That is so, a very basic simple stupid valve. In 3gen maxima, 2 pieces & the possibility to adjust makes maxima luxurious.
Take some other kind vehicle, hit brakes, due to weight redistribution, rear comes airborn. I might dangerously say: then braking effect in rear is pssibly even less than 5%.

Matt93SE: If u have ever driven all over the globe, u might know that all roads are the same - end in Rome. Blondie is a global phenomenon. If one feels drivin is dangerous, one might change habits - like stay at home: doesnt hlp, most ppl die in bed.

How many times have to be repeated: 4balanced brakes is bonus for safe drivin, ABS shortens stop distance, even saves from crash. Rear calipers rust solid because safe daily drive doesnt actuate 'em "at all". And/Or ppl dont do basic maintenance. With my habits they do NOT. And also, I do intentionally periodically exercise 'all features fully', like brakes, just to keep the functional:

 

Do you understand brake bias? Try disabling your rear brakes and do some aggressive driving. Then you might know what the rears do. I should know what I'm talking about as I've run my bbk in the fronts only. So the bias was more forward. I know what too much front bias does.

So why have them at all regardless of their simplicity???

 

Wiking, do YOU understand balanced brakes?
our brake proportioning valve sends EQUAL HYDRAULIC PRESSURE to the front and rear brakes for the first 427psi of fluid pressure, and then retards the rear at a slope of 0.4.

427psi of fluid pressure on the brakes is enough to come to a pretty throrough, screeching halt. this makes the car brake flat and steady under most driving conditions and doesn't cause the front brakes (and tires) to wear out as quickly.
the 0.4 slope on the high end is to combat the rear end locking up upon heavy braking and the weight transfer to the front.

In fact, under normal driving conditions, the front/rear bias is approx 67/33- pretty close to the factory weight distribution of 61/39, but shifted to the front just a bit to maximize safety and induce some understeer into the system from the get-go.

ONLY when the car is nosediving and very hard on the brakes does the system start moving the bias to the front and finally wind up at approx 78% front, but that's ONLY when the front brakes are exerting approx 2500ft-lb of reverse torque.. which is enough to lock the front brakes with >80% of the weight up front on race tires on a stick track.

Thus your assertion of rear brakes not doing squat is totally absurd and VERY dangerous to put into practice.

Edit.. here's an illustration for you.

I lost the Maxima charts and graphs a few months ago when my hard drive crashed, and I don' thave the hours to redo the calculations, BUT.. the Z32 brake curve is very close to ours.. (that's the pink on on the graph.. one of the most rearward biased curves on the list).

 

Owned!!!!!!!!!!

You guys DO realize the load adjusters ADD rear bias when more weight in the car right?

 

Relax. Reread. I have not spoken of aggressive writin/drivin, but:
a. nice city cruise.
b. mirror ice
c. what happens if rear brakes are disabled.
Dont try to tell me I have not been racing with any disabled brake configuration. I have told here with illustrations how to increase security in brakes. Instead of aggressive drivin, try polite writin.

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Simple cars have no weight related adjustment. More simpler ones, dont even have any valve.

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Fluid pressure is NOT equal to braking force applied to each wheel. (rear smaller cyl, pads)

Fluid pressure is NOT equal to braking force applied from wheel to road. (weight redistribution = rear will raise, be lighter, less contact.)

Local mandatory yearly tst results on my maxima forces on tester, NOT ROAD (force applied to road w/o weight redistr)
Front left 2.93 / right. 2.87 / dev 0.1% /accptd deviation 30%
Rear left 1.30 / right. 1.38 / dev 3% /accptd deviation 30%

Again, This force is not applied to road surface, b/c of weight redistribution to front during deceleration. Rear 'gets far less' than the about 40% shown above.



Repeat: on some instances some vehicles rear gets AIRBORNE durin hard decel. Where the fluid pressure effect then goes? Glob all Warmupphoax?

 

Hahaha. Okay everyone, please raise your hand if you EVER were able to get the front end to actually come off the ground during a braking session!

FACT from Matt. During ALL of your discussion, you were mentioning easy crusing AND easy braking. BOTH SITUATIONS DICTATE THAT THE REAR TIRES HAVE PLENTY OF TRACTION. AND DURING THE INTIAL BRAKE FORCE APPLICATION THE PRESSURE APPLIED TO THE FRONT AND REAR CALIPERS IS THE SAME! You can't even begin to argue that. That completly blows your "rear brakes aren't necessary during easy everday driving" theory to pieces.

The plain and simple fact of the matter is the maxima rear bias adjusters are designed to increase the bias toward the rear as more weight is loaded into the car. This device no matter how simple or complicated is designed to INCREASE braking effectiveness and safety.

Just because "simple" cars DON'T have bias valves and load bias adjusters, doesn't make them able to brake better. In reality, those cars are LESS safe and would perform WORSE vs the same car WITH these features.

In regards to hard braking, this is where the designed brake bias comes into play. The weight transferred to the rear is compensated by less brake force being applied to each rear caliper via the porportioning valve. In reality, the factory bias settings are too CONSERVATIVE. Not too high.

 

Before you try to shoot holes in my calculations above, realize I factored in brake pad, rotor, piston size and number, friction coefficient of the pad, etc.
the calculations are to torque at the wheel, not hydraulic pressure.

 

Does not make them any safer or better braking cars.

True but is ALOT more than your quoted 5%

During anything but a full on agressive brake, the rears tires have PLENTY of traction correct??

Not during the "crusing" example you stated. Rear gets plenty of weight

 

Motorcycles can do "stoppies" easily.

But back on topic:

Its all really simple if you think about the physics behind front and rear brakes.

if you have only front brakes and you try and stop while going around a corner, your going to understeer.

If you have only rears and brake while going around corners your going to oversteer.

The only reason why brakes are biased to the front on most cars is because that is where most of the weight is due to the engine and other fun machinery. Thanks to that weight, you can apply more braking force to the front tires and not have them lockup as easily as the lightweight rear of the car.

On 50/50 cars, the best traction in braking is ususally achieved in about 50/50 brake bias. Some systems are a bit more advanced and take the forward inertia of the car into account, but thats about the jist of it.

Ice racing in crappy tires really has no bearing on anything brake related, as the tires themselves don't have enough traction to support any kind of braking.

 

50 / 50 bias huh? Can you site some data to support that? I really do NOT think most modern cars feature 50/50 bias when the braking forces ramp up. Especially when we are seeing rear rotors that are almost the same size as the fronts. Regardless of the fact that the rear caliper sizing is still smaller.

Take a look at my mods in my sig and decided if I know about brakes or not.

 

Ok, this thread has gotten out of hand...suffice it to say: the laws of physics are not the same between here (usa) and sweeden. As for the guy asking for our advice, about whether or not to do a rear disk conversion, sure why not, just start do a google or yahoo search of the forum for all the details of what you need.

 

Jeffy... notice he said 50/50 cars.. when you look at things like Porsche, Viper, Elise, etc.. you'll notice they have bias much more rearward than a Maxima. not 50/50 on most of them, but it's a lot closer to that under initial braking than you'd imagine.

 

I realize this. Why mention 50/50 cars in relation to weight dist when we are on a maxima forum?

I know makers are moving the bias much more towards the rears now. Look at the rear rotor dimensions now. Some cars have bigger rear rotors than we do in the front! By more than 1" in alot of cases. How else can the Viper haul **** down from 60 in less than 100ft! That's crazy. Even the G35 is the range of 110ft. If the G slammed on it's brakes right in front of ANY stock maxima, the maxima would be doing to the G

But hey, everyone says the maxima brakes are great even though it's the largest Nissan sedan to still use the puny 11.X" rotors and small single piston calipers. Wee

 

Clear statement... I have nothin to add.

Ppl living around bullies have hell of a life. Shame on you.

 

I just said it was a simple device, it does however do an important job. It is also true that the factory setting is conservative and the front end locks up first on dry asphalt.

I have managed to get the inner back wheel airborne when driving on a racetrack so it is possible even if the maxima-body is very soft.

 

Either hes intoxicated, or he wants to warp every word.

 

It's your choice to flame or address the issues presented to you. European back pedal is interesting to see.

Shame on you too!

 

Originally Posted by Jeff92se: "Hahaha. ..."


Clear statement... I have nothin to add.

 

Contradiction. You did add plenty.

 

You overlooked it.

50/50 is just an easy example.

Braking is a straight line can be difficult to conceptualize, so thats why I gave the going around a long sweeping curve example. In a 50/50 car, if the brakes were 50/50 biased you would have optimal braking efficieny were all tires would lose traction at the same time. If a car with 60/40 weight was going around the corner, a 60/40 would be a good brake bias.

Straight line is a bit different, because thanks to the springs, the weight gets shifted to the front of the car when braking, so auto designers ususally choose an optimal braking inertia to set the bias to.

So, if the weight was 60/40 front/rear, and they wanted to optimize for a 100-0 brake distance, they would maybe choose a bias of 67/33 or 70/30 to counter the heavy mass shift of the braking action. This would optimize the 100-0 stop, but at any speed other than 100 it would be less than optimal, because as it slowed down, the interia would change and it would favor more a 60/40 bias. Car designers pick and choose their battles.

But this is all within the tires specifications of course, if no tire to ground traction is achieved then nothing can happen.

 

Actually if you read Matt's post, the bias is not set 50/50, 60/40 etc.... When you intially hit the brake pedal, it sends equal brake line pressure to all 4 wheels. But as you step on the pedal harder, greater force is being directed to the fronts vs the rears, thus achieving the front/rear splits you mention below. (a 60-0 or 100-0 brake stop would we well beyond the point where the brakes are putting down equal pressure to frnt/rear)

 

Settle down guys. I think both of you are right in your own way. I have a vid of me without rear brakes and it is possible to go pretty fast without them. the reason I had removed the calipers was because I overheated and warped the rotors so they do a lot of work when you use them.

http://www.youtube.com/?v=_h1c-rusgSE

 

Many vehicles can do stoppies easily.


Matt93SE: " ... Before you try to shoot holes in my calculations above, ..."
- every single soul is responsible to tst every theory
- I saw only graphs, no calc, so maybe I missed
- IF one variable missing: calculation can be used in 'provin' glob all warmuppetshow
- calculations are just calculations until proven via empirical tests

Do u homework = tst brakin distances w/o and with rear brakes. Current tech has to be used, jeff laughing with granpa timer wont do.

 

Except. One answers: "Hahahaha....

Its valid personal iq illustration, still does not cover these still unanswered FACTS

1. Why Nissan did not put discs to rear, drums in front

2. Why Nissan; BIGGER calipers in FRONT.
3. Why Nissan; COOLED discs in FRONT,

4. Why Nissan; SMALLER calipers in REAR.
5. Why Nissan; NON COOLED singles in REAR.

6. Why Nissan did tell
- front pressure 710psi , rear 550-700
- front pressure 1400psi , rear 740-940

7. TWO CIRCUITS, why like this: both circuits have bot front brakes, one rear

8. Anybody; why THE REAR calipers are first to be rusted solid?

 

because the caliper itself doesn't rust up, it's normally the iston gets stuck and that's due to people not using the E-brake regularly. It's a common occurence on that design rear caliper

 

FYI: Rust also colled corrosion means material interaction with oxygen. should we dive deeper into that issue?

Point 8. Now we are gettin nearer. Smbdy now admits that typically rear piston gets stuck first.

E-brake? Regularly? Rear? ...Reversing your statement: for FRONT calipers are never sticking b/c regular hand brake exercise.

This leads to a question: Who knows a maxima with E-brake to FRONT CALIPERS? (I dont.) Saab has... This leads to a question: why Saab rear caliper pistons gets stuck first, (general pop)?

Some more explanation, pls.

 

Just in my own experience. I have seen more caliper slider pins seize in Nissans with rear disc brakes than with the piston seizing. I would still attribute this to not using the handbrake regularly, keeping the pins sealed and lubed properly is a factor. Also, regarding rear drums on any car, people don't use the hand/parking brake either which is usually part of what keeps the rear shoes in adjustment depending on the design. At some point the shoes will become so out of adjustment that the fronts will be doing more work than what they were intended. I have inspected rear drum brakes in the past and it was obvious that there was no real contact between drums and shoes because the adjustment was so far out. When I took auto shop in high school and when I attended NADC the same theory was taught; The front brakes on a FWD car can do "up to 90%" of the braking. This doesn't mean that they do 90% all of the time but under hard stopping it can reach that level. Factors also include the weight of the drivetrain on the front of the car and also the weight transfer to the front of the car when can increase with harder braking. A RWD doesn't have as much bias but there still is weight transfer. I don't remember the ratio right off for RWD. Those numbers aren't neccisarily specific for a Max but typical for a FWD front enging setup. Personally, I'd take rear disc over drum any day. They don't need quite as much as attention as a drum setup and are simpler, but they still ned to be maintained (properly sealed and lubed slider pins) In the midwest, I have seen a lot of seized cables which people won't repair thus adding to the issue of using the hand/parking brake.

 

wiking: the piston on the rear caliper is a different design than the front is. the rear piston screws in and out for use with the ebrake rather than just sliding in and out like the front does.

of course if you look at an older subaru you'l see the reverse.

 

IF handbrake theory was true, then Saab front calipers would stick first. Revelation: that doesnt happen. Ppl need more ammo to keep h-brake theory afloat.

8. How can two things 'rust' solid? Only if they do not move for long periods. And this is the basic issue I stated, granpa regular citydrive doesnt exercise rearbrakes, no not at all. (from that point of view, theyre useless dead weight) ... I can hear jeff laugh his pants off.

This time, will not go to racing ...

 

My handbrake and rear slider pins have never seized so ????

 

I've done my homework. have you? empirical tests say little to what is actually going on under the wheels if you don't know what you're looking at to begin with.

I have done said tests on the road course. real driving on real surfaces. Ice doesn't count since that's not encountered in 99.5% of everyday driving.
In the last 8 years, I have used several different front and rear brake setups. even simply changing to aggressive front brake pads for the track throws the bias off enough that the fronts will lock on a whim. With my original brake kits I had to dial down the front brake pressure quite a bit in order to maintain short stopping distances for the track. After screwing with thousands of $$ in parts and messing with piston sizes to get the car to brake consistently and reliably witht he shortest distances, I've learned that the factory brake bias is very much to the rear, and my calculations support that as well.

i'm not showing my calculations because my hard drive crashed a few months ago and I lost all of that data. I still have a few graphs I made for a different forum, but do not have the software anymore to recreate them. But my previous numbers showed that.. the FSM shows it as well based on the listed hydraulic pressures in the testing section and the specs in the back of the brake section. it can be easily calculated based on rotor diameter, brake pad size (to determin exact center for the torque/moment arm), caliper piston size and number, and hydraulic pressure at the caliper. If you want to get fancy with it, you can also add in friction coefficient of the brake pads, which I have to do when factoring in my race compounds have roughly twice the friction of the stock pads.

Why are the fronts so much larger than the rears?
under normal braking conditions when the fronts are doing 60% of the work, the system simply never gets hot enough to need anything larger in the back.
As one drives harder and uses more brake, the bias shifts to the front-- up to 80%-- and the fronts are subjected to exponentially more heat.
that does not mean the rears are useless. they are still used quite a bit actually. If you don't believe me, I'll be glad to take pics of my gouged up rear rotors. If they weren't used at all, you would have surface rust forming on the friction surface of the rotor. you don't see that, now do you?

why do the rear calipers always sieze? honestly, I see the fronts go just about as often. the big issue with the rears is that they don't get as hot as the fronts- remember, the fronts do MOST of the work on hard driving. NOT ALL. during regular city driving, the rears do a fair amount of work. that said, the rears simply don't get hot enough to cause the quick pad wear of the fronts.... since the parking brake keeps the piston very close to engaging against the rotor, there is very little movement in the caliper before the pads engage and start slowing the car. since there is very little pad wear and very little movement in the slider pins, it's easy to sieze a caliper. It's also exacerbated by the low pad wear as people assume the calipers don't need to be maintained since there is little wear. Thus, they largely ignore the rear brakes and that is mainly what causes the parts to sieze. front gets regular rebuild and lubrication. rears are ignored for the most part.

all that being said, I go through front and rear brake pads on a regular basis. the fronts last me about 6 months and rears last about a year.
I have NEVER had a slider pin sieze on any of my cars. I have piston seals leak before I have slider pins freeze.
I also use my ebrake on a regular basis since I have a sloped driveway, but I didn't for years and still never had the issues with calipers siezing.

Care to keep shooting? you're about out of ammo.

 

Edit: After what matt just posted this post probably won't mean ****.. But i will post it anyway....

On my seized rear calipers i found that there was rust inside the piston area...
2 things you need for rust....
1. moisture[water]
2.oxygen..
These 2 things are getting into rear caliper somehow...Most likely source would be the rubber boot that seals the piston is not doing it's job..[i.e broken boot]

Another point would be the owner/owners over the years are not bleeding the old fluid regularly to get all the moisture out of them that could cause the rusting of the caliper...

 

Good stuff! But i think the answer kinda comes down to how you drive your car. F Disc R drums will basically be fine for your everyday driving and them some...by swapping to rear disc you'll get some better braking but the benefits of it are in direct relation to how "spirited" your driving is..as well any changes to the front brakes system ( BBK). I personally can attest to rear discs being better having driven a 91 gxe with rear drum ( mine) and one with rear disc, only difference being color between the two option wise. The rear disc definitely does brake better. Me and a good friend spent a good hour and a half tearing up some back roads ( that road that connects austin to killeen that runs through Florence for you texas guys) and the rear disc does definitely brake better. That being said if you have the parts, funds, and desire i would definitely do it

 

Good points from "almost everyone"...When I commented on rear calipers seizing, I was speaking from my experience. The one case where it was on my NX2 (the rest were on customer cars) both front and rear pins were seized or close to it. In all cases where a pin was seized it was very evident that the little dust boots were gone or torn and the sliders were ran dry for however long. I have never had a piston seize on one of mine but that's not to say it doesn't happen. Many people can slap some lifetime warranty pads on their car but pretty much ignore the rest which is fundamental for the brakes to work properly. I had just bought my NX off a used car lot when I encountered that problem.

 

Yes this is a very worthly modification. Matt93se has peformed this mod many years back and it's worked out very well. With the bias that is built into the drum versions, adding the better discs works out very well.

Here is the link to the instructions:

http://www.4dsc.com/forum/viewtopic.php?t=11

 

am i the only one who stops reading wikings posts??


nice post matt. well said from experience.

 

Nope .

 

My friend just got himself the all new BMW E90 330i.. Front discs are 13in. and rears are 13.2 inches. Quite intriguing... Im guessing the set up works well with the cars driving aids.

 

[edit: This claim is] bs: "empirical tests say little"

Its the corner stone of scientific method.

- U did not address the questions. Pad wear example: ...racing = "pads on a regular basis" For me, front pads last 70kmiles, rear 140kmiles. Now if your pads wear out from racing, no relation to my txt or the issue why rear pistons do not move, rust solid, Pls. read again.

- Empirical tst means 60mph, no ABS, full stop. Repeat w/o rear brakes. Measure distance differences, time. Has to be done with current tech.

- Yes, I know. definitely you will not tst but print more. Why its 100% u ppl will not do this simple tst? Its b/c u hate FACTs which dont support u.

 

Wiking- you are right when you claim most of the effective stopping takes place in the front. That doesn´t mean that the rear brakes is not beeing used. As I tried to demonstrate in a previous reply, you can drive without rear brakes, no problem. But the stopping distance increases. I toasted my rear rotors on the track, a lot of hard breaking (=bias towrds the front), what does that tell you?

One more thing, ABS actually makes the stopping distance longer (check out swedish motor-magazines like "Vi bilägare" who test with and without ABS). The purpose of ABS is not to stop faster it is to be able to brake and steer at the same time.