Where to measure Nardi wheel dia.

[jmackro]

I just bought a 390mm Nardi Classico wheel for my CS coupe. When I opened the box, the wheel seemed small. But, I'm not sure where the diameter should be measured - at the outermost edge of the wheel, or at the midpoint?

The wheel I received measures 15 3/16" or 386mm at its outer edge - does Nardi round that up, and call it a "390"? The wood rim of this wheel has an inner diameter of 13 3/8" or 340mm. The average of 386 and 340 is 363mm, so the midpoint of my wheel (i.e., where the black stripe is) seems closer to 360mm than 390.

Before I call the vendor, does anyone know where Nardi takes the diameter measurement? Did the vendor mix up my order, or is a "390" wheel really a 363?

 

[bert35csi]

It's measured from outside edge to outside edge.

Bert

 

[jmackro]

OK, well maybe it was a silly question. So, I guess I do have a 390mm wheel.

For reference, my stock wheel measures 420mm in diameter at its outer rim. So, I guess the Nardi wheel will be 93% of the stock size.

 

[bert35csi]

Pretty sure there are no set standards for measuring steering wheel size between the various manufactures. Most do probably round off their numbers to a 5 or a 0 though. I've measured some of my steering wheels with their stated sizes, the 380mm Petri/CSL wheel, the 380mm Alpina 4-spoke wheel and the factory 385mm Motorsport 3-spoke wheel for my M6 and and a spare 400mm Petri sport steering wheel, all 4 wheels correspond with the outside edge measurements. I also have a measured 368mm, essentially a 370mm Nardi wheel, but I've found no references to this size in all the recent Nardi sales literatures. Some manufactures may measure their wheels from center of grip to center of grip though, this may logically explain the stated and your measured size discrepancies.

Bert