Ed, 1969 Electras had 8.55 x 15 inch tyres standard from the factory. (Sorry, I couldn't find the 1968 info) So that's 8.55 x 2.54 = 21.7 cm = 217 mm, this will result in a metric size of 225 (mm). Your choice to go for 225/70/15 or 225/75/15 The second figure indicates how many % of the tyre width, the hight of the tyre wall is. Multiply this by 2 (two times the wall hight) plus 381 mm (15 inch in mm) and you have the total wheel hight. Multiply this by 0.0394 and there you have the hight in inches. Example: 225/70/15: 70% of 225 mm = 157.5 mm wall hight 2 x wall hight = 157.5 x 2 = 315 mm plus 15 inch in mm = 315 + 381 = 696 mm 696 mm x 0.0394 = 27.4 inches wheel hight. 225/75/15: 75 % of 225 = 168.5 mm 168.5 x 2 = 337 mm 337 + 381 = 718 mm wheel hight 718 x 0.0394 = 28.2 inches wheel hight
Here is a link that might help you http://www.tireguides.com/tip6.html I agree with Erik on the sizing. I dont think they started using the letter designation on GM fullzsize unitl 1970. That year (70) the 225's came with J78's as standard (I remember the dual stripe whitewalls on my dads 225) HTH
Regarding 1969 Electra 225 models; all the 1969 Buick literature I have available including the owners manual, the chassis service manual, the dealer brochure and the Buick features book indicate the standard tire to be 8.85 x 15. The features book only lists two factory tire options-whitewall tires 8.85 x 15 and radial ply whitewall tires 225R-15. The chassis service manual also lists optional J78-15 fiberglass belted tires. The standard tire for the LeSabre and Wildcat models is listed at 8.55 x 15. I hope this information helps.
Thanks everybody I want to thank everybody that offered their input and I never thought about the letter codes note being available until later years. You guys rule! :TU: Thanks
