I am changing wheels and tires on my 70 442 from 14" to 15" so I can effectively lower the gear ratio to make it more highway friendly and full up the wheel well.
My thoughts, from doing a search of the forum, is P235-70-15 in the front and P255-70-15 in the rear.
Any comments or other recommendations appreciated.
Joe

 

Here is what 235 70s look like in the rear w/ 15x7 SSIIs. Would have liked to go wider but couldn't beat the price..... free! Grrr pics always upside down!

Bill

 

255 60 15 tires are 27.0" tall. We need to know what tire size you have now on your current 14" rims to calculate the rpm change that will be achieved by going to the 255 60 15s. You may want to move up to 275 60 15s which are 28" tall and will have a much bigger effect on highway rpm. Note if your have 3.23 gears or numerically lower ratio then you will hate the acceleration with the 275 60 15s.

 

The 235-60-14 tires that are on the car now are 25.1" tall and I have 3:43 gears. With the 455 cu in. on the highway at 60 MPH the RPM's are about 3000.
I am not thinking of 60's but I was going to go with 70's as I stated in my post.
The 255-70-15 are 29.1" diameter.
Thanks,
Joe

 

Oops. My bad. I read 60 series and you meant 70 series.

I have never seen 255 70 15s on an A body. They are typically a truck tire.

a 4" increase in tire height will result in approximately 400 rpm drop @ 60 mph with 3.42 gears

 

Thanks for the replies, 400 RPM drop is better than nothing.
Joe