New brake kits

[jamesroney]

Successful rickroll. Thanks for the laugh.

I’m not sure on the difference between early, later and aftermarket pedal assemblies. Maybe someone with more experience on that can chime in.

One other option is welding a lower brake rod attachment point on your existing pedal. That would lower your ratio. But that might give the rod a funny angle. A way to resolve that would be to modify your firewall so that your booster mounts lower. I’m not familiar with the firewall and obstructions on the EB. Is that even possible?

Congratulations. You have managed to re-state the Early Bronco brake booster conundrum in one sentence. That's pretty good.

The reason for the angled firewall bracket on the EB (and the Econoline Van) was to provide clearance for a booster. You are constrained by the inner apron, and the valve cover, and the hood, and as you state: The "obstructions." Currently, there are no early, late, or aftermarket pedal options. The factory pedal is retained, and pedal ratio is generally managed downstream in the firewall bracket bell-crank.

Something that you might not have considered: Hydroboost solutions are available, and since they are physically smaller in diameter than a vacuum booster, they have gained a lot of popularity. But I will not install a hydroboost. I actually prefer to run a manual master cylinder. The reason is somewhat unique, Sometimes you find yourself in a situation where you do not have engine power, but you need to be towed on the trail. Usually after you submerged your engine, or damaged your radiator, or burst a hose, or fuel pump failed, etc. Then you end up being pulled on a strap. Having no power assist available with your service brake is remarkably uncomfortable, even for a short distance. HB gives you a couple of stops on the accumulator. But after that...its murder.

But Back to the 99% of street driven Early Broncos: It would be super cool, (and awesome) if someone were to engineer a pedal support that optimized the booster location. Ford couldn't figure it out in 1976, but maybe a fresh look?

 

[ksagis]

@1969miller was kind enough to get us some good data on a brake booster bracket:

• Pedal rod to pivot arm is about 1.5" and pivot rod arm to booster rod is about 2.0"
• That gives a 33% increase in throw and effectively reduces pedal ratio from 6 to 4.5, or 7 to 5.3, whatever it started at
  • assuming pedal dimensions inside cabin is unchanged when Ford added booster, which seems likely to me
• Rods come in at roughly 90 degrees and for roughly 90 degrees, that would be a small affect anyway

Looking at this another way, going to a 1.25" MC bore from a 1.125" seems to produce better pedal travel and feel and is 23% increase in flow.

My take is reducing pedal ratio 23% to 33% is a good place to start if one has added hydro. May need some kind of bracket and bellcrank to avoid weird angles.

(anybody else want to fess up they got rick rolled besides @LittleBeefy ?)

 

[Yeller]

The problem you have is a combination of factors and so there are different ways to solve it. First, you have far too much mechanical advantage in the pedal so you are making up for it by reducing the hydraulic advantage in the MC (I’m sure you know that). That creates the second problem which is that you are needing a a bore size in your MC that is generally reserved for hydroboost based systems, but you are using a vacuum booster. It’s virtually impossible to find any MC with a bore that large that fits a vacuum booster. Consider a couple of options. First you can reduce your mechanical advantage with a pedal kit designed with lower ratio. Second, you could look for a booster mount that will reduce mechanical advantage of the pedal on the MC. Third, you can switch to an Astro boost setup which will give you significantly more options in MC.

Or you could use the MC from a 1983 Corvette . After cracking out on an MC search last night for a few hours I couldn’t find another MC like what you are looking for.

I sure appreciate the insight!

The only difference between the HB and vacuum in the 85 K30 application is the depth of the push rod, the HB model just happens to match the C3 corvette booster I'm running. My brakes feel very close to the feel of a stock 85 K30, not disappointed with overall performance, knowing there is a bias issue makes me crazy, but not crazy enough to pour a bunch of cash on it LOL

The most powerful combination I've run on this as far as input force was a stock 1" manual master with no booster. You could push the pedal to the floor by hand with no perceivable force change. The brakes would lock up just as the pedal slapped the floor, in a panic it was quite spooky LOL. Oh and the rears locked up just as easily with that set up as well, I've not changed anything in the calipers, rotors. I have gone to crappy organic pads on the rear which did help some, I'd love to go to a more aggressive pad on the front but like a Ford the K30 has limited selections.

I'm assuming the rotor thickness issue could be resolved with a 2pc hat and rotor. I'm not a fan of the aftermarket aluminum hats since the hat is held in place with the wheel studs on the back of the hub. They also are not always readily available, which is big to me.

Enjoying this conversation everyone, thank you!

 

[fordguy]

I don't know of anyone that does that except one of the hydro kits that mounts to the stock-type angled booster is probably in that range (it's been years since I've measured anything on those brackets so I don't remember what they change the ratio to). Tom's h-boost bracket might change the ratio as well too. I did one conversion on a buddy's truck years ago with the stock angled bracket and as I recall, it had a real good pedal feel when I was done (Ford discs in front, Eldorado's out back and a 1.125" Corvette master iirc).

Within the last year or so, I bumped my master cylinder up to a 1.25" Dodge unit after 20+ years of running a 1.125" Dodge unit (various brake caliper configurations - all 4 wheel disc) and the pedal feel is much better. Much less touchy, better pedal height, less pedal travel, and firmer pedal at the bottom of the travel, and feels more like an OEM installation (my '01 Super Duty as a baseline for pedal feel).

Todd Z.

power or hydro brakes on your rig?

 

[toddz69]

power or hydro brakes on your rig?

Hydroboost.

Todd Z.

 

[ksagis]

I took a quick measurement of my pedal inside cabin, roughly 5.4 pedal ratio to my hydro.

Truck originally was equipped with power brakes so there would have been the reduction in the power brake booster bracket (post 62 above). I'm estimating OEM Bronco had about 4 total pedal ratio in power brakes config which actually jives pretty well with general guidance, maybe on low end tho.

 

[Broncobowsher]

Don't forget that the bias ratio goes with the square of the piston diameter. So your 3.368 front pistons have 8.9 square inches of piston area. Your rear calipers have 2-3/4 pistons with 5.93 square inches of area. (that's 66% bigger) Typical D60 (1 ton) front rotors are 12-7/8 diameter, and the 3/4 ton GM fronts (adapted for use on the rear) are 12-1/2. Most people think that the 1 ton GM brakes are a lot bigger than the 3/4 ton stuff. But it's really not. It's just a lot heavier. They had to stay relatively small diameter to fit under the 16 inch wheel. Braking force acts linear with rotor diameter, and that contributes another 3% difference. (and yes, I know it's really an (r cross F) vector.)

Nominal values for ideal brake bias in a 3800 lb, 93 inch wheelbase high CG vehicle can be found in the 2003 Wrangler Rubicon. It has:
Front Disc piston = 2.60
Rear Disc piston = 1.89
Front rotor dia = 11.03
Rear rotor dia = 11.22
Intrinsic bias = caliper bias, rear area 2.80 sq in / front piston 5.3 sq in = 53% + rotor bias, 11.03/11.22=2% so let's call it 51%.
(I use the '03 Rubicon because it approximates a Bronco dimensionally, and it came factory with 4 wheel disc brakes. I do not have the intellectual bandwidth to calculate the relative brake force in a disc/drum scenario, because I cannot calculate the self-energizing effect) But with 4 wheel discs, we can assume away a lot, and the net number is 51%.

Frankly, I am surprised that you need to choke down your rear hydraulic pressure.

The only issue I have with that is the rotors only look at total diameter, not swept area. The rear rotors are larger than the front. But I recall that they are drum in hat parking brake. I don't have the parts in front of me, but say the front brakes have 2" of pad contact and the rears only have 1½" of pad contact. The front will have a greater swept area than the rears even though the rears are larger.

Not even getting into vented rotors have better heat capacity over solid. That matters when pushing the whoa pedal from highway speeds, not so much at trail speeds.

 

[jamesroney]

The only issue I have with that is the rotors only look at total diameter, not swept area. The rear rotors are larger than the front. But I recall that they are drum in hat parking brake. I don't have the parts in front of me, but say the front brakes have 2" of pad contact and the rears only have 1½" of pad contact. The front will have a greater swept area than the rears even though the rears are larger.

Not even getting into vented rotors have better heat capacity over solid. That matters when pushing the whoa pedal from highway speeds, not so much at trail speeds.

Yeah, I didn’t want to get into that. Earlier in the thread, in post #39, @LittleBeefy makes the argument that braking is proportional to rotor radial distance, clamping force, and the ubiquitous Mu, or coefficient of dynamic friction.

At first glance, it is quite convenient…because it eliminates such things as swept area, thermal effects, pad configurations and a myriad of other factors in the analysis. But it is an engineering fact…that as long as you are in the design regime where Mu is constant, the simplified model is adequate.

So for a typical brake bias analysis, and looking at an impending lock up situation with wet traction at standard conditions…brake performance simplifies to (r x F) and F is (P/A) * Mu.

And Mu is constrained in the example as constant. So yeah…swept area, heat dissipation, speed, thermal mass, and friction non-linearities are all assumed away.

It’s a classic engineering blunder. You constrain the model, and then simplify the model, and then extrapolate the simple model beyond the constraints. Then you publish theoretical results based on the (now erroneous) model, and it does not align with empirical test data.

One analogy would be for me to estimate the time it will take me to jump to the moon. If I can jump 3 feet high today, and with proper training, I can jump 1 inch higher every month. Then in 360 months, I can jump 33 feet high. Except I can’t. And won’t, and no one ever has. And long before I get near the moon, I’ll be dead. And my bones will crush, and my muscles will explode. And there’s no oxygen. And it’s cold. And…and…and.

Similar issue with Mu. Mu is presumed constant and therefore all of the parameters that yield the singular value of Mu are presumed constant. But you and I both know from experience that brake fade is real, and heat dissipation is important. Swept area, thermal mass, contact area, etc. all contribute to the no longer constant, but highly Variable Mu.

Intellectually, it’s kind of cool that proportioning and braking power can be reduced to a pencil eraser dragging on a vinyl record.

LittleBeefy knows all that, so it’s a good model. And it is very clever. So I like it. But he answered a very specific question with a very specific reply.

 

[toddz69]

But you and I both know from experience that brake fade is real, and heat dissipation is important.

Speaking of that, I have a local mountain road that I've used for some intentional brake fade testing, and brake fade is scary. I don't recall the exact number but I think the rotors I use (and @LittleBeefy uses in his kits) weigh about 13 lb. more than the stock 11.75" rotors. That's a lot more thermal capacity when you're considering brake fade concerns.

Todd Z.

 

[ksagis]

Been thinking about this overnight.....

The measurements I took on my pedal were something like 2.5" pivot to brake rod, and 13.5" pivot to middle of pad. To get a 20% decrease of pedal ratio, I'm looking at moving the hole down about 7/8" of an inch (guess I could shorten the pedal but that would put it in a weird location). Given the size of existing hole for rod linkage, that pretty much means filling hole, and relocating the hole down 7/8".

Things I can think of to check (feedback appreciated):

• Push rod binding with the changed angle of the push rod, though doesn't seem too severe of a change, likely less than 10 degrees
• Bottoming out of hydroboost or MC due to increased stroke from pedal ratio change.

Some rough math of my geometry indicates with my current pedal ratio, that I'm getting about 1" of brake rod stroke if pedal hits floor. Changing pedal ratio to 4, will result in about 1.35" of stroke if pedal hits floor. Maybe it all comes out in wash, but seems like you don't want to overstroke hydro or overstroke the MC?

Anybody know what is acceptable stroke lengths for hydroboosts or MCs or have general thoughts on above, I seem to recall about 1" strokes but don't know I remember that number.
Currently running Hydratech hydroboost and a power disk MC from 1978ish C3 Vette.

 

[LittleBeefy]

Yeah, I didn’t want to get into that. Earlier in the thread, in post #39, @LittleBeefy makes the argument that braking is proportional to rotor radial distance, clamping force, and the ubiquitous Mu, or coefficient of dynamic friction.

At first glance, it is quite convenient…because it eliminates such things as swept area, thermal effects, pad configurations and a myriad of other factors in the analysis. But it is an engineering fact…that as long as you are in the design regime where Mu is constant, the simplified model is adequate.

So for a typical brake bias analysis, and looking at an impending lock up situation with wet traction at standard conditions…brake performance simplifies to (r x F) and F is (P/A) * Mu.

And Mu is constrained in the example as constant. So yeah…swept area, heat dissipation, speed, thermal mass, and friction non-linearities are all assumed away.

It’s a classic engineering blunder. You constrain the model, and then simplify the model, and then extrapolate the simple model beyond the constraints. Then you publish theoretical results based on the (now erroneous) model, and it does not align with empirical test data.

One analogy would be for me to estimate the time it will take me to jump to the moon. If I can jump 3 feet high today, and with proper training, I can jump 1 inch higher every month. Then in 360 months, I can jump 33 feet high. Except I can’t. And won’t, and no one ever has. And long before I get near the moon, I’ll be dead. And my bones will crush, and my muscles will explode. And there’s no oxygen. And it’s cold. And…and…and.

Similar issue with Mu. Mu is presumed constant and therefore all of the parameters that yield the singular value of Mu are presumed constant. But you and I both know from experience that brake fade is real, and heat dissipation is important. Swept area, thermal mass, contact area, etc. all contribute to the no longer constant, but highly Variable Mu.

Intellectually, it’s kind of cool that proportioning and braking power can be reduced to a pencil eraser dragging on a vinyl record.

LittleBeefy knows all that, so it’s a good model. And it is very clever. So I like it. But he answered a very specific question with a very specific reply.

Very relevant points here. Mu is absolutely not constant in real world use of brakes, and heat is absolutely your enemy. Friction creates heat and brake fade is the result of heat lowering the the coefficient of dynamic friction and the grip that your pads have on your rotor.

As @toddz69 points out, increasing the mass of the rotor (either in diameter or thickness or both) will spread the heating energy across a larger thermal mass, thus absorbing and dissipating the heat better (like a larger heat sink). Another method for dealing with heat is using aluminum calipers, which is why they are so common is sports cars (they also have the added benefit of reducing unsprung weight to help improve traction in "spirited" cornering maneuvers).

But the reality is that we often don't have a choice in the size of our rotors, or the material our caliper is made out of. That's one reason why there are so many pad options out there, and so many materials choice when it comes to pads. Ceramic, semi metallic and carbon fiber, just to name a few. These create the trade-offs between friction, thermal absorption, lifespan, noise and dust. Choosing the right pad for your application isn't just about "getting the ones that fit"; you have to consider all the upsides and downsides of each.

One other note: how you brake has a huge impact on heat creation. When I worked at Porsche we had a lot of ceramic composite rotors from the Carerra GT come back with warranty claims because they were "flaking apart" on the surface. An investigation into the cause determined that the rotors were over-heating due to "amateur" drivers using the car on the track. At the time, this was arguably the best performing car on the track that money could buy (just ask the Stig). It wasn't the track use that was the problem, it was the fact that less experienced drivers had a tendency to brake "softer for longer" which will add to the overall heat on the rotor. Although counterintuitive, being firmer on the brake pedal, while not as comfortable, is better for keeping heat under control and reducing brake fade. Ultimately, the design of the rotor was modified to include small circular temperature sensitive inserts in the PCCB rotors which would break or pop out if you overheated the rotor. These are still in the rotors used to this day in the 911 Turbo S (for example) so Porsche knows whether to warranty the rotor or not (those suckers are expensive).

 

[Speedrdr]

Has nothing to do with selection of or anything like that, but….This discussion has me “harken back” to my days of high school /college days. While I don’t remember the formulas for thermal dynamics and such, I’m happy that some 40+ years later the understanding is still there.

Randy

 

[jamesroney]

One other note:
1. how you brake has a huge impact on heat creation.
2. rotors were over-heating due to "amateur" drivers using the car on the track.
2A. it was the fact that less experienced drivers had a tendency to brake "softer for longer" which will add to the overall heat on the rotor.
2B. counterintuitive.
3. being firmer on the brake pedal, snip...is better for keeping heat under control and reducing brake fade.
4. Ultimately, the design of the rotor was modified to include small circular temperature sensitive inserts in the PCCB rotors which would break or pop out if you overheated the rotor.
5. These are still in the rotors used to this day in the 911 Turbo S (for example) so Porsche knows whether to warranty the rotor or not.

Thread-jack warning...
OK, I would like to evaluate something that has bothered me for a while. DISCLAIMER: I did not attend a discount public engineering school, and I am not a braking expert, or even a casual enthusiast. But your note above reminded me of a similar problem that exists off the track as well. You might recall the ill-fated 1995 Bronco external hub front disc brake fiasco. That design was woefully flawed, but provided some insight to my opinion. So here we go:

1. Why? How I brake should have zero impact on heat creation. From a thermodynamic perspective, ALL of the heat generated by the friction interface is equal to the energy transferred motion into heat.
2. Yes, but again...why? Notionally, it should be that converting energy into heat over a longer time SHOULD result in lower temperatures. Not higher ones.
2B, 2C. Corollary to item 2. Terms here are important. Item 1 is a misnomer. Brakes get hot. Hot comes from higher temperature. Heat is delta energy. We agree that softer for longer increases TEMPERATURE. Again...why?
3. Firm on the brake pedal reduces temperature, and therefore reduces fade. But Heat Energy is conserved. So why does the Porsche rotor reach such elevated temperatures? Is it the same as the 95 Bronco? Doesn't have to be high speed, and doesn't have to be massive weight. What we KNOW empirically is that long, slow, soft brake application generates very high temperatures.
4. I understand. If you can't execute an adequate design, and you continue to fail...find a way to measure the failure. Then implement a tattle-tale.
5. Yes, use the result of #4 to blame your customer and deny warranty coverage for your inadequate design.

TRIGGER warning! This might piss you off...The answer is kind of interesting...and it is going to turn out that it has little to do with rotor mass, or diameter, or caliper construction, or any of the things that should be important. I'm spitballing here, because I am not an expert...but if we assume that all of the heat is generated by the friction interface between the pad and the rotor...some things become evident pretty quickly. First, the heat does NOT transfer out thru the caliper. It can't, it doesn't, and the notion that caliper thermal transfer is interesting is just silly. The heat has to get thru the pad material, which has relatively low thermal conductivity, then it has to get thru the pad backing plate, thru the piston to pad interface, into the piston, and then to the caliper body. Given that the temperature of the rotor/pad interface is in excess of 1500F, and carbon steel glows cherry red at 1500F, and we know that aluminum melts at 1200F, powdercoat melts at 400F, and DOT3 wet fluid boils at 300F...we know darned well that the energy is getting stuck in the rotor, and not out the caliper.

So how can a rotor dissipate heat? Same way as every other piece of metal. Conduction, Convection, and Radiation. Let's assume that we have a solid rotor, and we are pushing energy into the metal at the friction interface. We can see the rotor glowing cherry red. The contribution from radiation is low. Conduction is significant, but that just elevates the temperature of the wheel hub, and eventually melts the hub dial on the aforementioned 95 Bronco. So the vast majority of heat has to go out via convection of the exposed disc. But when the pad is in contact with the rotor, it cannot convect in that location. The bigger the swept area, the WORSE the convection. I would surmise that in the limiting case of 100% swept area, the disc pad material would effectively create a near adiabatic condition wherin there would be zero convection during brake application, (regardless of application effort) and nominal convection at zero application force. So you are not increasing heat by braking applying longer, but you are preventing convection, and the release of that heat. Soft or hard wouldn't matter once the pad contacts the rotor! And "bigger pads" would actually make things much worse!

Ventilating the rotor would improve things, and I have no idea how much heat is convected via the internal rotor passages, but at the end of the day, you have to get the heat out. And I prefer to use straight line braking versus cornering braking just to simplify the math. But I'm going to say that two identical Porsche's, (or Broncos, or whatever...) that start at the same velocity, and brake to zero will dissipate the same energy into the brakes. But the one who holds the pedal longer will have hotter rotors.

Your Porsche engineer should have installed smaller pads, and cheaper rotors. Yikes!

 

[Yeller]

I relate it back to driving a semi off of your chosen mountian pass, Donner, Cabbage, Loveland, Wolf Creek, Cumberland, whichever you choose. Do the old school idea of light steady pressure and the brakes smoke, make enough heat to potentially melt the seals and cause a leak then potentially a fire. Hit the brakes hard, scrub off 10mph let it build back, repeat, keep doing so to the bottom. Far less heat is generated. I know some old school drivers that will disagree but they continue to smoke their brakes, go figure.

 

[LittleBeefy]

For those still following, here's our upgraded kit in red powder coat that I just installed.

 

[ntsqd]

I did a SAS a couple of years ago using a 78/79 D44HP. These brakes fit just fine!

We don't have a solution for the TTB (yet) but I really want to solve that problem. As you point out, the cast in slider mount is problematic and you can't swap the knuckle due to camber differences. We're considering an option to grind off the mounts from the knuckle and doing a core swap for the knuckles when you buy the kit. The TTB kit is highly requested because the T-bird calipers don't fit without clearancing the knuckle for the banjo bolt so options are limited.

We are also looking at options for the D60 that would use opposing 4 piston calipers and 14" rotors. We have the parts, but the kit would be spendy and we just don't know whether people would want to upgrade. The D60 twin piston's are already pretty good.

BT, DT, both ends on my '96. With 35's my experience with the stock TTB brakes is that you get one hard stop and then you need to let them cool. Forget a long descent using only the brakes to control speed.

My requirements were off the shelf wear parts. I failed with the rear rotors, but everything else worked as-is. With a semi float rear axle the rotor spacer might not be needed so long as the flange to flange distance is the same as the donor's. The lone caveat that I suspect most won't like is that I moved to 8 lug to make it all work.

GM 3/4t front brakes here: https://www.gofastbroncos.com/forum/viewtopic.php?p=156389#p156389

Expedition rear discs here: https://www.gofastbroncos.com/forum/viewtopic.php?p=156285#p156285

Or all of it here: https://socalbroncos.com/forum/thre...rear-d60-and-large-disc-brake-conversions.29/

 

[sprdv1]

Not saying it's wrong, just dang, it's been a while since I priced brakes. I remember us talking here decade or so ago into cheap by finding $50 setups off the old trucks.

oh yeah, soo different than a few years ago

 

[sprdv1]

For those still following, here's our upgraded kit in red powder coat that I just installed.

Looks great, and should perform well too I'd think

 

[LittleBeefy]

We did another install over the weekend on a D44HP. The customer is very pleased with the additional braking power. Unfortunately he upgraded his booster and master cylinder at the same time and it appears that the booster he got is a Super Dooty, so he's getting that replaced before he can really test out his new brakes. Stay tuned for more feedback.

 

[duffymahoney]

No rear brake to match?