Original Tire Specs for a 1976 Buick Electra 225?

[Sweet64rivi]

Does anyone know what the original brand and model tire was factory installed on the 1976 Buick Electra 225?  And how large of a white wall?  

[Barney Eaton]

The reference book I found says Electra and Riviera came with JR 78 X15 ("J" is the size "R" =radial)

On the Tire rack site, their chart shows a 15'  "J" =  225/75R15  or 235/70R15 or 265/60R15

Using another source (powerdog.com) those sizes convert to...a diameter of about 28 inches, circumference  of about 88 inches, the sidewall would be 6.5 inches.

Looking at 1976 sales pictures, the ones you have on the car may be slightly small......for some reason the big Buicks had wider white walls than the smaller Buicks.

[NTX5467]

Prior to the alpha-numeric tire size nomenclature, the JR78-15 was preceded by 8.85x15.   HR78x15 was 8.55x15 and LR78x15 was 9.15x15.  I believe the P225/75R-15 size has a section width of approximately 8.85", or very close to it.  LeSabres with factory a/c would have had the HR78-15 as standard equipment, which is also covered by the P225/75R-15 size, but slightly larger and taller.

 

Many of the larger GM cars of that era did have (at least from the factory) the slightly wider white wall width which Barney mentions.  After a year or so, that width of white wall was no more in the replacement area of things.  I believe the only place to get custom-width white walls is from Diamond Back Classics?

 

NTX5467

[Dynaflash8]

Do you guys know the correct whitewall width for a 1964 Wildcat?  I think I'll use 225's from Diamond Back on this car.  I have 235's on my 71 Riviera.  I also have a set of 5 new J78x15 whitewalls at my winter place, still mounted on my show rims.  Since I've made the car a tour driver after winning the AACA Senior, I want to put my radials on my best wheels and sell the J78x15 tires.