I measured a diameter of 22mm and the thread pitch looked like about 1..25. Email Honda America for the exact size.. I thought it would be similar to the lugnut size, but they are 12mm by 1.5. Sometimes metric sizes and SAE sizes "crossover", and a 13/16 SAE size is closer. I am sorry that I cannot give you an exact size...but you have a bolt size that you should be able to measure too. I wrote to them today and asked them for you.