Brakes without a Booster

[EarlsflyinCobra]

I am running a Mustang II front end with the 9" disc, a Mustang rear converted to disc's, and a Wilwood reverse pedal setup with the master cylinder mounted in the engine bay serving both the clutch and brakes and have found you have to stand on the pedal to stop. Not real comfortable with the outcome. I tried to upgrade the front to 11" rotors and found they hit the lower control arm. I was told I would need to grind the control arm down a little to make the rotors fit? Not sure I'm, comfortable with that either. Any advice would be greatly appreciated.
NO dropped spindles....I do understand how hydraulics work so I'll have to look further into the mc bore....running Wilwood reverse pedal mounted compact remote master cylinder 3/4" bore with 1 13/32" stroke, with the reservoir mounted in engine compartment.
Not sure on the pedal leverage ratio, but it looks like Wilwood lists it as 5.1:1?
Any thoughts on what to do about the pedal ratio, change out the pedals maybe?? Are they adjustable??

[Tommy]

Disregard.

[strictlypersonl]

Leverage-wise, you are losing 20% leverage by using the 9" rotors, so I would make every effort to increase the rotor size. Your only other path is to reduce the master cylinder diameter at the expense of pedal firmness.

[pormgb]

9" rotors are tiny and scary. I'm running a Mustang 2 front end with tubular lower and upper control arms; I also have large Sierra calipers with 11" Granada rotors and no clearance problems apart for the calipers touching the lower control arms at full steering lock.

What 11" rotors did you try? were they Granada rotors?

[Michael C Henry]

I bought a built car. I have changed some stuff but the mid size GM front brakes and Jag rear, are not enough. Tilton 3/4" cylinders with adjustable balance bar on the pedal. the biggest thing was the clutch It had a Tilton 7/8" cylinder. and normal engine mounted slave cylinder. The slave cylinder went bad and I walked into a brake and clutch shop and bought a better replacement. It was all shinny and better boot than original. Back to the clutch master cylinder, Tilton 7/8" dia cylinder afforded very little pedal free play and barely enough clutch release. I bought 15/16" and 1" master cylinder kits. The 15/16" worked much better but the 1" cylinder has generous free play and full clutch release. But it came with a price, the McLeod 12" clutch was stiff. Shoes were almost mandatory with the small Cobra pedals.
My car, as I said has midsized GM brakes front, 16" aluminum wheels, PSE I think. I think I'd have to change the appropriate Cobra looking wheels to get anything bigger brake rotors. It stops pretty good but sliding the tires on pavement hasn't been a problem. I do get a good balance front to rear. Their are things that I would have done differently if starting from scratch. power steering would also be a thing.

[Michael C Henry]

I bought a completed car, are they ever complete, I should say running car. It has the mustang front with 9" rotors and mid sized GM calipers and pads. It has PSE aluminum 16" Cobra wheels.. Tilton master cylinders reservoirs. I used for the brakes are fire wall mounted reservoirs, the two 3/4" ID brake master cylinders are under floor, now I'm using a 1" ID mater cylinder for the hydraulic clutch with a engine mounted hydraulic slave cylinder. The Clutch master cylinder started with a 7/8" ID cylinder but had not enough volume to have much pedal ( throw out bearing) free travel and complete clutch release. You give up leverage with a volume gain, over the same travel distance. The clutch pedal (with the 7/8" ID master cylinder, was marginally slipper on foot doable but Now with the 1" ID master cylinder requires shoes to use the pedal.
The brakes have a threaded adjustable balance bar between the two brake master cylinder push rods for bias adjustment front to rear . The Cobra style brake pedal is between the two brake master cylinder push rods. The pedal bias adjustment will stay once adjusted, but there is a remote bias adjustment kit available. It has a knob with flexible shaft that could turn the bias bar screw adjustment shaft when needed , mostly a competition option. I agree the brakes, once bias is adjusted are still not as forceful as I would like The tires make noise but not lock up and slide on dry pavement. I think a brake booster or larger rotors would help But not a real option at this time or point. just one of many other choices I now would have made, if I were to build another car.

[40k Later]

Earl, to quote Master Power Brakes directly from their website.........."When using disc brakes, you cannot have too much assist in the system"

I have a dual diaphragm 7" booster from Master Power Brakes and because my camshaft doesn't make the required vacuum, I have installed a vacuum pump and I have 12" rotors all around with 4 piston calipers from Stainless Steel Brake Corp. The entire brake package has performed flawlessly. Save for the Vacuum pump, shortly after install the vacuum pump shaft sheared leaving me no vacuum therefore it took quite a lot of foot on the brake pedal to slow down. Pretty much what you speak of. You need a booster I have the same car with the same Mustang II upper and lowers and I didn't have to grind on either for these brakes to fit. They are incredible and I highly recommend them. You can steer lock to lock without an issue, nothing touches. Of course you'll need 17" wheels to clear the disc's
Your 9in discs all around are more than adequate for a car as light as a Cobra, but install a booster. It is a night and day difference

Visit http://www.mpbrakes.com/techtalk/boo...ur-classic-car

[Michael C Henry]

How big and what kind of wheel did you use with 12" rotors?

[bobcowan]

Originally Posted by EarlsflyinCobra

Not sure on the pedal leverage ratio, but it looks like Wilwood lists it as 5.1:1?

This is the issue right here. You have a pedal ratio for a power booster on a non-boosted application. Until you fix this, nothing you do will make much of a difference.

The smaller discs you have work fine in heavier cars, so don't focus on that. Bigger is better, of course. But it's not your main issue.

Larger bores on the MC will move more fluid, but produce less pressure. That's not what you want. You go to a smaller bore. That would create more pressure, but move less fluid. And it would increase pedal travel. Life's full of trade off's.

Adjusting the balance bar is pretty important for balance. But the lack of pressure is still the primary issue.

Either change the pedal ratio to 7.5-8, or add a booster.

[FWB]

you guys realize Earl posted this a year ago?

[bobcowan]

Yes, but the information is still good for new builders. Nothing worse than doing a google search for answers and finding a dead end.

[40k Later]

17" Halibrand III's and I guess I replied to a very old thread which was reincarnated