I have seen the question asked many times: "How do I know if those shoes I want to buy will fit my bike"?
Many people, myself included, can't remember or can't find reliable web information as to the exact measurments of the brake shoes that are hiding behind their brake plate.
The only way you are going to know for sure is to remove the wheel and find out, in milimeters, the diameter of the brake drum,
and the width of the shoes. You could rely on measument specifications that you may have found on your bike, but the wheels
from different bikes are interchangable. You don't know if you are in possesion of the factory wheels, or if the PO has upgraded
from somthing else.
My 78 Hobbit has the front wheel from a 1970 Honda CT90 on it because the shoes and drum is 50% bigger.
Because it is on hand, I will use this wheel and brake plate from a 77 Peugeot. Of course you will first remove the wheel from the bike and then unscrew and remove the axle nut and washer. This will allow you to slide the brake plate/shoe assembly off of the axle, exposing the brake drum.
If you plan to take up Moped as a dedicated hobby like myself, then I sugest you invest 25.00 in a digital caliper as all mopeds are built on a metric scale. This tool will prove invaluable. As I spread it across the width of the brake drum it reads, 79.39 or 80mm. Most shoe sizes will go up or down in 5mm incriments. Thats alot, so you can round up or down to the nearest 5mm incriment. For example, I've never seen 78mm, or 83mm drum measurments.
Now , also measure the depth of the shoes. These shoes have a depth reading of 18.12 or 18mm in general. Now when I go online I can shop for brake shoes with the measurments of 80mm X 18mm.
Also important when shopping for shoes is to remember what the shoes look like and what the spring configuration is. A good snap shot can help a lot especially if you have reassembled your bike in anticipation of a delay in getting shoes through the mail.