Master Cylinder and Bore Size

[69TAPoser]

My 1st Gen FB will have Dynalite Pros 10.75 brakes on the front and rear. I have decided to go with manual brakes and a Wilwood tandem chamber master cylinder. I spoke with Wilwood, and they recommend a 7/8" master and using the lower hole on the brake pedal.

I just wanted to make sure that this is correct? :dunno: Also, I assume that a prop valve should be used?

Thanks,

Phil

[andrewb70]

My 1st Gen FB will have Dynalite Pros 10.75 brakes on the front and rear. I have decided to go with manual brakes and a Wilwood tandem chamber master cylinder. I spoke with Wilwood, and they recommend a 7/8" master and using the lower hole on the brake pedal.

I just wanted to make sure that this is correct? :dunno: Also, I assume that a prop valve should be used?

Thanks,

Phil

If Wilwood recommended it why are you doubting it? What do we know that they don't? :drive2:

Andrew

[69TAPoser]

If Wilwood recommended it why are you doubting it? What do we know that they don't? :drive2:

Andrew

The tech support guy that didn't sound overally confident or experienced and the reality is that there are many guys here with 1st Gens, some of which I assume have the same or similar setup, and have actually driven their cars and "experienced" the best options.

A little validation before throwing down $230 seems prudent to me! :)

Phil

[RSX302]

My 1st Gen FB will have Dynalite Pros 10.75 brakes on the front and rear. I have decided to go with manual brakes and a Wilwood tandem chamber master cylinder. I spoke with Wilwood, and they recommend a 7/8" master and using the lower hole on the brake pedal.

I just wanted to make sure that this is correct? :dunno: Also, I assume that a prop valve should be used?

Thanks,

Phil

I got a story with Wilwood, I've re-engineered my system and they kept telling me that I needed another part that they recommended to me in the first place. :confused: 5 times...

Here's my story:
Unfortunately I found something out with the Wildwood's that I'm not to pleased about. The Wilwood Billet SL 6 Lug mount, 6 piston caliper doesn't work as well as I thought they should have. I think this is why people are adding the Hydraboost system to them. Less pedal pressure needed. Without it you need to put your foot through the floor in order to stop the damn car. Wilwood screwed-up and undersized the pistons. There SL4 caliper has more total piston area then the SL6. So less pedal pressure is required. Lame! I went from a 1 1/16" bore to a 1" bore master as specified by Wilwood..No change..I when from the ceramic pad the the BP20 pad...little change...I went from a 6:1 pedal ratio to an 8:1 ratio...best change yet, but still not what I'm looking for. Wilwood says that is more then is needed. I can't even lock up the wheels I told them. Wilwood suggested I then go to an "E" pad. little better, but still sucks. Wilwood then says I should put in the 7/8" bore master....I'm done with Wilwood....I took matters into my own hands and began my own calculations. I found that to make the 6 piston calipers work at half the pedal pressure, they need a 3/4" bore master cylinder. Since they don't sell a 3/4" tandem master, I decided to engineer a triple 3/4" bore master set-up with the front/rear adjustable bias bar and clutch that will bolt to the factory pedals. So far so good....Mock-up assembly is in and brakes are bled. I still need to put the front of the car back together and road test. Fingers crossed!

So, This is my issue, but yours may not. Give me your caliper piston size and pedal ratio and I can get you what kind of pedal pressure you'll be looking at.

[RSX302]

Oh yea...If my new master assembly works I will have a brand new 7/8" Wilwood tandem master for sale.

[69TAPoser]

I can't find any specs on the piston size of the Wilwood Dynalite Pro Series 10.75" kit, but my pedal ratio using the lower hole is only 4.5:1.

Is you 7/8 bore cylinder polished?

Phil

[RSX302]

I can't find any specs on the piston size of the Wilwood Dynalite Pro Series 10.75" kit, but my pedal ratio using the lower hole is only 4.5:1.

Is you 7/8 bore cylinder polished?

Phil

Your piston size is critical to this operation. Wilwood makes 1.00", 1.38", 1.62" & 1.75". Do you have the kit? With such a light pedal ratio you will need the 1.75" pistons. (3000+# car) At 100# pedal pressure and your 4.5:1 ratio, this is 450# at the master. So a 1.38" piston will give you 7449# clamping force and a 1.75" piston will give you 11979# clamping force. 38% increase.

I was running an 8:1 pedal ratio with a 1" MC with 6 piston calipers. This came to 10462# clamping force and I couldn't lock up the brake with BP20 Pads. It was down right scary with the ceramics.

I would say I need to be at the 15000# clamping force so this it why I re-engineered my system to work with the 3/4" bore MC.

With your situation, I would run the 1.75" caliper pistons, 7/8" MC and a 6:1 pedal ratio. (15972# Clamping Force)

Yes, My tandem is polished...

Oh yea...I never got this kind of infomation from Wilwood. They like you to continue buying there parts.

[69TAPoser]

Arrrgh. My pedal ratio is actually 6.5 not 4.5. :hand:

Still working on getting the piston size.

How much $$ for the m/c?

Phil

[RSX302]

Arrrgh. My pedal ratio is actually 6.5 not 4.5. :hand:

Still working on getting the piston size.

How much $$ for the m/c?

Phil

Then you should be good with the 1.75" calipers.

I bought the master for $240+tax, but I will sell it to you for $175. That's if my new brake assembly works! When do you need it by? I hope I will have my car back on the road in a couple of months to test. If your intrested, give me your e-mail so I can keep in touch.

[GMachineDartGT]

The ECI Hotrod Brakes site has a nice chart with bore sizes/output pressures. I rigged up a brake gage for my brakes. I found out I can put 1200/800 psi F/R when I stand on it, with my factory dual diaphragm booster and 15/16 master.

[RSX302]

The ECI Hotrod Brakes site has a nice chart with bore sizes/output pressures. I rigged up a brake gage for my brakes. I found out I can put 1200/800 psi F/R when I stand on it, with my factory dual diaphragm booster and 15/16 master.

I was running 1200 psi on mine and it didn't stop worth a *****. So I took matters into my own hands.

The equation tells me just because you have 1200 psi doesn't mean it will stop your car.

Master Cylinder:
Pressure= Force (in) / Area (in)

Now it's all about what the calipers do with that pressure is what matters.

Caliper:
Force (out) = Pressure x Caliper Piston Area (out) / Master Cylinder Area (in)

The smaller the caliper pistons, the less clamping force it will have with the same pressure.

Ron

[gsxrken]

Hey Ron, these posts were from February. What did you figure out with the brakes? Did you get it to where you can lock up the wheels under hard braking?

[RSX302]

Hey Ken...Got your email. Here are my results.

I'm still using the SL6's (1.68/1.12/1.12) and NDL's(1.38") with the factory pedals modified to an 8:1 ratio. I purchased a couple of the Wilwoods 3/4" remote mount masters and a there bias/balance bar and fab'd an enclosure. Although I only have 200 miles on them, it seems to be working perfectly. I'm very happy with the results. The 3/4" MC work the best on this set-up with BP20 pads and I would suspect the 7/8" for the GNIII. If my car were more track duty I would change over to the GNIII's (same mounting)

I was at a local car gathering and met a guy from Wilwood. He said he was the manager of R&D. I tryed not to unload too much,but I couldn't help myself :naughty: He then saw what I did...It'll be intresting if they come out with something, but then again it my be to small of a market...

Sould I start mass producing? The kit (masters, balance bar, push rods and box) would be around $500.

I know everyone likes pics, so here ya go...You'll notice that I had to use the clutch/small brake master for my rear brakes due to the turbo waste gate clearance.
http://users.adelphia.net/~rderaad/DSCF0001.JPG

[RSX302]

Hey Ken...Got your email. Here are my results.

I'm still using the SL6's (1.68/1.12/1.12) and NDL's(1.38") with the factory pedals modified to an 8:1 ratio. I purchased a couple of the Wilwoods 3/4" remote mount masters and a there bias/balance bar and fab'd an enclosure. Although I only have 200 miles on them, it seems to be working perfectly. I'm very happy with the results. The 3/4" MC work the best on this set-up with BP20 pads and I would suspect the 7/8" for the GNIII. If my car were more track duty I would change over to the GNIII's (same mounting)

I was at a local car gathering and met a guy from Wilwood. He said he was the manager of R&D. I tryed not to unload too much,but I couldn't help myself :naughty: He then saw what I did...It'll be intresting if they come out with something, but then again it my be to small of a market...

Sould I start mass producing? The kit (masters, balance bar, push rods and box) would be around $500.

I know everyone likes pics, so here ya go...You'll notice that I had to use the clutch/small brake master for my rear brakes due to the turbo waste gate clearance.
http://users.adelphia.net/~rderaad/DSCF0001.JPG

[gsxrken]

Thanks Ron. Did the Wilwood guy defend why the SL6 only has 4.02 total bore area? My stock 2-3/8"s single piston had slightly more area.

I didn't know you were going that route, but it sounds like it worked. JMC makes a side-by-side MC setup that may be along the lines of yours. I'll try to post it here. My issue is that the mustang manual pedal is a 6:1, so it may still be a bit heavier than I'd like.
http://www.autoworksracing.com/ford_brake_master_cylinder.htm
https://static1.pt-content.com/images/noimg.gif

[RSX302]

That's pretty much the exact same thing I built. This set-up is the way to go for stock pedals. You have more options on master cylinders and with options its usually cheaper from mass production.

As for the pedal ratio..I haven't looked at the Mustang pedals, but I would think you should be able to somehow raise the pedal link 1/4-1/2" with out to much trouble. On a 6:1, 12" pedal, rasing 1/2" will get you to 8:1.

[David Pozzi]

Keep an eye on your pedal brackets and balance bar with an 8 to 1 ratio. 100 lbs of foot pressure turns into 800 lbs force on the pushrod and master cyl brackets. Dual cyls are based on the old Girling master cylinders which were generally used with a 4 to 1 pedal ratio and on very light British cars. The newer versions by Willwood or others may be much stronger but I'd be watchful.
David

[el-camino]

take a look on my mastercylinder in my Camino.
the master comes out from a BMW 750il with 25mm bore and the right stuff for rear disc breaks
https://static1.pt-content.com/images/pt/2007/09/20060423_27-1.jpg

the double membrane brake booster comes from a BMW E34 series.
i close my mouth for breaking:ssst:
https://static1.pt-content.com/images/pt/2006/06/20060514_11-1.jpg

[RSX302]

David, very good point. I fab'd my set-up with 1/2" steel tubing .100 wall pushrod and 1/2" aluminum plate. As hard as I can push, nothing moves or flexes.

as for the 100# pedal pressure...thats where I was and beyond with the 1" mc 8:1 and it wasn't stopping me or locking. I swear I was pushing so hard I thought my foot was going to go threw the floorboard. (well past 100#) Now with the 3/4" mc, I don't get to 100# before it locks up. world of difference not to mension saving my leg and my life.

In hidesight, I should have gone with the GNIII caliper instead (More pad and more piston area- a true 6 piston). The SL6 is the SL4 with more pistons, but the 6 pistons have less area because they had to get them to fit. Wilwood keeps telling me that this is what they would put on this car, but I think I will swap over to the GNIII's down the road. At least its safe to drive now.

[Chad-1stGen]

Not really specific to willwood but keep in mind that for a lot of companies, especially the bigger they get, the guy who answers the phone or does sales knows a whole lot less about the products that the designer.

[RSX302]

That's what I thought! but the guy that told me this was the R&D Manager...

I guess I have a different opinion as to how brakes should work.

[6'9"Witha69]

FWIW, The 7/8" Wilwood MC works MUCH better than the larger sized ones available.
Yes, the pistons are smaller on the 6LR which reduces clamping force.
And there is NO topping a well set up dual MC with a balance bar. PERIOD. That is essentially why you are having better luck with the duals. The 7/8" would have worked well for you, but you now have the best. I just don't want to let anyone get discouraged that the 7/8" MC will not work properly as it is truly an awesome MC.

[chicane67]

FYI... The JMC item is actually from CNC Brakes... and it was originally for a Pantera, then that same device was machined for the Fox-chassis.

The 67-69 Camaro utilizes a 6:1.

My recommendation would have been for the 7/8"s as well, in a singular unit... or a 3/4 - 7/8" in a dual.

[gsxrken]

FYI... The JMC item is actually from CNC Brakes... and it was originally for a Pantera, then that same device was machined for the Fox-chassis.

Just the hydraulics, or the whole thing? Could I source it elsewhere for less than their we-have-it-you-want-it $369 pricepoint? I'd be interested in that.

[chicane67]

Nope... Chuck makes the whole kit and cabootle. You'll find the device under "Street Rod Assemblies": http://www.cncbrakes.com/

Chuck doesnt have the prices on his site... but you could even call a sand-rail/dune-buggy/off-road place and maybe get it cheaper. Maybe... but most likely from an old school sand rail place on the left coast.

Not that I want to take money out of John's pocket (lord knows that man has lined my pockets over the years)... because $369 is actually pretty cheap. In comparison, a Tilton set-up would run you $350 and then you would still have to adapt it to the firewall mount. Besides, John will take care of you in the long run. If you have a problem... he'll find (or make) a solution that suits both parties.

On a side note, Chucks schwag is the shizzy for custom made stuff. He and his brother (Neal brake systems) before they split... were and still are the shizzy in the off-road world, where the parts have to be bullet-proof to even be considered for use in Baja. Neal went to the way of the sand-rail industry and Chuck stayed in the professional motorsports arena.

CNC, Neal and JMC are all good people. I can guarantee that...

[RSX302]

FWIW, The 7/8" Wilwood MC works MUCH better than the larger sized ones available.
Yes, the pistons are smaller on the 6LR which reduces clamping force.
And there is NO topping a well set up dual MC with a balance bar. PERIOD. That is essentially why you are having better luck with the duals. The 7/8" would have worked well for you, but you now have the best. I just don't want to let anyone get discouraged that the 7/8" MC will not work properly as it is truly an awesome MC.

Yes, I don't want to give anyone the impression that Wilwood has a bad product. What I have talked about in this thread is what I've done to make myself happy. Its been a learning curve to say the least. I have a love for lots of brakes that continue to work without fade. Its just a matter of finding what works for me and the car. As the system that I have now works very well, I know I will be upgrading again in the near future. I can never leave well enough alone!

[6'9"Witha69]

I can never leave well enough alone!The creedo of our breed!

[gsxrken]

Nope... Chuck makes the whole kit and cabootle. You'll find the device under "Street Rod Assemblies": http://www.cncbrakes.com/

Chuck doesnt have the prices on his site... but you could even call a sand-rail/dune-buggy/off-road place and maybe get it cheaper. Maybe... but most likely from an old school sand rail place on the left coast.

On a side note, Chucks schwag is the shizzy for custom made stuff. He and his brother (Neal brake systems) before they split... were and still are the shizzy in the off-road world, where the parts have to be bullet-proof to even be considered for use in Baja. Neal went to the way of the sand-rail industry and Chuck stayed in the professional motorsports arena.


Chicane, thanks for the lead. I ordered the CNC dualie this afternoon, to go along with the manual pedal I have stashed away for my mustang.
Interestingly, the woman that took the order recommended that I go with 2lb residual valves front and rear. I told her I didn't think discs below a MC needed that, but she said it will result in a higher pedal and they see it time after time. So I went with that recommendation.

When I get back from XV's track day next week, it looks like I have my next project lined up.

[nx74ls6]

Your piston size is critical to this operation. Wilwood makes 1.00", 1.38", 1.62" & 1.75". Do you have the kit? With such a light pedal ratio you will need the 1.75" pistons. (3000+# car) At 100# pedal pressure and your 4.5:1 ratio, this is 450# at the master. So a 1.38" piston will give you 7449# clamping force and a 1.75" piston will give you 11979# clamping force. 38% increase.

I was running an 8:1 pedal ratio with a 1" MC with 6 piston calipers. This came to 10462# clamping force and I couldn't lock up the brake with BP20 Pads. It was down right scary with the ceramics.

I would say I need to be at the 15000# clamping force so this it why I re-engineered my system to work with the 3/4" bore MC.

With your situation, I would run the 1.75" caliper pistons, 7/8" MC and a 6:1 pedal ratio. (15972# Clamping Force)

Yes, My tandem is polished...

Oh yea...I never got this kind of infomation from Wilwood. They like you to continue buying there parts.

Just curious , how do the factory C6 Z06 6 piston caliper compare in size to 6 piston Wilwood ?

[andrewb70]

Just curious , how do the factory C6 Z06 6 piston caliper compare in size to 6 piston Wilwood ?

Wilwood makes several 6 piston calipers. Which one are you talking about?

Andrew