Tire size in Europe versus the US

[jbannon]

I currently live and work in Austria and was curious why stock tire size for pre 1967 beetles is 155 r 15 versus 165 r 15 that is common stock in the US?

[FritzCP]

it has to do with the original tires being bias ply 5.60-15. Bias Plies have narrow tread width that doesnt reach the sidewall (piecrust style) by design, but are also rather tall.

The radial equivalent of 155 matches the the 5.60" tread width road contact patch closer, but the tread goes all the way to the sidewall. Now the common sidewall aspect ratio of 80% is used, vs 82% back in the day makes it so the tire is shorter in diameter than factory specs. the 165 tire has a wider tread contact patch than the 5.60 by design, but using the aspect ratio of modern 80% the diameter (not 82 like old days) closer matches the 5.60-15 diameter.

and today 165r15 are common and inexpensive in the US, the 155 are harder to find and cost more. Bias ply looking radial 5.60 r15s are available.

This also goes for buses using the 6.40-14 tires. The tread width converts to a 185 radial, but those are shorter. a 195r14 is a closer fit to the diameter and better choice in stock applications in todays tires. 6.70s were also used and looked like balloons compared to the radials.
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[jbannon]

Thanks for the great information. Very helpful.

I can easily get 165s and 155s in Europe. In your opinion what is the better tire to use? Is it purely aesthetics or are there functional / wear issues?

[FritzCP]

165s being wider provide more contact patch and as such better handling and braking. also the diameter is closer to factory spec, so the gearing is correct and also your speedo reads right. But tire brands and quality differ and plays a bigger role in choice of safety and longevity. Go with what looks the best to you and is available and cost effective given its use. 195/65 are the same diameter and offer improved drivablilty and are cheaper / more common over here with better selection on brands. bias look radials are the cats meow, but at $250 a tire is not a good value for daily use on something that is not a stock vintage restoration. choice is yours
_________________
Fritz Custom Products
Fritz 10 - Tin Screw Torquer
Fritz 124 - Crank Pulley Puller
Fritz 70 - 6306 Bearing Puller
Fritz 44 - Dizzy Puller