KH Discs vs 73+ Discs

KH or 73+ Discs

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    74
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MuuMuu101

MuuMuu101

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So, I have a friend with a '67 Dart that wants to do a suspension rebuild and update his front 9" drums to disc brakes. He's got a friend of a friend who may offer him a set of 73+ disc brakes with 10.75" rotors and 1 piston calipers. He's also interested in my KH disc setup and he was wondering what would offer the best stopping power. I was thinking the KH discs due to the larger rotors and pad surface area, but I'm not sure.

Currently, the guy is running small bolt pattern all the way around. He's thinking about replacing his rear end and he could either take some of my sbp 8 3/4 stuff (axle, 10" drums, ring and gear, differential, etc.), or he has a line with the other guy on taking his 8 3/4 stuff (B-body with A-body perches, axles, and 11" drum; no center section). I don't really care if he buys my parts or not, but I just want to help him get a good and safe car.

Personally, I think he should go with the bbp stuff as it will give him more options on brake setups, wheels, and tires (he talks about potentially autocrossing the car in the very distant future). What are your thoughts?
 
If he is thinking auto crossing, he should just go strait to the 11 7/8 rotor single piston set up, same caliper, just a taller caliper stand with the bigger rotor, bbp with the better bearing and wheel possibility.
 
I voted KH, cuz they re awesome.
However, because of his situation, I would kinda lean towards the single piston set-up.
Naw. I love my KH/Dot5/braided lines set-up. Its been working 100% for 15 years and 125,000 miles with zero maintenance. ZERO. You wont get that with the other.
 
AJ/FormS said:
I voted KH, cuz they re awesome.
However, because of his situation, I would kinda lean towards the single piston set-up.
Naw. I love my KH/Dot5/braided lines set-up. Its been working 100% for 15 years and 125,000 miles with zero maintenance. ZERO. You wont get that with the other.
Click to expand...

I can't quite live up to that kind of longevity, but I've put over 50k miles on the pin-style, single piston calipers on my Challenger. In fact, the calipers are the same ones that came with the car, I've never done anything to the calipers themselves, so I have no idea how many miles are on them. They appeared factory when I bought the car, but who knows. When I installed my 11.75" rotors I just changed out the caliper brackets to run the larger disks and installed new pins just because I was in there doing the work. Since then I've changed the pads once, but that's it.

I don't have a set of KH's, so I really can't comment on them too much. The multi-piston set up should actually provide better braking than the single pistons, as long as the seals aren't a problem. I've heard of people having issues with the seals, but AJ seems to have had great luck with them so that may be overblown. But I still think they lose out because of the SBP and difficulty of finding parts, wheels, etc.

If he's considering autoX'ing the car, I would go straight to the 11.75 mopar disks from the B/R bodies as spl440 suggested. It's a bolt on deal if you have 73+ spindles, you just need the rotors, caliper brackets, and at least 15" rims. Doesn't seem like much, but it makes a significant improvement in braking even compared to the stock 10.98" rotors. When I upgraded my Challenger I even kept the smaller piston original calipers, and it was still a noticeable difference. The later calipers that went with the 11.75" disks on the B/R bodies have a larger piston. Not a little larger either, it's almost a 1/2" difference in the bore.

Not to mention if he's looking to do any significant amount of autoX'ing, he should be looking for performance tires, which means 17" or larger if he's looking for something DOT legal he can still drive on the street between races. And that will make the SBP deal even more inconvenient. There are SBP 17/18" rims out there, but there's only a couple of choices.
 
For me, I had KH discs. They were fine, but I was fighting braking bugs still when I removed them. I didn't get a chance to experiment with them completely. They didn't offer me good braking because I used the cheapest pads on the market (stupid mistake) However, I wouldn't rule them out as bad brakes. I have them off to the side for now... I kind of want an early-A wagon or convertible in the next couple years and I might want to put those on there, but I also have 10" drum spindles I was thinking about using for a bbp swap. So, whether I sell them or use them it's fine.

The guy won't be autocrossing anytime soon. His slant six has a major exhaust leak that he should attend to beforehand. He kind of wants to turbo it.
 
Yea the 73s have way more options available the KH really just get used if you want disc with the Small bolt pattern.
 
Well, for short term, the good thing about using the KH stuff is he won't have to get new wheels and tires. he could run his 7 1/4 for now just to save weight (or swap in my spare to get the 10" drums). If he really wanted to he could buy my 8 3/4 sbp axles, 10" drums, and extra misc parts in case he wants to hunt for parts here and there to build up an 8 3/4.
 
A quick word about caliper/piston maintenance.
It is well known that the non-dot5 fluids are hygroscopic. The moisture they absorb gravitates to the lowest point in the system.The caliper bores can rust and the iron oxide would occupy the very valuable space between the piston and the bore.Furthermore moisture can enter from the atmospheric side and accumulate in the O-ring bore.When oxydation piles up there, the room in the groove diminishes and/or the seal swells up. This puts a lot of friction on the pistons and eventually seal-retraction no longer works and the pads remain in closer contact with the rotors, eventually glazing up and or wearing out the rotors prematurely.This can/will happen in any brake system with non Dot5 fluid. Its worse in aluminum bodied calipers.

Now the KH having 4 tight fitting pistons, are or have been. somewhat susceptible in the past,to sticking due to this phenomenon.The absolute best thing you can do for your KH system is to use the silicon brakefluid and to grease your sq. section O-rings and their grooves with a silicon grease. Problem solved. I also run my wheel bearings on the looser side of spec, to aid in piston knock-back, and I dont use any anti-rattle springs.When I hear the pads rattling, I know the system is free-running.I believe my success with these KH tips speak for themselves.

As an aside, when I slip my 4-speed into neutral at 60 mph, the car coasts what seems like forever.It coasts better/further than any car I have ever owned.Whats the big deal about that you ask? Rolling resistance. The less of it you have, the less your engine has to work to overcome it;ergo, the less fuel you have to burn to either accelerate the mass, or maintain it at a cruise speed.
To that end, I can tell you that its easily possible to get a 68 cuda360MT into the 30mpgUSg, and still go 12.9/106.

Now, a word about the single piston calipers. These pistons are much looser fitting in the bores, and survive a long time with sludge in them. One of the consequences of their looseness,is that they can "****" in their bores. This can allow more pressure to be applied to the rear/trailing edge of the pads, and they wear at an angle. The same thing can happen if the pins are not straight, or the caliper-ways are not at the proper angle.The point is the pads may need to be replaced more often than necessary.When the pads are replaced, the pistons have to be pushed back into the bores, plowing through the accumulated rust/sludge.And this is when trouble can start. So again, the silicon can come to the rescue. Then theres the slider ways which have to absorb all the brake force and send it into the chassis. They also like to rust up, and/or wear out.
All-in-all, I just prefer the zero-maintenance of a fixed caliper. And the KH is a fine example.
Just my 2cents
 
I
AJ/FormS said:
A quick word about caliper/piston maintenance.
It is well known that the non-dot5 fluids are hygroscopic. The moisture they absorb gravitates to the lowest point in the system.The caliper bores can rust and the iron oxide would occupy the very valuable space between the piston and the bore.Furthermore moisture can enter from the atmospheric side and accumulate in the O-ring bore.When oxydation piles up there, the room in the groove diminishes and/or the seal swells up. This puts a lot of friction on the pistons and eventually seal-retraction no longer works and the pads remain in closer contact with the rotors, eventually glazing up and or wearing out the rotors prematurely.This can/will happen in any brake system with non Dot5 fluid. Its worse in aluminum bodied calipers.

Now the KH having 4 tight fitting pistons, are or have been. somewhat susceptible in the past,to sticking due to this phenomenon.The absolute best thing you can do for your KH system is to use the silicon brakefluid and to grease your sq. section O-rings and their grooves with a silicon grease. Problem solved. I also run my wheel bearings on the looser side of spec, to aid in piston knock-back, and I dont use any anti-rattle springs.When I hear the pads rattling, I know the system is free-running.I believe my success with these KH tips speak for themselves.

As an aside, when I slip my 4-speed into neutral at 60 mph, the car coasts what seems like forever.It coasts better/further than any car I have ever owned.Whats the big deal about that you ask? Rolling resistance. The less of it you have, the less your engine has to work to overcome it;ergo, the less fuel you have to burn to either accelerate the mass, or maintain it at a cruise speed.
To that end, I can tell you that its easily possible to get a 360 into the 30mpgUSg, and still go 12.9/106.

Now, a word about the single piston calipers. These pistons are much looser fitting in the bores, and survive a long time with sludge in them. One of the consequences of their looseness,is that they can "****" in their bores. This can allow more pressure to be applied to the rear/trailing edge of the pads, and they wear at an angle. The same thing can happen if the pins are not straight, or the caliper-ways are not at the proper angle.The point is the pads may need to be replaced more often than necessary.When the pads are replaced, the pistons have to be pushed back into the bores, plowing through the accumulated rust/sludge.And this is when trouble can start. So again, the silicon can come to the rescue. Then theres the slider ways which have to absorb all the brake force and send it into the chassis. They also like to rust up, and/or wear out.
All-in-all, I just prefer the zero-maintenance of a fixed caliper. And the KH is a fine example.
Just my 2cents
Click to expand...
Friggin awesome! Thank you! :) great info.
 
Well, by that instruction, I guess my KHers should be seized by now.
The system is supposed to be sealed(mine is), and with the correctly sized reservoirs there is no need to ever open it unless it develops a leak.And if it leaks, its the best time for a flush.I wouldnt run anything but silicon.
But then, I run straight water(with additive pkg) in my cooling system too;contrary to common/popular thinking. I have no brake issues, and no cooling issues either.
Again, just my 2cents


BTW; that "bath-tub ring of rust on the bottom of the reservoir",should tell you something, along with having to replace "nearly all of the hydraulics".Without having seen it I would hesitate to offer an opinion, other than, I highly doubt it had anything to do with silicon fluid.
 
all good points...i'll add a couple more
..KH are fixed callipers and wheel bearing clearance is critical where single piston callipers float and are very forgiving
..'73 and later have beefier rotors, parts are more available and economical
..both in good repair are fine systems
 
Voting for the KH because they are awesome or because they are 4 piston or whatever is dumb. The 73 and up brakes are far superior in every way.
 
i prefer the 73-up set up.. cost, parts availability, better choice of wheels and they just work. i also run DOT 5 and have never had any issues. if you are worried about it then bleed them at the beginning of the year.
 
The KH brakes are just archaic from ever single perspective.
 
73-up set up for me, I have read and read posts here on these and watched on u-tube the greatness of having all mopar parts under my front end... jmo..
 
I agree with you on the BBP conversion for all of the reasons you gave. IIRC the largest SBP wheel was 5½" wide. Even at that width, Ma Mopar's wheels were known to be a little bit flexible along a vertical axis. This allowed my first Dart to shed wheel covers when cornering vigorously.

Just finding a tire in a 14" or 15" size is getting tougher all the time. Selection is not good.
 
Well i ended up rebuilding my KH calipers with new pistons seals etc had my hubs made up so i run a BBP wheels and they still use the std bearings dust seals,run 73 & up rotors and could still use the Kelsey Hayes calipers.4 wheel disk brake set up non power.Works well for the street as its no track car.I dont have the luxury of any junk yards to pull later model stuff off and shipping hubs etc adds up $$$$.I bleed the brake system once a year with new fluid to avoid moisture issues,rust or leaking seals.
 
So, I talked to him more about what he's looking for short and long term. Essentially he wants to make his Dart into a "240SX" (believe me, I rolled my eyes at that one). He wants to carve canyons while still having a comfortable daily. I asked him if he wanted a high horsepower with big brakes, wheels, and tires or a budget build. He said he wants a budget build for now, but when he gets more money he'd like to get larger and more modern caliper and rotors.

I think if he goes bbp he's going to be spending quite a bit as he's going to need a new rear end, driveshaft, UCA's, and suspension/steering components; however, like you guys said, he has more freedom to upgrade.

If he wants big wheels, there are Show Wheels and Coy Wheels, but he's not going to get anything much larger than a 225 on front and a 245 on the rear.
 
The K-H calipers are technically superior, but are they really an option? You can't buy the parts new. You can buy rebuilt calipers and new rotors, but also need the special spindles and hubs. The rare rusty ones that show up on ebay command high $$$. A member here has offered nicely rebuilt setups, but at high price (~$750) and don't know if he can even scrounge parts anymore. For the same price, you can buy a Wilwood setup w/ 4-piston fixed calipers.

Re SBP, you can now buy new 17" alloy wheels in SBP, so you aren't limited in any way.

Re DOT 5, I have run it in several cars for decades and have not seen a spot of internal rust since. If water drops got in the system they would not be absorbed and could theoretically cause rust depending on where they settle. Don't let water drip into your reservoir, which is true for any brake system. Fill it carefully and don't touch it, and you will never have to fuss with it again. I have newer MC reservoirs with tight-fitting plastic caps on all my cars, so no concerns.
 
I just disagree the KH stuff is superior. Why were they replaced? Why didn't the bigger cars get a version? Bottom line is they SUCKED. They were replaced with a better, newer, more modern version.
 
BillGrissom said:
Re SBP, you can now buy new 17" alloy wheels in SBP, so you aren't limited in any way.
Click to expand...

Not limited in any way?

Coys makes 1 off the shelf wheel (the C-5) for the 5x4" pattern. 1. It's available in quite a few sizes, but the backspacing is so limited you'll only be able to use a 7" wide rim up front and an 8" wide rim out back, although you'll have your choice of 17, 18, or 20" rims for those sizes. Still, the backspacing will limit your tire options on even those rims.

Show Wheels makes 2, one of which is a 5 spoke style very similar to the Coys wheel. They are available in 17x7 and 17x8 only, and the backspace again is going to limit tire width.

My point is, yes, there are 17, 18, and even 20" rims available for the SBP. But only if you like 1 of the 3 wheels available off the shelf, and only if you're getting those rims for looks, not maximizing your cornering ability. If you want something other than those 3, or something with the right backspace to run wider tires, you're looking at paying for custom rims, and it would be cheaper to convert the whole car to BBP and then buy rims than do that.
 
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