Proper Clearance for Hubcentric Adapter Rings for 17" Cragars S/S - Chevelle Tech
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post #1 of 6 (permalink) Old Nov 8th, 19, 11:45 PM Thread Starter
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Aaron "A.E."
 
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Location: West Frederick Highlands, Maryland, USA
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Proper Clearance for Hubcentric Adapter Rings for 17" Cragars S/S

I have 17" Cragars S/S wheels on my 1971 Chevelle SS. I want to make sure they are installed properly by using correctly sized hubcentric adapter rings. The Cragars have an inner hub diameter of 90.7mm and I measured the hubs on my car at 70mm (which internet research shows to actually be something like 70.3mm or 70.5mm. I have found 90mmX70mm adapter rings on eBay and am wondering how tight the clearance is supposed to be for the wheel-hub distance. Is a 90mm outer diameter hub ring too small for a 90.7mm wheel? Will a 70mm inner-diameter hub ring fit on a 70.3-70.5mm hub, or will it need to be machined larger?

My car has factory rear axles, but has 12" rotors that are to spec for a late-model Camaro. The front hub of the rotor appears to measure equal to that in the rear.

Thanks in advance!

-A.E.
----------------------------------------------
1971 Chevelle SS
Modified Original Frame-Off Resto-Mod
#-Matching Drivetrain (Exc. Powerglide Swap) Fully Built
Complete Chassis Customization
~25K Original Miles (Just had first oil change since overhaul)
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post #2 of 6 (permalink) Old Nov 9th, 19, 7:41 AM
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Ed
 
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Re: Proper Clearance for Hubcentric Adapter Rings for 17" Cragars S/S

First, I assume your hubs are 2.75" back then they weren't designed in metric, just an assumption. If so, that is a smidge under 70mm I believe.
Second 90.7 is pretty dang close to the 90 adapter, and literally a ring of tape around it would probably exceed it. I'd buy one and try it if they are cheap enough. Also, if using taper seat lug nuts, I wouldn't even bother, but using mag style, maybe.

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post #3 of 6 (permalink) Old Nov 9th, 19, 9:19 PM Thread Starter
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Aaron "A.E."
 
Join Date: May 2002
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Re: Proper Clearance for Hubcentric Adapter Rings for 17" Cragars S/S

Quote:
Originally Posted by Pioneer4x4 View Post
First, I assume your hubs are 2.75" back then they weren't designed in metric, just an assumption.
Most of the cool stuff on the car is metric now.

The 12" Camaro slotted rotors up front have 12mm studs and a hub that would accordingly be measured in millimeters.

The fast-ratio Saginaw steering box is metric-spec too. That isn't relevant here other than me noting that fast-ratio steering is, in my opinion, the #1 modification/upgrade to make a Chevelle steer like something that just drove out of a Chevrolet showroom. (I have the Jeep steering system in mine, modified to connect to the original Chevelle pump)

The axles in the original Eaton-Posi 12-Bolt have 7/16" studs, and I suppose deserve SAE measurement for the hub diameter as you suggested. Part of this hubcentric adaptation project is to give me matching 12mm studs for all four wheels. I am planning on adding a pair of hubcentric spacers in the back, which will be complemented by the car's existing lowering springs and near-future plans to roll the fender lips on the rear quarter panels. The manufacturer specifies the hubcentric diameter to be 70.5mm and state this to be correct for the Camaro upon which my car's brake system is based.

****AN IMPORTANT QUESTION FOR ANYONE HERE IS: Can anyone confirm the exact diameter of the rear axle hubs on a 1971 Chevelle SS with a 3.31 Eaton-Posi 12-Bolt? Is it 2.75" as suggested? I don't have a caliper/mic handy, yet I need to know exactly. ****

Cragar did give their wheel specs in SAE measurements, at least for the old-school S/S models, and I converted it to 90.7mm hub bore. This is close enough to likely work well, as was previously said.

If any of the rings/adapters/spacers need to be bored out, I can put them on a brake lathe and take some material off.

As far as the use of the metric system as it relates to my Chevelle; where I lack in nostalgia, I make up for in innovation and performance.

I think metrics are easier anyway. It makes more sense to understand and at the time that we are at the inch to the second decimal, a portion of a millimeter makes for a narrower guess range when the legible limits of a ruler or tape have been exceeded.

I attached pics of each type of adapter to be used. The rear would have rings on top of the spacer plate hubs. The front would have rings on rotors.

Thanks again everyone and thank you sir for your reply.
Attached Thumbnails
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Name:	Hubcentric Rings 1971 Chevelle SS Cragar Wheels.jpg
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ID:	607440   Click image for larger version

Name:	Camaro Spec Wheel Spacers for Chevelle.jpg
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-A.E.
----------------------------------------------
1971 Chevelle SS
Modified Original Frame-Off Resto-Mod
#-Matching Drivetrain (Exc. Powerglide Swap) Fully Built
Complete Chassis Customization
~25K Original Miles (Just had first oil change since overhaul)
fast71ss is offline  
 
post #4 of 6 (permalink) Old Yesterday, 9:15 AM
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Ed
 
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Re: Proper Clearance for Hubcentric Adapter Rings for 17" Cragars S/S

Quote:
Originally Posted by fast71ss View Post
...

My car has factory rear axles, but has 12" rotors that are to spec for a late-model Camaro. The front hub of the rotor appears to measure equal to that in the rear.

Thanks in advance!
Yeah, I totally skipped that part!

1967 El Camino Malibu - Deepwater Blue
ZZ4 350, FiTech 600 complete!,Roadmaster tank, 700R4, Underdash A/C in progress, JGC Steering, 1990s truck serpentine.
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post #5 of 6 (permalink) Old Today, 9:34 AM
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Jeff
 
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Re: Proper Clearance for Hubcentric Adapter Rings for 17" Cragars S/S

I get them just right by buying the next size bigger then hitting them with Emery cloth until they fit snugly..

BTW I have a set of four for sale that fit the Wheel Vintiques Series 62 or 64 wheels on a Chevelle or el Camino... They are aluminum and look nice..
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post #6 of 6 (permalink) Old Today, 9:38 AM
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Jeff
 
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Re: Proper Clearance for Hubcentric Adapter Rings for 17" Cragars S/S

[QUOTE=fast71ss;11176332]Most of the cool stuff on the car is metric now.
As far as the use of the metric system as it relates to my Chevelle; where I lack in nostalgia, I make up for in innovation and performance. I think metrics are easier anyway. It makes more sense to understand and at the time that we are at the inch to the second decimal, a portion of a millimeter makes for a narrower guess range when the legible limits of a ruler or tape have been exceeded. quote...


Back in the seventies we were almost all the way in with the metric system but they stopped it and went back words again.. I wished we would of kept going, the whole world is metric except us, how stupid...
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