Race/Track Brake master cylinder set-up questions.

[GACM3]

Hey guys,

 

New to the forum but have been lurking for awhile. I own an auto repair facility and have been commissioned by a good friend to build an all-out race style build on a 2002 that will be driven on street and track days. My direct question is regarding master cylinder sizes to be used. I will give you a quick rundown on what we have so far:

 

Front AP Racing CP8350 4-piston calipers 1.62/1.5 sizes. 310mm discs

Rear AP Racing CP8350 4-piston calipers 1.12/1.12 sizes. 300mm discs

 

I am considering going to Lee's (Massive Brakes) booster delete and incorporating two master cylinders with balance Bars. Which is where my question relates to. Which MC and which size MC do I use?

 

Worth noting - the car is going to have a 350HP+ S14 engine which is why we are going larger brakes and why I am considering the Booster delete to gain room engine components.  Also, this build is going to be over the top as requested by the customer. Therefore we are looking for the top products possible to complete this at the highest performance possible. 

 

Any help is appreciated!!

[Leucadian]

Some of the S14 swap guys use the Tilton firewall pedal mount setup, which includes master cylinders in the assembly.  Can't speak to how this would hook up with your brakes of choice, but it makes for a clean install.  

 

paging @M3This

 

 

[GACM3]

43 minutes ago, Leucadian said:

Some of the S14 swap guys use the Tilton firewall pedal mount setup, which includes master cylinders in the assembly.  Can't speak to how this would hook up with your brakes of choice, but it makes for a clean install.  

 

paging @M3This

 

 

Exactly the set-up im considering. The system I am looking at does not come with MC's. And there are a lot of options. Tilton, wilwood, AP, lots of others all have about 8 or so rod thickness which affects pedal feel and pressure. Which is something I cannot say I have any experience with. 

Edited November 30, 2023 by GACM3
quote

[M3This]

Here is a screen shot of what I used:

 

 

However, I can't confirm that's the master cylinder we went with as I just sent to list over to Matt @Ronin Autowerks and he ordered everything up since they did the fab and install on my car. I'm running the IE 13" Wilwood BBK on my car for reference so Matt sized it based on that. I'm pretty sure if you call Tilton and tell them the brake sizes they can help recommend the correct master cylinder sizes. 

 

EDIT: here is link to photos of what they look like installed: 

Kris Derentz (@kris.derentz) • Instagram photos and videos

WWW.INSTAGRAM.COM

---

159 likes, 15 comments - kris.derentz on July 1, 2023: "Posted this earlier in my stories but here are some better shots of the floor boards back from po..."

 

Edited November 30, 2023 by M3This

[tzei]

That’s a lot of brake for rears. I’m running 345 discs front and 260 at the back. 4 pot AP’s front and 2-pot AP’s rear & b/box (Tilton copy). There is some fancy maths involved that i can’t remeber rn but i got me in the ballpark.

[TobyB]

It's a light car, and has all the aerodynamics of a sheet of plywood above 100mph, so 

brakes aren't such a big deal... especially if you make more than a token attempt at venting.

And have sticky tires.

 

As to a starting place, Tilton recommends 70% front pressure, and I found that to be accurate 

within a few turns.  For actual size, you need to know the piston hydraulic area of the calipers 

you're using, and then determine maximum pedal pressure your customer will tolerate on a cold stop.

Then multiply that by pedal ratio.  I'm using the stock 4:1 pedal, so I've got a smaller master (front) than the 6:1 setup above.

I seem to recall I'm using something like 13/16" on tii- sized calipers, and they don't do shit until 

there's some heat in the pads.  Once the pads are up to temp, it's just about perfect,

as it keeps the pedal relatively stiff but provides good modulation at the limits of adhesion.

 

I find that the 320 vented front (255?) and a solid Saturn rear (250)   is plenty- I get 4 weekends out of a set of pads,

8 weekends out of the rotors, and just don't have any fade or heating issues whatsoever.  Even at Mission

 

t

 

Edited December 1, 2023 by TobyB

[Tommy]

I consider master selection as a tuning question. Based on volumes, get two different size cylinders from the middle of the range. Use larger for front. Adjust with balance bar and test on track. See if something needs to be changed.

[uai]

@Tommy's approach isn't that bad. Go for cheaper Cylinders. If you've set your sizes get good ones.
However that's a lot of brake. 

[GACM3]

21 hours ago, M3This said:

Here is a screen shot of what I used:

 

 

However, I can't confirm that's the master cylinder we went with as I just sent to list over to Matt @Ronin Autowerks and he ordered everything up since they did the fab and install on my car. I'm running the IE 13" Wilwood BBK on my car for reference so Matt sized it based on that. I'm pretty sure if you call Tilton and tell them the brake sizes they can help recommend the correct master cylinder sizes. 

 

EDIT: here is link to photos of what they look like installed: 

Kris Derentz (@kris.derentz) • Instagram photos and videos

WWW.INSTAGRAM.COM

---

159 likes, 15 comments - kris.derentz on July 1, 2023: "Posted this earlier in my stories but here are some better shots of the floor boards back from po..."

 

 

I dig this set-up. I think I am now being pulled to new pedals with everything integrated. Then I can lean on Tilton to give me a recommendation on MC's. Your set-up looks killer. 

[GACM3]

11 hours ago, Tommy said:

I consider master selection as a tuning question. Based on volumes, get two different size cylinders from the middle of the range. Use larger for front. Adjust with balance bar and test on track. See if something needs to be changed.

Good Recommendation. I will purchase a couple to test with. 

[Leucadian]

As a side-note, please keep us updated on this over-the-top S14 build.

 

Sounds exciting!

[TobyB]

You REALLY need to calculate the hydraulic area of the calipers first...

otherwise over the top can easily turn into backed it in.

 

t

 

[GACM3]

On 12/1/2023 at 9:33 AM, Leucadian said:

As a side-note, please keep us updated on this over-the-top S14 build.

 

Sounds exciting!

I will keep you updated. Just about every part suspension, brakes, driveline, engine, is or will be extensively modified. So far we have a fully caged chassis and IE box style flares to work with. I assume after all mechanical work is performed that we will tackle interior bits and possibly a full carbon body. But time will tell. First on the list is to make a mechanical monster.

[GACM3]

On 12/1/2023 at 4:05 PM, TobyB said:

You REALLY need to calculate the hydraulic area of the calipers first...

otherwise over the top can easily turn into backed it in.

 

t

 

100%. Calipers have been picked so this shouldn't be to hard a task.