Smaller Front Brakes?

[Karl Bebout]

Here is a situation that has me scratching my bald head: A friend discovered that the builder that put his FFR together, put smaller disc brakes on the front than on the rear. The car is strictly for the street and is a very mild set up. The builder subsequently told him that that's the proper set up and then charged him a very handsome fee to put larger front brakes on the car. Then to add insult to injury, the car left the shop without the screw in studs tightened so that some stuck out considerable farther than others. I've seen cars strictly set up for drag racing having smaller front brakes than rears since the front tires are much smaller, but never anything else. Have I missed something or what?

[Rick Parker]

Some builders have in the past used the front brakes from a 74-78 Mustang II, which are admitedly quite small for a vehicle with the speed potential of a Cobra regardless of engine size. Then they often combine the 9" Ford live axle sourced from a full size Ford Passenger car that has to be narrowed to fit any of the Cobra chassis. Most of the disc brake assemblies used on the 9" rears are 10.5"-11" diameter and very heavy. That combination may be what you have experienced, fortunately several upgrades have been made available.

[bobcowan]

Most factory cars have a significant weight bias towards the front. That and basic physics require more braking power to the front. That's why front rotors are generally bigger than rear.

The FFR Roadster has an almost perfect weight balance. With a 302 it's about 50:50. So I'v heard of people using the same sized rotors on the front as the rear. I have never heard of anyone using smaller rotors on the front; on an FFR it doesn't make sense.

On a mild street car the stock Mustang brakes are more than adequate. They will quickly over whelm available traction if you're not carefull; especially with PB.

When you say big bux for a brake upgrade, does that mean Wilwoods? If the studs are not even, that means the lugs are loose. They will back out enough to hit a suspension component, and literally bring the car to a screeching halt.

I'v had this problem with my car. As you try to tighten the lugs, the studs get loose. I use red lock tight, and used a centerpunch to stake them into the alum hub. That's seems to have fixed it

[Karl Bebout]

Both the front and rear brakes on my friend's car were Wilwood discs and although I didn't measure the front rotors, I'm sure they were bigger than the tiny Mustang II rotors I used to have on my car. My thought was that since the builder went to the expense of Wilwoods to begin with, why would he have used such small units? Maybe he just had them laying around and decided to put them to use, or maybe it was just a mistake and the larger brakes were installed on the rear. If that's the case, to my thinking, he should not have charged my buddy to correct the error. My opinions aside, my real question is why would anyone want to have smaller brakes on the front than the rear?

[mikiec]

Large up front small in back. As Bob says, most of the braking comes from the front.

Remember his backs, as is, lock up way before the fronts.


Mike

[Danr55]

Well, he is generally small in front, anyway. Maybe he should ask for a refund.

[Chaplain]

Some put larger rotors on the back because they want rotor hats that incorporate internal parking brake like those offered by Wilwood and still use the classic 15" wheel size. To accomplish this you need the 12.19" rotors. You can fit these inside a 15" wheel because the offset moves the disc away from the hub of the wheel to where the diameter is greater. The problem with the front is that you can only have so much offset because you have balljoints to deal with. Or if you have too much backspacing, it will look like a front wheel drive car. You can make up the difference in rotor size by going to larger calipers in the front with larger pistons and using a proportioning valve. This is a simplified explanation. At the end of the day someone would really have to look hard to detect a 1" difference in rotor diameter.

[Tim Brewer]

Front brake rotors should ALWAYS be larger than the rear..no question. It doesn't matter about the weight bias either. When brakes are applied to a car, inertia moves roughly 70 percent of the car's weight forward.

[Karl Bebout]

Thanks for all the responses. I'm glad to see that my thinking matches other's opinions. I was wondering if somewhere along the line this professional builder had found out something I'd never heard of. That's obviously not the case. Hmmmm.

[vettestr]

Karlos,
PM me with part #'s or info on the removed brakes/rotors if he wants to sell them. I have a friend who wants to add front brakes to his drag car. I will just pass on the info and the two of them can wrangle some price between them. THANKS Jeff c

[Gordon Levy]

Karl, there are several answers to your question and since I am probably the builder and know who the owner is I am uniquely qualified to answer. I am also the largest dealer of Wilwood in AZ.
There are a couple of things you need to understand about an FFR right off the bat. The car is 55% rear weight bias and requires much more rear brake than a Mustang or most other manufacturers of replicas. Any single piston rear system is totally inadaquate and I have tried them all. It is much easier to dial back to much rear brake than to try and get more out of an inadaquate syetem.
The front system used was directly related to the wheels that were used on the car. The 6 piston system that I prefer will not fit inter these wheels. It isn't the rotor size, it's the size of the caliper. The caliper needs 1 5/8" of clearance from the bolt face of the wheel to the spokes of the wheel. The wheel used on the car has about 1/2". Way to little to clear even with a large spacer. The option of an 11" 4 piston system that is $700 less expensive than the 6 piston was used because the 12.19" system was discontinued by Wilwood and was not avalable at that time.
Since then Wilwood has been making that kit specifically for Levy Racing and is only available through me. This kit was later added to that car as an upgrade over the 11" kit. There is nothing wrong with the 11" kit. I have and know of quite a few people that raced this kit with no issues what so ever.
I did discount the Kit by over $200 as well as discounted the labor. We also did a number of maintainance checks on the car at no charge.
Also the car did not leave the shop with the studs loose. They were all torqued to spec with red locktight. Concidering that the upgrade was done over 9 months ago the causes could be a number of things.

I hope this answers your questions. We have been around longer than anyone else related to these cars and will continue to be here.

[Mike Brasfield]

Karl...since the builder put the lug studs in with red locktite and torqued them to specs,how do you think they came loose? Some were only hand tight and there was no residue of the locktite on the studs. It's a real mystery since it happened on more than one wheel.

[Gordon Levy]

It happens sometimes when someone bangs off the lugs with an impact gun. It is recommended to break the lugs loose with a breaker bar and not an impact gun.

[Mike Brasfield]

Gordon...your comment makes sense. But,I think, if the lug nuts were taken off with a impact wrench it would tighten the studs since they are screwed in. Correct? Still a mystery, I think.

[Gordon Levy]

Banging on or off with an impact can break the locktite bond, especially if antiseaze is not used on the threads. The studs are 3.5" long and using an impact to thread them on or off creates a lot of heat, enough to where I have seen lugs friction welded to the stud.

[Karl Bebout]

OKOKOK. Gordon, So, with your explaination, I'm still missing why smaller front brakes, than the rears, were installed initially, but the larger, 4 piston calipers and rotors were able to be installed on the same wheel set up. Do you typically install smaller front brakes than rears? BTW, none of the three of us saw any locktite residue and we backed all 10 studs with our fingers, to clean the threads.

[Gordon Levy]

I did explain that. The current kit that is on the car was not available at the time the car was built. The 6 piston systems that were available would not fit under the wheels he wanted on the car. The only reason that kit is available is because it is custom made for me.
As for the other, I don't know what transpired in the 9 months since the kit was installed.

[Karl Bebout]

O I C Thanks, Gordon, I didn't comprehend, but do now.