in too deep: trying to go BBP on a 68 barracuda and its going.. poorly.

[72bluNblu]

My opinion: You are wasting time and money. SBP is just fine for most. They made millions of cars with SBP. For all the money you have spent, you could have bought a really nice set of SBP wheels and you could have moved on to something else.

I disagree, especially on a car that will see a lot of miles. 4 wheel drums are not adequate for modern driving. And KH disks have components that are not reproduced and are not always easily found in good condition. Even the SBP rear drums are not always available, there have been multiple occasions where the 10x1 3/4” drums could not be purchased for as long as a year.

The OP also said he wanted “wheel and tire selection”, which I assume means he wants something other than factory wheels or cragars, which is basically all you’ll get in SBP.

If you want to run 15” rally’s and don’t drive that much, SBP is fine. If you want to run a lot of miles (ie, wear out brake parts) and want to run 17/18” wheels and modern tires, SBP isn’t a good option.

 

[CudaFactHackJob]

I hear those 5x4 8.75 rearends can bring a grand. You should've sold it and went with something narrower. 8.8 are out there for $200. Easy to narrow cuz of extra short axles stock. Either stay with the 5x4 or go 8.8. I personally like the look of a wheel with a deeper reverse. So that's why I like a narrowed 8.8 with 7.5 axles for the narrower brakes; allowing for even a narrower rearend that still clears the springs. Now if you start talkin mini-tub...You can move the springs in a bit without mini-tubbing tho.

 

[66fs]

10" drums all around are fine for modern driving. My brother and I put close to a million miles on 64, 67, and 68 Barracudas from 273 to 383 with 10" Drums. They handle and stop fine. We don't run the cheapest stuff though. I've had everything from 9 in drums to 11.75 pinned calipers on them also.

 

[jos51700]

I wouldn't re drill a damn thing. I used the Moser axles with the offset for the f/m body rear drum plates. I robbed a full set of plates and hardware off a Diplomat sitting down the street and it was a pleasant afternoon that made life kinda cool. Pull the old axles, pull the e brake cables and brake lines, toss the A body drum setup with their hard to find drums in the trash (err, classifieds) and stab in the new **** and hook it all back up. By the time you sell the A body drums, this option got a lot less expensive and when all the rear brakes come from one car, getting parts just got a whole lot easier. I actually stamped what they were off of into the backing plates.

No custom parts, no machine work, no drilling anything, no hard to find drums, no headache, no messing anything up, and no one-off wear parts. Didn't even spill any oil in the driveway or wear any safety glasses.

And fu*k 'green' bearings, if we haven't got to that point in the arguments yet. Tapered Timken or go roll a Ford.

 

[jos51700]

10" drums all around are fine for modern driving. My brother and I put close to a million miles on 64, 67, and 68 Barracudas from 273 to 383 with 10" Drums. They handle and stop fine. We don't run the cheapest stuff though. I've had everything from 9 in drums to 11.75 pinned calipers on them also.

10" sure. 9" drums are a death trap.

 

[72bluNblu]

10" drums all around are fine for modern driving. My brother and I put close to a million miles on 64, 67, and 68 Barracudas from 273 to 383 with 10" Drums. They handle and stop fine. We don't run the cheapest stuff though. I've had everything from 9 in drums to 11.75 pinned calipers on them also.

If you think the factory 11.75” rotors & calipers and 10” drums stop the same you’re nuts.

 

[66fs]

If you think the factory 11.75” rotors & calipers and 10” drums stop the same you’re nuts.

Good enough for how I drive. I usually replace pads every 100,000 miles and rotors every 200,000 miles. I'm a defensive driver and rarely get into a panic situation. You can definitely lock up 10" drums with most tires. Maybe not yours but in everyday driving I don't need 11.75 pin calipers. The 11.75 rotors are on my brothers 67 Barracuda that is converted to 5 x 4.50 bolt pattern. Not worth the time or hassle for me and I doubt the OP needs to upgrade the brakes to get his Barracuda going if he has an 8 3/4 rear and 10 inch brakes.

 

[66fs]

10" sure. 9" drums are a death trap.

Those were gone quick.

 

[AJ/FormS]

OP
Nice ride!
As for a streeter;
As for the rear brakes, with four same-sized tires; here is my opinion.....
the factory rear brake proportioning is such that the rear brakes contribute very little to your stopping performance. For a streeter, this has been the norm for decades. I see no good reason to upsize the rear brakes unless you run big and little tires; and even then, you can re-engineer the 9incher performance with some combination of wheel-cylinder size and/or line pressure.
On the front, 235s are about all that fit without modifications, and so, the contact patch is gonna be limited. So then, on the street, when you upgrade your front brakes, they can very quickly overcome your tires.
On the back, it is possible to install 295s, and I did. This allowed me to re-engineer the rear brakes to do more work than the factory set up could. So much so, that my rear 10" shoes wear out about two or three times as often as the KH 4-piston units up front do. The front tires gotta steer the car, so to prevent loc-up in turns, they are the limiting factor. Which is why my rear brakes do more of the work, which necessitated ever bigger tires for more contact patch.
I'm a defensive driver too, but I still beat the tar out of my car.... on the street.
If I had to run same-sized tires all around, I wouldda left the 9inchers back there.
BTW, yes the Barracuda has such big tubs in the back, that you can use adapters no problem. All us big-tub A-body guys in hi-school, ran them back in the late60s/early70s. Of course that was with period offset wheels. Shoot I still have a pair that I last ran into the late 70s.
Happy HotRodding

 

[canyncarvr]

Hi! First off, im new at all this.

First off, welcome to mopars. Welcome to FABO.

I cringed when I read your post. It's been over 40 years, well before the www....but I've been there; all of the drilling, axle, spacer, wheel choice fit/fun, differential buttons, etc etc. I could write my story, but it isn't pertinent and you would learn nothing from it.

I encourage you to keep after it. It CAN be handled and you will get it done...with maybe a drill bit or two (metaphorically speaking) of breakage along the way. Try not to let people dumping on you discourage you too much. Yes, it's tough taking blowback from experts when you asked but a straightforward new-to-mopar question. I've 'been there' plenty, too, even driving mopar for 50-some years.

I would encourage you to be more careful in the asking and writing. The 714, 5.4x5, and the 10-spline comments didn't help me understand anything, but...I'm not an expert.

I got rid of a 4-bolt axle car (13" tires) just because I could not find fancy/schmancy wheels that suited me. That was stoopid. I wish had I had that hi-perf 273 4bbl hurst-linkaged car now.

I wish I'd kept my '68 HP440 833 9-3/4 Charger RT, too. More stoopid.

Those last two bits said to encourage you to keep after it. Your 'cuda is a keeper! Don't be stoopid like me. Don't give up on the car because you only know enough NOW to try to drill a hole in the wrong place.

 

[nckennyb]

I don't know what rims you're planning to use but I know Crager makes 15" rims with SBP because we put 15" Crager S/S rims on my daughter's Dart with SBP which gave us better tire size selection options.

 

[72bluNblu]

Good enough for how I drive. I usually replace pads every 100,000 miles and rotors every 200,000 miles. I'm a defensive driver and rarely get into a panic situation. You can definitely lock up 10" drums with most tires. Maybe not yours but in everyday driving I don't need 11.75 pin calipers. The 11.75 rotors are on my brothers 67 Barracuda that is converted to 5 x 4.50 bolt pattern. Not worth the time or hassle for me and I doubt the OP needs to upgrade the brakes to get his Barracuda going if he has an 8 3/4 rear and 10 inch brakes.

Locking up the brakes is not really a measure of braking performance, it's like the absolute minimum standard. Very small, inadequate brakes can still lock up the tires with a hard and fast application.

But locking the wheels is not the fastest way to stop, and it is not the most difficult thing for a brake to accomplish. Cars stop faster if the wheels remain rolling, called "threshold braking". Rolling and sliding friction coefficients are not the same. Which means, you put more heat and more energy through the brakes if they're NOT locked up. That's the whole reason ABS braking came about, because the average driver just yards on the pedal and locks the wheels. Which means they don't stop as fast as possible AND lose steering capability at the same time (can't steer a sliding tire).

There are much lighter cars that had bigger brakes than the A-bodies did, even a decade earlier! For example, in 1953 the Austin-Healey 100, which was a smidge under 2,000 lbs dry, came from the factory with 11x1.75" front drums. Those were an upgrade from the prototype, which had 10" brakes that were judged to be inadequate by Donald Healey and his other test drivers. And later even the 11's were upgraded further to 11x2.25's, which is the kind of thing you could only get on a B body Mopar. There are cars that stopped worse than our Mopar's for certain, but there were even 4 wheel drum cars that were MUCH better equipped.

It's great that you've never needed more bracing performance, but both the factory disks and the 11.75" disks will stop the car MUCH faster than 10" drums will. And on a modern freeway you can pretty much bet that most of the cars will have ABS and a stopping distance that's 50+ feet shorter than an A-body even with disks. So for a frequently driven A-body that sees modern driving, freeways etc, 4 wheel drums are a poor choice.

 

[66fs]

Locking up the brakes is not really a measure of braking performance, it's like the absolute minimum standard. Very small, inadequate brakes can still lock up the tires with a hard and fast application.

But locking the wheels is not the fastest way to stop, and it is not the most difficult thing for a brake to accomplish. Cars stop faster if the wheels remain rolling, called "threshold braking". Rolling and sliding friction coefficients are not the same. Which means, you put more heat and more energy through the brakes if they're NOT locked up. That's the whole reason ABS braking came about, because the average driver just yards on the pedal and locks the wheels. Which means they don't stop as fast as possible AND lose steering capability at the same time (can't steer a sliding tire).

There are much lighter cars that had bigger brakes than the A-bodies did, even a decade earlier! For example, in 1953 the Austin-Healey 100, which was a smidge under 2,000 lbs dry, came from the factory with 11x1.75" front drums. Those were an upgrade from the prototype, which had 10" brakes that were judged to be inadequate by Donald Healey and his other test drivers. And later even the 11's were upgraded further to 11x2.25's, which is the kind of thing you could only get on a B body Mopar. There are cars that stopped worse than our Mopar's for certain, but there were even 4 wheel drum cars that were MUCH better equipped.

It's great that you've never needed more bracing performance, but both the factory disks and the 11.75" disks will stop the car MUCH faster than 10" drums will. And on a modern freeway you can pretty much bet that most of the cars will have ABS and a stopping distance that's 50+ feet shorter than an A-body even with disks. So for a frequently driven A-body that sees modern driving, freeways etc, 4 wheel drums are a poor choice.

My first BBP swap was in 75 or 76 when I swapped the front manual discs from a low mileage 73 Duster to the front of my 64 Barracuda to replace the 9" drum brakes. Then I carried 2 spares. A year or two later I swapped in an A Body 8 1/4 rear with open carrier 3.21 gears. Now I am down to 1 spare again. Next came a 8 3/4 rear and I am back to 2 spares. Next the fronts went to 10" front drums, back to one spare. No noticeable difference in braking or stopping power in everyday driving. I'm not talking road racing where constant heavy braking is part of driving. My brother Tom's 67 Barracuda has ther 11.75 rotors with pin calipers and it does stop faster, but is way overkill and the custom 8 3/4 rear to keep standard offset 5 x 4.50 BC in the center of the wheelwell is well past the expense and bother of keeping the standard A Body 8 3/4 rear and 10 in drums and being done. Most people are better served getting and keeping their A Body running than hunting down and buying the "best" brakes possible, which is subjective and not a night and day difference. These cars are not under braked like our less than worthless Chevy pickup that would fly past an exit because you didn't hit the brakes soon enough. My point is not everyone needs the brakes to stop a 5,000 pound vehicle on a 3,000 pound vehicle.

 

[CudaFactHackJob]

It's been my experience that a locked wheel will stop a car faster than one that continues to roll; exposing new rubber. As the locked wheel heats the rubber in one spot, it heats up; improving traction. Isn't that why race cars do burnouts? To heat the tires for better traction?

 

[Dartswinger70]

 

[72bluNblu]

It's been my experience that a locked wheel will stop a car faster than one that continues to roll; exposing new rubber. As the locked wheel heats the rubber in one spot, it heats up; improving traction. Isn't that why race cars do burnouts? To heat the tires for better traction?

Lol. No sir, 100% wrong on all accounts.

A locked wheel is the slowest and most dangerous way to stop a car (since you also lose all steering ability), and physics is very clear as to why.

Traction is created by friction, and if you look up the coefficients of friction for a given material you will find there are different coefficients for different situations. The coefficient of friction for a rolling object is higher than that for a sliding object. So, a tire that is still rolling can exert more force on the ground, which means you stop faster.

Next up is the brakes themselves. Brakes stop the car by converting kinetic energy into heat. If your brakes are locked, they're not converting any motion to heat. They're stopped. So the only force acting to slow the car is coming from the tire sliding on the ground. Keep the wheel (and therefore the brakes) turning and you have both a higher coefficient of friction at the tire and also the brakes doing their job and converting motion energy into heat and dissipating it.

Then tires. Street tires and race tires have very different construction. Race tires do have better traction when they're hot, they're designed that way. They also have much shorter life spans, and are only good for a specific number of heat cycles before the composition of the tire starts to change/break down. The fancier and stickier the race tire, the fewer heat cycles they're good for. Street tires are a whole different ball game, they're designed to work over a wide range of temperatures and maintain their composition. The number of heat cycles a street tire goes through in 30k miles is enormous! So they don't see some massive improvement in traction with temperature, they can't. If they did, they'd be junk after a few thousand miles. So yeah, fancy drag race tires get a burnout to warm them up. But if you've drag raced on street tires, you should already know that a big smoky burnout is gonna make your tires slick and greasy an very little time at all. With street tires, if you do a burn out at all, it's just a VERY short one to clean the surface of debris. Anything longer is a detriment to traction. And hey, that applies to braking too! Better off keeping that tire rolling and distributing that heat.

And again, that's why ABS systems exist. It's faster to stop the car without the brakes locked, AND you can steer the car when the wheels are rolling too. Look up "threshold braking". That's the fastest way to stop a car. Unfortunately, it takes practice and skill, and since most drivers lack both of those things when it comes to a panic stop, an entire complicated system (ABS) was invented to the average driver can just slam on the pedal and have the car do the rest.

People's perception is pretty awful, your experiences will deceive you. That's why they set up complicated and regulated tests to get a real scientific answer, because it may feel like locking up the wheels stopped you fast, but it's not the fastest way. But don't take my word for it, look up "threshold braking". You can also get great explanations is any of the Carrol Smith books, or any high performance driving class, or book, or article, or whatever. You will find exactly nowhere that a trusted source tells you that locking your brakes and sliding is the fastest way to stop.

 

[Dfr360cuda]

I already had big bolt pattern but I did swap from drum to disc. The hardest part was removing the upper cam bolts. If I did it again, I would get a torch or an air arc. I used a die grinder and a shitload of sawzall blades.

Nice car, good luck.

 

[AJ/FormS]

Well and then there's this;
My car has a front wheel line-loc.
If I set the line-loc to do a modest low-rpm burn-out, and then slowly bring the rpm up; when the front starts to slide, I have to reduce engine output, else the rpm will run away. To me this proves that friction at the front wheels was lost when it began to slide.
In hi-school Science, we learned that a body at rest tends to remain at rest, and requires more energy to "break-loose" , than to maintain motion after motion has begun, because a body in motion tends to remain in motion.
And this fact relates very well to the torque wrench, in as much as, if you try to tighten the bolt after the wrench has clicked off, it will require a great deal more torque to re-innitiate a turning action.
And my favorite example; if you give a standing person a hard shove, he will take a step forward and that's the end of it. But if you apply the same shove to a running person, he's going down! Ok-Ok, I know not a good example but true and funny when it's the class bully going down, lol.

 

[72bluNblu]

Well and then there's this;
My car has a front wheel line-loc.
If I set the line-loc to do a modest low-rpm burn-out, and then slowly bring the rpm up; when the front starts to slide, I have to reduce engine output, else the rpm will run away. To me this proves that friction at the front wheels was lost when it began to slide.
In hi-school Science, we learned that a body at rest tends to remain at rest, and requires more energy to "break-loose" , than to maintain motion after motion has begun, because a body in motion tends to remain in motion.
And this fact relates very well to the torque wrench, in as much as, if you try to tighten the bolt after the wrench has clicked off, it will require a great deal more torque to re-innitiate a turning action.
And my favorite example; if you give a standing person a hard shove, he will take a step forward and that's the end of it. But if you apply the same shove to a running person, he's going down! Ok-Ok, I know not a good example but true and funny when it's the class bully going down, lol.

All true, but you have to be careful with the starting from a stop example and how your compare it. That's actually static friction, which is once again a different value than either rolling or sliding friction!

But yes, once you exceed the maximum traction of the front wheels at rest and they start to slide it takes less power to keep them sliding than it did to break them loose.

 

[Oldmanmopar]

The bottom line is slam on the brakes. When the tires start screaming join in with the screams from the passengers. Wait for the bang and then the "dead"silence. You are now stopped. No science of friction just common sense.

Next will be getting the chemical composition of the tires and the road with the value rates of their adherence to the application of the pressure after the geometrical force from the types of sneakers your wearing. This will all be in a book of quotes coming soon to a theater near you.

 

[72bluNblu]

The bottom line is slam on the brakes. When the tires start screaming join in with the screams from the passengers. Wait for the bang and then the "dead"silence. You are now stopped. No science of friction just common sense.

Next will be getting the chemical composition of the tires and the road with the value rates of their adherence to the application of the pressure after the geometrical force from the types of sneakers your wearing. This will all be in a book of quotes coming soon to a theater near you.

LOL!

Yeah, see most people want to stop before they hit stuff. If you understand a little bit of physics, you can do a lot of things. Like I dunno, understand how to bring your car to a controlled stop in the fastest way possible? Which just FYI, doesn't involve locking up your brakes. Seriously, check any legitimate source on that.

You don't have to learn about friction coefficients either, you can read it in pretty much any respectable automotive book that covers braking. Or tire construction. Or even driving!

 

[RustyRatRod]

Lol. No sir, 100% wrong on all accounts.

A locked wheel is the slowest and most dangerous way to stop a car (since you also lose all steering ability), and physics is very clear as to why.

Traction is created by friction, and if you look up the coefficients of friction for a given material you will find there are different coefficients for different situations. The coefficient of friction for a rolling object is higher than that for a sliding object. So, a tire that is still rolling can exert more force on the ground, which means you stop faster.

Next up is the brakes themselves. Brakes stop the car by converting kinetic energy into heat. If your brakes are locked, they're not converting any motion to heat. They're stopped. So the only force acting to slow the car is coming from the tire sliding on the ground. Keep the wheel (and therefore the brakes) turning and you have both a higher coefficient of friction at the tire and also the brakes doing their job and converting motion energy into heat and dissipating it.

Then tires. Street tires and race tires have very different construction. Race tires do have better traction when they're hot, they're designed that way. They also have much shorter life spans, and are only good for a specific number of heat cycles before the composition of the tire starts to change/break down. The fancier and stickier the race tire, the fewer heat cycles they're good for. Street tires are a whole different ball game, they're designed to work over a wide range of temperatures and maintain their composition. The number of heat cycles a street tire goes through in 30k miles is enormous! So they don't see some massive improvement in traction with temperature, they can't. If they did, they'd be junk after a few thousand miles. So yeah, fancy drag race tires get a burnout to warm them up. But if you've drag raced on street tires, you should already know that a big smoky burnout is gonna make your tires slick and greasy an very little time at all. With street tires, if you do a burn out at all, it's just a VERY short one to clean the surface of debris. Anything longer is a detriment to traction. And hey, that applies to braking too! Better off keeping that tire rolling and distributing that heat.

And again, that's why ABS systems exist. It's faster to stop the car without the brakes locked, AND you can steer the car when the wheels are rolling too. Look up "threshold braking". That's the fastest way to stop a car. Unfortunately, it takes practice and skill, and since most drivers lack both of those things when it comes to a panic stop, an entire complicated system (ABS) was invented to the average driver can just slam on the pedal and have the car do the rest.

People's perception is pretty awful, your experiences will deceive you. That's why they set up complicated and regulated tests to get a real scientific answer, because it may feel like locking up the wheels stopped you fast, but it's not the fastest way. But don't take my word for it, look up "threshold braking". You can also get great explanations is any of the Carrol Smith books, or any high performance driving class, or book, or article, or whatever. You will find exactly nowhere that a trusted source tells you that locking your brakes and sliding is the fastest way to stop.

Like our beloved high school auto shop teacher used to say "Braking is least effective during a skid".

 

[Kern Dog]

Good enough for how I drive.

 

[66fs]

View attachment 1716052295

I grew up driving boats before cars. I time lights. I'm not stupid enough to ride someones backside. If someone drives like a moron, I get as far away from them as possible. I've probably put half a million miles on A Body Barraudas with 10 in drum brakes and never needed more. Shouldn't she be driving a red Super Stock Dodge?

 

[Oldmanmopar]

LOL!

Yeah, see most people want to stop before they hit stuff. If you understand a little bit of physics, you can do a lot of things. Like I dunno, understand how to bring your car to a controlled stop in the fastest way possible? Which just FYI, doesn't involve locking up your brakes. Seriously, check any legitimate source on that.

You don't have to learn about friction coefficients either, you can read it in pretty much any respectable automotive book that covers braking. Or tire construction. Or even driving!

You my friend are a piece of work, Your's truly Steve Kiss