Is there a way to find original tire sizes for classic vehicles other than door tag or owners manuals?

Question

Need tire size for 66 Mercury Parklane with c6 and 3.25:1 rear. Current tires read "r78/15" and no one has heard of that before.

Answer 1

Note: After typing all the stuff below out, I found that if you need correct tires, Coker Tire has the original tire size online:

http://www.coker.com/store/customer/search.php?tire_model=Mercury&tire_year=1966&tire_make=MERCURY&in_category=108&x=3&y=7

I believe the modern equivalent of that would be 205/85R15 for the 845-15, or 205/75R15 for the 815-15. The latter is the only size you are likely to find in modern tires.

All right, now what I originally wrote - I can't bear to throw it away.

I don't believe that is the original tire size at all. This size appears to be from the early '70s. Unfortnately it seems that it's missing one letter before the R. See if you can find a tire shop with some old-timers behind the counter.

Alternatively, measure how wide the tire is (width, not diameter) at its widest part. Convert that number to mm and round to the nearest number ending in five. Take that number, and add "/78-R15" to the end. That'll give you your modern tire size that matches the tires you currently have. Whether these are actually the correct size is another story.

Answer 2

I believe (I do not have my resource handy) that the size is H78/15. Simply:

H=Load Carrying Capacity. The higher up the Alphabet, the more load.

78: the Aspect ratio of height to width

R: radial ply, not bias ply

15: rim diameter in inches

The closest equivalent(and feel free to correct me if I am wrong), is P215/75R15

There is a terrific source for tire sizes. The Bennet Garfield Tire Guide (AKA "The Tire Bible", at least by me). Look for the Old Timer's Tire Guide

Google it. If there is a tire size that exists in the Internet, they have it.

Answer 3

mad scientist is right on. Check out Coker Tire.

Answer 4

you can try the Vin Number its the number on your dash bord take it to the dealer and they will tell you every thing that car or truck came with new..

hope that helps