Help with configuring a Wilwood manual setup

[Blown353]

Have a brake setup question.

Right now my car is setup with 13" C6 front / 12" C4 rear PBR calieprs and a Hydroboost. 5 years ago when the car was still running it worked well… but now that I’ve switched to the LS2 and turbos the master cylinder is really close to the exhaust manifold and wastegate. Also, things under the hood are now tighter on space to locate a remote reservoir with air separator for the power steering plus all the hydroboost hoses and the Lee filter I used to run.

I'd like to change over to manual brakes for simplicity and to keep the master as far away as possible from the exhaust manifold and wastegate. While I’d love to be able to slap on a smaller bore master cylinder with my current brakes and go I know from testing it in the past that the PBR brakes and their small piston areas don't play all that nice in a manual setup. By the time you put on a small enough bore master to generate enough pressure to make them work the pedal stroke is really, really long… and they still don’t work all that well.

Thanks to all the spreadsheets Ron has been posting I've been running a lot of numbers. While I was thinking about sticking with a stock-style tandem master I've also found that CNC brakes makes a dual master cylinder with balance bar arrangement that will bolt to a GM firewall which opens the doors to a lot of options.

All these numbers assume 13” front and rear rotors-- if Wilwood could set me up with 13 x 1.25” front and rear rotors that would be great, but it looks like for some of these setups only 14” rotors are available.

For a stout manual setup, it looks like The Aero 6's up front are the hot ticket. I can’t argue with the numbers, lots of piston area.

Wilwood Aero 6 calipers up front with 1.75 / 1.375 / 1.375 pistons

For the rear, I see a couple of options. If I were to use a stock style 0.875 tandem master cylinder and use BP-10 pads at all 4 corners on the street, these calipers would provide the following front to rear brake force ratios and total torque with 100# of pedal input @ 6.25:1 ratio.

Wilwood Aero 4 with 1.125 / 1.125 pistons: 73/27 split, 3200 torque

Wilwood FNSL4R with 1.25 / 1.25 pistons: 68/32 split, 3400 torque

Wilwood FNSL4R with 1.375 / 1.375 pistons: 64/36 split, 3620 torque

If I run a stock style tandem master cylinder with a proportioning valve for the back brakes I'd choose the FNSL4R calipers with the 1.375 pistons. Since you can only decrease the braking force on the rear with a proportioning valve that should allow me to tune the back brake bias down to around 70/30 or whatever the car likes given the final tire selection and weight distribution. Since the car is primarily a street car maybe going with a stock-style tandem master and a rear proportioning valve would be simplest solution.

However, with the CNC dual master and balance bar arrangement any of the options could be made to work… I see the following options for the rear calipers & master bore setups.

1. Aero 4 1.125 pistons with a .875 front and .875 rear master. With the balance bar centered that would be a 73/27 torque split, adjusted for a 70/30 split that’s about 3100 torque for 100# pedal input.

2. Aero 4 1.125 pistons with a .875 front master and .750 rear master. With the balance bar centered that would be a 66/34 torque split, adjusted for a 70/30 split that’s about 3620 torque for 100# pedal input.

3. FNSL4R 1.25 pistons with .875 front and rear masters. With the balance bar centered that would be a 68/32 split. Should only take minor balance bar tweaking to get to 70/30, and adjusted to 70/30 100# pedal input produces about 3440 torque.

4. FNSL4R 1.375 pistons with .875 front and 1.0 rear master. That yields a 70/30 torque split with the balance bar centered and will produce about 3320 torque with 100# pedal input.

5. FNSL4R 1.375 pistons with .875 front and .875 rear master. That yields 64/36 torque split with the balance bar centered. With the balance bar adjusted for 70/30 it will produce about 3760 torque with 100# pedal input.

Thoughts? I know the FNSL4R calipers have a price advantage over the Aero 4s, but it will only be about $450 price difference for the pair. I'm sort of leaning towards setup #2 or #5 if I go with the twin masters and balance bar but I'd really appreciate some input. I'm also torn between a stock style tandem master & prop valve vs a dual master and balance bar on what is primarily a street car. Thanks!

[Vince@Meanstreets]

pretty sure you'll get an answer as soon as the Migraine meds kick in.

We run .875's on the C5 C6 and wilwood 6 piston stuff with great feel.

[Blown353]

Nah, no migraine from the numbers... I run a lot more complicated numbers at work every day. What *will* give me a migraine however is constantly thinking about the various options trying to make the best decision to only buy things once.

I tried a 7/8 bore MC with my current C6/C4 setup years ago when I first put it on... pedal feel was OK but the amount of pressure required to stop the car quickly with street friendly pads was excessive so I went hydroboost. That easily fixed the effort issue but required a lot more "stuff" under the hood.

Now with even more extra "stuff" under the hood from the turbos and with the hydroboost pushing the master too close to the wastegate for comfort I want to go back to manual for simplicity and room. A reasonable pedal effort even though the brakes are manual would be nice too-- and I know that can be achieved with correct component selection.

Still scratching my head on the dual MC with balance bar vs tandem master cylinder arrangement and the best rear caliper selection...

[Apogee]

I'm pretty sure you're not calculating the dual MC/balance bar setups correctly, as the input force into each MC is divided in half assuming a centered balance bar. A tandem 7/8" bore MC and (2) 7/8" bore MC's in a balance bar arrangement are not equivalent, as the piston in the tandem unit are in series whereas the MC's in the balance bar arrangement are in parallel to one another.

That said, I like the C5/C6 brakes (or Wilwood equivalents with respect to piston area/rotor diameter/etc) in a manual configuration with a 7/8" bore MC and "GG" friction rated pads. While many may not consider "GG" pads to be street friendly for dust/noise/wear reasons, they're the best solution IMHO when seeking a simple, low cost and highly effective manual braking solution.

Tobin
KORE3

[Blown353]

Tobin,

The spreadsheet I'm using does support both balance bar & tandem MC applications. The numbers it returns are nearly identical to Ron's spreadsheets when I checked it by inputting the same piston sizes & MC diameters that Ron has run for others in the past-- I'm only seeing a very small (<2%) deviation between my numbers and his numbers. The reason for the slight deviation is because the spreadsheet I have only supports a single CoF for both front and rear pads while Ron's has separate front & rear CoF inputs to account for the temperature differences. I still need to update my spreadsheet to account for separate front and rear CoF differences.

I could be wrong though, which is why I asked for a double-check on the numbers.

My current C6/C4 setup with no prop valve has a 69/31 torque split (which is good.) However, assuming street friendly pads with about a .43 CoF, a .875 OEM style tandem MC, and 100# of pedal input that's only about 1250# of brake torque... not very good at all, and that was my impression when I tried to run them in a manual setup. More aggressive pads would help but as you said that comes with a dust/noise/rotor life penalty. The hydroboost made them really work well though... wish I had taken some line pressure measurements when the car was still running to see just how much force the hydroboost was providing.

[Hydratech®]

Gokou - you DO know that your current discussion is reading to me as if saying "I would like to remove my power adder / supercharger from my engine and go back to running naturally aspirated and still make 1200 horse" - right? It can be done, but the trade offs are enormous. You have been running a Hydratech hydraulic brake assist system since 2003. 12 years later, you are wanting to taste braking in manual mode again because of an exhaust pipe?

Making more power than ever with your current twin turbo LS build will definitely thrill you with the "GO" pedal with your new twin whistler's, but "rotsa ruck" finding happiness in matching a higher rear wheel HP level to what you have been used to in the braking department.

Some exhaust pipe routing is taking you back to manual brakes again? You may have forgotten what alternate braking options feel like twelve years later - here comes your refresher course in why you went with Hydratech so many years ago (when you where running your earlier centrifugal supercharged configuration).

Sounds like: "I can't fit my turbo downpipe where I want it to go, so I'm switching back to manual steering".

I say this most definitely not to make a new sale (as you have already been tickled with your existing system since '03, and have been a great advocate since), much more so because we see this day after day / year after year and observe how the story ends all the time. A "silly" exhaust pipe routing clearance issue now has you wanting to go back to manual brakes? All these years later of running a Hydratech system, you have forgotten and now need a "relearning curve"... Go back to the DOJO and take your hits.

Did I just toss a rock at a beehive?

[Blown353]

Paul!

I was wondering if you were going to chime in. I'm impressed, if not a little disturbed, that you remembered my purchase date.

To be fair, it's a *really* expensive exhaust pipe that has me concerned-- and I'd rather not remake it. Seriously, 321 stainless mandrel bends, CNC'd stainless manifold & turbo flanges, and wastegate V-band flanges aren't cheap... plus my frustration involved with fitting and welding it up.

Everything you said makes perfect sense. Unfortunately for me turbos and all the extra plumbing really make things tight. I knew that going in, and I'm certainly feeling the pain now. With a heat shield and a little high temp insulation the master cylinder as it sits now will probably survive just fine even though the very nose of it is rather close to the wastegate. I'm also pretty sure there's room for the PSC remote power steering reservoir and the Lee filter. Actually, I see PSC now makes a much nicer hydroboost-compatible reservoir with a built in filter compared to the one I purchased from them about 4 years ago... that would make things easier.

Another option is to get one of your super-shorty masters to pick up about 3" of additional clearance and keep my current brake setup... and that is something I've thought about as well. It would save a ton of money being able to keep the current hydroboost and calipers which I know work well together.

The main reason I'm looking at a complete re-do of the brakes is I'm going to be changing to a 9" floater rear end... and that means new rear brakes. Seems the common setup with floater rears is Wilwood 4 piston radial mount calipers like the Aero 4 or FNSL4R and even with the smallest piston sizes they offer they will be *way* out of proportion to the front C6 PBR calipers in terms of piston area which is going to majorly screw up the front to rear balance of the system. Then again, maybe I can fab my own caliper brackets to use my current PBR rear calipers on the new floater-- but it's hard to say without having all the parts in front of me to take measurements. Besides, if I'm going through all that effort to switch to the new 9" floater I'm not sure I want to continue using the C4 PBR e-brake calipers; the e-brake is OK at best and the pads are so small the pad life is really short. When the car was still running and driving I recall the rear pad life was maybe 1/2 the mileage of the front pads.

Another option I'm considering is one of the Wilwood configurations I laid out in my first post but paired with the Hydroboost and a 1.125" tandem master... but I'm worried such a setup might be *too* touchy. The Wilwoods have a lot of piston area and thus don't need a great deal of line pressure to generate lots of clamping pressure-- and while the 1.125" master will increase the pedal effort I know the Hydroboost will have zero problems generating a *lot* of line pressure even with the 1.125" master. I suppose I could drop the piston sizes on the front calipers to 1.625/1.125/1.125 and use the 1.125/1.125 piston rear calipers with the hydroboost setup and 1.125" master cylinder to increase the pedal effort and decrease the "touchiness" of the pedal... maybe that's the path forward. Thoughts?

Paul, maybe you can help with some numbers, since my car is in pieces and I never put a pressure gauge on my calipers when it was together... what kind of brake pressures can you see out of a hydroboost and 1.125" master combo? With the Wilwood setups I have in mind it looks like 550-750psi (depending on caliper piston size) is going to provide "eat your steering wheel" brake torque on the order of 4000 with street friendly pads and a ~0.43 CoF. That's why I'm concerned things may be too touchy.

Just trying to look at the "big picture" and lay out a plan before changing or purchasing any parts. One little change leads to another-- in this case the new floater rear end is probably going to require changes to my entire brake system because of the need for new brakes for the rear end. Nothing has been decided as of yet but there are a lot of potential configurations to consider.

[Hydratech®]

I understand looks, symmetry, artful and tasteful placements, BUT form follows function, right?

You had it by the ass in this initial mockup:





It is my opinion that you then did the Ooopsey with the placement of your waste gates:





I do indeed understand the money you have into the "silly little exhaust pipe"

Take a look at our 2nd gen Camaro listing. You will see that the HotRod Magazine Nelson Racing Project F Bomb's waste gate is sitting "right there" also. They beat the snot out of that car mercilessly and never ran into a problem with MC overheat:

http://www.hydratechbraking.com/GM_2ndgenF_Body.html



Working with hundreds of TT builds over the years, I say you are better off editing the exhaust layout. The waste gate plumbing will not glow red hot unless you get into a standing mile / Bonneville salt flats type of run, so simple heat shielding with the current arrangement will also take care of business. Note that the highest heat put into a brake system / fluid is at the wheels themselves...

Now, going into further discussion, I truly do understand the shear simplicity and good looks of a properly set up manual brake system. As you know, the success of this will require large caliper piston surface area, along with pads that have considerable bite to them. Whether you ultimately choose to go manual or stay with power, look at the CNC balance bar arrangements - they can plug into you firewall just as easily as a typical tandem MC (Wilwood or whatever), but give you the balance bar and individually swappable MC's:

https://lateral-g.net/forums/showthread.php4?t=36692

This package may look long (camera angle), though the MC comes in at the same installed length as the Wilwood 260-8556.





Also, I'm not a big fan of chrome, though this MC comes in at 7 3/4" - a 1/2" shorter than the Wilwood while providing the 1 1/8" bore size:





http://www.hydratechbraking.com/mast...E121C330281461

Going back to numbers, the hydroboost systems are a variable output device. Since they are not a linear output device, it becomes very difficult to put numbers into graphs and charts. PS pump specs have a large input as to the power levels the hydroboost can produce, and can impact brake unit dynamics considerably (as the PS pump is ultimately the power supply to the brake unit). Here is a knob adjustable way to uptune / detune PS system characteristics:

https://lateral-g.net/forums/showthread.php4?t=29580

Adding complexity, but the ability to pull over and change your braking and steering response is cool - turn it up and down as your situations change in a multipurpose vehicle (or tune it exactly where you like it and be done).

The brake units themselves have also undergone many proprietary changes over the years, and the latest Hydratech offerings are considerably different in that they provide a wider margin of coverage for pedal effort and feel (load sensing to provide a crisp / clean response across a wider spectrum of variables in the braking system). The power curve is improved, providing less initial assist, though ramping up sharply at higher pedal assist "request". Here is one of the latest Lat-G builds where it is stated:

Paul, could NOT be happier with your braking system, perfect easy install, and the braking is phenomenal .. the setup feels as close to a production performance car as you could possibly get, and Jim was awesome to deal with


https://lateral-g.net/forums/show...t=50526&page=4

Hard pads wear MUCH longer, don't chew the rotors, allow for higher temperature use, and don't dust badly. Keeping your hydroboost will allow you run the hard pads.

If you need to plug some numbers in, the hydroboost systems will variably generate 1400 - 1800 PSI of brake line pressure at the 100# pedal input, with the variables being pedal ratio, PS pump max pressure relief, MC piston bore sizes.

Then there is also Jody's previous TT build sporting the 17 degree upward system with the Viper MC:





This is our 17 degree upward model that connects to the power brake hole in your brake pedal:

http://www.hydratechbraking.com/GM_A...920161312A1BD0

Let me know how I may be of further assistance.

[Blown353]

Thanks Paul.

I do remember Jody's 17 degree power brake angled booster and Viper MC setup to clear his Nelson headers and that's also something bouncing around at the back of my head-- I wouldn't be worried about clearances at all with that setup. A 17 degree bracket on my current setup would also provide more clearance.

Hindsight being 20/20 I'm not sure exactly why I put the driver's side wastegate where I did several years ago. Back when I fabbed them I remember putting that was the best spot I could come up with at the time for the wastegate based on the bend radii of the mandrel bends available, clearances to the inner fender/hood/steering/spark plugs/master cylinder, and also where I could dump the waste back into the downpipe (I didn't want dump to atmosphere wastegates.)

Looking at the driver's side now I could have done things differently and left a lot more room for the master cylinder-- but redoing it now will be money that I'd rather put towards the floater rear end and new brakes rather than reworking things that I already did. It may have to happen in the end though.

Regardless, I'm not set on either keeping the hydroboost or switching to manual brakes until i decide on a new floater rear end. The new rear brakes required for the floater will end up driving the front brake and master cylinder selection, so until I get the rear end nailed down everything else is undecided at this point.