I just bought a 225 Convertible and I will be driving it 2700 miles. I figure its not a good idea to drive it on the 30 year old tires it has on it. Any idea what the correct tire size is for this car? Searching the web I found 8.00-15 which converts to 225/75r15, but I'm not sure this is correct. Can someone help verify please?
Will, here's a handy conversion chart. Like Roberta said: 5 X 5 (Big GM) bolt circle :TU: 8.0 X 15 was the standard tyre size.
225/75r15 will work, but 235/75r15 will be closer the the original diameter/circumference and will look better.
While the bolt pattern is standard GM 5 on 5, standard GM wheels will not fit due to the large finned brake drums. I know because I took the wheels and tires from a '91 Caprice wagon to use to bring back my '61 from from Minnesota when I got it. Luckily we found a place to change over the tires to the Buick rims.
What did you use for the height of the tyre wall in your calculations? You also have to think about the width of the original rims and that these cars use skirts :TU: For what it's worth:
Other conversion charts differ: https://www.dbtires.com/crossreference.html 235's will fit inside skirts.
Standard rim size is 6J. That's 6 x 25.4 = 152.4 mm 235 tyres are 235 mm wide. 235 - 152.4 = 82.6 mm. So the tyres will stick out 82.6 : 2 = 41.3 mm out on each side of the rim. That's the balloon effect... 225 tyres are 225 mm wide. 225 - 152.4 = 72.6 mm. 72.6 : 2 = 36.3 mm on each side of the rim. So, the 225 tyre is much better for handling and it also looks better :TU:
I've got 235s on my Electra now, and the skirts still fit and haven't blown off when I hit a pothole.
