Dumb question alert..Why are the front sidewalls on tires usually taller?
 

Just wondering the above..... example:

I am looking at a set of 17 inch wheels and tires. The front tire size is a 50 series, the rear a 40 series. Would there be any problems with running a 40 series at the front as well?

The 50 and the 40 are a percentage to the width of the tire tread. For example, Lets say your tire is 275/40, your sidewall size is 40% the size of your tread(275). So in essence, as long as your rear tires are wider, your sidewalls should be about the same size.

40 series vs 50 series doesn't tell the whole story. The aspect ratio ("40" or "50" in this case) is simply the height of the sidewall as a percentage of the section width of the tire.

So...for instance, a 205/55 tire has a sidewall height that is 112.75 mm and a 225/50 has a sidewall height that is 112.50 mm. Very close.

Pay attention to overall diameter and the actual measurements of the sidewall heights as the specific aspect ratios aren't the issue.

Mike

That explains it, thanks guys!

The original basis for the 911 aspect ratios was to make the OD of the front and rear tires the same so a single spare tire could be used at either end. A 205/55-16 is roughly the same OD as a 225/50-16 or a 245/45-16.

Corvettes now run wildly different front and rear diameters because they use run-flat tires.

Regards,

Jerry Kroeger

That and they wanted to dial in more understeer, both the wider rear tire and the lower aspect ratio in the back increase grip at that end.