Ok I'm pretty sure that it has 14" on it right now but can someone help me with what rubber I should put on my 1966 Oldsmobile Delta 88.

 

My '67 Delta 88 uses 14" wheels, too. I put on a set of Firestone FR380, size 215/70R14 back in 2009. I think the car should have taken 215/75R14 to more closely match the original tire size, but the 75s weren't available. I wanted white sidewalls, too. 14" tires for these cars are getting harder to find, and I don't think even the ones I bought six years ago are available now.

Here's what the car looks like with the 14-inch Firestones.

 

The original, base tire for your car was 8.25 x 14" blackwall with 8.55 x 14 as optional.

8.25 x 14 converts to P215/75R14. 8.55 x 14 converts to P225/75R14.

http://www.tirerack.com/tires/tirete...sionchart.html


As I said, the specs call for a 75 tire, but I went with a 70 because that's what was available.

 

I used 15" rims and went with 215/60/15 tires