I have another thread going on my swap over to Single Rear Wheels, but an issue came up that seems universal. So I'm starting a new thread with a good title that will come up in a search for anyone looking for lug nut sizes and information.
My F350 dually has the large lug nuts with the built-in washer. These lug nuts will not fit with a standard wheel! Napa sucks and so does their website, but what I've gathered is that the thread size is 9/16"-18 for an '85 F350 dually, for about $6 a pop brand new.
Now, in my search for the correct lug nuts I've found that the F350 SRW trucks also have an acorn shaped lug nut wthout the built-in washer in the 9/16"-18 thread size, for about $4 a pop brand new.
I've also found that the F250's seem to have two different lug nut sizes depending on if the truck is 2wd or 4x4? Seems wacky to me...but supposedly the 2wd's are 1/2"-20 and the 4x4's are 9/16"-18.
I also looked up sizes for a 1978 K20 4x4 and they claim to have a 9/16"-18 thread, like what my truck has. I have a set of these I was able to borrow, but they don't fit. The trial stud was wire-brushed and even has a coat of grease. Installing the lug nut with the acorn side settling into the wheel, the nut goes on hard...while the stock lug nuts go on with a flick of the wrist. Funny thing, if the lug nut is installed backwards with the flat side settling into the wheel, it installs easier. But I need the acord side into the wheel, so everything it tough.
All these numbers are unreliable through this crappy Napa website, and it seems silly to me that F250s and F350s would have different lug nuts even though it's the same axle. Oh, the website was also claiming a difference between the D70 and Ford 10.25 axles...

Anybody have a clue? Thanks!

 

Standard tapered lug nuts (you call them acorn) have a tendency to shrink on the small end from use.

You could run a Tap through them or forget about it.

Those dually nuts with washers ... I'm looking for at least 7 if you want to get rid of them.

-Enjoy
fh : )_~

 

if you go down to your local tire shop, you can get them a hell of a lot cheaper. hell, i got a set of 36 (4 extras just incase) for $50 bucks. they arent open end either, they are fully encasing with the tapered base (for my aluminum wheels) they buy them in bulk, and highly discounted. you have two options. large body and small. the large is like 7/8 and is as fat from taper to tip. small body is ment for aluminum wheels where the lug nut is set into the wheel, basically only the tip is visible. those are 19mm or 3/4" BUT the covers over the end tend to pop off if you use an impact wrench to take them on and off.

 

I suspect that if it is a semi floating rear it could be different, but I'll also hazard a guess that the front would also be the same as the rear. The super duty I parted out had the same size wheel nuts front and rear, and they are also 9/16-18, as I used one to replace a messed up one when doing the rear brakes on my dually. I'm hunting my toolmaking sources for an 'economical' tap and die set in the 9/16-18 size, once one passes 1/2", they tend not to be as common.

Are you only looking for enough for the rear, or front too? If you're 2wd, I think that you have an easier job of going from dually rims to single rims, I'm thinking it's a matter of taking the adapter/extension off and installing studs in the rotor, but not 100% certain!!

Festus, are you still hunting for your nuts? (Sorry, couldn't resist!!)

Drop me another pm, I suspect that the nuts go along with another item you were asking me about a while back.......

 

I call BS on the 2wd having 1/2 studs on the F250's. My 88 and 92 F250's that I had used 9/16's, however the 88 used 1 1/16 nuts and the 92 used 7/8s, while most of the ranch trucks (1st PSD's) I'm around all used 15/16's nuts on 9/16's studs.

 

Thanks fellas!
Tapered! I couldn't for the life of me come up with that word and used acorn instead.
I've got 3 dually trucks total. 1 has been stripped and scrapped, so there are 32 available from that truck. Truck #2 is the parts truck, which is currently being stripped and scrapped, 32 more available there. And truck #3 is my driver which is being converted over to SRW...so there's another 32 available.
Holy crap, I have 96 lug nuts and they're all wrong! Festus, PM me if you want some...and anyone else for that matter!
Greywynd, converting the front over to Singles is super simple. Go to the parts store and buy a hub/rotor assembly for a 2wd F250. Bolt it on, and that's it. I checked out the prices already, ballpark $80 each, That gives me brand new rotors and puts me to SRW in one step.

I'll be heading to my tire guy this week to check out what he's got to say.
Anyone who is interested in the dually to SRW conversion, I have another thread started and plan to update that with all information I learn. DRW to SRW swap measurements - Ford Truck Enthusiasts Forums
Thanks again fellas!

 

my factory alcoa rims use 7/8" on 9/16"-18 studs. washers are used on drw to get a tighter fit/ better touque on the wheels. only other thing have saw use them is on my brother's Land Rover.

 

I call BS on the 1/2" studs too - I got a buddy with an '86 truck with a light-duty semi-float Sterling axle (has VSS so it must be a transplant, but that's beyond the point), and even that has 9/16" studs with tapered nuts that take 1-1/16" socket.

 

When the tapered SRW nuts get hard to turn on and off, that is usually from someone going banana's with an inpact wrench.

If you look down in the inside of the nut, you can see where the threads have been stretched, effectively changing the thread pitch from one end to the other.

That is why they screw on backwards easier.

SRW 250 and 350 should both be tapered nuts, 9/16" x 18
DRW should have the washered nuts, still 9/16" x 18
Two wheel drive should also be 9/16" x 18

Chevy if I remember right uses 1/2" lug nuts.

 

70's Fords have 1/2" studs, Chevy 3/4 tons do also, Chevy with a 60 front have 9/16th, while Dodge in their infinite wisdom used 1/2 on anything SRW 93 and older, and the duallys are 5/8"....
Ford at least used nice long studs on their trucks, the Chevy/Dodge stuff is very scary with aluminum wheels IMHO, not enough to get full engagement in a standard open acorn nut... Which is why my Dodge has steelies on it.

 

Thanks again fellas!
The '78 Chevy K20 actually has 9/16" - 18 threads as well. My lug nuts threaded very easily on to the Chevy axle.
The Chevy nuts had a tough time going onto my truck because the threads are all stretched out.
I didn't get a chance to get to the tire shop today, but I plan to get there this week and inquire about 9/16" - 18 thread, 1 1/16 hex head lug nuts.

 

BlueOval, You need some 9/16-18 with 1-1/16" head???

How many you want, I have something like 48 spares!

-Enjoy
fh : )_~

 

Odd, my 69 F250 has 9/16x18 studs with 13/16 lugs. Same for the Dodge truck bed trailer I have here, and the 70s D44/D60 under my F100. The E350 chassis I'm working on has the larger nuts with 5/8" studs. FWIW, on 2wd duallies the front extension is actually the hub, the rotor bolts to the back of it.

 

Yes Festus, PM sending now!

 

Yup yup, already warned him about it a while back, which is why he said he's getting a pair of 2wd rotors for a SRW truck, cause they got their own hubs machined in them.