Knockoff thread size

[Richard]

Sorry if this has already been answered somewhere on the forum but I would like to know what the thread size is for the wheel knockoffs (spinners). I have a Superformance GT40 if that make a difference.

 

[flatchat(Chris)]

Traditionally ? and I have 59mm O.D.(~= 2 5/16") 8 TPI (UNC) @60°

 

[Jay Cushman]

Originals were 55 degree wentworth threads

 

[Richard]

Thanks guys I had a number of 2" 21/64 x 8tpi which seemed strange but I some how knew Wentworth would come in here somewhere. Is this a standard size that race cars used for a long time or even on modern cars today.

 

[Ian Anderson]

Jay

Are you sure you don't meed Whitworth?

British Standard Whitworth - Wikipedia, the free encyclopedia

Ian

 

[Richard]

I got the 2" 21/46 for the guy at Vintage Wheels (nice guy) and he has knockoff's made. I think what it might be it just the closest SAE match to the Whitworth but that why I'm asking. I have a few engineering drawings from Superformance mostly of the suspension but they don't call out the threat specs for the wheel nut. Sure would be nice to have some more detailed information about these cars. Is it the same as they used on the Cobra's back then and now?

 

[flatchat(Chris)]

Its a "bastard " thread --probably derived from a 2" bsp (pipe) hence the 2 21/64" dia. and 8 TPI -- as Jay says Whitworth form of 55° (the best form of thread --as the crest and root are rounded )

UN and Metric are all 60°

 

[Tim Kay]

Sure would be nice to have some more detailed information about these cars.

Ditto that Richard :thumbsup: Stick to this forum for all the detailed info you need. If it weren't for this forum and the brainiacs contributing to it then a large percentage of us would have a heap of useless GT40 parts while we make 'vroom vroom' noises through our lips.

 

[Bob Putnam]

I believe that our hub's specifications are derived from the Trigo Cobra adapters that we used back in the '80s. They were probably identical the original Cobra's thread shape. I know that the Trigo wing nuts fit perfectly, and the Vintage wing nuts are just a few thousandths looser (but still usable). Thread OD is 2.325", pitch diameter is 2.245", with a 60 deg Unified Form shape.

 

[Jim Rosenthal]

Interesting... I have a KMS car also. They use Trigo wheels. I will have to see whether one oftheir spinners fits on the GT40 when the two are together.

 

[Richard]

Great info but I'm still not sure what Superformance used on my car. I took one of my knockoffs into the local "Nut and Bolt" shop and they just looked at it in a strange way with no real answer. If it's the same as the originally Cobra's I have a friend with a 66 427 car that might know. His car came with two steel and two aluminum knockoffs that are all stamped with the Halibrand name. Quality control?