Wilwood 12" Brake Part Numbers

[Sgt.Gator]

Because I bought my 818R used, I didn't have the original Wilwood boxes, instructions, part numbers. After spending hours trying to figure out exactly the Wilwood part numbers for the optional 4 pot 12" brake package I finally sorted it out. The issue being that Factory Five has the wrong rotor spec in their parts catalog for the brake rotors; they say it is a 1.25" rotor. And they don't list the actual Wilwood Kit model numbers. If you do searches for a Wilwood rotor in 1.25" width you won't find the right caliper or the right rotor for our setup.
"The enhanced brake capacity and pad performance of the DynaPro 4 piston calipers are combined with 12.00" and 12.19" diameter 1.25" thick rotors to provide excellent braking performance on Factory Five Racing 818 kits."

So I measured my rotors, they are in fact .81" front and rear.

They also have the wrong front pad size, they say it's 7812, Wilwood says it's a 7816. The difference is the thickness, the 7812 are .49" thick, the 7816 are .60" thick.

Which explains why my front brake pads don't seem to last as long as I expect them to!
The pro of that is you can carry the 7812 pads in your track kit and have pads that will fit either end in an emergency replacement at the track. But to maximize life I will run the 7816 when I swap pads in the shop.

See: http://www.factoryfiveparts.com/wilw...ear-brake-kit/

The correct info:
Front Brake Kit – Part No: 140-9193-DR
https://www.wilwood.com/BrakeKits/Br...no=140-9193-DR
12.00" x .81" rotors
Rotor: Left: 160-8497-BK
Rotor Right: 160-8496-BK
Pad Size: 7816

Rear Brake Kit – Part No: 140-7006-DR
https://www.wilwood.com/BrakeKits/Br...no=140-7006-DR
12.19" x .081" rotors
Rotor Left: 160-6925-BK
Rotor Right: 160-6924-BK
Pad Size: 7812

Assembly and Fitment for Front 140-9193-DR:
https://www.wilwood.com/PDF/DataSheets/ds522.pdf

Assembly and Fitment for Rear 140-7006-DR:
https://www.wilwood.com/PDF/DataSheets/ds411.pdf

If you screw up and strip the threads in the adaptor plate for the rear caliper you can either order a new plate from Summit or Jegs, it's part number 250-6982 ($41.62); or you can order the clinch nuts themselves to replace in the adaptor plates, Wilwood 230-0355 ($5.99 also at Summit, Bracket Clinch Nut, 3/8 in.-24, WIL-230-0355). It took me many hours to find out they offer these special clinch nuts as an item. Don't ask me why I needed to know this!

[J R Jones]

Sgt, My 2014 818S has the Wilwood brakes but they are set-up differently.
The calipers on the 12.00 dia rotors will not accept a 1.25 in thick rotor. All rotors are 0.81 thick.

The 12.19 dia rotors are in front as I prefer, given the dynamics of braking. The radial mount calipers barely clear the rotor diameter, but it looks like with fabrication a 1.25 thick rotor might fit..
My front pad friction material is about 12mm thick, total pad thickness 0.6 in.

The 12.00 dia rotors are on the rear have more radial clearance to the side mount calipers.
My rear pad friction material is about 9mm thick, total pad thickness is 0.5 in. I don't understand why the rear pads are thinner., maybe the calipers are not wide enough.

I have no data on my brake parts and my assembly manual does not address Wilwood brakes.
jim

[Sgt.Gator]

Jim,
I think you misread my post....I was pointing out that FF got the rotor thickness wrong in their parts description.
And yes, you have the system reversed. It's good to hear that we can run the .60" pads (7816) in the 12.19" inch system (140-7006-DR). Looking at the parts schematic / assembly/fitment pdfs in the above links I suspected that the .60" pads would fit.

[J R Jones]

Sgt, Yes I have been confused on this combination of parts. Based upon previous experience I made assumptions: The front gets larger calipers and rotors, the smaller parts to the rear.
My speculation that the thicker 7816 pads will fit in the rear (transverse fastening) calipers is unlikely. The caliper does not center on the rotor with 4mm clearance on the outside and 2mm clearance on the inside. The thinner 7812s are specified.

The FFR spec page does not specify which brake assembly goes where. It does list the pads and rotors incorrectly. Wilwood application page matches the 12.19 rotors with the 7816 pads in the radial mount caliper as a front assembly.

The 7812 pads on the rear are not a hardship as those calipers have 1.0 inch diameter pistons. The front radial mount calipers with 7816 pads have 1.62 inch diameter pistons. That is what I expect, the front brakes work harder and wear faster than the rear.
jim

[J R Jones]

Sgt, more confusion by conflicting fitment data.
The brake package data from your link: https://www.wilwood.com/BrakeKits/Br...no=140-9193-DR does list a 12.0 inch diameter rotor.
If you click on that page's caliper we find the specified rotor as 12.19 inch diameter: https://www.wilwood.com/Calipers/Cal...o=120-14706-RD

We might assume both will fit.

If you click on the rear caliper we find the specified rotor at 13.06 inch diameter! https://www.wilwood.com/Calipers/Cal...no=120-9706-RD

In my case the 12.19 rotor is most appropriate front and rear.
My front radial calipers and pads match the 12.19 rotor perfectly.
My rear transverse mount calipers and pads extend beyond the 12.0 rotor diameter by about 0.10 inch. That will reduce service life.
I will get the 12.19 rotors for the rear. I wonder if I can get a refund?

A abundance of discrepancies to go around. Maybe we should start a class action suit. (ha)
I am interested to know how your brake parts fit together.
jim

[Bob_n_Cincy]

A abundance of discrepancies to go around. Maybe we should start a class action suit. (ha)
I am interested to know how your brake parts fit together.
jim

My 2 cents,
The 140-9193 kit with front caliper 120-14706 has a piston area of 4.12 sq-inch.
The 140-7006 kit with Rear caliper 120-9706 has a piston area of 1.58 sq-inch.
That is a ratio of 2.6 to 1.
From all my testing the rear mid engine 818 needs calipers that are closer to one to one.
I believe the setup above is for a front-engine setup.
I don't know if the Wilwood balance bar pedal assembly will adjust far enough.
Bob

[J R Jones]

Bob, Empirically one would prefer a brake balance that causes front and rear brakes to lock-up with common pedal pressure.
The weight proportion has an effect but dynamics may be more influential. If you are braking at 1G the weight on the front tires is way more than static weight proportion.
Measuring the difference would require load cells on the shock/spring mounts.
Measuring your balance bar effect could also be load cells or line pressure. (more gauges to watch) Are your master cylinder bores the same front and rear?

I do not understand Wilwood's piston area specs.
The equation for surface area of a circle is A= pi r squared.
The Wilwood caliper specs are as you state: 4.12 sq-in front, and 1.58 sq-in rear, which represents two pistons, not four. Your proportions are still correct.

I have a proportioning valve for my 818S brake balance but I am a long way from running and testing.
Long ago I raced a Shelby GT350 and the proportioning valve made four piston front disc brakes work with two piston / wheel cylinder rear drums.
jim

[Bob_n_Cincy]

Bob, Empirically one would prefer a brake balance that causes front and rear brakes to lock-up with common pedal pressure.
The weight proportion has an effect but dynamics may be more influential. If you are braking at 1G the weight on the front tires is way more than static weight proportion.
Measuring the difference would require load cells on the shock/spring mounts.
Measuring your balance bar effect could also be load cells or line pressure. (more gauges to watch) Are your master cylinder bores the same front and rear?

I do not understand Wilwood's piston area specs.
The equation for surface area of a circle is A= pi r squared.
The Wilwood caliper specs are as you state: 4.12 sq-in front, and 1.58 sq-in rear, which represents two pistons, not four. Your proportions are still correct.

I have a proportioning valve for my 818S brake balance but I am a long way from running and testing.
Long ago I raced a Shelby GT350 and the proportioning valve made four piston front disc brakes work with two piston / wheel cylinder rear drums.
jim

I didn't use load cells but I have about 500 autocross runs and a dozen track days running the same calipers on each wheel and same size master cylinder front and rear (no balance bar). I have 235 tires in front and 255 in the rear. My 818 is 60% weight-biased to the rear. With it's low center of gravity, the weight on each tire is about the same during 1g braking.

Typical autocross video, At the end I always do a hard stop to test the brakes.




Below is the calculated weight transfer

B_C_weight_transfer.jpg

[J R Jones]

Bob, We (you) could entertain yourself with a crude measurement of weight transfer.
Fabricate travel tell-tails for your coil spring/shock. Maybe just the snubber slid down to the shock body, or slip-rod devices.

My front springs are 350lb, rears are 275lb. That is pounds per inch.
If you did a 1G stop and the front tell-tail registered 0.5 inch travel, you transfered 175lb (2) = 350lb.

So with your AX & TD experience the brakes are balanced? Your balance bar worked within it's physical limits?
If not, which axle skids first?
jim

[J R Jones]

Bob, My #&%*! software will not play the video but the graph is interesting. How is that calculated, with a data acq system?
jim
BTW a tell-tail could be a tie wrap on the shock rod, although it would not work for lift in the rear.

[Bob_n_Cincy]

Bob, My #&%*! software will not play the video but the graph is interesting. How is that calculated, with a data acq system?
jim
BTW a tell-tail could be a tie wrap on the shock rod, although it would not work for lift in the rear.

Jim,
I changed the post above so you should be able to see it video now.
I don't have a balance bar. I am actually using the OEM Subaru master cylinder.
I ran that way for a couple of years. The rears locked up just a smidge before the fronts. I did eventually add a PV to the rears with maybe a 5% reduction in pressure. Franc5r did a calculation for me.

B_C_para_21_cg.jpg

Here is a thread from 4 years ago talking about brakes.
https://thefactoryfiveforum.com/show...ifferent-rears

[Sgt.Gator]

Bob, thanks for the info and links, particularly this one got me doing more research. https://thefactoryfiveforum.com/show...ifferent-rears

I thought I'd see what other mid and rear engine performance cars setups are for piston area, So I went to the AP Racing (Essex Brakes) site and checked the Porsche 987, 981, 718 Boxster & Cayman. Their AP Racing setup for those cars has Front Piston Area of 40.1 cm sq; and the rears are 22.8 cm sq. That's puts the Front to Rear ratio at 1.75 to 1.
The optional 4 pot Wilwood system I have on my 818R is at 2.6 to 1.

More to chew on...

[J R Jones]

Sgt, I have a 1991 Toyota MR2 turbo, and the brakes are great.
To add to your data search:

Front (2) pistons, 1.417 dia, 1.577 sq in (2) 3.154 sp in, 10.8 in dia rotor
Rear (1) piston, 1.968 dia, 3.04 sq in, 10.3 rotor
Ratio: 1.0375 to 1

This is the car that made me enthusiastic about mid-engine. The suspension and engine are upgraded; it is formidable.
jim