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PrincePaul

Yes - another Brake Thread. S12W and drums?

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Posted (edited)

Hello Guys,

 

first post and straight a brake thread - I`m sorry, but I read hours on hours in the FAQ section and in a lot of other brake related threads but couldn't find anybody who has done this.

So on the weekend I bought a 78 280Z and I´d like to go down the performance road while still keep it kinda periodic correct so I don`t get problems with TÜV in germany and a historic licence plate.

 

So the car will get fully striped down, an exterior backdate to 240z, suspension upgrades, fender flares, exhaust, maybe tripple weber (have to inform myself a bit more on that vs EFI) etc. etc.

 

A lot of people go straight to a rear disk brake conversion and complain about the brake bias and sometimes even damaged axels due to a different load on them compared to drums.

Basically thats not what I wanna do plus the TÜV thing mentioned above.

 

But what about keeping the drums in the rear, change the front to S12W and go with a 15/16 master. If I`ve seen that correctly thats what they did back in the day with the original FIA brake upgrade out of the competition catalog. They just went with 13/16 wheel cylinders inside the drums. (not sure about the mastercylinder with FIA brakes...) I just can`t find the size of the original cylinders inside the drums...

 

Somebody did that conversion here in the forums? Is it working well with the original proportion valve or is a manual one capable of dialing in a proper brake bias?

Probably have to run a couple calculations to find out (which seems not that easy with drums). But as of the drums are able to create a higher brake force with less hydraulic input they should work better as a rear disc conversion.

 

What do you think? Any help or experience is welcome ;)

Edited by PrincePaul

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Keep the brakes stock with SS braided brake lines and Carbotech pads.

 

If you can't resist doing an "upgrade" then install SS braided brake lines and the Toyota 4x4 pickup solid rotor calipers with Carbotech pads and a 15/16 in. master cylinder. And then don't do anything else.

 

If you do the Toyota caliper swap, use generic A/N SS braided brake lines with A/N to metric adaptors to connect to the caliper. This allows you to go to any speed shop and buy generic A/N lines and not have to special order custom brake lines. It also avoids having the re-bend the stock 240Z  "S"  shaped brake line that goes from the hose to the caliper.

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If you look at a brake bias calculator you will see that by switching to the s12w with the stock drums is a bad idea... The s12w overall are bad. They require more wheel space and the duel large cylinders makes them hard to match. The later years before the 12w they made the 12+8 with a large and small cylinder which makes it easier to match while also allowing you to run vented calipers. Even these however I would never run with stock drums.

 

My set up I believe works very well. 

 

S12+8 and vented calipers with the needed spacer in the front.

 

Maxima calipers and 300zx roters in the back with needed bracket.

 

This set up when calculated gives me 67 to 33 front to rear ratio which depending on use, weather pad materials... should be between 55-70% front.

 

If you don't get enough bite in the rear you will fish tail/ spin out. Best test of brake bias is stopping in the rain and still going straight.

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Posted (edited)

I don't think that I've ever read anyone actually write down what they thought the improvement would be, for any of the various brake "upgrades".  Most performance "upgrades" are done for looks, from what I've seen.  If you can't describe the performance benefits in words, then you're just doing it for looks.

 

 

 

The brake upgrade world typically involves a lot of effort and expense to create new problems.  Figure out what you're trying to accomplish first.

Edited by NewZed
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Newzed: I completely agree with you. Everyone just wants to slap a set of brakes together to look better. I personally hated the drum brakes when it came time to change pads. At the end of the day I could lock brakes before and after the upgrades. The only difference is cooling abilities of the vented roters over solid and the solid disk over the drums.

 

Drum brakes when set up right work great. My 36ft trailer will stop my truck fully loaded with only drums on two of the wheels.

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Posted (edited)

Alright, thanks for the input.

So I`ll definitely buy steel braided lines and I also replace all hardlines to be on the safe side. 

 

The looks point of a disk setup is really strong in this forum I have to agree. Just when you scroll through the brake threads. The first thing is rear disk conversion...

 

 

What I want to accomplish with that "upgrade", is a longer lasting brake that makes use out of the semi slick tires and holds that level of brake bite.

 

As I`m replacing every component which is in touch with fluid or has o rings inside anyway. My way of thinking was to spend a little bit more and get better parts in straight away. So basically it doesn`t make any difference if I buy a new 7/8 master or a new 15/16 master.

 

By the way willwood or Arizona Z or whatever setup where you see straight away that this is not factory. Massiv milled aluminium parts in red, orange etc. is not gonna happen here in germany if you want the car road legal. With the toyota setup you are still able to show them the nissan competition catalog and that should be alright. Its not that easy here with all these regulations...

 

 

 

 

I just found out that the rear wheel cylinder is 7/8 original iaw the FSM. So thats actually bigger than what they used for the FIA brake with the vented rotors. Which were 13/16".

Edited by PrincePaul

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^Right, I imagine if they are taking note of casting seeing a shiny rebuilt caliper where drums are supposed to be would be a red flag. Period correct, and tire width restrictions have been noted, that would also be a limitation if you can't put on bigger wheels as some conversion kits run bigger rotors.

 

Honestly the drums kind of scare the piss out of me which is why I would go for an "upgrade." A friend said his brakes suddenly went out, when we got the drums off the o-ring for the wheel cylinder had gone and fluid was just gushing out. Being behind the drum you wouldn't notice until it filled the cavity to leak past the inspection port.  At least with calipers if the brakes don't feel right you can poke your head under the car and see all the components. Technically the calipers could do the same, but the piston would never dislodge like that since the pad would keep it in place. Just kind of a scary realization.

 

@walkerbk is there a calculator somewhere for the drums and other common swaps? Mind sharing a link?

 

 

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Basically nothing without proper certification about the strengt and its function. I don`t know the specific test they have go trough to get that tiny piece of paper so I can bolt it on my car. But all these cnc machined aluminium suspension parts from T3 for example will never be road legal here. This whole certification process is so expensive that a lot of aftermarket parts are not available in germany.

 

Even steel braided lines have to be certified in a specific way. So if I would buy some in the US which are pressure tested to amount X and lets say aircraft grade hoses what ever. They still won`t accept it even thou you know they are working fine.

 

So everything has to look kinda OEM. That together with an old car they probably have never seen before makes it easier to get it trough. 

 

Wheels will be another story, sometimes your lucky and the rim has the material stamped in. So with the axle load they can check in their database if it works or not together with a clearance check and everything.

 

 

Do you know a company which sells a 12-8 vented Kit?

 

@seattlejester

 thats why I will replace any component which has orings or fluid contact with new parts. If the rear went the front should still work. Isn`t that the reason why the Z has this dual reservoir setup on the master?

 

Tire sizes are not a big problem as long as they don`t rub and the speedo is still correct. So they drive up a ramp only with the front right and rear left so the car goes on full compression and there has to be a certain amount of space between the body panels and the tire. Steering has to be safe as well while doing that.

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Posted (edited)
15 minutes ago, seattlejester said:

A friend said his brakes suddenly went out, when we got the drums off the o-ring for the wheel cylinder had gone and fluid was just gushing out. Being behind the drum you wouldn't notice until it filled the cavity to leak past the inspection port.

 

That's what the brake pressure differential switch is for.  To light up the Brake light.  Caliper seals can blow out too.

 

You're kind of giving the irrational "reason" to upgrade.  Better to just admit that you want shiny brake parts.

 

One rational reason, to me anyway, to convert the backs to disc is that they stay in fine adjustment.  The drum brakes will feel different before and after a click on the adjusting wheel.  The pedal will be higher after a click.

Edited by NewZed

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http://www.silverminemotors.com/datsun/datsun-240z/brake-upgrades

 

They have the S12+8 kit under their stage 4 brake upgrade heading.

 

@NewZed True, given enough time calipers would probably go as well, although the ones on my car and my friend's 280z were still holding before I swapped and he replaced, where as his wheel cylinder blew out, and mine disintegrated. I'm not sure if the concern is irrational. Hmm, maybe a bit alarmist in retrospect, but being able to inspect for leaks quickly as part of routine service seems to be fairly rational. I will also add, swapping out pads is quite a bit easier than changing out shoes.

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Drum brakes have been around and dependable for many years and are still in use on brand new cars from reputable manufacturers.  Worrying about a cylinder blow-out, or a spin-out just doesn't seem to have much weight.  Just trying to stay on the  path of solid reason.

 

image.thumb.png.9ecba9c1f4cfdae5dab7881666e7148a.png

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Are you sure about that stage 4 kit? Because it says 43mm pistons. So that should be the S12W.

 

I don`t worry about drums in the back. The all new VW up GTI for example weighs also around 1 to and has drums in the back like the Z.

I just want to know if somebody runs them with the S12W in the front. 

 

Alright how about that:

 

So the FIA Brakes are 4 piston with 41,3 mm dia the rear drum cylinder are 13/16" so 20,6375 mm dia. So in total you`ve 8 pistons up front which combined have 10717,168mm² while the backs are two pistons each side so four in total with 2676,048 mm² together.

S12W are 43 mm dia and stock 280z rear drum cylinder are 7/8 so 22,225 mm dia. Same number of pistons so up front 11617,608 mm² and rear 3103,584 mm².

 

That makes a 80/20 distribution with the MK63 FIA brakes

and 78,9/21,1 with the S12W and stock drums.

 

Mounting points are the same so you don`t have different leaver. Considering you run the same pad compounds. Which have almost the same dimensions as well.

 

What do you think, can you calculate it like that? As far as my understanding goes that was all they changed when you upgraded to the MK63 brakes. Front calipers and the rear wheel cylinders. So even with a stock proportion valve the S12W should work. I mean its a 1% difference...

I know thats not the real brake Distribution but to have a comparison value between these two systems.

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Fair point, I don't see a point in getting unreasonable in a discussion. Counterpoint to the fact they are being made used today, the motivation isn't anything impressive. It is because a drum setup is cheaper. Manufacturers don't like to say as much for obvious reasons, but if it is cheaper and performs adequately for most consumers of the vehicle while providing them a savings, then in business sense it would be foolish not to do so. If a disc brake option was available that added no cost to the manufacturer, I can't imagine they would choose the drum. Given some newer cars have a disc and a drum in the back (drum for parking purposes), then using a wheel cylinder, forgoing the rotors, caliper bracket, and caliper is a considerable savings on say an economy car.

 

 

Oops S12+8 is for the non vented right? That would be their stage 3 kit.

 

I'm not sure that is the correct way to calculate bias is it? That just determines area the force is acting on, things like leverage aren't included which plays a factor.

 

http://www.tceperformanceproducts.com/bias-calculator/

 

I mean following your assumption if you factor out leverage, pad compound, pad shape,pad size, etc than just force remains, but really they are different at least fairly drastically in leverage if recollection calls.

 

Link to a thread where we hashed out some numbers, still not perfect since that is more or less strictly from a moment perspective (leverage x force)

 

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Ill have a look on that thread tomorrow. But the leverage shout be the same as the mounting points are the same. And with something that stays the same you don`t need to take it into account. If you check the length and width of the front brakes pads the just vary a couple mm. 

 

Now its definitely not the "real" brake bias. But for a comparison between sys A and B should be sufficient. Just have to check the distance between the mounting points and the cylinders but that should be also vary minimal from MK63 and S12W.

 

I know of someone running that setup, but he is just driving normal. So I don`T know if he ever tried or checked which locks up first. thought that at least a couple are running that setup.

 

Anyway, thanks for the link. Will study it tomorrow ;)

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This took a while to wrap my head around. My concern wasn't between the front comparisons, but more so your front to rear to end up at the bias ratio you have the 80/20 you arrived at. We were having some discussion on how to accurately determine the moment arm of a drum brake as well as the leverages involved on the shoes so looking at your math was a bit startling as that just removed the moment arm, but since you are comparing the same moment arms between two setups and looking for the difference between the same setups (moment arms wise) the moment arms cancel out and you are left with a force ratio, which you could compare using your method.

 

Speaking of factors given you are multiplying both the fronts and rear by two to get total pistons you can remove those and work with some smaller numbers.

 

You are increasing the fronts somewhat by 43mm vs the FIA 41.3mm so using the bigger 7/8 vs the 13/16 of the FIA rear cylinder would raise the force in the rear enough to maintain the ratio between the forces, in theory you should be able to run the stock proportioning valve given the very minor difference. You could use a manual one and dial in some more rear brake to improve performance somewhat, but the bottomline is compared to the FIA setup running the S12W setup would be somewhat comparable with the 7/8 rear cylinder math wise.

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Posted (edited)
5 hours ago, seattlejester said:

Fair point, I don't see a point in getting unreasonable in a discussion. Counterpoint to the fact they are being made used today, the motivation isn't anything impressive. It is because a drum setup is cheaper. 

 

That's not a counterpoint to my point.  Which was to your point about wheel cylinder "blow-outs" as a reason to switch to discs and calipers.  Your statement implied that drum brakes are inherently unsafe.  I was showing that they are not.  You're digressing.  

 

Back to the original point about performance - I'm pretty sure that some of the guys that race their cars, or have, have pointed out that the typical front brake "upgrade" to bigger calipers and discs adds unsprung weight.  Which is a suspension performance downgrade.

 

My main point is to define clearly what you're trying to accomplish.  Don't just bolt on parts that somebody on the internet said were an upgrade or that one of the aftermarket suppliers is selling as an upgrade.  The advancements come from the people that think out their projects and choose the parts that do the job.  The thread seems to be trending that way, so carry on.

Edited by NewZed

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The above mentioned thread was one of which I read the past couple of days and is exactly what I meant. The majority is going to a rear disc conversion straight away and there is not much information about combinations with rear drums.

 

yeah the calculation is simple but to compare the two variances it should be sufficient. I will try to go a bit deeper into pad sizes and piston to mounting position distance later.

 

benefits of a manual proportion valve would also be a bit reduced hose/line clutter in the engine bay. If I use this black one from willwood with two Front outputs. So there is no need for the Hydraulic block on the left side plus the original proportion valve. As I’m building new lines anyway I can get the right adapters for the willwood part straight on the lines.

 

my way of thinking was if Nissan design a system like that it’s properly working and properly thought after. 

The question is am I right with my understanding of the competition catalog that they really just changed the front to mk63 and the rear cylinders and nothing else.

 

yes unsprung weight is a thing. I have to find the article but there was a Swiss guy who weight both. The stock and the non vented 4 piston calipers and the Toyota’s were actually lighter. Of course the vented disks are heavier than the solid ones. So does the wider wheel/tire package I want to use.

 

the question is what do you notice more. I don’t know. Probably a discussion for another thread.

KW coilovers, poly bushings and swaybars should upgrade the suspension in a way that it should take care of. 

A bit off topic but the tc rod problems with poly bushings is still the same on 280z’s or only on 240’s? 

 

 

@NewZed what do you think about the calculations do they make sense to you?

 

 

still hoping that someone who actually runs this system sees that thread ;)

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I see that a proportioning valve (PV) came up again..  It always seems to.

 

1. All of the Toyota swaps result in front bias  (nominal 60% front - 40% rear).  A proportioning valve reduces pressure to the rear brakes so adding a proportioning valve to the rear would make no sense.

2. Never install a proportioning valve on the front brakes.

4. Never add a proportioning valve to a brake system that has a stock PV installed.

 

Many people who do these brake swaps are often disappointed with the results. Mostly because the brakes on your car were designed as a system by the manufacturer.  That is,  the calipers, wheel cylinders, master cylinder, pads, shoes and proportioning valve all were selected to work together. When you change one component,  you create a domino effect such that you then end up needing to change the MC because the pedal is too stiff or the pedal is too long and hits the floor or adding a larger diameter booster to deal with a stiff pedal etc. etc. In the end the brake system performance actually degrades.

 

In the brake section there are many discussions about brake balance calculations.  Suggest you study those threads.

 

Again, if you feel strongly compelled to swap parts, leave the drums alone,  and install the Toyota solid disk calipers on the front and run Carbotech pads and shoes. Rebuild the rest of the stock brake system. And then quit.  You will notice a bit more front bias the first time you apply the brakes.

 

Otherwise leave it stock and install Carbotech pads and shoes.

 

If you are not sure if a modification will pass German law, ask an inspector.

 

BTW: There are two styles of the vented Toyota calipers.   One with four 43mm pistons and the other one has two 43mm pistons and two 34mm pistons  (same caliper as the solid caliper, but the slot was machined wider for the vented rotor.

 

 

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Posted (edited)

@Miles Thanks, yeah I read a lot of these threads. I think you already wrote some similar lines in the other ones. As far as I am aware of the other thread with bias calculations were always with rear disc conversion.

 

So we all know that the original MK63 conversion works well. It was designed by nissan... so big vented brakes in the front and a drum in the back. Sumitomo build both calipers the MK63 and later the S12W and according to other threads they are not so different in design.

 

BTW out of jdmjunkies.ch:

MK63 Solid disk type including brake-pads: 4.300 Kgs
Standard two pot OEM including brake-pads: 4.445 Kgs

 

what I found on an other side is 3,8 kg for the vented MK63 without pads - not really comparable.

 

I guess the disc would be the most in weight difference between solid and vented.

Can`t find any figures for the S12W, everybody is saying that its heavier but no one postet weights.

 

For the distance from piston center to mounting point I didn`t found proper drawings yet. Because the one you find for MK63 say 261mm disc diameter with the non vented version. But that has to be 271mm as they used the stock rotor...

 

I`ve seen another thread here with a guy who ran S12-8 vented and swapped to S12W due to better race pad availability and was saying that they are more or less the same - driving wise.

 

The other Toyota vented version (different piston sizes in each caliper) should be the S12-8s but I can`t find a kit anywhere.

 

 

So the question is: Is there a noticeable difference between the MK63 vented with 13/16 rear cylinder (FIA brake setup) and the S12W with 7/8 rear cylinder. Brake bias, weight etc - noticeable difference while driving, not only on the calculator. If there is a bigger difference in brake bias, is that changeable via a manual proportion valve or is it hopeless like with some rear disc swaps where even NO proportionvalve is not enough pressure to the rear.

Edited by PrincePaul

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@NewZed My point was an ease of inspection and later on adding in ease of maintenance being a reason to swap to discs. My fright was centered around how they failed and how the failure is kept hidden. If I truly feared blowouts of the wheel cylinder I would have a panic attack anytime a car with drums pulls up next to me or I am offered a ride in one, and that is not the case. 

 

I think it was a fair counter point, but you are allowed to disagree. You brought up the fact they are being used dependably today by reputable manufacturers, my counter point was the only reason they still are being used is financially motivated. While I am not disputing the fact they are dependable enough to be used today, I am disputing the fact the reason they still are. There are also some whisperings by some sources as to alternative reasons why they still are, dependability and performance have nothing to do with it according to them.

 

Regardless in the face of data, my few anecdotal experiences truly are insignificant. While the experience left enough of an impression on me to change my mind, I'm sure an analysis of the data on how many systems are in use even in older cars with no malady to report would counter my views easily, therefore irrational could be applied. Bummer when that is the case for the person who holds the view, but I concede on that front. 

 

 

@PrincePaul jdmjunkies.ch is actually on this board I think, I believe the two becomes one build thread is his.

 

Having the stock bias values to compare with would be a real treat as we could compare how far off the values for popular swaps can be.

 

I think Miles has been answering your question from the beginning. Keep the stock system, but upgrade pads and lines, maybe add better fluid. If you have to do an upgrade what you outline should be sufficient with a bigger bore master to compensate for additional fluid required.

 

The vented differing piston caliper setup seems to be on I4 4-Runner (also vented rotor): 43mm/34mm according to the thread above. Not sure if anyone supplies a kit, but I'm sure silvermine would be able to make a custom kit if that is what you really want, it would just be a matter of grabbing different calipers from the parts supplier.

 

To get a specific answer to your question I might suggest classiczcar, I was only slightly familiar with the Mk63 setup before this week, looking it up I see a lot more hits over there, so someone might actually be running this setup to give you a positive real world "feel" answer rather than numbers.

 

 

 

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Yeah seems that the 1988 l4 4runner setup is best suited together with rear disc conversion - balance wise.

 

With the calculations in the beginning that setup would have 75/25 bias. So thats more off the MK63 (80/20) to the S12W (79/21), but the gained clearance to the wheel is a nice benefit.

Ah... so many options. Stock seems to be the easiest - yes.

I check that forum out - thanks for the tip.

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Im not sure which brakes those are, but the later years before they switched to the s12w, they took the s12+8 calipers and widened the channel in order to accommodate the vented roter. That gives you the best bias.

 

As for calculating for front/rear bias with disk/drum set up, the calculations are completely different between disks and drums. Disks the force is applied equally on both sides sandwitching the roter. With drums, the cylinder pushes outward but then the pad material further from the cylinder has less effect on the drum itself.

 

When I was doing my calculations, i could never find a clear cut way to calculate drum brake bias.

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