Dual Piston Caliper with 5 on 5.5

TAWL_BOY · Jan 1, 2015

I'm getting all my parts together for my full width swap, mild stretch, extended radius arms, and rear four link.

I started digging through my Bronco Bookmarks and came across an FourWheeler Mag article and running dual piston F250 calipers while remaining 5 on 5.5

I hadn't seen this particular swap discussed in detail. So I though, I'd contribute to the collective a little.

154_1206_01+vintage_big_brakes+dana_44_with_big_brake_kit-1.jpg

Why go through this hassle instead of go with 8 on 6.5?
You already have a build 5 on 5.5 9" rear(or other).
You already have expensive 5 on 5.5 headlocks. Hell, to me it's worth it not to have to dismount and remount 4 or 5 beadlocks.
-or in my case
I did want the added WMS of going to the 8 lug hubs. I definitely like the width of going full width but I still want to be able to keep my tires in as close as I can without a bad scrub radius.

Fourwheeler Article

toddz69 · Jan 1, 2015

There are a few mentions/threads on this swap on the board. I don't know of anyone actually driving a truck with this swap (with the 5.x5.5 bolt pattern) though. Some guys with the 8 bolt pattern front ends have it.

Todd Z.

galen1970b · Jan 2, 2015

the article mentions machining parts and scrounging parts from the big three to make this work.....Whats the main hangup from just swapping the backing plate over and using the stock bronco dana 44 spindals?(disc brake ones....) Is it the offset of the rotors to the caliper not lining up? or the bronco spindal not fitting in the backing plate? Just brainstorming.....stuck in Afghanistan.....not much else to ponder about after 4 months....

xcntrk · Jan 2, 2015

Looking good! What size rims are needed to clear those? Obviously 15" isn't going to cut it.

TAWL_BOY · Jan 2, 2015

The article said 17s cleared fine, and 16s would possibly clear with less backspacing.

But I ran 15s on a 79 Ford Dana 60, just took a lot of grinding on the calipers.

welndmn · Jan 2, 2015

I made brackets and put the 2010 Dodge Ram 1500 rotors and calipers on mine (need 17" wheels for clearance) , I'm still 5 lug.
It was a huge improvement over the chevy calipers.

I kept mine 5 lug because i have a few rigs and I like to swap tires around.

mavereq · Jan 2, 2015

welndmn said:
I made brackets and put the 2010 Dodge Ram 1500 rotors and calipers on mine (need 17" wheels for clearance) , I'm still 5 lug.
It was a huge improvement over the chevy calipers.

I kept mine 5 lug because i have a few rigs and I like to swap tires around.

I'd really like to see pictures of that setup

welndmn · Jan 2, 2015

Just don't pick on me for the clown colors (the calipers came powder coated, they are black now)
Its also a dana 60 that was redrilled to 5 lug.
Finally a reason to run 17" inch wheels!

My new 14 inch rotor and modern dual piston calipers!

Minor lathe work to open up the rotor center hole, but I already know how I'd do the next set different, with a lot more time on the lathe and using a slip on rotor
The bracket is just flat 3/8 plate.

76Broncofromhell · Jan 2, 2015

TAWL_BOY said:
I'm getting all my parts together for my full width swap, mild stretch, extended radius arms, and rear four link.

I started digging through my Bronco Bookmarks and came across an FourWheeler Mag article and running dual piston F250 calipers while remaining 5 on 5.5

I hadn't seen this particular swap discussed in detail. So I though, I'd contribute to the collective a little.

Fourwheeler Article

Blackbird Customs used to offer a similar adapter kit. He's since shut down his major business, but maybe he would build you brackets for what you're trying to do.

Personally, I've found the Ford dual piston stuff of the 70-90s to be kind of shitty especially with regard to those rubber bonded caliper wedges that always manage to wear out. The captive late model dual piston calipers on Ford/Chevy/Dodge (as seen in Welndmn's post) are far superior IMO.

As far as braking force, I don't see a real big improvement in performance given you aren't upgrading rotor diameter. It's still a cool idea though. I'm thinking you could probably adapt an F-150/Silverado/Ram1500 caliper set to the front of an EB with the addition of a floating rotor.

Apogee · Jan 2, 2015

76Broncofromhell said:
...The captive late model dual piston calipers on Ford/Chevy/Dodge (as seen in Welndmn's post) are far superior IMO.

As far as braking force, I don't see a real big improvement in performance given you aren't upgrading rotor diameter. It's still a cool idea though. I'm thinking you could probably adapt an F-150/Silverado/Ram1500 caliper set to the front of an EB with the addition of a floating rotor.

I couldn't agree with you more regarding the late-model, pad abutment design calipers, however I don't follow your statement regarding rotor diameter. Rotor diameter is a variable involved with determining the given brake brake torque of a system, however it's generally a much smaller contributor than is caliper piston area and pad coefficient of friction.

Ultimately, more brake torque doesn't equal higher performance brakes, just lower pedal effort to achieve lockup...you only have so much traction and threshold braking is threshold braking, whether you get there with single-piston or 6-piston calipers.

Now if we're talking about brake capacity in the thermal sense, then larger rotors with more thermal mass have a clear advantage over smaller ones.

Tobin

toddz69 · Jan 2, 2015

76Broncofromhell said:
Personally, I've found the Ford dual piston stuff of the 70-90s to be kind of shitty especially with regard to those rubber bonded caliper wedges that always manage to wear out. The captive late model dual piston calipers on Ford/Chevy/Dodge (as seen in Welndmn's post) are far superior IMO.

The calipers used in the conversion listed pre-date the rubber-bonded captive wedges (their mounts mimic the '76-'79 F150/Bronco caliper style) although I have read that the calipers get sticky and uneven pad wear results.

I also agree on liking the later model floating 2 piston calipers. The Dodge pieces seem to be a good option to use. AEV and TeraFlex both offer big brake kits that seem to be based around those calipers. I'm going to use the same Dodge rotors in a floating application when I finally get a chance to update mine.

Todd Z.

76Broncofromhell · Jan 2, 2015

Apogee said:
I couldn't agree with you more regarding the late-model, pad abutment design calipers, however I don't follow your statement regarding rotor diameter. Rotor diameter is a variable involved with determining the given brake brake torque of a system, however it's generally a much smaller contributor than is caliper piston area and pad coefficient of friction.

Ultimately, more brake torque doesn't equal higher performance brakes, just lower pedal effort to achieve lockup...you only have so much traction and threshold braking is threshold braking, whether you get there with single-piston or 6-piston calipers.

Now if we're talking about brake capacity in the thermal sense, then larger rotors with more thermal mass have a clear advantage over smaller ones.

Tobin

Correct. I should have specified more.

Larger pad surface area means more effective braking at a given force, and larger rotor surface and diameter equate to more torque in braking along with increased thermal capacity. But who wants to type all that?

Realistically, you will not see a huge gain in braking performance in something like an Early Bronco because its not that heavy, you don't run 23" wheels, road race or tow heavy trailers with one, so brake heat soak is somewhat rare.

toddz69 · Jan 2, 2015

76Broncofromhell said:
Realistically, you will not see a huge gain in braking performance in something like an Early Bronco because its not that heavy, you don't run 23" wheels, road race or tow heavy trailers with one, so brake heat soak is somewhat rare.

I had brake fade happen a few years ago and it was unnerving, to say the least. I have a local paved hill climb, about 4-5 miles long, fairly steep, that I use for testing changes in transmission cooling configurations, among other things. On one trip, I decided to throw caution to the wind and not use any engine braking or other common sense driving measures to help slow the Bronco other than massive applications of the brakes. By the time I was about a mile from the bottom of the hill, my brake pedal was extremely soft and rapidly losing effectiveness. I decided at that point to drive a little more carefully!

On a related note, one of the aforementioned Dodge brake rotors weighs about 8 lb. more than the common 11.75" diameter Ford rotors we use on our common disc conversions.

Todd Z.

RustyShackelfor · Jan 3, 2015

If you really wanted dual pistons wouldn't the easiest be the chevy brake swap with a set of dual piston wilwoods d52?

Apogee · Jan 3, 2015

RustyShackelfor said:
If you really wanted dual pistons wouldn't the easiest be the chevy brake swap with a set of dual piston wilwoods d52?

That would be the easiest way to get dual piston calipers if that was the end goal, but not necessarily the most effective means to improve braking performance IMO. The Wilwood D52's may have twice the piston count, but they also have less effectively piston area that is less than an OE D52 caliper, 6.28 sq. inches versus 6.79 sq. inches, so you would actually be decreasing the effective brake torque by about 7.5% assuming everything else stayed the same. relative to the standard Ford caliper with the 2.88" piston diameter, it would only be a 3.2% decrease. This difference only becomes larger if you're already running the larger T-Bird/LTD or larger piston version of the GM calipers.

The goal shouldn't be solely to have more pistons in the caliper, but rather better braking performance overall. While the Wilwood D52 calipers are an excellent means to shed some weight and possibly improve pad contact pressure at elevated temps due to better pad support provided by dual pistons, it isn't any improvement if the goal is increased brake torque or thermal capacity for the system.

ntsqd · Jan 3, 2015

76Broncofromhell said:
Correct. I should have specified more.

Larger pad surface area means more effective braking at a given force, and larger rotor surface and diameter equate to more torque in braking along with increased thermal capacity. But who wants to type all that?

Brake torque calcs have to be based on the centroid of the pad's contact area. So a larger pad contact area may act to reduce brake torque depending on where the comparative centroids are radially. If the OD of the rotor doesn't change then a larger pad could easily reduce brake torque.

Frankly the only advantage that I ever saw to a larger pad or a pad with more friction compound volume was life-span or wear life. The pads used at Martinsville used to have 13 cubic inches of pad compound, and they still usually finished the race at metal to metal!

Apogee said:
I couldn't agree with you more regarding the late-model, pad abutment design calipers, however I don't follow your statement regarding rotor diameter. Rotor diameter is a variable involved with determining the given brake brake torque of a system, however it's generally a much smaller contributor than is caliper piston area and pad coefficient of friction.

Look at it this way: caliper piston area's range of adjustment is pretty small if pedal feel is going to be considered. Excluding any booster (which seriously messes with the desired O/A ratio) you have a total system leverage range of 93:1 to ~99:1 with right about 95:1 being ideal for most people.
Doesn't leave much wiggle room to messing about with different piston sizes.

So take that preferred caliper (what ever it might be) and put it on a larger OD rotor. Brake torque just went up; brake system initial performance just went up with it. To maintain that performance thermal management and pad compound choice have to be balanced.

To the OP, why do you want to do this? What are the gains that you're hoping for?

FWIW floating calipers flex, a LOT. I don't know of any dedicated race vehicle, as opposed to a street vehicle converted to race use, that uses floating calipers. If pedal feel and brake modulation are important then moving to these should be the goal.

Grinding on a caliper is a sin and should have been listed as the 11th commandment.

mortimersnerd · Jan 3, 2015

So if the swap is done to the dual piston ford calipers from singles, is the rotor larger?

toddz69 · Jan 3, 2015

RustyShackelfor said:
If you really wanted dual pistons wouldn't the easiest be the chevy brake swap with a set of dual piston wilwoods d52?

The D52s are certainly an option but don't really help meet any of the goals I have for improving my braking situation. They would require changing back to the drum brake knuckles with the small holes that I don't like. There aren't any options for larger rotors with them (without custom bracketry) and as Apogee noted, they have a smaller total piston area than the regular D52 single piston calipers. I also prefer the caliper modern mounting configurations that he mentions. I've also always had a hangup with Wilwood calipers in that they don't use DOT dust seals on their caliper pistons. I have better things to be doing than rebuilding calipers every few years.

I keep waffling between 2 piston floating calipers and more $exy 6 piston versions. If I can achieve a desirable pedal feel and modulation with the floating calipers, I'll be happy (for awhile

).

Todd Z.

toddz69 · Jan 3, 2015

mortimersnerd said:
So if the swap is done to the dual piston ford calipers from singles, is the rotor larger?

Yes, slightly. Machining the 13.25" Dodge rotors down to about 12.8" is part of the conversion.

Todd Z.

Apogee · Jan 4, 2015

ntsqd said:
...Look at it this way: caliper piston area's range of adjustment is pretty small if pedal feel is going to be considered. Excluding any booster (which seriously messes with the desired O/A ratio) you have a total system leverage range of 93:1 to ~99:1 with right about 95:1 being ideal for most people.
Doesn't leave much wiggle room to messing about with different piston sizes....

O/A ratio? I'm not familiar with that term, but you obviously have a fair amount of brake knowledge. Pedal feel though is a function of pedal ratio, (booster), MC bore size, caliper piston area and overall system compliance which should include pad compressibility. Are you making the assumption that an increase in piston area wouldn't be accompanied by a corresponding increase in MC piston area? Regardless, if we assume that the vehicle only has so much traction, more brake torque only results in less pedal effort, not necessarily better brakes, contrary to the ever-present hydroboost argument...it's all in how we choose to qualify and/or quantify it, and I say to each his own.

As for fixed calipers being the be-all, end-all, you're right that most pinnacle motosports use fixed calipers, however that doesn't mean that the modern floating caliper designs aren't still vastly superior to the stuff designed in the 60's and 70's, not to mention the significantly better wheel fitment options versus most fixed mount options.

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