Brake questions

Krewton · #1 (**permalink**) 09-16-2009, 05:15 AM

I posted a question regarding breaks in a different area of the site and didn't get what I was looking for. My CR2 came with rear brakes installed. 12" Wilwood 4 piston caliper (I believe the ultralites). I'm trying to decide what to put on the front brake system. This will be more of a street car than a track car, and I'm sure my wife will drive as well. I've been told that if I go with a similiar setup on the front (maybe 6 piston caliper), that it is overkill and it is going to be difficult to get enough pressure and fluid displacement, as well as it being a difficult finish of the system. Any insight or suggestions would be appreciated.
Kenton

tcrist · #2 (**permalink**) 09-16-2009, 05:44 AM

Kenton,
I am running Wilwood 4 piston front and rear with a wilwood master and a power booster. It stops on a dime. To me, unless you are racing you really do not need a 6 piston.

Terry

CobraEd · #3 (**permalink**) 09-16-2009, 06:45 AM

I have the standard mustang II brakes in the front but with performance pads and mustang drum brakes in the back. These are power brakes. The car stops amazingly well. Easy to lock up all 4 wheels with little effort. Hell, the car only weighs 2,400 lbs, it is easy to stop on a dime. I think with a car this light, you don't need fancy aftermarket performance brakes on the street. Only if you are racing at the track and have to do constant/repeated high speed braking.

.

rustyBob · #4 (**permalink**) 09-16-2009, 07:03 AM

Speedway lists in their catalogue a Wilwood medium duty disc brake kit for mustang 2 that is rated for cars up to 2800 lbs. you get aluminum hubs,bearings,seals,brackets,4 piston calipers,pads,hardware,and 10.75 rotors that are .35 thick nonvented for $614.oo bucks . that should be more than what you need to stop when you need to.

Krewton · #5 (**permalink**) 09-16-2009, 06:21 PM

Terry,
What kind of power booster are you running? Are they difficult to install?
Kenton

tcrist · #6 (**permalink**) 09-16-2009, 08:15 PM

Kenton,
My booster is a stock 75-78 302CI Mustang II with a 9" diaphragm. The same one that it calls for in my manual in the detailed components section. I don't know if your manual calls it out.

It is simple to install as long as you have the correct pedal housing that will accept the booster bolts.

Terry

MaSnaka · #7 (**permalink**) 02-28-2010, 08:24 PM

Guys,
I'm having trouble getting my car stopped. For years this has been the issue. In fact one of the first things I noticed on my first drive was wow the brake pedal really needs some foot pressure compared to my truck and modern day drivers. This has been on my wish list but recently it moved to the top.

My car has the MII 9" front rotors and 10" drum rear brakes, no booster. Not racing on the track or anything but it takes a lot to stop. A couple weeks ago I blew through a red light that had changed on me because ultimately I was going too fast, but it was like there was no effort from the brakes when I stood on the pedal.

I was looking things over today and pads and shoes are intact, there is fluid in the MC but it is brown and atleast 5 years old...perhaps cooked. Would that be the problem? I did have to replace clutch fluid because it was in the same state. The pedal is not spongy, just doesn't want to grab.

I know I can upgrade the whole system for a $2,000.00 + or - investment. But I see that these are original brake sizes for Mustangs and the like which outweigh me by 1000 lbs or so. Would I be wrong to think the system I have is capable to work acceptably well? Or is the high $$$ full upgrade in my best interest, ie Wilwood 11" front and rear with a new MC.

If you have any ideas that you think might help please let me know thanks.

John

FWB · #8 (**permalink**) 02-28-2010, 09:08 PM

i had the same braking issues with the 9" mustang II, heidt's sells a wilwood 4 piston upgrade with the granada type rotors. it's a bolt up on the must II spindle, couple that with a power booster and now i have to be careful when i hit the brake or my face will come in contact with the steering wheel. it's safe to say i can stop just as well as i can go

p.s. much cheaper than 2000 bucks

bobcowan · #9 (**permalink**) 02-28-2010, 10:16 PM

Quote:

Originally Posted by MaSnaka

Guys,
I'm having trouble getting my car stopped.

If you have any ideas that you think might help please let me know thanks.

John

My first roadster was a CRII. Nice car, well built. Anyway, I used the simple brake set up as recommended by CR. Essentially what you have now - except I added a power booster. With the power booster, I could easily lock them up at anythiing under 45mph or so. I remember thinking I should have skipped the booster - didn't really need it.

Go back to the basics and make sure everything is as it should be:
- Fresh fluid all the way to the calipers.
- Resurface the rotors - use 120grit sanding disc in a drill motor
- Resurface the pads - sand lightly on a flat surface
- Clean and grease the caliper mounting pins.
- Make sure you have a manual brake pedal, and not power.

I think if you do all those things, your brakes will be fine.

Double Venom · #10 (**permalink**) 03-01-2010, 02:03 AM

John,
You description feeds the physics of the master cylinder with wrong bores, OR YOUR PEDAL IS assembled in the wrong hole creating the wrong pedal ratio.

6 caliber is absolutely 'ridiculous' for these cars. If you're traveling 100 mph + to 20 mph for a hair pin turn, maybe.......

Corvette MC's 7" work well, simple two nut installation. (+/- '87 4 wheel disc). Adjust your rod length to allow less than a 1/4" movement before the piston in the MC starts to move.

Buying a full brake system is always better as a supplied kit, unless you know everything there is about a full braking system.

CobraEd · #11 (**permalink**) 03-01-2010, 05:11 AM

DV raises a good point. When my master cylinder rod was in the wrong (lower) hole on the pedal, the brakes were not so good. i moved it to the upper hole and they are awsome! The upper hole generates way more leverage.

.

MaSnaka · #12 (**permalink**) 03-02-2010, 03:29 PM

Thanks guys for the responses. First I will flush the fluid from the brake lines and start fresh. No matter what happens in the future this has to get done. I will sand the 9" discs and pads to get a fresh surface. Clean and lubricate where needed.

The pedal has only one hole and it lines up directly inline with the rod. Even if there were other holes on the pedal arm it would put things out of alignment to change. Unless I'm missing something there. I don't know the differences in manual pedals or power so I don't know what to look for.

I'll have results this weekend, if the rain holds off long enough.

John

Double Venom · #13 (**permalink**) 03-02-2010, 07:53 PM

John,
Not talking about the singular rod hole! Get on your back and look at the pedal BOX you WILL have two holes available to mount the pivot. Years and years ago the 'other' hole was used on circle track set ups. Never have been used in the Cobra that I know of. they sould have quit punching that hole in '79!

427mudflap · #14 (**permalink**) 03-02-2010, 08:32 PM

Get a master cylinder with a smaller bore, 1.00 dia. is too big.
There is a aluminum small bore cylinder (metric about .75) on
1986 mustangs. Or a tilton .625 - .75 dia.

MaSnaka · #15 (**permalink**) 03-04-2010, 08:15 PM

DV, I only see one pivot hole and one rod hole. Looks like the pedal arm has a bushing welded to each side of it with a bolt being used as a pivot running through it. There are some other holes in the box but none even close to what looks like an alternative place to go. Any change there would seriously throw off the aligment and depth of the pedal in relation to the master cylinder rod. I measured a distance of 3 3/4 " from the pivot to the MC rod center to center. Does that sound about right?

I don't know the bore of my MC but I do have part number stamped on the bottom of it. Does it sound familiar or indicat what bore I have? 29922 and 30371 Both sets of numbers appear on the bottom of my MC.

Thanks,
John

mickmate · #16 (**permalink**) 03-04-2010, 08:22 PM

Measure between your pedal pivot and the clevis or pushrod then measure from the pivot to the pedal pad. It should have about a 7:1 ratio.

MaSnaka · #17 (**permalink**) 03-04-2010, 09:29 PM

Mickmate,
Thanks for taking time to help me here. My pivot to clevis (push rod) is 3 3/4" center to center. My pivot to pedal pad is 12" center to center. Is that a 3.2 to 1 ratio? Please check my math. Maybe that's the problem. Looking at the manual...It looks like everything is right accordingly except I don't have a booster. So is it possible I have a ratio set for power brakes?

John

bobcowan · #18 (**permalink**) 03-04-2010, 10:19 PM

You are correct. And that's exactly what your problem is. You need to change the pedal, or the MC to compensate.

http://www.hotrodheaven.com/tech/brakes/brakes6.htm

mickmate · #19 (**permalink**) 03-05-2010, 04:05 AM

That's it, power brakes ratio with manual brakes. The article calls for 6.5:1 where I said 7, somewhere around there will work.

Double Venom · #20 (**permalink**) 03-05-2010, 04:13 AM

Bobcowan,
Thanks for explaining the situation so well! Great web site.