mel Gross, these were the desired find at automotive flea markets. Many have done the "change over" to hydraulic brakes using the 39 up setup. They don't fit exactly on the Model A axles, but "shim kits" are available. Without compensation somehow, the later brakes/drums are entirely too "strong" for the lighter Model A car. There are some advantages not the least of which is the cast iron drum. The earlier backing plates still require you to manually adjust. Later post WWII hydraulic backing plates have the advantage of "self adjusting." Clings had/has a good system and actually reverse engineered and "fine tuned" the 39-47 brakes. Nkaminar above describes another change aimed at fine tuning the mechanical brakes of the Model A (and describes PERFECTLY the error in design built into the Model A brakes - an error which can be corrected in adjustment or swapping the levers.) He brings back memory of my working with my Dad to adjust the brakes the first time by driving the car on a gravel driveway and noting from the skid marks which wheel skids first. Dad had limited knowledge of the car "tilting forward" on braking, but the skid on the driveway tells all. Really, the BEST thing you can do for Model A brakes is to retain the mechanical system. Buy the "widest" tires that fit your model year rims AND do Mel Gross' cast iron drums. Widest tire - For a while Firestone tires were the widest available for the 28-29 Model year rims with a stated 5.25/5.75 inches. Some users then noted that the wheels were SO wide that when you take a tight curve the wheels rub against the fender supports (and spall off the inner edge of the tire.) These tires/width may not be available now Good luck however you go with this. Joe K __________________ Shudda kept the horse. Last edited by Joe K; 03-25-2023 at 08:00 PM.