How to measure tire size?

[stretch cab]

I am ready to buy tires for my project that is shown in the Restoration section of this site.  It is listed as Grandpa's Car.  I believe the running gear is from a 1919 Chevy or older but I really do not know.  How should I measure the rims to know what size tires I need?  I know that one of the old tires was 30x3 1/2 but I have since found that one rim is a little wider than the others.  What I do not know is whether this was the rim that held the tire that I saw the size listed above on.  My spare rim never had a tire so it may be the wider one.  The tires were shot and I threw them away long ago.

[stretch cab]

The picture was taken from a home movie and my grandfather is at the wheel.

[Bloo]

30x3-1/2 is the Ford model T size, and goes on a 23" clincher rim. The size was also used on several other makes of car (Chevrolet, Maxwell, Studebaker, etc.). If the rims are indeed 23" and clincher (not straight sided), then 30x3-1/2 will be the only economical choice, and maybe the only choice.

 

Measure the rim from where the bottom of the bead sits.

 

Edited December 24, 2019 by Bloo (see edit history)

[C Carl]

And if I understand your terminology correctly , the width you mention is not an extremely critical dimension in this case. Not rim width, but rim DIAMETER as measured : 

 

5 hours ago, Bloo said:

30x3-1/2 is.....................23" 

 

Measure the rim from where the bottom of the bead sits.

 

 

Merry Christmas, and I sure hope the New Year turns out to be a very happy one for you. I know you have had some extremely trying times recently.    -    Carl 

[Bloo]

Merry Christmas to you and yours, Carl!

 

[mikewest]

Stand the rim up and using a framing square make a mark on the floor with one leg against where the tire rests. Flip the square around and do the same thing without moving the rim, now measure between the marks.