Early Bronco and F150 disc knuckle differences and wheel clearance?

[Bluebolt]

I am planning on putting US Mags aluminum slots on my Bronco that has 1977 era F150 disc brakes. Is there a difference in the 76-77 Bronco knuckle and the 1976-79 F150/1978-79 Bronco knuckle? They use the same calipers and rotors apparently? From Bronco Graveyard:

Will NOT work with 76-77 Ford Bronco disk brake knuckles.
76-79 F150 and 78-79 Bronco disk brake applications will require 10908 low profile bolt.
PLEASE TEST FIT THE WHEEL PRIOR TO MOUNTING AND BALACING

I just don't understand LOL.

 

[garberz]

I know the 76-77' steering arm part of the knuckle is located higher. It's different than the F-150's and the earlier Bronco 44's. That would make the TRE interfere with the rim. Hence the attraction of 17" wheels.

 

[bmc69]

The F-150 knuckles provide more clearance than do the 76-77 EB knuckles. The steering arms are indeed different. The backspacing on many aftermarket rims is not sufficient to allow them to be mounted on the 76-77 EB knuckles while still OK on the F-150/78-79 Bronco knuckles.

I found this out the hard way...and 250 dollars in billet spacers later, I had my fancy aluminum rims finally fitting my '76 EB. %)

 

[DirtDonk]

There are also instances where the inner rim face interferes even with the GM brake conversion. We just "fixed" one of those this morning with a few well-placed whacks with a BFH.

In this case, it wasn't the substantial 4.25" backspacing alone that was the main issue (though it didn't help!) but the caliper mounting bracket was just 1/8" too large in the area within 2" of each side of the caliper.

They fit now...
Or at least the initial inspection looked good. Won't have tires mounted and back on the truck for a couple more hours.
These are the 15x9 version by the way.

Paul

 

[70_Steve]

As was said (inferred), the 76-77 EB Dana 44 knuckles are unique in that the steering arm turns out towards the rim significantly more than the other knuckles. Even with 3 1/2" backspacing on my Centerline Hellcats, the tierod ends would knock the inside wheel weights off. I bought a pair of 79 F150 knuckles so I could do a TRO. The steering arm on those knuckles are a little lower than the 76-77 knuckles, but give more clearance from the rim.

 

[plumbdoctor]

Just mounted som US mag 15x10's on the 76... Tie rods weren't the problem, just had to grind the "caliper holder" or what ever you call the piece that the bolt goes thru... Just a tiny bit to clear the weights

 

[DirtDonk]

That's the same part we "tweaked" with the hammer. Grinding is a more elegant (and correct I would think) solution.
How much did you have to grind? Just a tiny bit I'm guessing? The 15x9's only had an eentsy bit of interference.
I'd say they'll still interfere with some weights if they're not put in just the right spot, but we'll leave that to the balancer. Hopefully!

What is the backspacing on your 10's plumbdoctor?

Paul

 

[plumbdoctor]

Paul, I didn't have to grind very much at all. More or less just the corner opposite the bolt... Maybe 4 passes with a disk.

Then after looking at it closer, if the tire shop would have put the weights in a straight line, I wouldn't have had to grind anything... It was catching the last 2 weights and barely skimming the others.
I believe they are 3 1/2 " backspace. To be honest I got them from Randy at Driven and didn't give a second thought what the spacing was or that they might not fit

 

[Bluebolt]

Thanks for the info guys sure glad I have F150 knuckles on mine!