Tires: tire question, Vintage Tires

Question
I have a 1950 ford coupe the tires on it are from sears and all they say on the side is 7.10-15 sears allstate guardsman 4ply polyester. What would the size be  i would need to get by todays standards. I cant seem to find sizes to fit what my tires say on the side.

Answer
Jason,,

At the moment I am away from my reference books, and I have to have them to go back to that era to see what an equivalent tire might be.

But be aware that tires have changed considerably since that time frame and things are quite different.  For one, 7.10-15's are bias ply tires - and the rims of that era were not designed to hold up under the more concentrated loads that radial tires develop.  When radial tires were first introduced, there were many instances of rims cracking.  They eventually fixed that problem and modern rims are a bit stronger.

Another thing that has changed is tire sizing.  That has changed 3 times since 1950.  Tires in that era were in the 80 and 90 aspect ratio range, where today it is hard to find 75 series tires.  That also means the rims were considerably narrower and that may limit what is available in a modern radial tire to fit the rim.

But if you want to use authentic tires, then you'll want to talk to the folks at Coker Tire.

When I looked at their web site, I noticed that they say a 7.10-15 can be replaced by a P205/75R15.  However,they also say a 1950 Ford came with both 15" and 16" and the tire size for a 15" was 6.70-15 - and they say that can be replaced by P205/75R15's.

But I have some reservations about that - and would like to verify some things before I give you my final answer.

I'll make addition to this response in a few days when I'm back with the reference books again.


FOLLOWUP:

Jason,

At the moment, I am having trouble accessing some older tire load and dimension tables.  Those will help me with the load carrying characteristics and such dimensions as overall diameter and allowable rim width range.

They are currently locked in a storage room and the key to the room is with a person on vacation.  It may be as long as 2 weeks before I can get into the room.  When that happens, I'll post a followup to this post.

Please be patient.


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Good News!  I found someone who had a key to the storag room and was able to copy load tables from 1950 (I also did load tables from the 1960's and 1970's while I was at it.)

Short version:  I've reviewed everything and I think Cokes is right except for the bit about rim width - and I think they are making an assumption that the most important thing is that the tires are adequate to hold up the vehicle - so they don't have to worry about ride and handling issues.  So my potential objection to the narrow rim width appears to be moot with that consideration.