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PostPosted: Tue Apr 21, 2020 8:12 am 
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Supercharged
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I Stumbled on these:

https://www.summitracing.com/parts/sph-127-63005l

https://www.summitracing.com/parts/sph-127-63005r

Stoptech makes New performance rotors for the OE 4 Piston Brakes on the SBP cars.

I might Buy a set for the 69 Dart and toss on some EBC Yellowstuff pads for Fun and Giggles.

I have Solid wheels on that car so no one will see them anyway.

Sneaky!

Greg

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PostPosted: Wed Apr 22, 2020 12:40 pm 
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Car Model: 68 Valiant
Nice. I saw someone (forgot who) was selling them with big bolt pattern, too. Wish I had paid more attention....

The 4 piston brakes are probably a better brake than the later single piston brakes.

Although now that I think about it....Are they KH? I thought they were Budd? Maybe just on the larger cars?


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PostPosted: Wed Apr 22, 2020 12:58 pm 
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GregCon wrote:
The 4 piston brakes are probably a better brake than the later single piston brakes


How are we defining "better"? The single-piston brakes have a fair number of advantages.

Quote:
Although now that I think about it....Are they KH? I thought they were Budd? Maybe just on the larger cars?


Both the 4-piston pre-'73 and the 1-piston '73 up A-body disc brake setups were KH.

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PostPosted: Wed Apr 22, 2020 2:07 pm 
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Better pedal feel, lighter, smaller package, and (possibly) better stopping ability. But more costly and probably a little more prone to leaks given the added number of seals. I'd also guess the 4 piston design is less prone to pad/caliper chatter as there are no sliding pieces.

I don't see any modern cars of a high-performance nature using single piston front discs. My Challenger has some wicked-good 6 piston Brembo's. The old KH 4 piston A Body brakes are much closer to that than the single piston design.


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PostPosted: Wed Apr 22, 2020 2:30 pm 
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Supercharged
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GregCon wrote:
Nice. I saw someone (forgot who) was selling them with big bolt pattern, too. Wish I had paid more attention....


See Here:

viewtopic.php?f=13&t=64790


Greg

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PostPosted: Wed Apr 22, 2020 3:32 pm 
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Location: Houston
Car Model: 68 Valiant
Ahh. So it was you!


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PostPosted: Wed Apr 22, 2020 5:11 pm 
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I worked in a service station in the late '70s early '80s. The big thing I remember about the K-H brakes was it being very common for the calipers to leak, and it was pretty to to get seal kits to hold in them. Corvettes were the same way. I think they started doing to stainless liners in them like they did Vette brakes.

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PostPosted: Wed Apr 22, 2020 5:33 pm 
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GregCon wrote:
I don't see any modern cars of a high-performance nature using single piston front discs.


Okeh, but the cars we talk about on this forum are about as similar to modern high-performance cars as an orange is to an orange jelly bean, so what modern cars of a high-performance nature do is not really relevant to A-body disc brakes.

As to superiority, you're arguing theory when practice is a whole lot more important. Sure, it's possible to list theoretical benefits of multi-piston brakes, but that doesn't mean every one of those theoretical benefits (or any of them) necessarily translates to a practical, usable benefit on the car. Multi-piston disc brakes are not categorically, uniformly, or necessarily better than single-piston disc brakes; a good single-piston setup is better than a poor multi-piston setup. The KH 4-piston A-body disc brakes aren't poor, but they have shortcomings. Some of their shortcomings are because they are a relatively primitive, first-generation design. Others are because they weren't as widely used, and still others are because of simple age.

Here are some practical reasons why the single-piston A-body disc brakes are better: much less sensitive to rotor warp (much easier to get a smooth pedal), much lower parts count—especially a 4:1 reduction in the number of potential leak points. Much wider selection of components so you can put together a braking system that does just what you want (multiple different rotors, at least two different piston diameters, huge variety of pads, etc). Much easier and less expensive availability of components, much less prone to piston seizing, much easier to rebuild, and I'm probably leaving some out. They're all real, but at the end of the day outside the box under the bus going forward, both systems can be made to work well.

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PostPosted: Wed Apr 22, 2020 6:13 pm 
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Joined: Thu Jun 07, 2012 4:29 pm
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Location: Houston
Car Model: 68 Valiant
Those are all valid points, but most are practicality-based, given what can be sourced in today's world. They reflect the ease and cost of ownership which is always of importance.

But...the pedal feel is where I place the most value (just like I value throttle feel) and the single piston brakes just don't have the same feel. That's a subjective measure, for sure, but for my tastes the single piston pedal has more of a 'soccer mom Suburban' feel. You have every confidence they will stop you but they're not as 'crisp' feeling. The aforementioned Challenger? I never use all the brakes, ever, and the car would be fine with lesser brakes. But the pedal feel makes it worth the premium price. No doubt.

I've had one car - a 70 Dart Swinger 340 - with the factory small bolt pattern discs. At the same time I owned the '68 cuda with '73 single piston discs. Both cars were in top shape and to a person everyone liked the brakes better in the Dart. That's just my opinion of them.


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PostPosted: Wed Apr 22, 2020 10:40 pm 
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Supercharged
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Location: SW Washington
Car Model: 1965 Plymouth Barracuda, 1954 Dodge C1-B8
I've only had the 4-piston brakes with power assist so I can't say much about the pedal feel. I can say that the '72 Duster needed 5 new caliper pistons in 1998 and that the rear brakes locked up well before the front.

I road raced with single piston brakes and both 10.87" and 11.75" rotors. I always had tremendous pedal reserve and a quite firm pedal. I could have easily gone with a smaller master cylinder to reduce effort, but the bigger issue was finding a pad that would take open road racing. The larger piston F/M/J caliper would have helped too.

I have also used B-body single piston calipers. The pin-guided ones with rubber bushings. Those had terrible pedal feel. The car stopped fine, but it was like there was sponge rubber in the system. A friend who road raced a '66 Barracuda had chronic spongy pedal. Turns out he had pin calipers and guess what? The caliper piston is not centered between the pins so the caliper rotates on the flexible bushings when you step on the brakes. Sliding calipers made a huge improvement to pedal feel on that car and eventually racing 4-piston calipers went on.

I had a 1997 BMW M3 with single piston brakes. Those felt and worked quite well. I have a 1994 Corvette with 2-piston sliding calipers and they work and feel quite good.

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PostPosted: Thu Apr 23, 2020 5:58 am 
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Car Model: 68 Valiant
The best single piston caliper car I've had was a 71 Challenger. I don't remember what the brakes came off of, but they were the normal type as used on a 73 Duster etc. But, I used the booster and master cylinder from an 80's Diplomat 'cop car'. That combination gave a very sensitive pedal, you needed hardly any foot pressure and you'd get a good apply.


I've never driven one....but I read once that the Lamborghini Miura (I think) used a weird brake system that involved no pedal movement. It was some sort of pressure-only deal where the harder you pressed, the more the brakes applied. But the pedal doesn't move at all.


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PostPosted: Thu Apr 23, 2020 7:22 am 
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I had KH 4-pistons on my 68 Dart for about 8 yrs. Not a fan, but I think the pads they gave with them were very hard. You could not get close to locking them and the pedal feel was too stiff. I initially had to take calipers back twice to the parts store because they leaked just sitting there. Once I got a good pair (sleeved, I believe), then they were fine after that. My buddy's 66 Mustang with same KH rotors and calipers (except for bearings and bolt pattern, from factory) were also OK but not great.

I have never had power brakes on an A-body - no need and worse feel from the ones I have driven. The 4-piston Wilwoods have been excellent in every combo, are easy to modulate, and the pedal effort is low with up to a 1.032" MC. I have run 10.87" stock single pistons on a couple of cars and they are OK, but never "right," even when you use EBC pads. The 11.75" stock single pistons work quite well on an A-body, when I have driven those.

My 3 cents...

Lou

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PostPosted: Thu Apr 23, 2020 7:29 am 
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I never had problems with my 4 piston Caliper on the 69 dart.

The car Originally had 9" drums as so many of the cheap(not factory Hi-po) darts did back then.
on of the goals with the build of this car was to keep everything as stock as possible.

I used old original KH 4 piston calipers, Honed and rebuilt them etc, Never had any Leaks, or problems. (re)Made my own Transfer tubes, cleaned them all up and installed them almost 20 years ago now.

They work okay for me, but I don't think I am as picky about the brakes as some of you yet..
Maybe 'cause I never had good ones yet.


I think the pedal feel is okay, and I don't run a Power booster on the car. I put some newer parts store pads on last year, but If I get these Rotors I will try them with EBC Yellow stuff.


Greg

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PostPosted: Thu Apr 23, 2020 8:17 am 
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If I had a car that used the 4 piston brakes, I'd buy a set of those rotors. That's because we all have seen the way it goes....they're available, then they go on sale, then there are just a few left, then they're gone forever. Then, you decide to buy some.


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PostPosted: Thu Apr 23, 2020 8:40 am 
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GregCon wrote:
If I had a car that used the 4 piston brakes, I'd buy a set of those rotors. That's because we all have seen the way it goes....they're available, then they go on sale, then there are just a few left, then they're gone forever. Then, you decide to buy some.

Brad's Life Story- by Gregcon :mrgreen:

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