Argument over A body brake shoes

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jimharvard

jimharvard

JimHarvard
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I always go to the "experts" here at FABO to get answers to my barracuda questions.

I've gotten into a somewhat uncivil argument with a guy on ebay who has advertised "NOS" front shoes for a 67-69 barracuda sized 9"x2 1/2". he says these are for the 6 cyl cudas. i have a factory correct 340 4 sp formula s that has 10"x2" shoes on the front. doing a little math shows that the noted "6 cyl" shoes would have a surface area of 22.5" with the 340 s shoe only having 20" in surface area. this doesn't make sense to me that a 6 cyl cuda would have had bigger brakes on it than what came with the formula s package.

can anyone give me some insight/history to settle this argument?

thanks.
jim coster, pittsburgh, pa aka "jimharvard" at FABO
 
You have to measure the pad size on each shoe instead of calculating 9x2 1/2"=22.5" to get the actual surface area. The pads are going to be shorter on 9" brake shoes.
 
Going by memory here, I believe the 10" drums were 2-1/4" in front and 1-3/4" rear. I'm pretty sure the sizes are listed in the FSM.
 
thanks for the replies...

the real question i want to settle with mr. rude ebay guy is: did 6cyl cudas come with 9x2 1/2" front shoes?

jimharvard
 
jimharvard said:
thanks for the replies...

the real question i want to settle with mr. rude ebay guy is: did 6cyl cudas come with 9x2 1/2" front shoes?

jimharvard
Click to expand...



2 1/2" width sounds a little wide to me, but I do not have the information to verify it at this time.....
 
Keep in mind that less area means more psi on the shoe surface, so a more performance minded car may very well have smaller area of shoe surface.

Just a thought.
 
To add to above..............

make sure you are measuring "around the arc" IE as if circumferance to figure surface

Also, there's an issue with DIAMETER. The simple fact is, regardless of surface, the LARGER you make a brake, either disc or drum, the more LEVERAGE you have on stopping the wheel. You could have a brake that is five feet wide and 2 inches in diameter and it probably would not stop very well, but one 15" in diameter and relatively narrow has much more leverage.

Last, I don't know about these brakes SPECIFICALLY, but it's very possible that the 9" brakes have inferior "efficiency" shall we say, mechanically. What I mean is the servo action, and general mechanical advantage they have as inherent in design.

For example, the old Landcruiser FJ-40 brakes were a TERRIBLE design, right out of the 40's compared to modern drums at the time

Also, smaller drums "might" be more sensitive to shoe fit, that is, if someone puts new shoes into worn drums, you have a difference of diameter (arc). It just might be that "percentage wise" 9" are "more fussy" that is lose more braking more quickly.
 
wow...
i never thought i would get so much technical data regarding drum brakes on a 68 cuda.

let me ask this question a different way ... the "formula s" package included better shocks and a sway bar. i think it also improved the steering box. i also thought the S package included better brakes for the 340/383 v/8. so simply put: does anyone know if the front drum brakes on a formula s cuda (340 or 383) were bigger/better than what came on the non-"S" cudas like a 6 cyl model?

thanks again..
jimharvard
 
jimharvard said:
wow...
i never thought i would get so much technical data regarding drum brakes on a 68 cuda.

let me ask this question a different way ... the "formula s" package included better shocks and a sway bar. i think it also improved the steering box. i also thought the S package included better brakes for the 340/383 v/8. so simply put: does anyone know if the front drum brakes on a formula s cuda (340 or 383) were bigger/better than what came on the non-"S" cudas like a 6 cyl model?

thanks again..
jimharvard
Click to expand...

There was only three possible front brake systems on a 68 A-body. 9", 10" and Kelsey Hayes discs. The 10" or the discs were standard for the most part on all V8 cars and could be had on /6 as well. Rears were either 9" or 10" drums.

Steering boxes were the same across the board if you had an automatic. There was a fast ratio manual steering box available but all I have ever personally owned or seen has been the same across the board also. I have a non S 68 small block Barracuda that has a factory sway bar.

The page 12 below shows the Firm-Ride shocks.
 

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My question is, if your car is running 10" drums and this guy is selling 9" shoes, how did you even get in an arguement with him and why are you continuing to waste your time with him?

The shoes don't fit your car so don't waste your time, thats my advice.

Unless you have too much time on your hands that is...:D
 
I was thinking the slant 6 a-body had a 9X3 front drum. Been years since I've owned or serviced any of those.
 
jimharvard said:
wow...
i never thought i would get so much technical data regarding drum brakes on a 68 cuda.

let me ask this question a different way ... the "formula s" package included better shocks and a sway bar. i think it also improved the steering box. i also thought the S package included better brakes for the 340/383 v/8. so simply put: does anyone know if the front drum brakes on a formula s cuda (340 or 383) were bigger/better than what came on the non-"S" cudas like a 6 cyl model?

thanks again..
jimharvard
Click to expand...

The formula S among other has disc brakes on the front. It was a small diameter rotor but it had a long 4 piston caliper and a long pad.
 
RedFish said:
The formula S among other has disc brakes on the front. It was a small diameter rotor but it had a long 4 piston caliper and a long pad.
Click to expand...



My 68 340 S has front 10" drums. The discs were optional.
 
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