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

[speedracer]

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?

[BeauBlues]

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.

[IROC]

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

[speedracer]

That explains it, thanks guys!

[SC-targa]

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

[Bill Verburg]

Originally posted by SC-targa
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.
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.