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09-15-2011, 12:03 PM
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#1 |
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Registered User
Join Date: May 2010
Location: Tucson, Az
Posts: 13
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66 C20 lug size
So I picked up a sweet set of 16" MB Razor wheels for my 66 C20 Custom Camper on CL. Problem is my existing lugs are too large for these wheels. Through some research I figured out I need to switch from bulge acorn to a spline acorn lug to fit the rims and was told that I needed 9/16" diameter. I ordered a set but when they arrived the lugs just slip right over the studs.
Anyone out there know what size I actually need? John |
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09-15-2011, 12:28 PM
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#2 |
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Registered User
Join Date: Feb 2008
Location: Sidney,b.c.
Posts: 4,425
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Re: 66 C20 lug size
are you talking about the nuts that go on the lugs which is the male threaded portion which protrudes from the hub. what you more than like need are the 1/2" wheel nuts (internal thread) that are larger externally that are 13/16 or 7/8"(wrench size)
ron |
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09-16-2011, 12:50 AM
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#3 |
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60-66 Nut
  Join Date: Mar 2007
Location: Coeur d'Alene, Idaho
Posts: 23,248
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Re: 66 C20 lug size
I believe the older C20's had 1/2"-20 wheel studs.
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09-16-2011, 02:23 AM
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#4 |
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Registered User
Join Date: Feb 2008
Location: Sidney,b.c.
Posts: 4,425
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Re: 66 C20 lug size
C30's take 1/2" to but I think that the external size is larger. it is a heavier nut.
ron |
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09-16-2011, 02:30 AM
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#5 |
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Account Suspended
Join Date: Jul 2007
Location: Plumas Lake, Ca.
Posts: 1,009
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Re: 66 C20 lug size
Wheel stud sizes on 3/4 ton trucks went to 9/16 x 18 in about 1971 or 1972. This coincided with the introduction of disc brakes on GM trucks.
Drum brake trucks had smaller wheel studs. Example: '60-'70 drum brake equipped C-10's had 7/16" X 20 studs. '71 & Up disc brake C-10's had 1/2" X 20 studs. So your '66 C-20 (with drum brakes) has 1/2"x20 studs while a '72 C-20 (with disc brakes) will have 9/16"X18 studs. The type of lug nuts will be determined by the wheel you plan on running. |
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09-16-2011, 05:34 PM
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#6 |
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Registered User
Join Date: May 2010
Location: Tucson, Az
Posts: 13
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Re: 66 C20 lug size
The wheels I purchased require the splined acorn lugs. I ordered some 1/2" 20's today so hopefully those work out..... will keep you posted.
Thanks for the help. |
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09-16-2011, 10:26 PM
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#7 |
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Senior Member
Join Date: Feb 2010
Location: Lambertville, MI
Posts: 1,860
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Re: 66 C20 lug size
I googled "splined acorn lugs" and i cant see how they would be required. they just look an anti theft lug. What counts is the seat angle and diameter of the angle. Older steel lugs have a smaller diameter angle than the new aluminum ones. Because obviously of the difference in stud diameter.
Post some pics of what you have and the new ones when you get em. |
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10-03-2011, 06:09 PM
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#8 |
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Registered User
Join Date: May 2010
Location: Tucson, Az
Posts: 13
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Re: 66 C20 lug size
Here are some pics of why I needed the splined acorn nuts. The first pic is of the original bulge acorn nut with the 7/8" socket that was needed to tighten them down. The splined acorn nuts are much smaller around and come with a special socket that fits the smaller hole in the rim. You can see that the 7/8" socket wont fit in the hole on these particular rims.
The last pic is how the truck looks yesterday...... I know.... rain in Tucson......but it does happen. |
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