Oldsmobile/Buick Repair: Rear brakes, oldsmobile cutlas ciera, heavy duty brakes

Question
I have a 1989 Oldsmobile Cutlas Ciera.  It is a V6 with a 3.3, front wheel drive.  I need to replace me back brakes.  My brakes are heavy duty.  I need to replace both sides.  I need Wheel Cylinders, Drums, Springs, and Shoes.  My problem is that they keep asking me what my bolt pattern is.  I am having a really hard time ordering my parts.  My rims are 15 inch and it is a 5 bolt.  It is a 4 door car not station wagon like they keep asking me.  In order to take my lug nuts off, I have to use a 3/4 inch socket which converts to a 19mm.  I have no idea what to do to find out how to figure out what parts to aks for.  I have explained all this to them.  Please help.

Answer
Hello Christine,
I assume you are in Alaska, at some remote place where you can't flop one of your drums on the counter and say "Just like that one".
So I called my local "O"Reilly parts person, and found that there are different drums, one of which is for station wagon, or car with heavy duty brakes, and one is for cars with standard and medium duty.
It has a 115 MM bolt pattern, which means if you lay the drum on a piece of paper, and mark the Center of each lug bolt hole with a dot. Then use a compass, or thumbtack and string, and draw a circle that touches each dot. Measure from side to side across the center, and that will be the diameter they need.

The diameter of the drums is also something that would help. Measure across where the shoes touch, and it should be either 8 55/64 inches, or 8 49/64.  Measure carefully, since six sixty fourths isn't very much.

But my person said it looks like the station wagon, and the car with heavy duty, look like the same.

You might also measure the width of the brake shoe, but we didn't talk about that, and I bet they would be the same. But if you tell your parts people, that might help.
You can also look at the tag in the glove compartment that has about a hundred three digit numbers, and if you are talking to a Olds dealer, they will tell you what digits to look for, which will tell them what brake system you have.

But that measuring of the bolt circle should answer the question. Either 115 MM, or something different.

I hope I hear that all went well.
Van