Feel difference between 1" and 1 1/8" MC with C5 brakes

[Mr Nick]

How would the brakes feel and act differently with a 1" MC or 1 1/8" MC, both with a dual 9" booster and C5 brakes front and rear?

I'm looking for a "modern feel" on my brakes.

[Mr Nick]

Forgot to add, engine creates low vacuum. Car is at the shop, but IIRC about 13" of vac.

[woody80z28]

With a power booster I'm not sure how much you will notice. Manual pedal feel is very sensitive though. The 1" will have more pedal travel, but more pressure given a certain input force.

[Mr Nick]

Thanks. Turns out I need a 8" booster to clear the hydraulic clutch master, so I'm going with a 1" MC to help out with a little extra pressure, like you mentioned.

[PhillipM]

With 13" of Vacuum and an 8" booster I can promise you, you will not have "modern feeling" brakes. The vacuum is too low to get the pressure you need.

Reference http://www.mpbrakes.com/uploads/documents/optomize.pdf

I would suggest either go manual brakes with a 15/16" (more travel but good pressure) or if you want assist, then start looking into a hydroboost of some kind and run an 1.125" master. Hydroboost is far from my idea of a good system but no question about it... Pressure will be there.

[Mr Nick]

It has manual brakes on it now, with 15/16 MC, and I don't like the feel. I also have my reservations about Hydroboost, and the price tag for a ready to run kit kills it for me.

If the dual 8" booster doesn't make me happy, then I'll probably run an electric pump and get creative with mounting it... I hear they are rather noisy.

[dontlifttoshift]

8" with a 1" master and you should be good to go.

The vacuum pump isn't as bad as you think noise wise, but I have had guys complain about the vibration, even when rubber mounted. They only run when needed, though.

[PhillipM]

With 13" of vacuum I'd go ahead and plan on the vacuum pump. It's just not enough IMO. Be sure to post back here and let us know what you end up doing. If you can, post up caliper pressure readings with your setup too.

[Skip Fix]

My TA was always happy at 13" vacuum but I have a dual diaphragm factory 4WD booster. When it gets 10" or lower then it can get a little iffy. That was with a big solid cam(255/259 @ 0.050) and a single plane intake and a 400ci motor. Same cam with a dual plane intake was fine. Feels as good as my 04 GTO modern brakes.

[Apogee]

Just another suggestion, however since you already have a 15/16" bore master cylinder, why not start there with the dual-8" diameter booster. That's going to be the closest "feel" to a dual-9" with a 1" bore MC IMO.

Tobin
KORE3