The clamps and spacers have to be made for each other. If you have a wider spacer the clamps have to be shorter. When properly torqued the heel of the clamp should not be in contact with the hub. Other wise you are not putting the correct crush on the spacer. If the heel of the clamp is too far from the hub, you are putting too much stress on the studs. Spacers come in from about 3 1/2 inch to about 4 1/4 in about 1/4 increments. On wheels manufactured from the 70's on up, the manufacturer recommended spacer and clamp or cleat sizes. Not many tire shops understand spoke wheels any more because they are no longer common. You must also consider the width of the rim when going to a larger tire size. I think we used 7 1/2 on 10's and 6 1/2 on 9's. If you are really not going to haul a load it doesn't matter much, but your cleats must be right or the rims will slip during hard braking.