Tallpaul67

I am hoping some one can help me with this problem. I am trying to find out what rim and tire size to buy to be able to fit the largest tires possible in the rear of my 67 442. I have read a few posts on this site but I am still a little confused. I want to buy the aftermarket 15" SSI rims. I have QA1 adjustable coil overs front and rear so have some room to adjust the height, but want the car sitting as close to factory height as possible with just a subtle rake to it. Has anyone gone down this road who can recommend the proper back spacing and possibly a rim manufacture that they used. I have been seeing a lot of people saying that a 4.5" back space will allow for the wides tire, but I get confused on the tire sizes. Also my car is a convertible so I am not sure that if that makes a difference. Any help or advice would be greatly appreciated.
Thanks Paul

joe_padavano

This discussion comes up a LOT. You need to understand that the measurement you care about is OFFSET. Backspace is a useless measurement unless you also know rim width, since wheels of different width that have the same offset will have different backspace measurements. You need a wheel with near zero offset.

Run to Rund

On my 66 442, I run 30x9 Hoosier drag slicks on 9" wheels with 4-3/8" backspace. The rear is the narrower type like used on 66 Chevelles. If you run the wider Olds width rear, BS should be about 4" ON A 9" WHEEL. If you use an 8" wheel, for example, split the difference in wheel width and you get a 3.5" BS with the wider rear, or about 4" with the narrow rear. That tire is the biggest that will fit easily/safely to clear the frame and wheel opening lips. You may have to trim the front edge of the wheel well at the bottom (rocker panel area) for that diameter (95" circumference).

Run to Rund

BTW, I have run wheels from 8" to 10" wide and have varied the offset a bit over the years, about +/- .125" so you may have to fine tune for your individual car. I have a number of wheels with stock centers and with HD centers that I have used over the years, but they are in Vegas, not too close to LI.

joe_padavano

I think you have that reversed, Joe. The wider rear will push the tires closer to the outer fender lip, and a smaller backspace (for the same wheel width) pushes the tire ever further towards the outer fender lip. You'd want a larger backspace with the wider Type O axle to keep the tire centerline in the same place.

Tallpaul67

Hi guys, thanks so much for the replies. I will have to do a little more research but that information definitely helped.

Run to Rund

Yeah, thanks. With the wider rear, BS would be about 4.8" for a 9" wheel.