#21  
Old 05-19-2020, 09:29 PM
John V. John V. is offline
Ultimate Warrior
 
Join Date: Sep 2005
Posts: 4,747
Default

Bill, the history of tire sizing will tell you why the sizing change occurred for '65.

For '64, the "normal" aspect ratio was higher (IIRC roughly 82%). The tire sizing convention at the time was tire width (7.50) x rim dia. (14). The aspect ratio was a calculation based on the ht. of the tire from which you could derive the sidewall ht.

in '65, there was a modest change to the aspect ratio (IIRC it might have gone to 78%),

The sizing convention did not change but the decrease in aspect ratio meant the nominally same ht. tire now had a slightly wider tread.

I don't know what drove the change in "normal" tire aspect ratio. It may have been an effort by the tire industry to standardize and possibly reduce the number of tire sizes manufactured.

During that period of time auto and tire safety were under increasing scrutiny by the Fed gov't. Perhaps there was some effort made to increase the safety of tires that resulted in the change in the aspect ratio. Higher load rating may have been the reason.

Whatever the case, the 7.50x14 was replaced for '65 by the 7.75x14. Later, a letter system was introduced, this size tire became the F tire size. In fact, even in '64, the F coding was already in use by GM for the 7.50 tire width for manifest coding purposes.

Don't know what the J9189 could mean. There was/is an SAE Standard J1981 that was developed to standardize tire testing. But assuming you didn't post the wrong nos., I assume the code on your tire is unrelated.

Seems to me there is a high likelihood that the tire that you found in your trunk in 1989 was original to the car.

  #22  
Old 05-21-2020, 06:31 AM
Jeff Hamlin's Avatar
Jeff Hamlin Jeff Hamlin is offline
Ultimate Warrior
 
Join Date: Jan 2000
Location: Beach side of Virginia
Posts: 9,371
Talking Don't forget the

Snow Belt REDLINE option

__________________
When I die, I want to go peacefully like my grandfather did, in his sleep.
Not screaming like the passengers in his car.

Last edited by Jeff Hamlin; 02-26-2024 at 07:15 AM.
  #23  
Old 05-21-2020, 09:38 AM
The Champ's Avatar
The Champ The Champ is offline
Ultimate Warrior
 
Join Date: May 2002
Location: Rochester, MN
Posts: 2,534
Default

Quote:
Originally Posted by Jeff Hamlin View Post
Snow Belt REDLINE option
I'm sure plenty of those were sold in MN....

  #24  
Old 06-22-2020, 03:32 PM
aceaceca's Avatar
aceaceca aceaceca is offline
Chief Ponti-yacker
 
Join Date: Nov 2004
Location: San Francisco,Bay Area
Posts: 557
Default Real Red Line

Official red line tire from Kansas City Plant. Contains air from Kansas City, Houston, Los Angeles, SF Bay Area.
Attached Thumbnails
Click image for larger version

Name:	IMG_0838.jpg
Views:	116
Size:	65.3 KB
ID:	543029   Click image for larger version

Name:	IMG_0839.jpg
Views:	103
Size:	52.9 KB
ID:	543030   Click image for larger version

Name:	IMG_0840.jpg
Views:	223
Size:	61.7 KB
ID:	543031  

  #25  
Old 06-22-2020, 03:40 PM
aceaceca's Avatar
aceaceca aceaceca is offline
Chief Ponti-yacker
 
Join Date: Nov 2004
Location: San Francisco,Bay Area
Posts: 557
Default Real Red Line

More pics
Attached Thumbnails
Click image for larger version

Name:	IMG_0843.jpg
Views:	88
Size:	62.6 KB
ID:	543035   Click image for larger version

Name:	IMG_0842.jpg
Views:	81
Size:	60.2 KB
ID:	543036   Click image for larger version

Name:	IMG_0844.jpg
Views:	86
Size:	56.7 KB
ID:	543037  

  #26  
Old 06-22-2020, 03:47 PM
Chief of the 60's Chief of the 60's is offline
Suspended
 
Join Date: Nov 2017
Location: On the Rez
Posts: 3,233
Default

Quote:
Originally Posted by aceaceca View Post
Official red line tire from Kansas City Plant. Contains air from Kansas City, Houston, Los Angeles, SF Bay Area.


I noticed your red is bleaching out too. Mine was fairly red back in the 70's but now is almost completely white with maybe a faint pink tint.


  #27  
Old 06-22-2020, 09:23 PM
John V. John V. is offline
Ultimate Warrior
 
Join Date: Sep 2005
Posts: 4,747
Default

‘65 Red Line, correct?

Since the ‘65 tire had the lower aspect ratio vs ‘64, I’m guessing the ‘64 7.50x14 tire did NOT say LOW PROFILE on the sidewall.

Can anybody confirm that?

Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 10:36 AM.

 

About Us

The PY Online Forums is the largest online gathering of Pontiac enthusiasts anywhere in the world. Founded in 1991, it was also the first online forum for people to gather and talk about their Pontiacs. Since then, it has become the mecca of Pontiac technical data and knowledge that no other place can surpass.

 




Copyright © 2017