I have a set of nokian gazza extreme studded tires, sometimes replacement studs can be difficult to come by at retail. Are the studs interchangable between brands typically or should I stick to only the studs sold by the same manufacturer as the tire?
This article measures the sizes of studs between manufacturers. The upshot of the article is that if you have Nokian, Schwalbe, Continental, Innova studs, the dimensions are essentially the same and can be swapped around.
In any case, I'd expect Nokian (Suomi) studs to be the easiest ones to find these days anyway...
For reference, the essential from teh article linked above is that the studs are approximately: "Overall height: 5.8mm (pointed), and 5.5mm (domed)
Base height: 1.0mm
Base diameter: 6.5mm
Shaft diameter: 3.4mm
Tip diameter: 2.0mm"