Tire Size Conversion
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Laughing Gas
Joined: Jan 2004
Posts: 813
Likes: 5
From: Meade, KS
Tire Size Conversion
Hey all-
I recently acquired a new project that needs new tires. The problem I've run into is that the tires I currently have are R78-15. I'm not at all familiar with this sizing. I'm familiar with the "255/75/16" style sizing, and don't know how to convert the old sizes to the new sizes. Can anyone help me with this?
Thanks!
I recently acquired a new project that needs new tires. The problem I've run into is that the tires I currently have are R78-15. I'm not at all familiar with this sizing. I'm familiar with the "255/75/16" style sizing, and don't know how to convert the old sizes to the new sizes. Can anyone help me with this?
Thanks!
5th Wheeling
Joined: Mar 2002
Posts: 47
Likes: 0
From: Lufkin, TX
Here's one but it don't go high enough for you. I got some on paper at home I can look up later.
http://www.tirerack.com/tires/tirete...sionchart.html
http://www.tirerack.com/tires/tirete...sionchart.html
Last edited by glazer1972; Aug 28, 2006 at 11:54 AM.
Posting Guru
Joined: Apr 2004
Posts: 1,921
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From: central TX
One site I found said it was basically a 37x12.5-15. Is it a pretty big tire? Sound about right?
If correct, the metric sizing would be ~ 315/85-15 (the exact conversions was 318/88-15).
http://www.4crawler.com/Diesel/Tires.shtml
If correct, the metric sizing would be ~ 315/85-15 (the exact conversions was 318/88-15).
http://www.4crawler.com/Diesel/Tires.shtml
Thread Starter
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Laughing Gas
Joined: Jan 2004
Posts: 813
Likes: 5
From: Meade, KS
It is a big tire. It's actually on a 66 Merc passenger car, but since FTE is my web home, I'm asking around here. Some other guys said (in another thread) that there's probably a letter that should be infront of the R, so when I get a chance I'm going to check it out.
Thanks!
Thanks!
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Laughing Gas
Joined: Jan 2004
Posts: 813
Likes: 5
From: Meade, KS
Well, SRD, I wish you were right. That would make a lot of sense. The car's not local, so I had my uncle (mechanic that's currently rebuilding the engine for me) double check the tire size.
All there is on the rear tires is R/78/15. On the front tires: 1 is P/205/75R15 the other is P215/75B15. So I've got three radials, 2 R/78/15, and 1 205/75/15, and a bias ply 215/75/15. Now I'm really lost!
Anybody know of a way to figure out the original tire size requirement for a given car? I believe that this would change depending on the rear gear, so it would have to be vehicle specific.
The reason for all this, btw, is that the vehicle needs new rubber, and I'd like to get something that is going to make the speedo correct (as speedos go).
Thanks all!
James
All there is on the rear tires is R/78/15. On the front tires: 1 is P/205/75R15 the other is P215/75B15. So I've got three radials, 2 R/78/15, and 1 205/75/15, and a bias ply 215/75/15. Now I'm really lost!
Anybody know of a way to figure out the original tire size requirement for a given car? I believe that this would change depending on the rear gear, so it would have to be vehicle specific.
The reason for all this, btw, is that the vehicle needs new rubber, and I'd like to get something that is going to make the speedo correct (as speedos go).
Thanks all!
James
Cargo Master
Joined: Aug 2004
Posts: 2,899
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From: Lynnwood, WA
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Posting Legend
Joined: Sep 2001
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Check the Read First: FAQ thread at the top of the 73-9 forum for tire size info.
https://www.ford-trucks.com/forums/1...ease-read.html
https://www.ford-trucks.com/forums/1...ease-read.html
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From: Annapolis,MD.
As mentioned,check the door if possible also double check that letter,to the best of my knowledge the highest letter code was "N".Most likely the "original" size will be numeric i.e. 7.60/15,8.15/15,etc.
Last edited by SRD4X4; Aug 31, 2006 at 05:19 AM.
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Laughing Gas
Joined: Jan 2004
Posts: 813
Likes: 5
From: Meade, KS
Thanks for all your help fellas (and any ladies I'm unaware of), but I'm afraid I'm going to have to put this on hold. I can't get to the rig in person right now. It'll be a couple weeks--I'm in the midst of a condensed class right now, and then the regular semester will start, but once I've got everything sorted, I'll be able to make the 5hr drive to get there and check it over.
I'll let you know what I find out then.
I'll let you know what I find out then.
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