I have also been using the SD-5 on my Gl. I've had them on for more than a
year. Except for the added noise, they are great tires, stiff side walls,
can't stop them in snow or rain. I am using  215/75/15's. They do bottom
out on the front right when heavily loaded, I turn sharply to the right and
go over a large bump. Other than that I love them.
 Dave
91 GL