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Discussion Starter #1
I've done a few searches using several differign key words.

I see a lot of people wringing their hands about how dangerous pinion brakes are, but no facts.

is there anyone on this board who has been in an accident in which one or both vehicles was equipped with a pinion brake, and can give proof that the lack of hub mounted brakes was the cause of the accident?

or, anyone who witnessed such an accident, and again can provide proof?

NQS
 

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the only problem with pinion brakes are high speed fading. they will get very hot when you clamp them down at any speeds over 45 or so. i have one pinion brake on my cruiser with rockwells and 44s. it will stop on a dime as long as i am in 4 wheel drive. they are really impressive when you can lock up 4 44s with a light push of the pedal. but i would not recomend them on a street rig. but i am going to put them f&r on the new rig just to have a back up brake system. mike
 

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Here's the only one I've seen. Guy with a pinion brake stood his Jeep up on the front tires locking them up in the shutdown area of a mud race. He then broke a front axle & lost braking until the rear tires touched back down. Result, he D/Q'd, but didn't hit anyone or anything. OTOH, he might have endo'd if he hadn't lost braking :D


TEX
 

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When you're messing with brakes, anytime you put more stuff between the pedal and the tires there is more chances for something to go wrong.

With normal brakes: master cylindar, brakelines, slave cylindar, lug studs.

Pinion brakes: above, plus pinion gear, ring gear, carrier, spider gears & crown gears or locker mechanism, axle shafts. Add Ujoints and stub shafts and drive flanges if steerable axle.

We're talking about tripling the number of parts that need to be functional for your brakes to work. I'm not saying you can't run pinion brakes on the street, I just really wish you wouldn't.

Think on this:
How many times have you had brake failure vs. breaking axles, R&P, lockers, Ujoints, etc..

-t
 

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Discussion Starter #5
I wonder if one could stop the fade with anti-lock brakes? I can think of part of how to do it ( use a HD flasher to make the circuit pump), but not how to get the pressure to release/repressurize

Also, how much brake fade is caused by tire size? I actually plan to stay in the mid 30's range, going for the 60 strenght at 1/2 60 cost. neither my skill nor needs dictate 44's. yet :flipoff2:

this would be a "fair weather" rig, driven to nearby trails, using a reversed 203 reduction box (gotta talk to ryeguy about that) to keep the rpm's low

wheel brakes are planned for, but right now not in the budget

NQS
 

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In addition to what LandCroozer said, also consider that you're making one rotor and caliper do the work of two.

Brakes convert the truck's momentum to heat- with normal brakes, there's four calipers and rotors to do this, in a truck with just pinion brakes, there's only two. Putting twice as much energy into the rotors can't help but make them heat up faster and fade quicker.

For trail use, they're okay. Slow speeds, no kid-filled minivans pulling out unexpectedly. But I would definitely NOT recommend them on the street.

Doc.
 

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Dude spend the time, energy, and neurons that you'd use engineering your combination blinker flasher / hydraulic brake solution, and go make enough money to buy some front wheel brakes for your junk. I know that sounds trite, but the brake fade (which would be perhaps better solved by drilled/slotted/thicker rotors and better pads anyway) is just one part of a bigger picture of pinion brake inadequacy, especially for street.

Disclaimer - my rocks are still sitting in my garage, but I was concerned enough by the prospect of shaft breakage to invest in wheel brakes, at least for the front. My feeling is this: if you aren't locked in that axle, and if you are braking in intermittently conditions, and suddenly the wheels either hydroplane or hit ice or snow (Colorado), the pinion brakes will easily lock up that side of the axle (or worst case, both sides). Then, once the rubber contacts grippy pavement again, they are going to be hard pressed to instantaneously move both the pinion brakes AND the center chunk hardware. I don't think that the change in inertia involved in suddenly trying to move that center chunk from 0 to 30 mph in a nanosecond will be a small one, and I think that such an instance will be really damaging to the axle shafts. I'm worried enough about breaking a shaft under throttle, and it's not like I'll be exactly roasting the shafts. I plan on being able to decellerate much faster than accelerate.

Generally, braking conditions aren't the ideal time to experience component failure, so I felt that it was judicious to spend more on my brakes than I did on my axles. If there is one thing I want to work 100% on my rig, it's my brakes.

Bob
 

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I have driven my rig on the street extensively with full hydraulic steering and pinion brakes. They work in the sense they stop the vehicle but usually if I tried to stop hard the rears would immediately lock and the fronts would start, it was more like an on-off switch than a pedal. I was very careful to leave a lot of space inetween the car in front of me. If you're thinking about spending a lot of time on the road with pinion brakes, forget it. I run brakes at both ends...the braking also got much better when i ditched the detroit and welded the rear.

On the other hand, pinion brakes are hands down one of the best trail mods, right up there with hydraulic steering.

CJ
 

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NotQuiteSane said:
I actually plan to stay in the mid 30's range, going for the 60 strenght at 1/2 60 cost. neither my skill nor needs dictate 44's. yet :flipoff2:
Rockwell 2.5s aren't for you unless "mid 30's" = 39.5"s
:laughing:
 

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I think the biggest issue I would worry about, is the fact that on a rockwell, your rotors are spinning almost 7 times as fast as normal. also the heat from the brakes might cook the pinion seals fairly easy. Safetywise, it's really not much different from the inboard discs they use on hummers and hot rods..
 

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I run them on mine and drive it on the street daily. I don't do more than 30 miles total in a day, though, so I can get away with it, especially since I don't see speeds of higher than 40 mph at any point during my drive. If I did any more than that then I would go to wheel brakes, but the pinion brakes are fine for limited street use. I did manage to crack a rotor last year during a panic stop on my way home. that should tell you about the heat and stress these things see on the street.
 

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Discussion Starter #12
JEEP_TJ_FREAK said:


Rockwell 2.5s aren't for you unless "mid 30's" = 39.5"s
:laughing:
Sorry, What I've found searching says otherwise:

same clearance as a dana 44 after shaving
3..36 gears after a 50% reduction
the birf style, while not as good is strong enough for my immediate needs, and can be found for under (how much under depends on where you buy) $1000 for a pair.

"easy" to narrow, and pinion brakes can be added for around $500.

NQS
 

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By the looks of this thread the people running pinion brakes on the street are dangerous and they know it.

Keep your pinion braked rigs of the street. They dont belong there. Put the fawkers on a trailer.

Look at what these guys have said - "I don't do more than 30 miles total in a day, though, so I can get away with it" or "I was very careful to leave a lot of space inetween the car in front of me" These are not the excuses you want to be making to defend your pinion brake system.

When that minivan full of kids pulls out in front of you you need to be able to stop (and possibly steer a little bit as well)

Sam
 

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Strange Rover said:


When that minivan full of kids pulls out in front of you you need to be able to stop (and possibly steer a little bit as well)


They stop too well, that's the problem.
 

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I can provide proof and facts - but not based on being (or not being0 in an accident - only based on a lil ol thing called physics.

if you don;t like proof based on physics, or will discount it if it's not what you want to hear - read no further.

Also, before I begin, may I caution you GREATLY against the philosophy of "If i can;t find anyone who it;s hurt yet, it must be ok" (if that's where you were going)

I see it all the time on the board, and it's totally wrong. That's like a fairly lucky russian Roulette player claiming "I've stuck this loaded gun to my head several times and never had a problem - so it must be safe and an ok thing to do" The logic just isn't there.

Pinion brakes are not safe on the street for a number of reasons, some already talked about. Let me go into the most important a bit more - thermal transfer capablitly.

you said you wanted FACTS, here they are:

FACT: Energy can niether be created nor destroyed, just transformed from one form to another
FACT: E=mc^2
FACT: The amount of kinetic energy your rig has at speeds is dependant on the velocity squared, and doesn't have a damn thing to do with your braking system
FACT: In order to stop, you must transfer that kinetic energy into another form - usually heat and noise through friction
FACT: Pinion brakes have a LOT less thermal absorbtion capability that 4 wheel brakes
FACT: Because of this - they will get hot very quickly, and then not work, and you will be fawked
FACT: They do appear to work well at slow speed / trail because of a concept known as the increase in effective swept area (what most people erroneously think is the gearing working for them)
FACT: Anybody claiming to have engineered and tested an effective street braking system because they can lock up the tires doesn;t know a damn thing about engineering a braking system, and is giving dangerous advice
FACT: Most people don;t know jack about how brakes really work
FACT: The street, especially emergency manouvers at speed, DEMAND a healthy safety margin and are no place for anythnig even slightly questionable.
FACT: If this doesn;t make complete sense by now - you have NO PLACE engineering a braking system for a street driven rig
FACT: Pinion brakes have NO PLACE on street driven rigs
FACT: I don't give a damn whose feeling i hurt with this post.

Brakes on street rigs are NO PLACE to screw around - even if hundreds ignorantly and dangerously do.

You asked :flipoff2:
 

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Add to that what will happen with an open diff, i.e. probably one wheel keeps turning, the other running in reverse, if not everything breaks first, which it probably will, as those shafts and universal joints will see extreme loads as you slam the brakes on paved road, throwing most weight to the front wheels, giving extreme amounts of grip + shock load as all your gears and joints probably shift from drive to coast and so on and soforth

My opinion is that it COULD work for crawling speeds with both axles welded, maaaybe with detroits, but the slack in the detroit would give you a jerky ride and be hard on your locker, shaft and u-joints, even if you have overkill axles


Those are my thoughts. But hey, what do I know, I'm just a web wheeling physics student
 

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DriveTime said:



They stop too well, that's the problem.
which is why I added the bit about steering as well. Having brake "feel" is very important because it is this that gives you control under hard braking.

Sam
 

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Discussion Starter #18
Strange Rover said:
By the looks of this thread the people running pinion brakes on the street are dangerous and they know it.
thats my take too. I suppose I could bne cheap and run the stock drums, although i'd need to double check just how big a rim i'd need.

I like the discs Steve has, and probably will end up running them

hmm. i've got a 44/60 already, I think I'll be using them for a few years till I get enough to do the rockwells right.

i've got another idea, but i need to research more before i divulge.

NQS
 

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You're right about the brake feel. It really is like an on/off switch, but at least it stays straight. Nonetheless, I still make sure to stay on back roads to stay as safe as is possible with these things on the street.
 

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NotQuiteSane said:
I wonder if one could stop the fade with anti-lock brakes? I

Also, how much brake fade is caused by tire size?


wheel brakes are planned for, but right now not in the budget

NQS
[/QUOTE
  • This is why pinion brakes F A D E, at 55 MPH the rotor at the wheel is turning 420 RPM, and the rotor on the pinion is turning 2,822 RPM, end of story. steve
 
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