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Yes - another Brake Thread. S12W and drums?


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@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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Some years Toyota S12 + 8 calipers (solid rotor application) were modified (wider slot) for vented rotors. The S12 + 8 caliper has two 43mm pistons and two 34mm pistons.

 

 

SW VS S8 CALIPER.jpg

SW12 VS S8 CAL.jpg

s12 + 8 vented.jpg

SW12 VS S12 8 CALIPER.jpg

Edited by Miles
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