CSX2xxx Cars & American Racing Wheels

Dan Case · #1 (**permalink**) 02-18-2018, 11:51 AM

A question came up on another forum about the optional (street and race) magnesium wheels with steel 'spline drive' adapters available for new Cobras. The topic has been touched on in the Wheels & Tires forum on this site before but I thought that my response would be interesting to some on this Originality Forum also.

Shelby American Inc. offered “spline drive” magnesium wheels made by American Racing as street and racing options. There were two design types, the original with ‘hidden lugs’ and the revised with ‘exposed lugs’. Both wheel assembly designs incorporated steel adapters bolted in from the rear of the wheel and steel sleeves on the outboard side to be hard wear surfaces for standard AC logo center lock “knock off” nuts. All wheels were for 15” diameter tires.

Cobra wise buyers could get widths between 6.0 and 8.5 inches with the 6.0 models being unique to Shelby American and Cobras. American Racing added 6.5 through 8.5 inches wide models to their aftermarket catalogs.

6.0 inches wide wheels generally work without coachwork modifications on all four corners. A popular combination was 6.0 inches wide front and 7.0 inches wide in rear. 7.0 inches wide wheels in rear and or extra large tires could require modification of wings depending on the particular chassis as some coachwork width variation was normal.

An additional strengthening revision was made at some point but I don’t know when, a rib was added inside each wheel spoke. See reverse side image of a WHEEL hub below.

Neither assembly design type was light weight as compared to any of the ‘pin drive’ magnesium wheels Shelby American used.

Street and road racing wise the first ‘hidden lug’ design assembly proved generally satisfactory durability wise. The first design was not good on the rear for drag racing as the lug bolts tended to wallow out the magnesium they were threaded into. The solution was the ‘exposed lug’ revision whereby acorn type ‘lug nuts’ and the bolts captured the hub of the magnesium wheel between them. The second Shelby works “Dragonsnake” used the new design exposed lug wheels.

This wheel is 8.50 wide and was used for many years on the rear of a Cobra and it illustrates the ‘hidden lugs.

This is a new old stock 6.0 wide made specifically for Cobras ‘exposed lug’ wheel I once owned shown front and reverse side.

Most wheels were used as delivered by American Racing. There were at least two cars outfitted with hidden lug wheels that had their outboard sides completely mirror polished.

Some old unrestored wheels on unrestored Cobras had stickers like these on them.

Dan

Dan Case · #2 (**permalink**) 02-18-2018, 11:58 AM

This box of old parts will give you an idea of components used with the exposed lug wheel assemblies.

The designs were bolts threaded into magnesium or into long shank steel lug nuts.

When the prototype 1965 MUSTANG GT350 race car was first completed and tested (SFM5R002) it also used the same lug nuts. When research for that car's restoration was in progress I reverse engineered the design into a set of drawings for the restoration team in case they didn't find any new old stock ones or enough new old stock ones. These are the general views I created but they illustrate the threading in the nuts.

The washers are captured. They have to be pressed on but will free turn once in the undercuts made for them.