Ford 9" Axle Offset For Wilwood Brakes

[duffymahoney]

I have a stock 1977 rear end. I cut the ends off and added the big bearing ends and 31 spline axles years ago. Wilwood makes their rear kit for either 2.00 or 2.36 offset, I have an oddball axle offsets of 2.125", what I can't figure out is how this offset is set? Is it from the axle design? How far the bearings are pressed on? Spline depth? From what I can see, the axles are semi floating?

I ended up buying the 2.36 kit, thinking I could simply space out the bracket, but that won't work, the drum parking brake ends up hitting the back side of the arp wheel studs. I can get bearing spacers, that push out the axles, but I don't have enough spline left to space it out the .235 I need. I have roughly 1" of spline engagement now, so spacing out a 1/4" isn't an option.

Any thoughts?

To make things worse, I narrowed my rear end years ago to clear 285/70-17s, but now I don't have that setup, I run .25" spacers, which gives me the look and clearance I like. Moving the axles out that amount and spacers will give me roughly .5" out from my cut off of 1" per side. Which might be even better.

I can't seem to find any axles that state 2.36 offset or anything like that. Is the offset from axles, bearings, or even the welded on ends?

 

[jamesroney]

I have a stock 1977 rear end. I cut the ends off and added the big bearing ends and 31 spline axles years ago. Wilwood makes their rear kit for either 2.00 or 2.36 offset, I have an oddball axle offsets of 2.125", what I can't figure out is how this offset is set? Is it from the axle design? How far the bearings are pressed on? Spline depth? From what I can see, the axles are semi floating?

I ended up buying the 2.36 kit, thinking I could simply space out the bracket, but that won't work, the drum parking brake ends up hitting the back side of the arp wheel studs. I can get bearing spacers, that push out the axles, but I don't have enough spline left to space it out the .235 I need. I have roughly 1" of spline engagement now, so spacing out a 1/4" isn't an option.

Any thoughts?

To make things worse, I narrowed my rear end years ago to clear 285/70-17s, but now I don't have that setup, I run .25" spacers, which gives me the look and clearance I like. Moving the axles out that amount and spacers will give me roughly .5" out from my cut off of 1" per side. Which might be even better.

I can't seem to find any axles that state 2.36 offset or anything like that. Is the offset from axles, bearings, or even the welded on ends?

The axle offset is determined by the machined shoulder on the axle itself. As you have figured out, there are three brake offsets for the Bronco. The normal 11 inch one is 1-7/8, and the other normal one is 2-3/8. All of the decimal conversion crap just confuses the issue. The third brake offset is the 2-1/2, which is the one you need for the Wilwoods. 2-1/2 is a strange number, but it is basically the 2-3/8 plus 1/8 more for the added thickness of the caliper / parking brake shoe mounting bracket plate.

If you run less than 2-1/2 axle offset, then the heads of the lug studs hit the parking brake shoes. This is worse if you run thick flange axles, or heavy duty studs. (so don't...) For whatever reason, Wilwood refuses to make a tech note regarding this problem. The vast majority of Wilwood 9 inch kits are for passenger cars, and they are 5x4.5 lug pattern, and no problem at all. But yeah...their application notes are worse than useless.

You can pick up "free" axle offset by putting a spacer or collar between the bearing and the shaft. Usually 1/8 inch won't hurt spline engagement. But you do have to watch out. If you are running SET-20 tapered rollers, then you don't need to worry about seal engagement.

Wild Horses 4x4 figured all of this out years ago when working with Currie on the Explorer conversion. So they know it backwards and forwards. They practically invented the Explorer 2.5 brake offset with ring spacer solution. It is elegant, and simple, and almost impossible to install.

I have a set of Wilwoods in the garage that will go in my next project. But I will either have to custom countersink flathead bolts and thread the 2.36 axles, or I will have to buy 2.5 offset axles and run standard press in studs. (Which explains why it's still in the garage...)

Turns out that if you CALL Wilwood, they actually know how to make it all work, and sell a special caliper mount spacer to get you to the 2-1/2 axle offset. My buddy ordered a set of spacers last week, and then ordered the brake kit from Wild H.

 

[duffymahoney]

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The axle offset is determined by the machined shoulder on the axle itself. As you have figured out, there are three brake offsets for the Bronco. The normal 11 inch one is 1-7/8, and the other normal one is 2-3/8. All of the decimal conversion crap just confuses the issue. The third brake offset is the 2-1/2, which is the one you need for the Wilwoods. 2-1/2 is a strange number, but it is basically the 2-3/8 plus 1/8 more for the added thickness of the caliper / parking brake shoe mounting bracket plate.

If you run less than 2-1/2 axle offset, then the heads of the lug studs hit the parking brake shoes. This is worse if you run thick flange axles, or heavy duty studs. (so don't...) For whatever reason, Wilwood refuses to make a tech note regarding this problem. The vast majority of Wilwood 9 inch kits are for passenger cars, and they are 5x4.5 lug pattern, and no problem at all. But yeah...their application notes are worse than useless.

You can pick up "free" axle offset by putting a spacer or collar between the bearing and the shaft. Usually 1/8 inch won't hurt spline engagement. But you do have to watch out. If you are running SET-20 tapered rollers, then you don't need to worry about seal engagement.

Wild Horses 4x4 figured all of this out years ago when working with Currie on the Explorer conversion. So they know it backwards and forwards. They practically invented the Explorer 2.5 brake offset with ring spacer solution. It is elegant, and simple, and almost impossible to install.

I have a set of Wilwoods in the garage that will go in my next project. But I will either have to custom countersink flathead bolts and thread the 2.36 axles, or I will have to buy 2.5 offset axles and run standard press in studs. (Which explains why it's still in the garage...)

Turns out that if you CALL Wilwood, they actually know how to make it all work, and sell a special caliper mount spacer to get you to the 2-1/2 axle offset. My buddy ordered a set of spacers last week, and then ordered the brake kit from Wild H.

Any clue on what the kit is called? Thanks for the info!

 

[toddz69]

Turns out that if you CALL Wilwood, they actually know how to make it all work, and sell a special caliper mount spacer to get you to the 2-1/2 axle offset. My buddy ordered a set of spacers last week, and then ordered the brake kit from Wild H.

I'll be curious what this is exactly too - as I'm trying to understand how you could add a caliper mount spacer to give more clearance between the parking brake shoes and the axle studs w/o adding axle offset?

Thanks,
Todd Z.

 

[jamesroney]

I'll be curious what this is exactly too - as I'm trying to understand how you could add a caliper mount spacer to give more clearance between the parking brake shoes and the axle studs w/o adding axle offset?

Thanks,
Todd Z.

You are thinking correctly. You must have the full 2.5 axle offset first. Then the spacers center the caliper on the rotor…and the parking brake shoes run shallower in the rotor hat.

 

[toddz69]

You are thinking correctly. You must have the full 2.5 axle offset first. Then the spacers center the caliper on the rotor…and the parking brake shoes run shallower in the rotor hat.

10-4. That makes perfect sense.

Todd Z.

 

[duffymahoney]

So no where does it state 2.5" offset. Is that a bronco measurement method compared to wilwood?

 

[toddz69]

So no where does it state 2.5" offset. Is that a bronco measurement method compared to wilwood?

I was looking around on the Wilwood site last night, as I often do, and noted that for the standard/early big bearing setup, which I think you have, Wilwood only mentions the 2.0 and 2.36"" brake offsets. I can't access the site here at work for some reason, but I bet if you look at the late model big bearing/Torino housing end section, you'll find the 2.5" brake offset as an option (only EBs with that offset stock were the 74-75 medium-duty housings).

It's my opinion that your only option at this point to get those brakes to work is to get a set of custom shafts from Moser. Currie no longer lists custom length shafts for the standard/early big bearing units on their website - at least I could not find them.

Todd Z.

 

[duffymahoney]

I have Toms Differentials in my town, they used to make custom axles. I will see what they say.

 

[toddz69]

Judging by the size of their catalog, they can probably do something.

Todd Z.

 

[jamesroney]

So no where does it state 2.5" offset. Is that a bronco measurement method compared to wilwood?

I'm a little lost by this question. 2.5 inch brake offset is the Ford standard for Torino flanges, and for the Explorer. Happens to be the standard for Jeep Wrangler as well. There's always confusion about brake offset measurement, because you can't actually make the measurement on the axle. So what happens is the axle makers "define" the axle offset as the distance from the flange to the bearing retainer. But the brake makers "define" the axle offset as the distance from the flange to an imaginary location at the bearing retainer minus the thickness of the brake backplate.

When everyone was running drum backplates, the nominal difference in the measurement systems was just considered 1/8 inch, and the world was happy. Nobody actually cared what the brake offset actually measured. All that mattered was that you could tell the difference between the heavy duty, medium duty, and the 76-77 shafts when you had no idea where your Bronco rear axle came from. When the disc brake backplates with parking shoes were invented...they had a much thicker casting (about 1/4 inch)

Now when you add in the complexity of the SET20 tapered roller, and the external seal...it gets even more difficult to measure. This makes it really hard for the Bronco vendors to get the right parts. You will note from the pics below that the axle offset literature is not consistent.

The Currie Explorer Disc swap kit is called the CE-6012. In the kit, you will find the CE-6012-SPACER which is .235 thick. The normal drum backplate is .115 thick. The Explorer Disc backplate is .285 thick. The Wilwood spacer is thinner. I don't remember how much.

Everybody pretty much knows that you want to buy the 74-75 medium duty axle shafts with the 2.5 inch brake offset and big bearings. Then you add the Currie CE-6012 spacer, and you can bolt in the Explorer Discs. But of course the CE-6012 spacer is obsolete, and no one will tell you that the replacement spacer is the CE-9005-TES and it costs $50. Wilwood makes their own spacer, but their crush distance is totally different, because their backplate is thinner. So you can buy the Wilwood 250-6285 spacer for the Torino ends for $10. But the lip is too short for Explorer castings. Or, you can buy the Wilwood 250-11223 spacer for big bolt, big bearing ends for $11. But again, short lip.

I made the mistake of buying the Wilwood 250-6285 spacer for my Explorer set up. Then I talked to Currie for about 15 minutes trying to get obsolete hardware. Then they tried to sell me a $10 spacer for $50 plus tax and shipping. Then I got mad, and then I machined my own spacers, welded them to the wilwood retainers and finished them at .236 thick, cut off my billet housing ends, welded in Torina ends and ran the Explorer brakes. But DON'T do what I did. Or you'll end up with a giant basket of really expensive rear disc parts in a box in your shed.

So what was your question? cc: @toddz69

 

[duffymahoney]

So I believe this is what happened with my rear end.

I had it rebuilt years ago, I didn't know better and the axles were replaced, I have no memory or paper trail on what was used. Since we have that axle company in my tiny town, maybe they grabbed the wrong offset and since I have the caddy setup, it would have been easy to add or remove spacers and make the caddy brake kit work.

My plan moving forward is new 1977 31 spline axles from wildhorses that should have the correct 2.36" offset and bolt right in. Then the wilwood kit is setup for the same offset and they should also just bolt right up. I will need to cut off 1" from them for my narrowed ford 9". Which will leave me 1.5" of spline engagement and should work great.

 

[toddz69]

So I believe this is what happened with my rear end.

I had it rebuilt years ago, I didn't know better and the axles were replaced, I have no memory or paper trail on what was used. Since we have that axle company in my tiny town, maybe they grabbed the wrong offset and since I have the caddy setup, it would have been easy to add or remove spacers and make the kit work.

My plan moving forward is new 1977 31 spline axles from wildhorses that should have the correct 2.36" offset and bolt right in. Then the wilwood kit is setup for the same offset and they should also just bolt right up. I will need to cut off 1" from them for my narrowed ford 9". Which will leave me 1.5" of spline engagement and should work great.

Sounds like a great plan.

Todd Z.

 

[duffymahoney]

Fingers crossed it works.