Wilwood brake dis(c)appointment

jdowen2

New Member
Dec 18, 2005
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Mesa, Az
I'll try and be brief. Bought a restomod 67 with Kelsey Hayes front discs, no power. Car was a disappointment in the braking department. Called The Mustang Shop in Chandler and made an appointment to install a vacuum booster. Talking to the tech there he recommended a Wilwood front disc setup with a new mastercylinder (15/16ths bore) and no booster. He said the difference in forty year old technology and what is available today should be significant. During the installation he called to tell me the car didn't have a proportioning valve. He recommended a adjustable valve on the rear brake line. After all is said and done, I notice a marginal difference from before. :shrug: . I'm at my wit's end :bang: . Anyone got a suggestion or two?
 
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Yeah, more info needed about the problem. Although 15/16ths is on the small side.

One thing I noticed though...if your car came with disc/drums from the factory you DO (at least did) have a proportionaing valve. It is the brass block on the inner fender well under the hood spring near the master cylinder. It is not the adjustable kind, it was pre-set from the factory for your manual disc/drum setup. If you change to a boosted setup you'll want a different prop-valve. If you change to an aftermarket caliper or MC you'll probably want to bypass the factory prop-valve entirely, certainly when you install the new adjustable one.

I cannot say that is causing your problem because...well...I don't know what the problem is...LOL.

Here's a photo of my lines and brass block, the original one had 5 brake lines in/out of it, this one has three and there's no valving in it...

mc2.jpg
 

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I've always been a little fuzzy on master cylinder sizes, but here's what I've heard: on non-power discs, a smaller bore (like your 15/16) is required to give a decent "feel". Much larger and the pedal may be very hard to push without actually making the brakes work. BUT, my boss has a Mustang drag car that weighs 2700 lbs, yet he has Wilwood drag discs and a 1 1/6 mastercylinder and his 120lb daughter drives the car and she says it stops just fine from 140mph! I'd sure be interested in what you find, since I want non-power discs and was leaning towards Wilwood. BTW, I've heard that Wilwood brakes move the front wheels out about 3/8" per side, is that true?
 
zookeeper said:
BTW, I've heard that Wilwood brakes move the front wheels out about 3/8" per side, is that true?
It is true. I have done 4 Mustang swaps and that is the exact amount that the trackwidth increased. Before I did the swap, I spoke to Wilwood and they confirmed 3/8 inch outward movement per side. This is with the .81 rotor like on this kit.

http://store.summitracing.com/defau...rch&DDS=1&N=115&target=egnsearch.asp&x=37&y=9

I then installed the super lite six piston kit with the thicker rotor on my 70 Mustang and the track width increased even more because of the thicker 1.1" rotor.

There is a guy on eBay that sells the kit for $200 more that supposedly does not increase the track width like the heavy disc kit and six piston kit do. The catch is you have to use 70-73 spindles. I purchased all my kits from him but he IS SLOW to ship.

http://cgi.ebay.com/ebaymotors/Wilw...33564QQitemZ8033314920QQrdZ1QQsspagenameZWDVW
 
Did you or the installer properly bed the pads and season the rotors? Also, how did you adjust the prop. valve?

I recently installed a Cobra brake retrofit on my 68 and it didn't stop well until after I bedded the pads and adjusted the prop. valve. Now it stops incredibly well and this is with a 15/16" master and no booster...

68Restoman
 
I'll try and be clear. The braking effort is high and the stopping distance is long. I was hoping the Wilwood front disc setup would allow me to drive the car with no fear of rear ending someone. I have to leave a rather large comfort zone in front of me.
 
you mentioned that you had the stock four pisons before. i am curious what the difference in piston volume between yuor wilwoods and the stockers is. i would be suspect of the master cylinder size. depending on what wilwood calipers you are using you probably have a good bit more fluid volume in the calipers themselves as compared to your stock calipers. the current master just isn't moving enough fluid to clamp the pistons to the rotors. that means your legs have to make up the difference, i.e. higher pedal effort. i guess that your stopping distance could increase if you can't physically apply enough pressure to the brake pedal.
 
What are you comparing the heavy pedal and long stopping distance to...the Kelsey Hayes setup, or new cars?

Are you able to lock up the wheels at will? Do the fronts lock first?

My car has Cobra front calipers (PBR) and Willwood 4-piston rears. I DEFINITELY have more volume in them than the factory PDB and rear drums ever did. That's why my new MC has a full 25 cubic inches of fluid and a large (1-1/8) piston.
 
I agree with the seasoning/break-in suggestion. Do this: find some empty road. Run up to 30 mph. Brake to a stop -- not a panic stop, but like you mean it. Take foot off brake pedal, in neutral or park. Sit for 30 seconds. Repeat 30 times. 30/30/30, geddit? If you still have a prob, get back to us.

If you do still have a prob, going up in MC diameter will INCREASE pedal effort. It will move more fluid, true. But the line pressure will be LOWER than with a smaller diameter MC using an equal amount of pedal travel. So if you have a hard pedal and poor braking, a larger diameter MC will make both things worse.
 
the other thing you need to do after bedding in the pads is to adjust your proportioning valve. you want to adjust it untill the rear brakes lock up just before the front brakes do. that will give you maximum braking on all four wheels.
 
rbohm said:
the other thing you need to do after bedding in the pads is to adjust your proportioning valve. you want to adjust it untill the rear brakes lock up just before the front brakes do. that will give you maximum braking on all four wheels.

Actually, you should have it set so the fronts lock up before the rears. It is MUCH safer on the roads this way. Otherwise, the front end becomes a pivot and your rear-end comes out (like my car does :( )

-Alan
 
Need a third opinion on that issue. From my years of motorcycle riding, and just the intuitive way, it seems that having the rears lockup first would be better, at least that way you still have steering.

In reality they should all go together but that is nearly impossible to get JUST RIGHT under all conditions.
 
I once was trained by GM to be a certified GM brake mechanic--hey it was free. . . .

Anyways, there is a slight delay built into the MC in the form of a spring. When the brake is depressed, the rear most section of the MC gets "activated" first then the front section.

Here is the layout of a typical MC:

42162614.gif


Note part 14 is a spring that must be overcome--it is not much but it is there.

When you apply this logic to our Fords, the rear most section of the MC (against the firewall-- the larger reservoir) goes to the front discs--the primary piston activates it. Of course that means the front-most section (the secondary piston) goes to the drums.
 

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Edbert, the problem with rear-heavy braking is that not all panic stops are done in a straight line. What happens when you see a deer in the road at the same time you're showing off the cornering abilities of your Mustang? With the brake bias more towards the rear, the car will quickly swap ends and there goes the steering! But if the fronts lock up a bit while the wheel is turned, yes it will plow a bit, but the driver has time to let off the brakes, let the car complete the turn and get back on the brakes. Trust me on that one, it's the only thing that kept my brother's new RX-7 out of someone's front yard (and fence, and house) one night when I was practicing my late braking techniques on a back road one night...
 
I'll be a dissident and say you very well could have been sold a bill of goods, depending on the specifics of the Wilwood kit. If it's the typical 11" Wilwood street kit, then no friggin wonder! The factory KH system is pretty much equal to that kit, if not a little better with good pads. OTOH, if it's a 13" kit with Cobra/PBR calipers, then I think everyone else is on the right track.

BTW: I was always taught to have the rears lock up first so's you can steer.
--Kyle
 
5.0ina66 said:
BTW: I was always taught to have the rears lock up first so's you can steer.

Most of your braking is done with the front brakes. Having the rears lock first might work in a straight line, MIGHT. If the rears lock first in any situation other than going straight you are all but guaranteed to swap ends and then where is your steering ability?

Cars (before ABS) were set up from the factory with a front brake bias for a reason.
 
68rustang said:
Most of your braking is done with the front brakes. Having the rears lock first might work in a straight line, MIGHT. If the rears lock first in any situation other than going straight you are all but guaranteed to swap ends and then where is your steering ability?

Cars (before ABS) were set up from the factory with a front brake bias for a reason.

Agreed. I think its something like 2/3 of your braking comes from the front brakes, and your front brakes should lock up slightly before the rear.
 
Here's what Ford Racing has to say about adjusting the prop. valve in their instructions for the Cobra brake kit:

STEP 23: Find a safe place to check and adjust your brake system for proper operation. The optimum adjustment will result in the front brakes locking just prior to the rear, under the worst conditions (minimum traction
surface and minimum rear wheel load).

68Restoman