the number on the left, using your example:
go that far).
in mind, and maintain overall outside diameter within 1/2" to preserve speedometer accuracy. I hope between what Nate posted and what I'm writing here clarifies what I aim to achieve. I do not necessarily want the whole wider thing.
I think the problem that you're going to find is that the tire size that will theoretically fit won't be available. Using the example above, even a 195/50R15 is narrow enough as to not be widely available anymore, and that's a very common "upgrade" size for a car made only 15-20 years ago (and was the factory size for a Corrado G60, IIRC.) Tire Rack only lists 7 tires in all categories in that size... Surprisingly, trying a
185/55R15 (my best guess at a "close" size without actually doing the math) yields 11 results which I didn't expect.But to answer your question, what you need to do is just "do the math" and match rolling diameters, which by the numbers should be, assuming the tires' size is given as follows:
S/A R D (for Section width, Aspect ratio, and wheel Diameter, respectively)
RD (in inches) = 2(S*A*0.254) + D
hold RD constant, plug in your desired numbers for S and D, then solve for A and then go to Tire Rack's site and see what's available in that size. A should be rounded to the nearest 5. (e.g. aspect ratios are commonly given as 50, 55, 60, 65, 70, 75 etc.) You probably won't run into this, but if a tire is given as 155R15 the aspect ratio is assumed to be 82. (that would be a size for an old Beetle or Porsche 914, I don't imagine that's what we're talking about here.)
nate