Need help with tire sizing

Do you have IRS or swing axle?

If IRS, the 185 may not fit.

Tire sizing chart.

Tire sizing calculator.

The 185/65-15 is a 24.5-inch diameter tire. A 155/80 is about the same height, 24.8 inches.

The 165/80 is 25.4 inches. A 165/70 (if you could find) would be 24.1 inches.

@Michael McKelvey it is an IRS car

Have you confirmed that the 5.5" wheels will fit on the back?

I have 5.5" wheels on my CMC but I have special wheels with the added inch toward the center of the car.

I have 5.5" wheels front and rear with 175/70R15 tires.

You can narrow irs arms and fit 7" Fuchs wheels with 195/60 (and possibly 205/60) tires , but it involves cutting the bearing/axle shaft carrier out of the arm, moving it in 1", welding and then reinforcing the arm around the carrier.  Shorter axles are also needed to make it all work.

For those with a swingaxle car looking for more room to put wider wheels and tires on the back- early (1961? -'66) axles and tubes are about 1¾" shorter than later '68+ parts.

Is anyone here running 175/70/15s.  It seems like a good happy medium between the tall skinny stock size tires and the wider thinner sidewall 185/65 that a lot of people seem to be running

@JoeyLegos, see my reply just above.

@Michael McKelvey Not sure how I missed that lol.  Do you have a pic? Is your car lowered? Disc brakes?

I have an adjustable beam on the front and adjustable swing plates on the rear.

When the attached picture was taken I had drop spindles on the front but removed them. The front is a bit higher now.

I do have front and rear disk brakes. I have Ghia disks in the front and in the rear I have AC Industries brakes. I used these in the rear because they are described as not increasing the track.  Even so, I had to have a bit milled off the hubs to get zero track increase.

Thanks a bunch. That helps quite a bit.  Are you happy with the tire selection? If you had to do it again would you go the same route or choose something different? It looks great imo 👍

@JoeyLegos, I am happy with the tire selection.  They are Vredestein Sprint Classic.

The widest I could go in the back is 175.  I didn't want an aspect ratio less than 70 because I wanted to keep the tire's outside diameter as close as I could to that of a 165/80 tire.

Sounds like a good compromise.  The 185s are a bit wide for my liking, and I'm only running 4.5" rims. I know they'll fit and people have had success with them but they look a little too bulgy to me.  On the other hand the 165/80 are a bit too tall and skinny imo. I want a little more "sportier" look. Thank you for your help, I really appreciate it

@Michael McKelvey posted:

When the attached picture was taken I had drop spindles on the front but removed them. The front is a bit higher now.

I know it was probably too low, but WOW does the look righteous.

@Stan Galat posted:

I know it was probably too low, but WOW does the look righteous.

That's not too low, Stan; it's just right...                                                                              And I've driven Michael's Speedster- it scoots!