A body 73 and up vs 72 and older front track width questions.

[Carnut76]

I know this subject has probably been beat to death but I am looking for some clarification. I currently have a 73 and up front brake setup that was installed by the previous owner, this and the B body rear worked fine with the wheels that were previously on the car (which were off a n early 2000s mustang) I absolutely hated the mustang wheels so I changed the car back to an A body 8-3/4 and put a set of Convo Pros which should fit just fine since the tire size is the same height, however the fronts just barely nick the front fenders at full lock.

So here is my question on the brakes.

I read somewhere that 73 and up will widen the track width 1-1/2 inch from the 72 and earlier cars, can anyone confirm this? I am now considering going back to the 72 and older spindle with a Willwood brake setup, I already know the 72 and older will take the smaller upper ball joint so i will buy the QA1 upper tubular control arms for 72 and older cars.

Can anyone confirm that the older spindle with Willwood brakes will narrow my track width from the 73 and up conversion?

Previous wheel combo in my profile picture.

Thanks in advance!

 

[Professor Fate]

Yup, the later brakes add 3/4" per side.
You'll either need more backspace on your front wheels or a shorter tire.
Since it just barely nicks the fender at full lock, you could also try adding some fender braces (or extending your existing ones) to push the lower edge out another 1/2" or so- some A bodies had them, some didn't. I don't believe the Barracudas did.

 

[Inertia]

If the fronts just " nick" the fender, perhaps consider just adjusting the fender brace, that small rod.
Moving it forward or back may move the fender out a bit, or extend the brace a "tad" .
You will likely be the only one to know/notice .

 

[Carnut76]

Yup, the later brakes add 3/4" per side.
You'll either need more backspace on your front wheels or a shorter tire.
Since it just barely nicks the fender at full lock, you could also try adding some fender braces (or extending your existing ones) to push the lower edge out another 1/2" or so- some A bodies had them, some didn't. I don't believe the Barracudas did.

I just needed to confirm the 73 and up was 3/4" on each side wider, and if I use a pre 72 spindle with Willwood brake conversion if that would bring them back in. 3/4" should give me more than enough room.

Modifying the fenders any more than I have is not an option, honestly I don't care for the overbite look from the wide track width in the front vs the rear. I had 26" tall tires before but the Mustang wheels have 5.75 backspacing , more of a modern flat faced wheel than what is supposed to be on this car. I just drove to Chicago to pickup a set of 72 and older drum spindles so hopefully this cures the problem.

 

[Professor Fate]

The Wilwoods still widen the front, although they say it's only .20, so a hair under a quarter inch.
I'm gonna bet that if the tires touched at rest with the factory discs, they'll still touch with the Wilwoods as the suspension cycles.
For less than the cost of the Wilwood kit and the extra parts and hassles involved, you could have just gotten wheels with the correct offset.
But it's your dime. Hope it works out the way you hope.

 

[Inertia]

The Wilwoods still widen the front, although they say it's only .20, so a hair under a quarter inch.
I'm gonna bet that if the tires touched at rest with the factory discs, they'll still touch with the Wilwoods as the suspension cycles.
For less than the cost of the Wilwood kit and the extra parts and hassles involved, you could have just gotten wheels with the correct offset.
But it's your dime. Hope it works out the way you hope.

That's kinda my thought, that the spindles are the same as earlier, the transverse torsion bar k-frame is wider .
Musing .

 

[72bluNblu]

This is the difference in the track from the 67-72 cars to the 73-76 cars- 57.74" for 67-72 and 59.15" for 73-76. That is track width so it does include the wheel specs

The difference is in the spindle/brakes and possibly some in the wheel specs, but it's not in the K frame, UCA's, LCA's etc. Using the later FMJ spindles (that came with the transverse torsion bars) results in the same track width change on a 67-76 A body as the 73+ A body spindles (same brakes).

Barracuda's do not have the lower fender corner to frame braces like Darts, Dusters, Demons, etc., although you can add about 2" of push with those rods without really doing anything bodywork-wise.

The '67-69 Barracuda's have the most restrictive fender openings of pretty much all the 67-76 A's, and a 26" tall tire in the front is a stretch regardless of the spindle/brakes used. This is even more true with lowered cars, as ride height makes a big difference. The OP's car is most decidedly lower than stock, so that's part of the issue too.

What are the specs on those back to the 80's convo pro's? Width and backspace? And what size are the tires?

 

[Carnut76]

This is the difference in the track from the 67-72 cars to the 73-76 cars- 57.74" for 67-72 and 59.15" for 73-76. That is track width so it does include the wheel specs

View attachment 1716236825

The difference is in the spindle/brakes and possibly some in the wheel specs, but it's not in the K frame, UCA's, LCA's etc. Using the later FMJ spindles (that came with the transverse torsion bars) results in the same track width change on a 67-76 A body as the 73+ A body spindles (same brakes).

Barracuda's do not have the lower fender corner to frame braces like Darts, Dusters, Demons, etc., although you can add about 2" of push with those rods without really doing anything bodywork-wise.

The '67-69 Barracuda's have the most restrictive fender openings of pretty much all the 67-76 A's, and a 26" tall tire in the front is a stretch regardless of the spindle/brakes used. This is even more true with lowered cars, as ride height makes a big difference. The OP's car is most decidedly lower than stock, so that's part of the issue too.

What are the specs on those back to the 80's convo pro's? Width and backspace? And what size are the tires?

The Wilwood brake kit for the 72 and older spec to have zero offset but they have 3 different kits, the tires are 26x6.0015LT Mickey Thompson, the rims if I remember correctly are 4" or 4.5 with zero offset. I paid a good buck for these because they were in very nice condition, you can't buy them off the shelf anymore. I will be cool when they make a comeback like torque thrust wheels did, they just seem to be the look I like for this car, not really into the pro touring look. With the Willwoods and older spindles I should be Aok, I drove the car to a few places but I have to be very careful when articulating the suspension and turning. Very nice diagram for the track width BTW.

 

[72bluNblu]

The Wilwood brake kit for the 72 and older spec to have zero offset but they have 3 different kits, the tires are 26x6.0015LT Mickey Thompson, the rims if I remember correctly are 4" or 4.5 with zero offset. I paid a good buck for these because they were in very nice condition, you can't buy them off the shelf anymore. I will be cool when they make a comeback like torque thrust wheels did, they just seem to be the look I like for this car, not really into the pro touring look. With the Willwoods and older spindles I should be Aok, I drove the car to a few places but I have to be very careful when articulating the suspension and turning. Very nice diagram for the track width BTW.

The diagram is from a factory TSB that's available on The 1970 Hamtramck Registry Home Page

I'm not at all convinced that narrowing the track width more will make up for the 26" tall tire. That combination of rim and tire is already over ~1" inside of the fender lip. I suspect all you'll do is move your interference point to a slightly higher turning angle. I think if you want to make those rims work you'll either need a slightly shorter tire or you'll need to add some ride height up front.

There are TONS of threads about different tire combinations on this forum, and when you start looking at front tire heights for Barracuda's you'll find that very, very few of them involve tires that approach 26" tall. And on the ones that do, you'll likely find that the owners of those Barracuda's modified their lower front fenders to make it work. Removing a small triangle or pie shaped section from the lower front corner of the Barracuda fenders is a pretty popular modification because of the tire height limitations of the stock fenders.

Best of luck

 

[junkyardhero]

I think if you want to make those rims work you'll either need a slightly shorter tire or you'll need to add some ride height up front.

this is probably the best answer.

bringing up the ride height and a slightly shorter tire will probably keep you out of trouble, even better if you have some stiff bars to limit the travel. on my 69 i'm at 26" with the 73~76 parts and quite low. i'm clear of the fenders except at the center of top lip which hangs occasionally if i'm at or near full lock going into a drive way aggressively.