66 GMC wheels

[d4rksp1dy]

Hi everyone, i recently got a 66 GMC stepside and was wondering about the wheels. 1. What are the stock rim size? 2. What is the biggest size wheel and tire combo that will fit on the side where the spare goes? 3. I was thinking of getting some 15 x 8 with all terrain tires, would this work? And if not that then some 18s with some street tires. Also reason i ask about the spare is that i want to have a full size spare so what ever works on the side mount will be what i use all around.
This won't be my last post i have many questions on different topics about the truck. Thanks

 

[Lakeroadster]

Welcome!

Need more information to answer your query:

• Is your '66 a long bed or a short bed?
• Is your '66 a 1/2 ton or a 3/4 ton?

 

[Rich 5150 69]

One thing to keep in mind, if you have posi or limited slip rear axle, your spare needs to be the same size as your driving wheels, one wheel smaller on the drive axle is fine for very short distance, but any distance on it will burn up the friction plates...!

 

[d4rksp1dy]

Sorey. Short bed 1/4 ton

 

[Lakeroadster]

Sorey. Short bed 1/4 ton

Assuming you meant 1/2 ton...

The following is per GM Heritage Center Data for a 1966 C10. I know you have a GMC, but the data should still be good as a ref.

1. What are the stock rim size?

Wheels were 15 inch standard with a 16 inch wheel as an option​

2. What is the biggest size wheel and tire combo that will fit on the side where the spare goes?

Stock Tire Combinations were
7.75-15
8.15-15 which is 27.68 O.D. x 8.05 wide
6.00-16
6.50-16 which is 29.10 O.D. x 7.00 Wide
​

Bigger diameters than this are no doubt possible... you just need to do some measuring on your truck. Measure twice, buy once.