The previous owner put a 16" tire and wheel on my '70 cb750 so I ordered a used 18" from a yard. Had a new tire mounted and balanced, ordered new brake shoes for it, went to put them on this afternoon and the new shoes are too small. Dealer double checked the book and it shows the same shoes for '69-'78. Was an 18" rim with larger diameter drum made for the 750 or might it be for another model?