ERA Brake Master Cylinders 3/4 or 7/8 bore?

[frankym]

Hello,

I went to apply the brakes this morning and heard a snap. One of my hydraulic push rods into the 3/4 master broke the snap ring that holds the plunger rod inside the master. I ordered new masters but on ERA575, I had a 7/8 bore and 3/4 bore master from Tilton. The master closest to the center of the car was the 3/4 and the outer master is 7/8. I am curious if people are running their ERAs with 2 masters that are 3/4 or mixed as mine was. The brake pedal required a lot of effort to stop the car but it also had very old brake fluid that needs to be replaced so it's hard to determine which is the best setup. Curious what others are running.

[Argess]

Mine are mixed (#392), and the braking has never felt strong. I've improved it a bit with different brake pads and different front calipers.

[frankym]

I’ve owned 3 superformances a Contemporary and a Shell Valley, before the ERA, All of the braking systems were about what you would expect for a car modeled on 60-year-old technology. I’m tempted to try using 3/4 bore for front and rear masters. I would imagine a brake booster would make a big difference. Peter at ERA was very helpful and suggested the new fluid and a good bleed would help a lot. That said, it can’t hurt to try the matching bore 3/4. I will have a little more pedal travel but gain some leverage.

[Sargie]

You can change pedal effort by increasing or decreasing length of the pedal arm. Both Wilwood and Tilton have suggested sizes on their websites. When I raced we used a 7:1 box. Haven’t checked the ratio on my ERA2045 but should. Car requires a lot of effort to stop compared to cars I raced which were heavier. As Franky noted if you go down in size you add a little extra stroke.
I dropped links from a couple of websites that might help you consider how you want to approach changes. More aggressive pads might be a good place to start.

https://www.joesracing.com/master-cylinder-math/
https://shop.wilwood.com/blogs/news/...w-to-find-them

[Tommy]

frankym - This may be an apples and grapefruit comparison, but on my Cheetah build I ended up with 0.625" diameter MC for front and 0.750" MC for rear. That was after consulting with Tech Support at Tilton. They had me fill out a complete data sheet for the car before recommending MC sizes.

[Argess]

Frankym: You may find an old post of mine interesting. It's post number 2 found here:

Front brake caliper pressure

[strictlypersonl]

The ERA master cylinders are sized to give about 65-70% braking effort to the front. The reason that the front master is larger than the rear is that the piston area in the front caliper is more than twice the rear's. The front requires more volume and less pressure to achieve my intended F/R balance.

[frankym]

Very helpful hints and explanations, and references / links. I get that the 7/8 bore is for front and 3/4 is for rear. Is it fair to say that the balance bar for the heim joints is supposed to distribute rod push disproportionately more to the rear than the front. I am posting a picture to figure out where my bias should be to start, realizing that I might need to road test and adjust...

longer rod to the rear?

https://uniim1.shutterfly.com/render...&ts=1657712832

or longer rod to the front?

https://uniim1.shutterfly.com/render...&ts=1657712833

[frankym]

Actually according to this video from Tilton, it states that the front brakes have the smaller bore, so not sure which one is which on the ERA. If this is true, then the 3/4 bore master should have about 1/4 longer rod position to start, meaning the master closest to the center of the car.

https://www.youtube.com/watch?v=ISLqGf0sMX0

[Argess]

I don't think it works that way. The different lengths are when the pedal is at rest. As you depress it, the balance bar becomes perpendicular to the rods as the pressure firms up.

ERA does show moving the balance bar to one side vs. the other for bias adjustment, but I suspect this would be minimal at best. My car doesn't even have that type of adjustment... no washers for shimming, just little tubes to act as spacers. I suppose it could be modified easily, but my main concern has ever been balance, just absolute stopping power.

[6TNCRZY]

You could go to 3/4" and 5/8' master cylinders and trade 15% to 20% more travel for 15% to 20% less pedal effort. In my opinion this would be a reasonable option as ERA cars with the 7/8" and 3/4" masters have very low pedal travel.

[twobjshelbys]

What is your brake configuration? Are they all 4 piston or are fronts 6? Are they split front to rear X config or are both front and rear on the one cylinder?

[strictlypersonl]

I'm very conservative when it comes to reducing available volume. I am, however, going to try a 13/16" / .700" combo soon. It's a little involved: It requires new lines and some interesting plumbing to include the brake light switch.

[frankym]

I’ve read multiple posts about upgrading calipers but most referenced SSBC 185 from Summit. These have been likely discontinued. Curious if anyone that’s done the front caliper upgrade recently from Sierra to SSBC and could post a link/reference/model number. calipers are 20+ years old and brake fluid at least 10 years.

Looks like this A193 could be a direct bolt on. They state "Rear" but given the small disc / rotors in front, looks like a possible bolt and fit.

https://www.summitracing.com/parts/tsb-a193-10

[ERA174]

If you don’t already know, ERA has an owners only website with a boatload of manuals and other technical information for their cars. I would not try to reinvent the wheel, ERA usually will have whatever you need for your specific ERA car. Go to the ERA owners only website, if you don’t have the address for said website ERA can provide you with it. You can then view/download/print the specific literature for your build#. The manual will explain the brake balance bar setup(longer rod for front master), the front master requires more stroke than the rear to engage the brake pads with the rotor. After reading the pertinent ERA literature, I believe everything will fall in line for you. I strongly recommend staying with replacement parts used/recommended by ERA, they’ve been doing this for a long time and I have always found them to be very helpful.

[strictlypersonl]

It looks like that the SSB-A185 calipers in clear, black or red are still available directly:
https://ssbc-usa.com/products/a185r?...maro%7Eha_base

[frankym]

ERA 174, your suggestion helped a ton because I was able to correctly align the front/rear brake balancer to the correct position.

Strictlypersonl thank you for the link to SSBC.

I didn't realize but I have the Big Brake front end, which I believe is a 4 piston?

Bob P said they have several replacement calipers on order - so in the meantime, we're going to flush the brake lines, bleed out and run clean fluid and this should be a vast improvement over current condition.

Here is my front brake...

https://uniim1.shutterfly.com/render...&ts=1657838743

[strictlypersonl]

We used the Sierra Calipers for quite a few years. They had 4 x 1.75 pistons. For some reason, we changed suppliers (probably because we couldn't get those any more). We currently use essentially the same caliper, made by Wilwood (120-11136). I wouldn't be surprised if their rebuild kits also fit the Sierras.

[patrickt]

Originally Posted by strictlypersonl

We used the Sierra Calipers for quite a few years. They had 4 x 1.75 pistons. For some reason, we changed suppliers (probably because we couldn't get those any more). We currently use essentially the same caliper, made by Wilwood (120-11136). I wouldn't be surprised if their rebuild kits also fit the Sierras.

The Wilwood Rebuild Kit #130-2655 on some sites also list my big Sierras and the JFZ calipers, that I think were the same as Sierras before Sierra bought them. I think they're all the same as the Wilwoods.

[strictlypersonl]

Originally Posted by patrickt

The Wilwood Rebuild Kit #130-2655 on some sites also list my big Sierras and the JFZ calipers, that I think were the same as Sierras before Sierra bought them. I think they're all the same as the Wilwoods.

Thanks for that research. It makes my job easier.