Whats the bolt pattern on the 99 4x4s? And how do I know which ones will fit my Blazer? I found some 18x7.5s, will they fit? Why or why not? And what tire would you recoment on a 18-20" wheel?

 

the bolt pattern should be 5 on 4.75 if im not mistaken. This has been the bolt pattern on the s-series for a very long time...

 

Ok thank you. Can anyone else answer the rest of my questions. And help me make up my mind, go for the bigger rims look, but dont lower it since I do, do some off roading (wouldnt with the biger rims for that) or lift it and go for the off roader look.

 

We really need to know the offset on the rims to answer anything else. For tire size choices, do you want your speedo to still be accurate or doesn't that matter. To keep it accurate, you need to get a tire that has close to the same OD as the originals. What was the original tire size on your truck?

 

+38 is the offset. Yes I want the speedo to be accurate. The originals are 235/75-15

 

So you need a tire that is 29" in diameter.

At an offset of +38mm, you are sitting at 1.5" from the center of the rim to the hub mounting face. So with a 7.5" rim, you are looking at 5.25" worth of back spacing. I believe the stock 4wd rims have 6" backspacing... With these rims, the inner edge of the tire will be 3/4" closer to the frame when straight. You may run into problems when the tires are turned.

 

How do you figure that? I would rather know how to figure it instead of having to ask someone all the time.

 

Easy, less backspacing = wheels will be closer to the frame.

A7.5" rim width with 5.25" backspacing means the wheels will be tucked further under the wheel well. Thus when you turn in either direction, wheel rub may occur as Kyle stated.

 

Actually I stated that wrong in my previous post... That's what I get for posting while at work.

The more the backspacing, the further from the frame with the wheels pointed straight as this would move the hub mounting surface on the rim further from the inner edge of the rim. Where you could wind up with problems is when you turn as the outer edge of the tire now travels in a wider arc while turning.

Offset is from the center of the rim. Positive offset is towards the outside of the rim (the side you see) while negative is to the inside.